MSP430x4xx Family User`s Guide (Rev. L)
MSP430x4xx Family
User’s Guide
April 2013
SLAU056L
Related Documentation From Texas Instruments
Preface
Read This First
About This Manual
This manual discusses modules and peripherals of the MSP430x4xx family of
devices. Each discussion presents the module or peripheral in a general
sense. Not all features and functions of all modules or peripherals are present
on all devices. In addition, modules or peripherals may differ in their exact
implementation between device families, or may not be fully implemented on
an individual device or device family.
Pin functions, internal signal connections and operational parameters differ
from device to device. The user should consult the device-specific data sheet
for these details.
Related Documentation From Texas Instruments
For related documentation see the web site http://www.ti.com/msp430.
FCC Warning
This equipment is intended for use in a laboratory test environment only. It
generates, uses, and can radiate radio frequency energy and has not been
tested for compliance with the limits of computing devices pursuant to subpart
J of part 15 of FCC rules, which are designed to provide reasonable protection
against radio frequency interference. Operation of this equipment in other
environments may cause interference with radio communications, in which
case the user at his own expense will be required to take whatever measures
may be required to correct this interference.
Notational Conventions
Program examples, are shown in a special typeface.
iii
Glossary
Glossary
ACLK
Auxiliary Clock
See Basic Clock Module
ADC
Analog-to-Digital Converter
BOR
Brown-Out Reset
See System Resets, Interrupts, and Operating Modes
BSL
Bootstrap Loader
See www.ti.com/msp430 for application reports
CPU
Central Processing Unit
See RISC 16-Bit CPU
DAC
Digital-to-Analog Converter
DCO
Digitally Controlled Oscillator See FLL+ Module
dst
Destination
See RISC 16-Bit CPU
FLL
Frequency Locked Loop
See FLL+ Module
GIE
General Interrupt Enable
See System Resets Interrupts and Operating Modes
INT(N/2) Integer portion of N/2
I/O
Input/Output
ISR
Interrupt Service Routine
LSB
Least-Significant Bit
LSD
Least-Significant Digit
LPM
Low-Power Mode
MAB
Memory Address Bus
MCLK
Master Clock
MDB
Memory Data Bus
MSB
Most-Significant Bit
MSD
Most-Significant Digit
NMI
(Non)-Maskable Interrupt
See System Resets Interrupts and Operating Modes
PC
Program Counter
See RISC 16-Bit CPU
POR
Power-On Reset
See System Resets Interrupts and Operating Modes
PUC
Power-Up Clear
See System Resets Interrupts and Operating Modes
RAM
Random Access Memory
SCG
System Clock Generator
SFR
Special Function Register
SMCLK
Sub-System Master Clock
See FLL+ Module
SP
Stack Pointer
See RISC 16-Bit CPU
SR
Status Register
See RISC 16-Bit CPU
src
Source
See RISC 16-Bit CPU
TOS
Top-of-Stack
See RISC 16-Bit CPU
WDT
Watchdog Timer
See Watchdog Timer
iv
See Digital I/O
See System Resets Interrupts and Operating Modes
See FLL+ Module
See System Resets Interrupts and Operating Modes
Register Bit Conventions
Register Bit Conventions
Each register is shown with a key indicating the accessibility of the each
individual bit, and the initial condition:
Register Bit Accessibility and Initial Condition
Key
Bit Accessibility
rw
Read/write
r
Read only
r0
Read as 0
r1
Read as 1
w
Write only
w0
Write as 0
w1
Write as 1
(w)
No register bit implemented; writing a 1 results in a pulse.
The register bit is always read as 0.
h0
Cleared by hardware
h1
Set by hardware
−0,−1
Condition after PUC
−(0),−(1) Condition after POR
v
vi
Contents
&RQWHQWV
1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1
Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2
Flexible Clock System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3
Embedded Emulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4
Address Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.1 Flash/ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.2 RAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.3 Peripheral Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.4 Special Function Registers (SFRs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.5 Memory Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1
1-2
1-2
1-3
1-4
1-4
1-5
1-5
1-5
1-5
2
System Resets, Interrupts, and Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1
System Reset and Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.1 Brownout Reset (BOR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.2 Device Initial Conditions After System Reset . . . . . . . . . . . . . . . . . . . . . . . .
2.2
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.1 (Non)-Maskable Interrupts (NMI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.2 Maskable Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.3 Interrupt Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.4 Interrupt Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.5 Special Function Registers (SFRs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3
Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Entering and Exiting Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4
Principles for Low-Power Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5
Connection of Unused Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-1
2-2
2-3
2-4
2-5
2-6
2-9
2-10
2-12
2-12
2-13
2-15
2-16
2-16
vii
Contents
3
RISC 16-Bit CPU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1
CPU Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.1 Program Counter (PC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.2 Stack Pointer (SP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.3 Status Register (SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.4 Constant Generator Registers CG1 and CG2 . . . . . . . . . . . . . . . . . . . . . . .
3.2.5 General-Purpose Registers R4 to R15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3
Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.1 Register Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.2 Indexed Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.3 Symbolic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.4 Absolute Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.5 Indirect Register Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.6 Indirect Autoincrement Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.7 Immediate Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4
Instruction Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.1 Double-Operand (Format I) Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.2 Single-Operand (Format II) Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.3 Jumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.4 Instruction Cycles and Lengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.5 Instruction Set Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
16-Bit MSP430X CPU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.1
CPU Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-2
4.2
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-4
4.3
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-5
4.3.1 The Program Counter PC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-5
4.3.2 Stack Pointer (SP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-7
4.3.3 Status Register (SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-9
4.3.4 The Constant Generator Registers CG1 and CG2 . . . . . . . . . . . . . . . . . . .
4-11
4.3.5 The General Purpose Registers R4 to R15 . . . . . . . . . . . . . . . . . . . . . . . . .
4-12
4.4
Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-15
4.4.1 Register Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-16
4.4.2 Indexed Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-18
4.4.3 Symbolic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-24
4.4.4 Absolute Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-29
4.4.5 Indirect Register Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-32
4.4.6 Indirect, Autoincrement Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-33
4.4.7 Immediate Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-34
4.5
MSP430 and MSP430X Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-36
4.5.1 MSP430 Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-37
4.5.2 MSP430X Extended Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-44
4.6
Instruction Set Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-58
4.6.1 Extended Instruction Binary Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-59
4.6.2
MSP430 Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-61
4.6.3 Extended Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-113
4.6.4 Address Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-156
viii
3-1
3-2
3-4
3-4
3-5
3-6
3-7
3-8
3-9
3-10
3-11
3-12
3-13
3-14
3-15
3-16
3-17
3-18
3-19
3-20
3-72
3-74
Contents
5
FLL+ Clock Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1
FLL+ Clock Module Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2
FLL+ Clock Module Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.1 FLL+ Clock features for Low-Power Applications . . . . . . . . . . . . . . . . . . . .
5.2.2 Internal Very Low-Power, Low-Frequency Oscillator . . . . . . . . . . . . . . . . . .
5.2.3 LFXT1 Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.4 XT2 Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.5 Digitally Controlled Oscillator (DCO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.6 Frequency Locked Loop (FLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.7 DCO Modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.8 Disabling the FLL Hardware and Modulator . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.9 FLL Operation from Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.10 Buffered Clock Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.11 FLL+ Fail-Safe Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3
FLL+ Clock Module Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5-1
5-2
5-8
5-8
5-9
5-9
5-10
5-11
5-11
5-12
5-13
5-13
5-13
5-14
5-15
6
Flash Memory Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1
Flash Memory Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2
Flash Memory Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.1 SegmentA on MSP430FG47x, MSP430F47x, MSP430F47x3/4,
MSP430F471xx Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3
Flash Memory Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.1 Flash Memory Timing Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.2 Erasing Flash Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.3 Writing Flash Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.4 Flash Memory Access During Write or Erase . . . . . . . . . . . . . . . . . . . . . . . .
6.3.5 Stopping a Write or Erase Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.6 Marginal Read Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.7 Configuring and Accessing the Flash Memory Controller . . . . . . . . . . . . . .
6.3.8 Flash Memory Controller Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.9 Programming Flash Memory Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4
Flash Memory Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6-1
6-2
6-4
and
6-5
6-6
6-6
6-7
6-11
6-17
6-18
6-18
6-18
6-19
6-19
6-21
7
Supply Voltage Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1
SVS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2
SVS Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.1 Configuring the SVS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.2 SVS Comparator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.3 Changing the VLDx Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.4 SVS Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3
SVS Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1
7-2
7-4
7-4
7-4
7-5
7-6
7-7
8
16-Bit Hardware Multiplier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.1
Hardware Multiplier Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2
Hardware Multiplier Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.1 Operand Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.2 Result Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.3 Software Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.4 Indirect Addressing of RESLO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.5 Using Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.3
Hardware Multiplier Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1
8-2
8-3
8-3
8-4
8-5
8-6
8-6
8-7
ix
Contents
9
32-Bit Hardware Multiplier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.1
32-Bit Hardware Multiplier Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2
32-Bit Hardware Multiplier Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.1 Operand Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.2 Result Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.3 Software Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.4 Fractional Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.5 Putting It All Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.6 Indirect Addressing of Result Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.7 Using Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.8 Using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.3
32-Bit Hardware Multiplier Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9-1
9-2
9-4
9-5
9-7
9-9
9-10
9-15
9-17
9-18
9-20
9-21
10 DMA Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1
10.1 DMA Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-2
10.2 DMA Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-4
10.2.1 DMA Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-4
10.2.2 DMA Transfer Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-5
10.2.3 Initiating DMA Transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12
10.2.4 Stopping DMA Transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-15
10.2.5 DMA Channel Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-15
10.2.6 DMA Transfer Cycle Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-16
10.2.7 Using DMA with System Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-17
10.2.8 DMA Controller Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-17
10.2.9 DMAIV, DMA Interrupt Vector Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-17
10.2.10 Using the USCI_B I2C Module with the DMA Controller . . . . . . . . . . . . . . 10-19
10.2.11 Using ADC12 with the DMA Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-19
10.2.12 Using DAC12 With the DMA Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-19
10.2.13 Using SD16 or SD16_A With the DMA Controller . . . . . . . . . . . . . . . . . . . . 10-20
10.2.14 Writing to Flash With the DMA Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-20
10.3 DMA Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-21
11 Digital I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.1 Digital I/O Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2 Digital I/O Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.1 Input Register PxIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.2 Output Registers PxOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.3 Direction Registers PxDIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.4 Pullup/Pulldown Resistor Enable Registers PxREN
(MSP430F47x3/4 and MSP430F471xx only) . . . . . . . . . . . . . . . . . . . . . . . .
11.2.5 Function Select Registers PxSEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.6 P1 and P2 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.7 Configuring Unused Port Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.3 Digital I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
x
11-1
11-2
11-3
11-3
11-3
11-3
11-4
11-4
11-5
11-6
11-7
Contents
12 Watchdog Timer, Watchdog Timer+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.1 Watchdog Timer Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2 Watchdog Timer Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.1 Watchdog Timer Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.2 Watchdog Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.3 Interval Timer Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.4 Watchdog Timer Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.5 WDT+ Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.6 Operation in Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.7 Software Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3 Watchdog Timer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12-1
12-2
12-4
12-4
12-4
12-4
12-5
12-5
12-6
12-6
12-7
13 Basic Timer1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.1 Basic Timer1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2 Basic Timer1 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.1 Basic Timer1 Counter One . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.2 Basic Timer1 Counter Two . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.3 16-Bit Counter Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.4 Basic Timer1 Operation: Signal fLCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.5 Basic Timer1 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3 Basic Timer1 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13-1
13-2
13-4
13-4
13-4
13-4
13-5
13-5
13-6
14 Real Time Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.1 RTC Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2 Real-Time Clock Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.1 Counter Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.2 Calendar Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.3 RTC and Basic Timer1 Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.4 Real-Time Clock Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3 Real-Time Clock Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14-1
14-2
14-4
14-4
14-5
14-5
14-6
14-7
15 Timer_A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1
15.1 Timer_A Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15-2
15.2 Timer_A Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15-4
15.2.1 16-Bit Timer Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15-4
15.2.2 Starting the Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15-5
15.2.3 Timer Mode Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15-5
15.2.4 Capture/Compare Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-11
15.2.5 Output Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-13
15.2.6 Timer_A Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-17
15.3 Timer_A Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-19
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Contents
16 Timer_B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1
16.1 Timer_B Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-2
16.1.1 Similarities and Differences From Timer_A . . . . . . . . . . . . . . . . . . . . . . . . . .
16-2
16.2 Timer_B Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-4
16.2.1 16-Bit Timer Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-4
16.2.2 Starting the Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-5
16.2.3 Timer Mode Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-5
16.2.4 Capture/Compare Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-11
16.2.5 Output Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-14
16.2.6 Timer_B Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-18
16.3 Timer_B Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-20
17 USART Peripheral Interface, UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1
17.1 USART Introduction: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17-2
17.2 USART Operation: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17-4
17.2.1 USART Initialization and Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17-4
17.2.2 Character Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17-4
17.2.3 Asynchronous Communication Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17-5
17.2.4 USART Receive Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17-9
17.2.5 USART Transmit Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-10
17.2.6 USART Baud Rate Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11
17.2.7 USART Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-17
17.3 USART Registers: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-21
18 USART Peripheral Interface, SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1
18.1 USART Introduction: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18-2
18.2 USART Operation: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18-4
18.2.1 USART Initialization and Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18-4
18.2.2 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18-5
18.2.3 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18-6
18.2.4 SPI Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18-7
18.2.5 Serial Clock Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18-9
18.2.6 SPI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-11
18.3 USART Registers: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-13
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Contents
19 Universal Serial Communication Interface, UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 19-1
19.1 USCI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19-2
19.2 USCI Introduction: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19-3
19.3 USCI Operation: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19-5
19.3.1 USCI Initialization and Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19-5
19.3.2 Character Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19-5
19.3.3 Asynchronous Communication Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19-6
19.3.4 Automatic Baud Rate Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-10
19.3.5 IrDA Encoding and Decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-12
19.3.6 Automatic Error Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-13
19.3.7 USCI Receive Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-14
19.3.8 Receive Data Glitch Suppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-14
19.3.9 USCI Transmit Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-15
19.3.10 UART Baud Rate Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-15
19.3.11 Setting a Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-18
19.3.12 Transmit Bit Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-19
19.3.13 Receive Bit Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-20
19.3.14 Typical Baud Rates and Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-21
19.3.15 Using the USCI Module in UART Mode with Low-Power Modes . . . . . . . 19-25
19.3.16 USCI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-25
19.4 USCI Registers: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-27
20 Universal Serial Communication Interface, SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-1
20.1 USCI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20-2
20.2 USCI Introduction: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20-3
20.3 USCI Operation: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20-5
20.3.1 USCI Initialization and Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20-6
20.3.2 Character Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20-6
20.3.3 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20-7
20.3.4 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20-9
20.3.5 SPI Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-10
20.3.6 Serial Clock Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-11
20.3.7 Using the SPI Mode with Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . 20-12
20.3.8 SPI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-12
20.4 USCI Registers: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-14
21 Universal Serial Communication Interface, I2C Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-1
21.1 USCI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21-2
21.2 USCI Introduction: I2C Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21-3
21.3 USCI Operation: I2C Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21-5
21.3.1 USCI Initialization and Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21-6
21.3.2 I2C Serial Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21-7
21.3.3 I2C Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21-8
21.3.4 I2C Module Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21-9
21.3.5 I2C Clock Generation and Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . 21-22
21.3.6 Using the USCI Module in I2C Mode With Low-Power Modes . . . . . . . . . 21-23
21.3.7 USCI Interrupts in I2C Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-24
21.4 USCI Registers: I2C Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-26
xiii
Contents
22 OA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-1
22.1 OA Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22-2
22.2 OA Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22-4
22.2.1 OA Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22-4
22.2.2 OA Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22-4
22.2.3 OA Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22-4
22.2.4 OA Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22-5
22.3 OA Modules in MSP430FG42x0 Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-11
22.3.1 OA Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-12
22.3.2 OA Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-12
22.3.3 OA Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-12
22.3.4 OA Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-12
22.3.5 Switch Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-14
22.3.6 Offset Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-15
22.4 OA Modules in MSP430FG47x Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-16
22.4.1 OA Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-18
22.4.2 OA Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-18
22.4.3 OA Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-18
22.4.4 OA Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-18
22.4.5 Switch Control of the FG47x devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-22
22.4.6 Offset Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-23
22.5 OA Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-24
22.6 OA Registers in MSP430FG42x0 Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-27
22.7 OA Registers in MSP430FG47x Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-31
23 Comparator_A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.1 Comparator_A Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.2 Comparator_A Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.2.1 Comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.2.2 Input Analog Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.2.3 Output Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.2.4 Voltage Reference Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.2.5 Comparator_A, Port Disable Register CAPD . . . . . . . . . . . . . . . . . . . . . . . .
23.2.6 Comparator_A Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.2.7 Comparator_A Used to Measure Resistive Elements . . . . . . . . . . . . . . . . .
23.3 Comparator_A Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23-1
23-2
23-4
23-4
23-4
23-5
23-5
23-6
23-6
23-7
23-9
24 Comparator_A+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-1
24.1 Comparator_A+ Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24-2
24.2 Comparator_A+ Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24-4
24.2.1 Comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24-4
24.2.2 Input Analog Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24-4
24.2.3 Input Short Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24-5
24.2.4 Output Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24-6
24.2.5 Voltage Reference Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24-6
24.2.6 Comparator_A+, Port Disable Register CAPD . . . . . . . . . . . . . . . . . . . . . . .
24-7
24.2.7 Comparator_A+ Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24-7
24.2.8 Comparator_A+ Used to Measure Resistive Elements . . . . . . . . . . . . . . . .
24-8
24.3 Comparator_A+ Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-10
xiv
Contents
25 LCD Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-1
25.1 LCD Controller Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-2
25.2 LCD Controller Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-4
25.2.1 LCD Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-4
25.2.2 Blinking the LCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-4
25.2.3 LCD Timing Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-4
25.2.4 LCD Voltage Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-5
25.2.5 LCD Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-5
25.2.6 Static Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-6
25.2.7 2-Mux Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25-9
25.2.8 3-Mux Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-12
25.2.9 4-Mux Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-15
25.3 LCD Controller Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-18
26 LCD_A Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-1
26.1 LCD_A Controller Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26-2
26.2 LCD_A Controller Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26-4
26.2.1 LCD Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26-4
26.2.2 Blinking the LCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26-4
26.2.3 LCD_A Voltage And Bias Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26-5
26.2.4 LCD Timing Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26-8
26.2.5 LCD Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26-8
26.2.6 Static Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26-9
26.2.7 2-Mux Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-12
26.2.8 3-Mux Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-15
26.2.9 4-Mux Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-18
26.3 LCD Controller Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-21
27 ADC10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27-1
27.1 ADC10 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27-2
27.2 ADC10 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27-4
27.2.1 10-Bit ADC Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27-4
27.2.2 ADC10 Inputs and Multiplexer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27-5
27.2.3 Voltage Reference Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27-6
27.2.4 Auto Power-Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27-6
27.2.5 Sample and Conversion Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27-7
27.2.6 Conversion Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27-9
27.2.7 ADC10 Data Transfer Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27-15
27.2.8 Using the Integrated Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . 27-21
27.2.9 ADC10 Grounding and Noise Considerations . . . . . . . . . . . . . . . . . . . . . . . 27-22
27.2.10 ADC10 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27-23
27.3 ADC10 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27-24
xv
Contents
28 ADC12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-1
28.1 ADC12 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28-2
28.2 ADC12 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28-4
28.2.1 12-Bit ADC Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28-4
28.2.2 ADC12 Inputs and Multiplexer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28-5
28.2.3 Voltage Reference Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28-6
28.2.4 Auto Power-Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28-6
28.2.5 Sample and Conversion Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28-7
28.2.6 Conversion Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-10
28.2.7 ADC12 Conversion Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-10
28.2.8 Using the Integrated Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . 28-16
28.2.9 ADC12 Grounding and Noise Considerations . . . . . . . . . . . . . . . . . . . . . . . 28-17
28.2.10 ADC12 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-18
28.3 ADC12 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-20
29 SD16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-1
29.1 SD16 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-2
29.2 SD16 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-4
29.2.1 ADC Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-4
29.2.2 Analog Input Range and PGA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-4
29.2.3 Voltage Reference Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-4
29.2.4 Auto Power-Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-4
29.2.5 Analog Input Pair Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-5
29.2.6 Analog Input Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-6
29.2.7 Digital Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29-7
29.2.8 Conversion Memory Registers: SD16MEMx . . . . . . . . . . . . . . . . . . . . . . . . 29-10
29.2.9 Conversion Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-11
29.2.10 Conversion Operation Using Preload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-14
29.2.11 Using the Integrated Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . 29-16
29.2.12 Interrupt Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-17
29.3 SD16 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-19
30 SD16_A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-1
30.1 SD16_A Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-2
30.2 SD16_A Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-5
30.2.1 ADC Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-5
30.2.2 Analog Input Range and PGA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-5
30.2.3 Voltage Reference Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-5
30.2.4 Auto Power-Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-5
30.2.5 Analog Input Pair Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-6
30.2.6 Analog Input Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-7
30.2.7 Digital Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30-8
30.2.8 Conversion Memory Register: SD16MEMx . . . . . . . . . . . . . . . . . . . . . . . . . 30-12
30.2.9 Conversion Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-14
30.2.10 Conversion Operation Using Preload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-17
30.2.11 Using the Integrated Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . 30-19
30.2.12 Interrupt Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-20
30.3 SD16_A Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-22
xvi
Contents
31 DAC12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31-1
31.1 DAC12 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31-2
31.2 DAC12 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31-6
31.2.1 DAC12 Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31-6
31.2.2 DAC12 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31-7
31.2.3 Updating the DAC12 Voltage Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31-8
31.2.4 DAC12_xDAT Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31-9
31.2.5 DAC12 Output Amplifier Offset Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . 31-10
31.2.6 Grouping Multiple DAC12 Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31-11
31.2.7 DAC12 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31-12
31.3 DAC12 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31-13
32 Scan IF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-1
32.1 Scan IF Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32-2
32.2 Scan IF Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32-4
32.2.1 Scan IF Analog Front End . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32-4
32.2.2 Scan IF Timing State Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-14
32.2.3 Scan IF Processing State Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-20
32.2.4 Scan IF Debug Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-26
32.2.5 Scan IF Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-27
32.2.6 Using the Scan IF with LC Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-28
32.2.7 Using the Scan IF With Resistive Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . 32-32
32.2.8 Quadrature Decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-33
32.3 Scan IF Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-35
33 Embedded Emulation Module (EEM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33.1 EEM Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33.2 EEM Building Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33.2.1 Triggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33.2.2 Trigger Sequencer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33.2.3 State Storage (Internal Trace Buffer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33.2.4 Clock Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33.3 EEM Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33-1
33-2
33-4
33-4
33-5
33-5
33-5
33-6
xvii
xviii
Chapter 1
Introduction
This chapter describes the architecture of the MSP430.
Topic
Page
1.1
Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2
Flexible Clock System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.3
Embedded Emulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.4
Address Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Introduction
1-1
Architecture
1.1 Architecture
The MSP430 incorporates a 16-bit RISC CPU, peripherals, and a flexible clock
system that interconnect using a von Neumann common memory address bus
(MAB) and memory data bus (MDB). Partnering a modern CPU with modular
memory-mapped analog and digital peripherals, the MSP430 offers solutions
for demanding mixed-signal applications.
Key features of the MSP430x4xx family include:
- Ultralow-power architecture extends battery life
J
0.1-μA RAM retention
J
0.8-μA real-time clock mode
J
250-μA / MIPS active
- High-performance analog ideal for precision measurement
J
12-bit or 10-bit ADC — 200 ksps, temperature sensor, VRef
J
12-bit dual DAC
J
Comparator-gated timers for measuring resistive elements
J
Supply voltage supervisor
- 16-bit RISC CPU enables new applications at a fraction of the code size.
J
Large register file eliminates working file bottleneck
J
Compact core design reduces power consumption and cost
J
Optimized for modern high-level programming
J
Only 27 core instructions and seven addressing modes
J
Extensive vectored-interrupt capability
- In-system programmable Flash permits flexible code changes, field
upgrades, and data logging
1.2 Flexible Clock System
The clock system is designed specifically for battery-powered applications. A
low-frequency auxiliary clock (ACLK) is driven directly from a common 32-kHz
watch crystal. The ACLK can be used for a background real-time clock self
wake-up function. An integrated high-speed digitally controlled oscillator
(DCO) can source the master clock (MCLK) used by the CPU and high-speed
peripherals. By design, the DCO is active and stable in less than 6 μs.
MSP430-based solutions effectively use the high-performance 16-bit RISC
CPU in very short bursts.
- Low-frequency auxiliary clock = Ultralow-power standby mode
- High-speed master clock = High performance signal processing
1-2
Introduction
Embedded Emulation
Figure 1−1. MSP430 Architecture
ACLK
Clock
System
SMCLK
Flash/
ROM
RAM
Peripheral
Peripheral
Peripheral
RISC CPU
16-Bit
JTAG/Debug
MCLK
MAB 16-Bit
MDB 16-Bit
Bus
Conv.
MDB 8-Bit
JTAG
ACLK
SMCLK
Watchdog
Peripheral
Peripheral
Peripheral
Peripheral
1.3 Embedded Emulation
Dedicated embedded emulation logic resides on the device itself and is
accessed via JTAG using no additional system resources.
The benefits of embedded emulation include:
- Unobtrusive
development and debug with full-speed execution,
breakpoints, and single steps in an application are supported.
- Development is in-system and subject to the same characteristics as the
final application.
- Mixed-signal integrity is preserved and not subject to cabling interference.
Introduction
1-3
Address Space
1.4 Address Space
The MSP430 von Neumann architecture has one address space shared with
special function registers (SFRs), peripherals, RAM, and Flash/ROM memory
as shown in Figure 1−2. See the device-specific data sheets for specific
memory maps. Code access are always performed on even addresses. Data
can be accessed as bytes or words.
The addressable memory space is 128 KB with future expansion planned.
Figure 1−2. Memory Map
Access
Flash/ROM
Word/Byte
Interrupt Vector Table
Word/Byte
Flash/ROM
Word/Byte
RAM
Word/Byte
10000h
0FFFFh
0FFE0h
0FFDFh
0200h
01FFh
16-Bit Peripheral Modules
Word
8-Bit Peripheral Modules
Byte
Special Function Registers
Byte
0100h
0FFh
010h
0Fh
0h
1.4.1
Flash/ROM
The start address of Flash/ROM depends on the amount of Flash/ROM
present and varies by device. The end address for Flash/ROM is 0FFFFh for
devices with less than 60kB of Flash/ROM; otherwise, it is device dependent.
Flash can be used for both code and data. Word or byte tables can be stored
and used in Flash/ROM without the need to copy the tables to RAM before
using them.
The interrupt vector table is mapped into the upper 16 words of Flash/ROM
address space, with the highest priority interrupt vector at the highest
Flash/ROM word address (0FFFEh).
1-4
Introduction
Address Space
1.4.2
RAM
RAM starts at 0200h. The end address of RAM depends on the amount of RAM
present and varies by device. RAM can be used for both code and data.
1.4.3
Peripheral Modules
Peripheral modules are mapped into the address space. The address space
from 0100 to 01FFh is reserved for 16-bit peripheral modules. These modules
should be accessed with word instructions. If byte instructions are used, only
even addresses are permissible, and the high byte of the result is always 0.
The address space from 010h to 0FFh is reserved for 8-bit peripheral modules.
These modules should be accessed with byte instructions. Read access of
byte modules using word instructions results in unpredictable data in the high
byte. If word data is written to a byte module only the low byte is written into
the peripheral register, ignoring the high byte.
1.4.4
Special Function Registers (SFRs)
Some peripheral functions are configured in the SFRs. The SFRs are located
in the lower 16 bytes of the address space and are organized by byte. SFRs
must be accessed using byte instructions only. See the device-specific data
sheets for applicable SFR bits.
1.4.5
Memory Organization
Bytes are located at even or odd addresses. Words are only located at even
addresses as shown in Figure 1−3. When using word instructions, only even
addresses may be used. The low byte of a word is always an even address.
The high byte is at the next odd address. For example, if a data word is located
at address xxx4h, then the low byte of that data word is located at address
xxx4h, and the high byte of that word is located at address xxx5h.
Introduction
1-5
Address Space
Figure 1−3. Bits, Bytes, and Words in a Byte-Organized Memory
xxxAh
15
14
. . Bits . .
9
8
xxx9h
7
6
. . Bits . .
1
0
xxx8h
Byte
xxx7h
Byte
xxx6h
Word (High Byte)
xxx5h
Word (Low Byte)
xxx4h
xxx3h
1-6
Introduction
Chapter 2
System Resets, Interrupts,
and Operating Modes
This chapter describes the MSP430x4xx system resets, interrupts, and
operating modes.
Topic
Page
2.1
System Reset and Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.2
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.3
Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
2.4
Principles for Low-Power Applications . . . . . . . . . . . . . . . . . . . . . . . . 2-16
2.5
Connection of Unused Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16
System Resets, Interrupts, and Operating Modes
2-1
System Reset and Initialization
2.1 System Reset and Initialization
The system reset circuitry shown in Figure 2−1 sources both a power-on reset
(POR) and a power-up clear (PUC) signal. Different events trigger these reset
signals and different initial conditions exist depending on which signal was
generated.
Figure 2−1. Power-On Reset and Power-Up Clear Schematic
VCC
Brownout
Reset
0V
S
R
POR
Latch
POR
~ 50us
Delay
SVS_POR
RST/NMI
WDTNMI†
WDTTMSEL†
WDTQn†
WDTIFG†
EQU†
KEYV
(from flash module)
S
Resetwd1
Resetwd2
S
PUC
S Latch
S
PUC
R
MCLK
† From watchdog timer peripheral module
A POR is a device reset. A POR is only generated by the following three
events:
- Powering up the device
- A low signal on the RST/NMI pin when configured in the reset mode
- An SVS low condition when PORON = 1.
A PUC is always generated when a POR is generated, but a POR is not
generated by a PUC. The following events trigger a PUC:
- A POR signal
- Watchdog timer expiration when in watchdog mode only
- Watchdog timer security key violation
- A Flash memory security key violation
2-2
System Resets, Interrupts, and Operating Modes
System Reset and Initialization
2.1.1
Brownout Reset (BOR)
All MSP430x4xx devices have a brownout reset circuit. The brownout reset
circuit detects low supply voltages such as when a supply voltage is applied
to or removed from the VCC terminal. The brownout reset circuit resets the
device by triggering a POR signal when power is applied or removed. The
operating levels are shown in Figure 2−2.
The POR signal becomes active when VCC crosses the VCC(start) level. It
remains active until VCC crosses the V(B_IT+) threshold and the delay t(BOR)
elapses. The delay t(BOR) is adaptive being longer for a slow ramping VCC. The
hysteresis Vhys(B_ IT−) ensures that the supply voltage must drop below
V(B_IT−) to generate another POR signal from the brownout reset circuitry.
Figure 2−2. Brownout Timing
VCC
V hys(B_IT−)
V(B_IT+)
V(B_IT−)
VCC(start)
Set Signal for
POR circuitry
t
(BOR)
As the V(B_IT−) level is significantly above the V(MIN) level of the POR circuit,
the BOR provides a reset for power failures where VCC does not fall below
V(MIN). See the device-specific data sheet for parameters.
System Resets, Interrupts, and Operating Modes
2-3
System Reset and Initialization
2.1.2
Device Initial Conditions After System Reset
After a POR, the initial MSP430 conditions are:
- The RST/NMI pin is configured in the reset mode.
- I/O pins are switched to input mode as described in the Digital I/O chapter.
- Other peripheral modules and registers are initialized as described in their
respective chapters in this manual.
- Status register (SR) is reset.
- The watchdog timer powers up active in watchdog mode.
- Program counter (PC) is loaded with address contained at reset vector
location (0FFFEh). CPU execution begins at that address.
Software Initialization
After a system reset, user software must initialize the MSP430 for the
application requirements. The following must occur:
- Initialize the SP, typically to the top of RAM.
- Initialize the watchdog to the requirements of the application.
- Configure peripheral modules to the requirements of the application.
Additionally, the watchdog timer, oscillator fault, and flash memory flags can
be evaluated to determine the source of the reset.
2-4
System Resets, Interrupts, and Operating Modes
System Reset and Initialization
2.2 Interrupts
The interrupt priorities are fixed and defined by the arrangement of the
modules in the connection chain as shown in Figure 2−3. The nearer a module
is to the CPU/NMIRS, the higher the priority. Interrupt priorities determine what
interrupt is taken when more than one interrupt is pending simultaneously.
There are three types of interrupts:
- System reset
- (Non)-maskable NMI
- Maskable
Figure 2−3. Interrupt Priority
Priority
High
Low
GMIRS
GIE
CPU
NMIRS
PUC
Module
1
Module
2
1 2
WDT
Timer
1 2
Module
m
1
2
Module
n
1 2
1
Bus
Grant
PUC
Circuit
OSCfault
Flash ACCV
Reset/NMI
WDT Security Key
Flash Security Key
MAB − 5LSBs
System Resets, Interrupts, and Operating Modes
2-5
System Reset and Initialization
2.2.1
(Non)-Maskable Interrupts (NMI)
(Non)-maskable NMI interrupts are not masked by the general interrupt enable
bit (GIE), but are enabled by individual interrupt enable bits (ACCVIE, NMIIE,
OFIE). When a NMI interrupt is accepted, all NMI interrupt enable bits are
automatically reset. Program execution begins at the address stored in the
(non)-maskable interrupt vector, 0FFFCh. User software must set the required
NMI interrupt enable bits for the interrupt to be re-enabled. The block diagram
for NMI sources is shown in Figure 2−4.
A (non)-maskable NMI interrupt can be generated by three sources:
- An edge on the RST/NMI pin when configured in NMI mode
- An oscillator fault occurs
- An access violation to the flash memory
Reset/NMI Pin
At power-up, the RST/NMI pin is configured in the reset mode. The function
of the RST/NMI pins is selected in the watchdog control register WDTCTL. If
the RST/NMI pin is set to the reset function, the CPU is held in the reset state
as long as the RST/NMI pin is held low. After the input changes to a high state,
the CPU starts program execution at the word address stored in the reset
vector, 0FFFEh.
If the RST/NMI pin is configured by user software to the NMI function, a signal
edge selected by the WDTNMIES bit generates an NMI interrupt if the NMIIE
bit is set. The RST/NMI flag NMIIFG is also set.
Note: Holding RST/NMI Low
When configured in the NMI mode, a signal generating an NMI event should
not hold the RST/NMI pin low. If a PUC occurs from a different source while
the NMI signal is low, the device will be held in the reset state because a PUC
changes the RST/NMI pin to the reset function.
Note: Modifying WDTNMIES
When NMI mode is selected and the WDTNMIES bit is changed, an NMI can
be generated, depending on the actual level at the RST/NMI pin. When the
NMI edge select bit is changed before selecting the NMI mode, no NMI is
generated.
2-6
System Resets, Interrupts, and Operating Modes
System Reset and Initialization
Figure 2−4. Block Diagram of (Non)-Maskable Interrupt Sources
ACCV
S
ACCVIFG
FCTL3.2
ACCVIE
IE1.5
Clear
Flash Module
PUC
RST/NMI
POR
PUC
KEYV SVS_POR BOR
PUC
System Reset
Generator
POR
S
NMIIFG
NMIRS
IFG1.4
WDTTMSEL
WDTNMIES
WDTNMI
Clear
WDTQn
EQU
PUC
POR
PUC
NMIIE
S
IE1.4
Clear
WDTIFG
IRQ
IFG1.0
Clear
PUC
WDT
Counter
OSCFault
POR
S
OFIFG
IFG1.1
IRQA
OFIE
WDTTMSEL
WDTIE
IE1.1
Clear
IE1.0
NMI_IRQA
Clear
PUC
IRQA: Interrupt Request Accepted
Watchdog Timer Module
PUC
System Resets, Interrupts, and Operating Modes
2-7
System Reset and Initialization
Oscillator Fault
The oscillator fault signal warns of a possible error condition with the crystal
oscillator. The oscillator fault can be enabled to generate an NMI interrupt by
setting the OFIE bit. The OFIFG flag can then be tested by NMI the interrupt
service routine to determine if the NMI was caused by an oscillator fault.
A PUC signal can trigger an oscillator fault, because the PUC switches the
LFXT1 to LF mode, therefore switching off the HF mode. The PUC signal also
switches off the XT2 oscillator.
Flash Access Violation
The flash ACCVIFG flag is set when a flash access violation occurs. The flash
access violation can be enabled to generate an NMI interrupt by setting the
ACCVIE bit. The ACCVIFG flag can then be tested by NMI the interrupt service
routine to determine if the NMI was caused by a flash access violation.
2-8
System Resets, Interrupts, and Operating Modes
System Reset and Initialization
Example of an NMI Interrupt Handler
The NMI interrupt is a multiple-source interrupt. An NMI interrupt automatically
resets the NMIIE, OFIE, and ACCVIE interrupt-enable bits. The user NMI
service routine resets the interrupt flags and re-enables the interrupt-enable
bits according to the application needs as shown in Figure 2−5.
Figure 2−5. NMI Interrupt Handler
Start of NMI Interrupt Handler
Reset by HW:
OFIE, NMIIE, ACCVIE
no
no
OFIFG=1
no
ACCVIFG=1
NMIIFG=1
yes
yes
yes
Reset OFIFG
Reset ACCVIFG
Reset NMIIFG
User’s Software,
Oscillator Fault
Handler
User’s Software,
Flash Access
Violation Handler
User’s Software,
External NMI
Handler
Optional
RETI
End of NMI Interrupt
Handler
Note: Enabling NMI Interrupts with ACCVIE, NMIIE, and OFIE
To prevent nested NMI interrupts, the ACCVIE, NMIIE, and OFIE enable bits
should not be set inside of an NMI interrupt service routine.
2.2.2
Maskable Interrupts
Maskable interrupts are caused by peripherals with interrupt capability
including the watchdog timer overflow in interval-timer mode. Each maskable
interrupt source can be disabled individually by an interrupt enable bit, or all
maskable interrupts can be disabled by the general interrupt enable (GIE) bit
in the status register (SR).
Each individual peripheral interrupt is discussed in the associated peripheral
module chapter in this manual.
System Resets, Interrupts, and Operating Modes
2-9
System Reset and Initialization
2.2.3
Interrupt Processing
When an interrupt is requested from a peripheral and the peripheral interrupt
enable bit and GIE bit are set, the interrupt service routine is requested. Only
the individual enable bit must be set for (non)-maskable interrupts to be
requested.
Interrupt Acceptance
The interrupt latency is six cycles, starting with the acceptance of an interrupt
request and lasting until the start of execution of the first instruction of the
interrupt-service routine, as shown in Figure 2−6. The interrupt logic executes
the following:
1) Any currently executing instruction is completed.
2) The PC, which points to the next instruction, is pushed onto the stack.
3) The SR is pushed onto the stack.
4) The interrupt with the highest priority is selected if multiple interrupts
occurred during the last instruction and are pending for service.
5) The interrupt request flag resets automatically on single-source flags.
Multiple source flags remain set for servicing by software.
6) The SR is cleared with the exception of SCG0, which is left unchanged.
This terminates any low-power mode. Because the GIE bit is cleared,
further interrupts are disabled.
7) The content of the interrupt vector is loaded into the PC: the program
continues with the interrupt service routine at that address.
Figure 2−6. Interrupt Processing
Before
Interrupt
After
Interrupt
Item1
SP
Item2
Item1
TOS
Item2
PC
SP
2-10
System Resets, Interrupts, and Operating Modes
SR
TOS
System Reset and Initialization
Return From Interrupt
The interrupt handling routine terminates with the instruction:
RETI (return from an interrupt service routine)
The return from the interrupt takes 5 cycles to execute the following actions
and is illustrated in Figure 2−7.
1) The SR with all previous settings pops from the stack. All previous settings
of GIE, CPUOFF, etc. are now in effect, regardless of the settings used
during the interrupt service routine.
2) The PC pops from the stack and begins execution at the point where it was
interrupted.
Figure 2−7. Return From Interrupt
Before
After
Return From Interrupt
Item1
Item1
SP
Item2
PC
SP
SR
Item2
TOS
PC
TOS
SR
Interrupt nesting is enabled if the GIE bit is set inside an interrupt service
routine. When interrupt nesting is enabled, any interrupt occurring during an
interrupt service routine will interrupt the routine, regardless of the interrupt
priorities.
System Resets, Interrupts, and Operating Modes
2-11
System Reset and Initialization
2.2.4
Interrupt Vectors
The interrupt vectors and the power-up starting address are located in the
address range 0FFFFh to 0FFE0h as described in Table 2−1. A vector is
programmed by the user with the 16-bit address of the corresponding interrupt
service routine. Some devices may contain more interrupt vectors. See the
device-specific data sheet for the complete interrupt vector list.
Table 2−1. Interrupt Sources,Flags, and Vectors
INTERRUPT SOURCE
INTERRUPT
FLAG
SYSTEM
INTERRUPT
WORD
ADDRESS
PRIORITY
Power-up, external
reset, watchdog,
flash password
WDTIFG
KEYV
Reset
0FFFEh
15, highest
NMI, oscillator fault,
flash memory access
violation
NMIIFG
OFIFG
ACCVIFG
(non)-maskable
(non)-maskable
(non)-maskable
0FFFCh
14
Device-specific
0FFFAh
13
Device-specific
0FFF8h
12
Device-specific
0FFF6h
11
0FFF4h
10
Device-specific
0FFF2h
9
Device-specific
0FFF0h
8
Device-specific
0FFEEh
7
Device-specific
0FFECh
6
Device-specific
0FFEAh
5
Device-specific
0FFE8h
4
Device-specific
0FFE6h
3
Device-specific
0FFE4h
2
Device-specific
0FFE2h
1
Device-specific
0FFE0h
0, lowest
Watchdog timer
2.2.5
WDTIFG
maskable
Special Function Registers (SFRs)
Some module enable bits, interrupt enable bits, and interrupt flags are located
in the SFRs. The SFRs are located in the lower address range and are
implemented in byte format. SFRs must be accessed using byte instructions.
See the device-specific data sheet for the SFR configuration.
2-12
System Resets, Interrupts, and Operating Modes
Operating Modes
2.3 Operating Modes
The MSP430 family is designed for ultralow-power applications and uses
different operating modes shown in Figure 2−9.
The operating modes take into account three different needs:
- Ultralow-power
- Speed and data throughput
- Minimization of individual peripheral current consumption
The MSP430 typical current consumption is shown in Figure 2−8.
ICC/ μA @ 1 MHz
Figure 2−8. Typical Current Consumption of 41x Devices vs Operating Modes
315
300
270
225
180
200
VCC = 3 V
VCC = 2.2 V
135
90
55
45
32
0
AM
LPM0
17 11
0.9 0.7
0.1 0.1
LPM2
LPM3
LPM4
Operating Modes
The low-power modes 0 to 4 are configured with the CPUOFF, OSCOFF,
SCG0, and SCG1 bits in the status register. The advantage of including the
CPUOFF, OSCOFF, SCG0, and SCG1 mode-control bits in the status register
is that the present operating mode is saved onto the stack during an interrupt
service routine. Program flow returns to the previous operating mode if the
saved SR value is not altered during the interrupt service routine. Program flow
can be returned to a different operating mode by manipulating the saved SR
value on the stack inside of the interrupt service routine. The mode-control bits
and the stack can be accessed with any instruction.
When setting any of the mode-control bits, the selected operating mode takes
effect immediately. Peripherals operating with any disabled clock are disabled
until the clock becomes active. The peripherals may also be disabled with their
individual control register settings. All I/O port pins and RAM/registers are
unchanged. Wake up is possible through all enabled interrupts.
System Resets, Interrupts, and Operating Modes
2-13
Operating Modes
Figure 2−9. MSP430x4xx Operating Modes For FLL+ Clock System
RST/NMI
Reset Active
VCC On
POR
WDT Active,
Time Expired, Overflow
WDTIFG = 1
WDTIFG = 0
PUC
RST/NMI is Reset Pin
WDT is Active
WDTIFG = 1
RST/NMI
NMI Active
WDT Active,
Security Key Violation
Active Mode
CPU Is Active
Peripheral Modules Are Active
CPUOFF = 1
SCG0 = 0
SCG1 = 0
CPUOFF = 1
OSCOFF = 1
SCG0 = 1
SCG1 = 1
LPM0
CPU Off, FLL+ On,
41x/42x MCLK On, 43x/44x
MCLK off, ACLK On
LPM4
CPU Off, FLL+ Off,
MCLK Off, ACLK Off
CPUOFF = 1
SCG0 = 1
SCG1 = 0
LPM1
CPU Off, FLL+ Off,
41x/42x MCLK On, 43x/44x
MCLK off ACLK On
SCG1
2-14
SCG0 OSCOFF
CPUOFF
CPUOFF = 1
SCG0 = 0
SCG1 = 1
CPUOFF = 1
SCG0 = 1
SCG1 = 1
LPM2
CPU Off, FLL+ Off,
MCLK Off, ACLK On
Mode
DC Generator Off
LPM3
CPU Off, FLL+ Off,
MCLK Off, ACLK On
DC Generator Off
CPU and Clocks Status
0
0
0
0
Active
CPU is active, all enabled clocks are active
0
0
0
1
LPM0
CPU, MCLK are disabled (41x/42x peripheral MCLK
remains on)
SMCLK , ACLK are active
0
1
0
1
LPM1
CPU, MCLK, DCO oscillator are disabled (41x/42x
peripheral MCLK remains on)
DC generator is disabled if the DCO is not used for
MCLK or SMCLK in active mode
SMCLK , ACLK are active
1
0
0
1
LPM2
CPU, MCLK, SMCLK, DCO oscillator are disabled
DC generator remains enabled
ACLK is active
1
1
0
1
LPM3
CPU, MCLK, SMCLK, DCO oscillator are disabled
DC generator disabled
ACLK is active
1
1
1
1
LPM4
CPU and all clocks disabled
System Resets, Interrupts, and Operating Modes
Operating Modes
2.3.1
Entering and Exiting Low-Power Modes
An enabled interrupt event wakes the MSP430 from any of the low-power
operating modes. The program flow is:
- Enter interrupt service routine:
J
The PC and SR are stored on the stack
J
The CPUOFF, SCG1, and OSCOFF bits are automatically reset
- Options for returning from the interrupt service routine:
J
The original SR is popped from the stack, restoring the previous
operating mode.
J
The SR bits stored on the stack can be modified within the interrupt
service routine returning to a different operating mode when the RETI
instruction is executed.
; Enter LPM0 Example
BIS
#GIE+CPUOFF,SR
; Enter LPM0
; ...
; Program stops here
;
; Exit LPM0 Interrupt Service Routine
BIC
#CPUOFF,0(SP)
; Exit LPM0 on RETI
RETI
; Enter LPM3 Example
BIS
#GIE+CPUOFF+SCG1+SCG0,SR ; Enter LPM3
; ...
; Program stops here
;
; Exit LPM3 Interrupt Service Routine
BIC
#CPUOFF+SCG1+SCG0,0(SP) ; Exit LPM3 on RETI
RETI
Extended Time in Low-Power Modes
The negative temperature coefficient of the DCO should be considered when
the DCO is disabled for extended low-power mode periods. If the temperature
changes significantly, the DCO frequency at wake-up may be significantly
different from when the low-power mode was entered and may be out of the
specified operating range. To avoid this, the DCO can be set to it lowest value
before entering the low-power mode for extended periods of time where
temperature can change.
; Enter LPM4 Example with lowest DCO Setting
BIC.B
#FN_8+FN_4+FN_3+FN_2,&SCFI0 ; Lowest Range
MOV.B
#010h,&SCFI1
; Select Tap 2
BIS
#GIE+CPUOFF+OSCOFF+SCG1+SCG0,SR ; Enter LPM4
; ...
; Program stops
; Interrupt Service Routine
BIC
#CPUOFF+OSCOFF+SCG1+SCG0,0(SP); Exit LPM4 on RETI
RETI
System Resets, Interrupts, and Operating Modes
2-15
Principles for Low-Power Applications
2.4 Principles for Low-Power Applications
Often, the most important factor for reducing power consumption is using the
MSP430’s clock system to maximize the time in LPM3. LPM3 power
consumption is less than 2 μA typical with both a real-time clock function and
all interrupts active. A 32-kHz watch crystal is used for the ACLK, and the CPU
is clocked from the DCO (normally off) which has a 6-μs wake-up time.
- Use interrupts to wake the processor and control program flow.
- Peripherals should be switched on only when needed.
- Use low-power integrated peripheral modules in place of software driven
functions. For example Timer_A and Timer_B can automatically generate
PWM and capture external timing, with no CPU resources.
- Calculated branching and fast table look-ups should be used in place of
flag polling and long software calculations.
- Avoid frequent subroutine and function calls due to overhead.
- For longer software routines, single-cycle CPU registers should be used.
2.5 Connection of Unused Pins
The correct termination of all unused pins is listed in Table 2−2.
Table 2−2. Connection of Unused Pins
†
2-16
Pin
Potential
AVCC
DVCC
AVSS
DVSS
VREF+
Open
Comment
VeREF+
DVSS
VREF−/VeREF−
DVSS
XIN
DVCC
XOUT
Open
XT2IN
DVSS
43x, 44x. and 46x devices
XT2OUT
Open
43x, 44x, and 46x devices
Px.0 to Px.7
Open
Switched to port function, output direction
RST/NMI
DVCC or VCC
47-kΩ pullup with 10-nF (2.2 nF†) pulldown
R03
DVSS
COM0
Open
TDO/TDI/TMS/
TCK
Open
Ax (dedicated)
Open
Sxx
Open
42x devices
MSP430F41x2 only: The pulldown capacitor should not exceed 2.2 nF when using Spy-Bi-Wire
interface in Spy-Bi-Wire mode or in 4-wire JTAG mode with TI tools like FET interfaces or GANG
programmers.
System Resets, Interrupts, and Operating Modes
Chapter 3
RISC 16-Bit CPU
This chapter describes the MSP430 CPU, addressing modes, and instruction
set.
Topic
Page
3.1
CPU Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.2
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.3
Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
3.4
Instruction Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
RISC 16-Bit CPU
3-1
CPU Introduction
3.1 CPU Introduction
The CPU incorporates features specifically designed for modern
programming techniques such as calculated branching, table processing and
the use of high-level languages such as C. The CPU can address the complete
address range without paging.
The CPU features include:
- RISC architecture with 27 instructions and 7 addressing modes
- Orthogonal architecture with every instruction usable with every
addressing mode
- Full register access including program counter, status registers, and stack
pointer
- Single-cycle register operations
- Large 16-bit register file reduces fetches to memory
- 16-bit address bus allows direct access and branching throughout entire
memory range
- 16-bit data bus allows direct manipulation of word-wide arguments
- Constant generator provides six most used immediate values and
reduces code size
- Direct memory-to-memory transfers without intermediate register holding
- Word and byte addressing and instruction formats
The block diagram of the CPU is shown in Figure 3−1.
3-2
RISC 16-Bit CPU
CPU Introduction
Figure 3−1. CPU Block Diagram
MDB − Memory Data Bus
Memory Address Bus − MAB
15
0
R0/PC Program Counter
0
R1/SP Stack Pointer
0
R2/SR/CG1 Status
R3/CG2 Constant Generator
R4
General Purpose
R5
General Purpose
R6
General Purpose
R7
General Purpose
R8
General Purpose
R9
General Purpose
R10
General Purpose
R11
General Purpose
R12
General Purpose
R13
General Purpose
R14
General Purpose
R15
General Purpose
16
16
Zero, Z
Carry, C
Overflow, V
Negative, N
dst
src
16−bit ALU
MCLK
RISC 16-Bit CPU
3-3
CPU Registers
3.2 CPU Registers
The CPU incorporates sixteen 16-bit registers. R0, R1, R2 and R3 have
dedicated functions. R4 to R15 are working registers for general use.
3.2.1
Program Counter (PC)
The 16-bit program counter (PC/R0) points to the next instruction to be
executed. Each instruction uses an even number of bytes (two, four, or six),
and the PC is incremented accordingly. Instruction accesses in the 64-KB
address space are performed on word boundaries, and the PC is aligned to
even addresses. Figure 3−2 shows the program counter.
Figure 3−2. Program Counter
15
1
Program Counter Bits 15 to 1
0
0
The PC can be addressed with all instructions and addressing modes. A few
examples:
MOV
MOV
MOV
3-4
RISC 16-Bit CPU
#LABEL,PC ; Branch to address LABEL
LABEL,PC ; Branch to address contained in LABEL
@R14,PC ; Branch indirect to address in R14
CPU Registers
3.2.2
Stack Pointer (SP)
The stack pointer (SP/R1) is used by the CPU to store the return addresses
of subroutine calls and interrupts. It uses a predecrement, postincrement
scheme. In addition, the SP can be used by software with all instructions and
addressing modes. Figure 3−3 shows the SP. The SP is initialized into RAM
by the user, and is aligned to even addresses.
Figure 3−4 shows stack usage.
Figure 3−3. Stack Pointer
15
1
0
Stack Pointer Bits 15 to 1
MOV
MOV
PUSH
POP
2(SP),R6
R7,0(SP)
#0123h
R8
;
;
;
;
0
Item I2 −> R6
Overwrite TOS with R7
Put 0123h onto TOS
R8 = 0123h
Figure 3−4. Stack Usage
Address
PUSH #0123h
POP R8
0xxxh
I1
I1
I1
0xxxh − 2
I2
I2
I2
0xxxh − 4
I3
I3
I3
SP
0xxxh − 6
0123h
SP
SP
0123h
0xxxh − 8
The special cases of using the SP as an argument to the PUSH and POP
instructions are described and shown in Figure 3−5.
Figure 3−5. PUSH SP - POP SP Sequence
PUSH SP
POP SP
SPold
SP1
SP1
The stack pointer is changed after
a PUSH SP instruction.
SP2
SP1
The stack pointer is not changed after a POP SP
instruction. The POP SP instruction places SP1 into the
stack pointer SP (SP2=SP1)
RISC 16-Bit CPU
3-5
CPU Registers
3.2.3
Status Register (SR)
The status register (SR/R2), used as a source or destination register, can be
used in the register mode only addressed with word instructions. The
remaining combinations of addressing modes are used to support the
constant generator. Figure 3−6 shows the SR bits.
Figure 3−6. Status Register Bits
15
9
Reserved
8
V
7
SCG1
0
OSC CPU
SCG0
GIE
OFF OFF
N
Z C
rw-0
Table 3−1 describes the status register bits.
Table 3−1. Description of Status Register Bits
3-6
Bit
Description
V
Overflow bit. This bit is set when the result of an arithmetic operation
overflows the signed-variable range.
ADD(.B),ADDC(.B)
Set when:
Positive + Positive = Negative
Negative + Negative = Positive,
otherwise reset
SUB(.B),SUBC(.B),CMP(.B)
Set when:
Positive − Negative = Negative
Negative − Positive = Positive,
otherwise reset
SCG1
System clock generator 1. This bit, when set, turns off the DCO dc
generator, if DCOCLK is not used for MCLK or SMCLK.
SCG0
System clock generator 0. This bit, when set, turns off the FLL+ loop
control
OSCOFF
Oscillator Off. This bit, when set, turns off the LFXT1 crystal oscillator,
when LFXT1CLK is not use for MCLK or SMCLK
CPUOFF
CPU off. This bit, when set, turns off the CPU.
GIE
General interrupt enable. This bit, when set, enables maskable
interrupts. When reset, all maskable interrupts are disabled.
N
Negative bit. This bit is set when the result of a byte or word operation
is negative and cleared when the result is not negative.
Word operation:
N is set to the value of bit 15 of the
result
Byte operation:
N is set to the value of bit 7 of the
result
Z
Zero bit. This bit is set when the result of a byte or word operation is 0
and cleared when the result is not 0.
C
Carry bit. This bit is set when the result of a byte or word operation
produced a carry and cleared when no carry occurred.
RISC 16-Bit CPU
CPU Registers
3.2.4
Constant Generator Registers CG1 and CG2
Six commonly-used constants are generated with the constant generator
registers R2 and R3, without requiring an additional 16-bit word of program
code. The constants are selected with the source-register addressing modes
(As), as described in Table 3−2.
Table 3−2. Values of Constant Generators CG1, CG2
Register
As
Constant
Remarks
R2
00
−−−−−
Register mode
R2
01
(0)
Absolute address mode
R2
10
00004h
+4, bit processing
R2
11
00008h
+8, bit processing
R3
00
00000h
0, word processing
R3
01
00001h
+1
R3
10
00002h
+2, bit processing
R3
11
0FFFFh
−1, word processing
The constant generator advantages are:
- No special instructions required
- No additional code word for the six constants
- No code memory access required to retrieve the constant
The assembler uses the constant generator automatically if one of the six
constants is used as an immediate source operand. Registers R2 and R3,
used in the constant mode, cannot be addressed explicitly; they act as
source-only registers.
Constant Generator − Expanded Instruction Set
The RISC instruction set of the MSP430 has only 27 instructions. However, the
constant generator allows the MSP430 assembler to support 24 additional,
emulated instructions. For example, the single-operand instruction:
CLR
dst
is emulated by the double-operand instruction with the same length:
MOV
R3,dst
where the #0 is replaced by the assembler, and R3 is used with As = 00.
INC
dst
is replaced by:
ADD
0(R3),dst
RISC 16-Bit CPU
3-7
CPU Registers
3.2.5
General-Purpose Registers R4 to R15
Twelve registers, R4 to R15, are general-purpose registers. All of these
registers can be used as data registers, address pointers, or index values, and
they can be accessed with byte or word instructions as shown in Figure 3−7.
Figure 3−7. Register-Byte/Byte-Register Operations
Register-Byte Operation
High Byte
Low Byte
Unused
High Byte
Low Byte
Byte
Register
Byte
Memory
Example Byte-Register Operation
R5 = 0A28Fh
R5 = 01202h
R6 = 0203h
R6 = 0223h
Mem(0203h) = 012h
Mem(0223h) = 05Fh
ADD.B
ADD.B
R5,0(R6)
Memory
Register
0h
Example Register-Byte Operation
@R6,R5
08Fh
05Fh
+ 012h
+ 002h
0A1h
00061h
Mem (0203h) = 0A1h
R5 = 00061h
C = 0, Z = 0, N = 1
C = 0, Z = 0, N = 0
(Low byte of register)
3-8
Byte-Register Operation
(Addressed byte)
+ (Addressed byte)
+ (Low byte of register)
−>(Addressed byte)
−>(Low byte of register, zero to High byte)
RISC 16-Bit CPU
Addressing Modes
3.3 Addressing Modes
Seven addressing modes for the source operand and four addressing modes
for the destination operand can address the complete address space with no
exceptions. The bit numbers in Table 3−3 describe the contents of the As
(source) and Ad (destination) mode bits.
Table 3−3. Source/Destination Operand Addressing Modes
As/Ad
Addressing Mode
Syntax
Description
00/0
Register mode
Rn
Register contents are operand
01/1
Indexed mode
X(Rn)
(Rn + X) points to the operand. X
is stored in the next word.
01/1
Symbolic mode
ADDR
(PC + X) points to the operand. X
is stored in the next word. Indexed
mode X(PC) is used.
01/1
Absolute mode
&ADDR
The word following the instruction
contains the absolute address. X
is stored in the next word. Indexed
mode X(SR) is used.
10/−
Indirect register
mode
@Rn
Rn is used as a pointer to the
operand.
11/−
Indirect
autoincrement
@Rn+
Rn is used as a pointer to the
operand. Rn is incremented
afterwards by 1 for .B instructions
and by 2 for .W instructions.
11/−
Immediate mode
#N
The word following the instruction
contains the immediate constant
N. Indirect autoincrement mode
@PC+ is used.
The seven addressing modes are explained in detail in the following sections.
Most of the examples show the same addressing mode for the source and
destination, but any valid combination of source and destination addressing
modes is possible in an instruction.
Note: Use of Labels EDE, TONI, TOM, and LEO
Throughout MSP430 documentation, EDE, TONI, TOM, and LEO are used
as generic labels. They are only labels. They have no special meaning.
RISC 16-Bit CPU
3-9
Addressing Modes
3.3.1
Register Mode
The register mode is described in Table 3−4.
Table 3−4. Register Mode Description
Assembler Code
MOV
Content of ROM
R10,R11
MOV
R10,R11
Length:
One or two words
Operation:
Move the content of R10 to R11. R10 is not affected.
Comment:
Valid for source and destination
Example:
MOV
R10,R11
Before:
After:
R10
0A023h
R10
0A023h
R11
0FA15h
R11
0A023h
PC
PCold
PC
PCold + 2
Note: Data in Registers
The data in the register can be accessed using word or byte instructions. If
byte instructions are used, the high byte is always 0 in the result. The status
bits are handled according to the result of the byte instruction.
3-10
RISC 16-Bit CPU
Addressing Modes
3.3.2
Indexed Mode
The indexed mode is described in Table 3−5.
Table 3−5. Indexed Mode Description
Assembler Code
MOV
Content of ROM
2(R5),6(R6)
MOV
X(R5),Y(R6)
X=2
Y=6
Length:
Two or three words
Operation:
Move the contents of the source address (contents of R5 + 2)
to the destination address (contents of R6 + 6). The source
and destination registers (R5 and R6) are not affected. In
indexed mode, the program counter is incremented
automatically so that program execution continues with the
next instruction.
Comment:
Valid for source and destination
Example:
MOV
Before:
2(R5),6(R6);
Address
Space
After:
0FF16h
00006h
R5
01080h
Address
Space
0xxxxh
0FF16h 00006h
0FF14h
00002h
R6
0108Ch
0FF14h
00002h
0FF12h
04596h
0FF12h
04596h
01094h
0xxxxh
01094h
0xxxxh
01092h
01234h
01090h
0xxxxh
01084h
0xxxxh
01082h
01234h
01080h
0xxxxh
01092h
05555h
01090h
0xxxxh
01084h
0xxxxh
01082h
01234h
01080h
0xxxxh
Register
PC
0108Ch
+0006h
01092h
01080h
+0002h
01082h
Register
PC
R5
01080h
R6 0108Ch
RISC 16-Bit CPU
3-11
Addressing Modes
3.3.3
Symbolic Mode
The symbolic mode is described in Table 3−6.
Table 3−6. Symbolic Mode Description
Assembler Code
Content of ROM
MOV EDE,TONI
MOV
X(PC),Y(PC)
X = EDE − PC
Y = TONI − PC
Length:
Two or three words
Operation:
Move the contents of the source address EDE (contents of
PC + X) to the destination address TONI (contents of PC + Y).
The words after the instruction contain the differences
between the PC and the source or destination addresses.
The assembler computes and inserts offsets X and Y
automatically. With symbolic mode, the program counter (PC)
is incremented automatically so that program execution
continues with the next instruction.
Comment:
Valid for source and destination
Example:
MOV
Before:
3-12
Address
Space
0FF16h
011FEh
0FF14h
0F102h
0FF12h
04090h
0F018h
0xxxxh
0F016h
0A123h
0F014h
0xxxxh
01116h
0xxxxh
01114h
05555h
01112h
0xxxxh
RISC 16-Bit CPU
EDE,TONI ;Source address EDE = 0F016h
;Dest. address TONI=01114h
Register
PC
0FF14h
+0F102h
0F016h
0FF16h
+011FEh
01114h
After:
0FF16h
Address
Space
0xxxxh
011FEh
0FF14h
0F102h
0FF12h
04090h
0F018h
0xxxxh
0F016h
0A123h
0F014h
0xxxxh
01116h
0xxxxh
01114h
0A123h
01112h
0xxxxh
Register
PC
Addressing Modes
3.3.4
Absolute Mode
The absolute mode is described in Table 3−7.
Table 3−7. Absolute Mode Description
Assembler Code
MOV
&EDE,&TONI
Content of ROM
MOV
X(0),Y(0)
X = EDE
Y = TONI
Length:
Two or three words
Operation:
Move the contents of the source address EDE to the
destination address TONI. The words after the instruction
contain the absolute address of the source and destination
addresses. With absolute mode, the PC is incremented
automatically so that program execution continues with the
next instruction.
Comment:
Valid for source and destination
Example:
MOV
Before:
&EDE,&TONI ;Source address EDE=0F016h,
;dest. address TONI=01114h
Register
Address
Space
After:
0FF16h
01114h
0FF16h
Address
Space
0xxxxh
01114h
0FF14h
0F016h
0FF14h
0F016h
0FF12h
04292h
0FF12h
04292h
0F018h
0xxxxh
0F018h
0xxxxh
0F016h
0A123h
0F016h
0A123h
0F014h
0xxxxh
0F014h
0xxxxh
01116h
0xxxxh
01116h
0xxxxh
01114h
01234h
01114h
0A123h
01112h
0xxxxh
01112h
0xxxxh
PC
Register
PC
This address mode is mainly for hardware peripheral modules that are located
at an absolute, fixed address. These are addressed with absolute mode to
ensure software transportability (for example, position-independent code).
RISC 16-Bit CPU
3-13
Addressing Modes
3.3.5
Indirect Register Mode
The indirect register mode is described in Table 3−8.
Table 3−8. Indirect Mode Description
Assembler Code
MOV
@R10,0(R11)
MOV
@R10,0(R11)
Length:
One or two words
Operation:
Move the contents of the source address (contents of R10) to
the destination address (contents of R11). The registers are
not modified.
Comment:
Valid only for source operand. The substitute for destination
operand is 0(Rd).
Example:
MOV.B
Before:
3-14
Content of ROM
Address
Space
0xxxxh
@R10,0(R11)
After:
0FF16h
0000h
R10
0FA33h
Address
Space
0xxxxh
0FF16h 0000h
0FF14h
04AEBh
PC R11
002A7h
0FF14h
04AEBh
Register
0FF12h
0xxxxh
0FF12h
0xxxxh
0FA34h
0xxxxh
0FA34h
0xxxxh
0FA32h
05BC1h
0FA32h
05BC1h
0FA30h
0xxxxh
0FA30h
0xxxxh
002A8h
0xxh
002A8h
0xxh
002A7h
012h
002A7h
05Bh
002A6h
0xxh
002A6h
0xxh
RISC 16-Bit CPU
Register
PC
R10 0FA33h
R11 002A7h
Addressing Modes
3.3.6
Indirect Autoincrement Mode
The indirect autoincrement mode is described in Table 3−9.
Table 3−9. Indirect Autoincrement Mode Description
Assembler Code
MOV
Content of ROM
@R10+,0(R11)
MOV
@R10+,0(R11)
Length:
One or two words
Operation:
Move the contents of the source address (contents of R10) to
the destination address (contents of R11). Register R10 is
incremented by 1 for a byte operation, or 2 for a word
operation after the fetch; it points to the next address without
any overhead. This is useful for table processing.
Comment:
Valid only for source operand. The substitute for destination
operand is 0(Rd) plus second instruction INCD Rd.
Example:
MOV
Before:
0FF18h
0FF16h
@R10+,0(R11)
Register
Address
Space
0xxxxh
After:
Address
Space
0xxxxh
00000h
R10
0FA32h
0FF18h
0FF16h
0FF14h 04ABBh
PC R11
010A8h
0FF14h 04ABBh
00000h
0FF12h
0xxxxh
0FF12h
0xxxxh
0FA34h
0xxxxh
0FA34h
0xxxxh
0FA32h
05BC1h
0FA32h
05BC1h
0FA30h
0xxxxh
0FA30h
0xxxxh
010AAh
0xxxxh
010AAh
0xxxxh
010A8h
01234h
010A8h
05BC1h
010A6h
0xxxxh
010A6h
0xxxxh
Register
PC
R10 0FA34h
R11
010A8h
The autoincrementing of the register contents occurs after the operand is
fetched. This is shown in Figure 3−8.
Figure 3−8. Operand Fetch Operation
Instruction
Address
Operand
+1/ +2
RISC 16-Bit CPU
3-15
Addressing Modes
3.3.7
Immediate Mode
The immediate mode is described in Table 3−10.
Table 3−10.Immediate Mode Description
Assembler Code
MOV
Content of ROM
#45h,TONI
MOV @PC+,X(PC)
45
X = TONI − PC
Length:
Two or three words
It is one word less if a constant of CG1 or CG2 can be used.
Operation:
Move the immediate constant 45h, which is contained in the
word following the instruction, to destination address TONI.
When fetching the source, the program counter points to the
word following the instruction and moves the contents to the
destination.
Comment:
Valid only for a source operand.
Example:
MOV
Before:
3-16
#45h,TONI
Address
Space
After:
0FF16h
01192h
0FF18h
0FF16h
Address
Space
0xxxxh
01192h
0FF14h
00045h
0FF14h
00045h
0FF12h
040B0h
0FF12h
040B0h
010AAh
0xxxxh
010AAh
0xxxxh
010A8h
01234h
010A6h
0xxxxh
RISC 16-Bit CPU
Register
PC
0FF16h
+01192h
010A8h
010A8h
00045h
010A6h
0xxxxh
Register
PC
Instruction Set
3.4 Instruction Set
The complete MSP430 instruction set consists of 27 core instructions and 24
emulated instructions. The core instructions are instructions that have unique
op-codes decoded by the CPU. The emulated instructions are instructions that
make code easier to write and read, but do not have op-codes themselves,
instead they are replaced automatically by the assembler with an equivalent
core instruction. There is no code or performance penalty for using emulated
instruction.
There are three core-instruction formats:
- Dual operand
- Single operand
- Jump
All single-operand and dual-operand instructions can be byte or word
instructions by using .B or .W extensions. Byte instructions are used to access
byte data or byte peripherals. Word instructions are used to access word data
or word peripherals. If no extension is used, the instruction is a word
instruction.
The source and destination of an instruction are defined by the following fields:
src
The source operand defined by As and S-reg
dst
The destination operand defined by Ad and D-reg
As
The addressing bits responsible for the addressing mode used
for the source (src)
S-reg
The working register used for the source (src)
Ad
The addressing bits responsible for the addressing mode used
for the destination (dst)
D-reg
The working register used for the destination (dst)
B/W
Byte or word operation:
0: word operation
1: byte operation
Note: Destination Address
Destination addresses are valid anywhere in the memory map. However,
when using an instruction that modifies the contents of the destination, the
user must ensure the destination address is writable. For example, a
masked-ROM location would be a valid destination address, but the contents
are not modifiable, so the results of the instruction would be lost.
RISC 16-Bit CPU
3-17
Instruction Set
3.4.1
Double-Operand (Format I) Instructions
Figure 3−9 illustrates the double-operand instruction format.
Figure 3−9. Double-Operand Instruction Format
15
14
13
12
11
10
9
8
S-Reg
Op-code
7
6
Ad
B/W
5
4
3
2
As
1
0
D-Reg
Table 3−11 lists and describes the double operand instructions.
Table 3−11. Double-Operand Instructions
Mnemonic
S-Reg,
g,
D-Reg
Operation
Status Bits
V
N
Z
C
MOV(.B)
src,dst
src → dst
−
−
−
−
ADD(.B)
src,dst
src + dst → dst
*
*
*
*
ADDC(.B)
src,dst
src + dst + C → dst
*
*
*
*
SUB(.B)
src,dst
dst + .not.src + 1 → dst
*
*
*
*
SUBC(.B)
src,dst
dst + .not.src + C → dst
*
*
*
*
CMP(.B)
src,dst
dst − src
*
*
*
*
DADD(.B)
src,dst
src + dst + C → dst (decimally)
*
*
*
*
BIT(.B)
src,dst
src .and. dst
0
*
*
*
BIC(.B)
src,dst
.not.src .and. dst → dst
−
−
−
−
BIS(.B)
src,dst
src .or. dst → dst
−
−
−
−
XOR(.B)
src,dst
src .xor. dst → dst
*
*
*
*
AND(.B)
src,dst
src .and. dst → dst
0
*
*
*
*
The status bit is affected
−
The status bit is not affected
0
The status bit is cleared
1
The status bit is set
Note: Instructions CMP and SUB
The instructions CMP and SUB are identical except for the storage of the
result. The same is true for the BIT and AND instructions.
3-18
RISC 16-Bit CPU
Instruction Set
3.4.2
Single-Operand (Format II) Instructions
Figure 3−10 illustrates the single-operand instruction format.
Figure 3−10. Single-Operand Instruction Format
15
14
13
12
11
10
9
8
7
Op-code
6
5
B/W
4
3
Ad
2
1
0
D/S-Reg
Table 3−12 lists and describes the single operand instructions.
Table 3−12.Single-Operand Instructions
S-Reg,
D Reg
D-Reg
Operation
RRC(.B)
dst
C → MSB →.......LSB → C
*
*
*
*
RRA(.B)
dst
MSB → MSB →....LSB → C
0
*
*
*
PUSH(.B)
src
SP − 2 → SP, src → @SP
−
−
−
−
SWPB
dst
Swap bytes
−
−
−
−
CALL
dst
SP − 2 → SP, PC+2 → @SP
−
−
−
−
*
*
*
*
0
*
*
*
Mnemonic
Status Bits
V
N
Z
C
dst → PC
TOS → SR, SP + 2 → SP
RETI
TOS → PC,SP + 2 → SP
SXT
dst
Bit 7 → Bit 8........Bit 15
*
The status bit is affected
−
The status bit is not affected
0
The status bit is cleared
1
The status bit is set
All addressing modes are possible for the CALL instruction. If the symbolic
mode (ADDRESS), the immediate mode (#N), the absolute mode (&EDE), or
the indexed mode x(RN) is used, the word that follows contains the address
information.
RISC 16-Bit CPU
3-19
Instruction Set
3.4.3
Jumps
Figure 3−11 shows the conditional-jump instruction format.
Figure 3−11. Jump Instruction Format
15
14
13
Op-code
12
11
10
9
8
7
C
6
5
4
3
2
1
0
10-Bit PC Offset
Table 3−13 lists and describes the jump instructions.
Table 3−13.Jump Instructions
Mnemonic
S-Reg, D-Reg
Operation
JEQ/JZ
Label
Jump to label if zero bit is set
JNE/JNZ
Label
Jump to label if zero bit is reset
JC
Label
Jump to label if carry bit is set
JNC
Label
Jump to label if carry bit is reset
JN
Label
Jump to label if negative bit is set
JGE
Label
Jump to label if (N .XOR. V) = 0
JL
Label
Jump to label if (N .XOR. V) = 1
JMP
Label
Jump to label unconditionally
Conditional jumps support program branching relative to the PC and do not
affect the status bits. The possible jump range is from − 511 to +512 words
relative to the PC value at the jump instruction. The 10-bit program-counter
offset is treated as a signed 10-bit value that is doubled and added to the
program counter:
PCnew = PCold + 2 + PCoffset × 2
3-20
RISC 16-Bit CPU
Instruction Set
* ADC[.W]
* ADC.B
Add carry to destination
Add carry to destination
Syntax
ADC
ADC.B
Operation
dst + C −> dst
Emulation
ADDC
ADDC.B
Description
The carry bit (C) is added to the destination operand. The previous contents
of the destination are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Set if dst was incremented from 0FFFFh to 0000, reset otherwise
Set if dst was incremented from 0FFh to 00, reset otherwise
V: Set if an arithmetic overflow occurs, otherwise reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 16-bit counter pointed to by R13 is added to a 32-bit counter pointed to
by R12.
ADD
@R13,0(R12)
; Add LSDs
ADC
2(R12)
; Add carry to MSD
Example
The 8-bit counter pointed to by R13 is added to a 16-bit counter pointed to by
R12.
ADD.B
@R13,0(R12)
; Add LSDs
ADC.B
1(R12)
; Add carry to MSD
dst
dst
or
ADC.W
dst
#0,dst
#0,dst
RISC 16-Bit CPU
3-21
Instruction Set
ADD[.W]
ADD.B
Add source to destination
Add source to destination
Syntax
ADD
ADD.B
Operation
src + dst −> dst
Description
The source operand is added to the destination operand. The source operand
is not affected. The previous contents of the destination are lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R5 is increased by 10. The jump to TONI is performed on a carry.
ADD.W
src,dst
#10,R5
TONI
; Carry occurred
; No carry
R5 is increased by 10. The jump to TONI is performed on a carry.
ADD.B
JC
......
3-22
or
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Set if there is a carry from the result, cleared if not
Set if an arithmetic overflow occurs, otherwise reset
ADD
JC
......
Example
src,dst
src,dst
RISC 16-Bit CPU
#10,R5
TONI
; Add 10 to Lowbyte of R5
; Carry occurred, if (R5) ≥ 246 [0Ah+0F6h]
; No carry
Instruction Set
ADDC[.W]
ADDC.B
Add source and carry to destination
Add source and carry to destination
Syntax
ADDC
ADDC.B
Operation
src + dst + C −> dst
Description
The source operand and the carry bit (C) are added to the destination operand.
The source operand is not affected. The previous contents of the destination
are lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 32-bit counter pointed to by R13 is added to a 32-bit counter, eleven words
(20/2 + 2/2) above the pointer in R13.
or
ADDC.W
src,dst
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Set if there is a carry from the MSB of the result, reset otherwise
Set if an arithmetic overflow occurs, otherwise reset
ADD
ADDC
...
Example
src,dst
src,dst
@R13+,20(R13)
@R13+,20(R13)
; ADD LSDs with no carry in
; ADD MSDs with carry
; resulting from the LSDs
The 24-bit counter pointed to by R13 is added to a 24-bit counter, eleven words
above the pointer in R13.
ADD.B
ADDC.B
ADDC.B
...
@R13+,10(R13)
@R13+,10(R13)
@R13+,10(R13)
; ADD LSDs with no carry in
; ADD medium Bits with carry
; ADD MSDs with carry
; resulting from the LSDs
RISC 16-Bit CPU
3-23
Instruction Set
AND[.W]
AND.B
Source AND destination
Source AND destination
Syntax
AND
AND.B
Operation
src .AND. dst −> dst
Description
The source operand and the destination operand are logically ANDed. The
result is placed into the destination.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The bits set in R5 are used as a mask (#0AA55h) for the word addressed by
TOM. If the result is zero, a branch is taken to label TONI.
#0AA55h,R5
R5,TOM
TONI
; Load mask into register R5
; mask word addressed by TOM with R5
;
; Result is not zero
or
#0AA55h,TOM
TONI
The bits of mask #0A5h are logically ANDed with the low byte TOM. If the result
is zero, a branch is taken to label TONI.
AND.B
JZ
......
3-24
or AND.W src,dst
Set if result MSB is set, reset if not set
Set if result is zero, reset otherwise
Set if result is not zero, reset otherwise ( = .NOT. Zero)
Reset
MOV
AND
JZ
......
;
;
;
;
;
AND
JZ
Example
src,dst
src,dst
RISC 16-Bit CPU
#0A5h,TOM
TONI
; mask Lowbyte TOM with 0A5h
;
; Result is not zero
Instruction Set
BIC[.W]
BIC.B
Clear bits in destination
Clear bits in destination
Syntax
BIC
BIC.B
Operation
.NOT.src .AND. dst −> dst
Description
The inverted source operand and the destination operand are logically
ANDed. The result is placed into the destination. The source operand is not
affected.
Status Bits
Status bits are not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The six MSBs of the RAM word LEO are cleared.
BIC
Example
src,dst
src,dst
or BIC.W src,dst
#0FC00h,LEO
; Clear 6 MSBs in MEM(LEO)
The five MSBs of the RAM byte LEO are cleared.
BIC.B
#0F8h,LEO
; Clear 5 MSBs in Ram location LEO
RISC 16-Bit CPU
3-25
Instruction Set
BIS[.W]
BIS.B
Set bits in destination
Set bits in destination
Syntax
BIS
BIS.B
Operation
src .OR. dst −> dst
Description
The source operand and the destination operand are logically ORed. The
result is placed into the destination. The source operand is not affected.
Status Bits
Status bits are not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The six LSBs of the RAM word TOM are set.
BIS
Example
or BIS.W
src,dst
#003Fh,TOM; set the six LSBs in RAM location TOM
The three MSBs of RAM byte TOM are set.
BIS.B
3-26
src,dst
src,dst
RISC 16-Bit CPU
#0E0h,TOM
; set the three MSBs in RAM location TOM
Instruction Set
BIT[.W]
BIT.B
Test bits in destination
Test bits in destination
Syntax
BIT
Operation
src .AND. dst
Description
The source and destination operands are logically ANDed. The result affects
only the status bits. The source and destination operands are not affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
If bit 9 of R8 is set, a branch is taken to label TOM.
src,dst
Set if MSB of result is set, reset otherwise
Set if result is zero, reset otherwise
Set if result is not zero, reset otherwise (.NOT. zero)
Reset
BIT
JNZ
...
Example
#0200h,R8
TOM
; bit 9 of R8 set?
; Yes, branch to TOM
; No, proceed
If bit 3 of R8 is set, a branch is taken to label TOM.
BIT.B
JC
Example
or BIT.W src,dst
#8,R8
TOM
A serial communication receive bit (RCV) is tested. Because the carry bit is
equal to the state of the tested bit while using the BIT instruction to test a single
bit, the carry bit is used by the subsequent instruction; the read information is
shifted into register RECBUF.
;
; Serial communication with LSB is shifted first:
; xxxx xxxx
xxxx
xxxx
BIT.B
#RCV,RCCTL
; Bit info into carry
RRC
RECBUF
; Carry −> MSB of RECBUF
; cxxx xxxx
......
; repeat previous two instructions
......
; 8 times
; cccc cccc
; ^
^
; MSB
LSB
; Serial communication with MSB shifted first:
BIT.B
#RCV,RCCTL
; Bit info into carry
RLC.B
RECBUF
; Carry −> LSB of RECBUF
; xxxx
xxxc
......
; repeat previous two instructions
......
; 8 times
; cccc
cccc
;|
LSB
; MSB
RISC 16-Bit CPU
3-27
Instruction Set
* BR, BRANCH
Branch to .......... destination
Syntax
BR
Operation
dst −> PC
Emulation
MOV
Description
An unconditional branch is taken to an address anywhere in the 64K address
space. All source addressing modes can be used. The branch instruction is
a word instruction.
Status Bits
Status bits are not affected.
Example
Examples for all addressing modes are given.
3-28
dst
dst,PC
BR
#EXEC
;Branch to label EXEC or direct branch (e.g. #0A4h)
; Core instruction MOV @PC+,PC
BR
EXEC
; Branch to the address contained in EXEC
; Core instruction MOV X(PC),PC
; Indirect address
BR
&EXEC
; Branch to the address contained in absolute
; address EXEC
; Core instruction MOV X(0),PC
; Indirect address
BR
R5
; Branch to the address contained in R5
; Core instruction MOV R5,PC
; Indirect R5
BR
@R5
; Branch to the address contained in the word
; pointed to by R5.
; Core instruction MOV @R5,PC
; Indirect, indirect R5
BR
@R5+
; Branch to the address contained in the word pointed
; to by R5 and increment pointer in R5 afterwards.
; The next time—S/W flow uses R5 pointer—it can
; alter program execution due to access to
; next address in a table pointed to by R5
; Core instruction MOV @R5,PC
; Indirect, indirect R5 with autoincrement
BR
X(R5)
; Branch to the address contained in the address
; pointed to by R5 + X (e.g. table with address
; starting at X). X can be an address or a label
; Core instruction MOV X(R5),PC
; Indirect, indirect R5 + X
RISC 16-Bit CPU
Instruction Set
CALL
Subroutine
Syntax
CALL
dst
Operation
dst
SP − 2
PC
tmp
−> tmp
−> SP
−> @SP
−> PC
dst is evaluated and stored
PC updated to TOS
dst saved to PC
Description
A subroutine call is made to an address anywhere in the 64K address space.
All addressing modes can be used. The return address (the address of the
following instruction) is stored on the stack. The call instruction is a word
instruction.
Status Bits
Status bits are not affected.
Example
Examples for all addressing modes are given.
CALL
#EXEC
; Call on label EXEC or immediate address (e.g. #0A4h)
; SP−2 → SP, PC+2 → @SP, @PC+ → PC
CALL
EXEC
; Call on the address contained in EXEC
; SP−2 → SP, PC+2 → @SP, X(PC) → PC
; Indirect address
CALL
&EXEC
; Call on the address contained in absolute address
; EXEC
; SP−2 → SP, PC+2 → @SP, X(0) → PC
; Indirect address
CALL
R5
; Call on the address contained in R5
; SP−2 → SP, PC+2 → @SP, R5 → PC
; Indirect R5
CALL
@R5
; Call on the address contained in the word
; pointed to by R5
; SP−2 → SP, PC+2 → @SP, @R5 → PC
; Indirect, indirect R5
CALL
@R5+
; Call on the address contained in the word
; pointed to by R5 and increment pointer in R5.
; The next time—S/W flow uses R5 pointer—
; it can alter the program execution due to
; access to next address in a table pointed to by R5
; SP−2 → SP, PC+2 → @SP, @R5 → PC
; Indirect, indirect R5 with autoincrement
CALL
X(R5)
; Call on the address contained in the address pointed
; to by R5 + X (e.g. table with address starting at X)
; X can be an address or a label
; SP−2 → SP, PC+2 → @SP, X(R5) → PC
; Indirect, indirect R5 + X
RISC 16-Bit CPU
3-29
Instruction Set
* CLR[.W]
* CLR.B
Clear destination
Clear destination
Syntax
CLR
CLR.B
Operation
0 −> dst
Emulation
MOV
MOV.B
Description
The destination operand is cleared.
Status Bits
Status bits are not affected.
Example
RAM word TONI is cleared.
CLR
Example
#0,dst
#0,dst
TONI
; 0 −> TONI
R5
RAM byte TONI is cleared.
CLR.B
3-30
or CLR.W dst
Register R5 is cleared.
CLR
Example
dst
dst
RISC 16-Bit CPU
TONI
; 0 −> TONI
Instruction Set
* CLRC
Clear carry bit
Syntax
CLRC
Operation
0 −> C
Emulation
BIC
Description
The carry bit (C) is cleared. The clear carry instruction is a word instruction.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 16-bit decimal counter pointed to by R13 is added to a 32-bit counter
pointed to by R12.
#1,SR
Not affected
Not affected
Cleared
Not affected
CLRC
DADD
DADC
; C = 0: defines start
@R13,0(R12) ; add 16-bit counter to low word of 32-bit counter
2(R12)
; add carry to high word of 32-bit counter
RISC 16-Bit CPU
3-31
Instruction Set
* CLRN
Clear negative bit
Syntax
CLRN
Operation
0→N
or
(.NOT.src .AND. dst −> dst)
Emulation
BIC
Description
The constant 04h is inverted (0FFFBh) and is logically ANDed with the
destination operand. The result is placed into the destination. The clear
negative bit instruction is a word instruction.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The Negative bit in the status register is cleared. This avoids special treatment
with negative numbers of the subroutine called.
SUBR
SUBRET
3-32
#4,SR
Reset to 0
Not affected
Not affected
Not affected
CLRN
CALL
......
......
JN
......
......
......
RET
RISC 16-Bit CPU
SUBR
SUBRET
; If input is negative: do nothing and return
Instruction Set
* CLRZ
Clear zero bit
Syntax
CLRZ
Operation
0→Z
or
(.NOT.src .AND. dst −> dst)
Emulation
BIC
Description
The constant 02h is inverted (0FFFDh) and logically ANDed with the
destination operand. The result is placed into the destination. The clear zero
bit instruction is a word instruction.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The zero bit in the status register is cleared.
#2,SR
Not affected
Reset to 0
Not affected
Not affected
CLRZ
RISC 16-Bit CPU
3-33
Instruction Set
CMP[.W]
CMP.B
Compare source and destination
Compare source and destination
Syntax
CMP
CMP.B
Operation
dst + .NOT.src + 1
or
(dst − src)
Description
The source operand is subtracted from the destination operand. This is
accomplished by adding the 1s complement of the source operand plus 1. The
two operands are not affected and the result is not stored; only the status bits
are affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R5 and R6 are compared. If they are equal, the program continues at the label
EQUAL.
R5,R6
EQUAL
MOV
MOV
MOV
CMP
JNZ
INCD
DEC
JNZ
src,dst
; R5 = R6?
; YES, JUMP
#NUM,R5
#BLOCK1,R6
#BLOCK2,R7
@R6+,0(R7)
ERROR
R7
R5
L$1
; number of words to be compared
; BLOCK1 start address in R6
; BLOCK2 start address in R7
; Are Words equal? R6 increments
; No, branch to ERROR
; Increment R7 pointer
; Are all words compared?
; No, another compare
The RAM bytes addressed by EDE and TONI are compared. If they are equal,
the program continues at the label EQUAL.
CMP.B EDE,TONI
JEQ
EQUAL
3-34
CMP.W
Two RAM blocks are compared. If they are not equal, the program branches
to the label ERROR.
L$1
Example
or
Set if result is negative, reset if positive (src >= dst)
Set if result is zero, reset otherwise (src = dst)
Set if there is a carry from the MSB of the result, reset otherwise
Set if an arithmetic overflow occurs, otherwise reset
CMP
JEQ
Example
src,dst
src,dst
RISC 16-Bit CPU
; MEM(EDE) = MEM(TONI)?
; YES, JUMP
Instruction Set
* DADC[.W]
* DADC.B
Add carry decimally to destination
Add carry decimally to destination
Syntax
DADC
DADC.B
Operation
dst + C −> dst (decimally)
Emulation
DADD
DADD.B
Description
The carry bit (C) is added decimally to the destination.
Status Bits
N: Set if MSB is 1
Z: Set if dst is 0, reset otherwise
C: Set if destination increments from 9999 to 0000, reset otherwise
Set if destination increments from 99 to 00, reset otherwise
V: Undefined
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The four-digit decimal number contained in R5 is added to an eight-digit
decimal number pointed to by R8.
dst
dst
or
Example
src,dst
#0,dst
#0,dst
CLRC
DADD
DADC
DADC.W
R5,0(R8)
2(R8)
; Reset carry
; next instruction’s start condition is defined
; Add LSDs + C
; Add carry to MSD
The two-digit decimal number contained in R5 is added to a four-digit decimal
number pointed to by R8.
CLRC
DADD.B
DADC
R5,0(R8)
1(R8)
; Reset carry
; next instruction’s start condition is defined
; Add LSDs + C
; Add carry to MSDs
RISC 16-Bit CPU
3-35
Instruction Set
DADD[.W]
DADD.B
Source and carry added decimally to destination
Source and carry added decimally to destination
Syntax
DADD
DADD.B
Operation
src + dst + C −> dst (decimally)
Description
The source operand and the destination operand are treated as four binary
coded decimals (BCD) with positive signs. The source operand and the carry
bit (C) are added decimally to the destination operand. The source operand
is not affected. The previous contents of the destination are lost. The result is
not defined for non-BCD numbers.
Status Bits
N: Set if the MSB is 1, reset otherwise
Z: Set if result is zero, reset otherwise
C: Set if the result is greater than 9999
Set if the result is greater than 99
V: Undefined
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The eight-digit BCD number contained in R5 and R6 is added decimally to an
eight-digit BCD number contained in R3 and R4 (R6 and R4 contain the
MSDs).
CLRC
DADD
DADD
JC
Example
src,dst
src,dst
or DADD.W
src,dst
; clear carry
R5,R3
; add LSDs
R6,R4
; add MSDs with carry
OVERFLOW ; If carry occurs go to error handling routine
The two-digit decimal counter in the RAM byte CNT is incremented by one.
CLRC
DADD.B
#1,CNT
; clear carry
; increment decimal counter
#0,CNT
; ≡ DADC.B
or
SETC
DADD.B
3-36
RISC 16-Bit CPU
CNT
Instruction Set
* DEC[.W]
* DEC.B
Decrement destination
Decrement destination
Syntax
DEC
DEC.B
Operation
dst − 1 −> dst
Emulation
Emulation
SUB
SUB.B
Description
The destination operand is decremented by one. The original contents are
lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R10 is decremented by 1
dst
dst
or
DEC.W
dst
#1,dst
#1,dst
Set if result is negative, reset if positive
Set if dst contained 1, reset otherwise
Reset if dst contained 0, set otherwise
Set if an arithmetic overflow occurs, otherwise reset.
Set if initial value of destination was 08000h, otherwise reset.
Set if initial value of destination was 080h, otherwise reset.
DEC
R10
; Decrement R10
; Move a block of 255 bytes from memory location starting with EDE to memory location starting with
;TONI. Tables should not overlap: start of destination address TONI must not be within the range EDE
; to EDE+0FEh
;
MOV
#EDE,R6
MOV
#255,R10
L$1
MOV.B
@R6+,TONI−EDE−1(R6)
DEC
R10
JNZ
L$1
; Do not transfer tables using the routine above with the overlap shown in Figure 3−12.
Figure 3−12. Decrement Overlap
EDE
TONI
EDE+254
TONI+254
RISC 16-Bit CPU
3-37
Instruction Set
* DECD[.W]
* DECD.B
Double-decrement destination
Double-decrement destination
Syntax
DECD
DECD.B
Operation
dst − 2 −> dst
Emulation
Emulation
SUB
SUB.B
Description
The destination operand is decremented by two. The original contents are lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R10 is decremented by 2.
dst
dst
or
DECD.W
dst
#2,dst
#2,dst
Set if result is negative, reset if positive
Set if dst contained 2, reset otherwise
Reset if dst contained 0 or 1, set otherwise
Set if an arithmetic overflow occurs, otherwise reset.
Set if initial value of destination was 08001 or 08000h, otherwise reset.
Set if initial value of destination was 081 or 080h, otherwise reset.
DECD
R10
; Decrement R10 by two
; Move a block of 255 words from memory location starting with EDE to memory location
; starting with TONI
; Tables should not overlap: start of destination address TONI must not be within the
; range EDE to EDE+0FEh
;
MOV
#EDE,R6
MOV
#510,R10
L$1
MOV
@R6+,TONI−EDE−2(R6)
DECD
R10
JNZ
L$1
Example
Memory at location LEO is decremented by two.
DECD.B
LEO
Decrement status byte STATUS by two.
DECD.B
3-38
RISC 16-Bit CPU
STATUS
; Decrement MEM(LEO)
Instruction Set
* DINT
Disable (general) interrupts
Syntax
DINT
Operation
0 → GIE
or
(0FFF7h .AND. SR → SR
/
.NOT.src .AND. dst −> dst)
Emulation
BIC
Description
All interrupts are disabled.
The constant 08h is inverted and logically ANDed with the status register (SR).
The result is placed into the SR.
Status Bits
Status bits are not affected.
Mode Bits
GIE is reset. OSCOFF and CPUOFF are not affected.
Example
The general interrupt enable (GIE) bit in the status register is cleared to allow
a nondisrupted move of a 32-bit counter. This ensures that the counter is not
modified during the move by any interrupt.
DINT
NOP
MOV
MOV
EINT
#8,SR
; All interrupt events using the GIE bit are disabled
COUNTHI,R5 ; Copy counter
COUNTLO,R6
; All interrupt events using the GIE bit are enabled
Note: Disable Interrupt
If any code sequence needs to be protected from interruption, the DINT
should be executed at least one instruction before the beginning of the
uninterruptible sequence, or should be followed by a NOP instruction.
RISC 16-Bit CPU
3-39
Instruction Set
* EINT
Enable (general) interrupts
Syntax
EINT
Operation
1 → GIE
or
(0008h .OR. SR −> SR / .src .OR. dst −> dst)
Emulation
BIS
Description
All interrupts are enabled.
The constant #08h and the status register SR are logically ORed. The result
is placed into the SR.
Status Bits
Status bits are not affected.
Mode Bits
GIE is set. OSCOFF and CPUOFF are not affected.
Example
The general interrupt enable (GIE) bit in the status register is set.
#8,SR
; Interrupt routine of ports P1.2 to P1.7
; P1IN is the address of the register where all port bits are read. P1IFG is the address of
; the register where all interrupt events are latched.
;
PUSH.B &P1IN
BIC.B
@SP,&P1IFG ; Reset only accepted flags
EINT
; Preset port 1 interrupt flags stored on stack
; other interrupts are allowed
BIT
#Mask,@SP
JEQ
MaskOK
; Flags are present identically to mask: jump
......
MaskOK
BIC
#Mask,@SP
......
INCD
SP
; Housekeeping: inverse to PUSH instruction
; at the start of interrupt subroutine. Corrects
; the stack pointer.
RETI
Note: Enable Interrupt
The instruction following the enable interrupt instruction (EINT) is always
executed, even if an interrupt service request is pending when the interrupts
are enable.
3-40
RISC 16-Bit CPU
Instruction Set
* INC[.W]
* INC.B
Increment destination
Increment destination
Syntax
INC
INC.B
Operation
dst + 1 −> dst
Emulation
ADD
Description
The destination operand is incremented by one. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
C: Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
V: Set if dst contained 07FFFh, reset otherwise
Set if dst contained 07Fh, reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The status byte, STATUS, of a process is incremented. When it is equal to 11,
a branch to OVFL is taken.
dst
dst
or INC.W dst
#1,dst
INC.B
CMP.B
JEQ
STATUS
#11,STATUS
OVFL
RISC 16-Bit CPU
3-41
Instruction Set
* INCD[.W]
* INCD.B
Double-increment destination
Double-increment destination
Syntax
INCD
INCD.B
Operation
dst + 2 −> dst
Emulation
Emulation
ADD
ADD.B
Example
The destination operand is incremented by two. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFEh, reset otherwise
Set if dst contained 0FEh, reset otherwise
C: Set if dst contained 0FFFEh or 0FFFFh, reset otherwise
Set if dst contained 0FEh or 0FFh, reset otherwise
V: Set if dst contained 07FFEh or 07FFFh, reset otherwise
Set if dst contained 07Eh or 07Fh, reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The item on the top of the stack (TOS) is removed without using a register.
dst
dst
or INCD.W
dst
#2,dst
#2,dst
.......
PUSH
R5
INCD
SP
; R5 is the result of a calculation, which is stored
; in the system stack
; Remove TOS by double-increment from stack
; Do not use INCD.B, SP is a word-aligned
; register
RET
Example
The byte on the top of the stack is incremented by two.
INCD.B
3-42
RISC 16-Bit CPU
0(SP)
; Byte on TOS is increment by two
Instruction Set
* INV[.W]
* INV.B
Invert destination
Invert destination
Syntax
INV
INV.B
Operation
.NOT.dst −> dst
Emulation
Emulation
XOR
XOR.B
Description
The destination operand is inverted. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
C: Set if result is not zero, reset otherwise ( = .NOT. Zero)
Set if result is not zero, reset otherwise ( = .NOT. Zero)
V: Set if initial destination operand was negative, otherwise reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Content of R5 is negated (twos complement).
MOV
#00AEh,R5 ;
INV
R5
; Invert R5,
INC
R5
; R5 is now negated,
Example
dst
dst
#0FFFFh,dst
#0FFh,dst
R5 = 000AEh
R5 = 0FF51h
R5 = 0FF52h
Content of memory byte LEO is negated.
MOV.B
INV.B
INC.B
#0AEh,LEO ;
MEM(LEO) = 0AEh
LEO
; Invert LEO,
MEM(LEO) = 051h
LEO
; MEM(LEO) is negated,MEM(LEO) = 052h
RISC 16-Bit CPU
3-43
Instruction Set
JC
JHS
Jump if carry set
Jump if higher or same
Syntax
JC
JHS
Operation
If C = 1: PC + 2 × offset −> PC
If C = 0: execute following instruction
Description
The status register carry bit (C) is tested. If it is set, the 10-bit signed offset
contained in the instruction LSBs is added to the program counter. If C is reset,
the next instruction following the jump is executed. JC (jump if carry/higher or
same) is used for the comparison of unsigned numbers (0 to 65536).
Status Bits
Status bits are not affected.
Example
The P1IN.1 signal is used to define or control the program flow.
BIT
JC
......
Example
#01h,&P1IN
PROGA
; State of signal −> Carry
; If carry=1 then execute program routine A
; Carry=0, execute program here
R5 is compared to 15. If the content is higher or the same, branch to LABEL.
CMP
JHS
......
3-44
label
label
RISC 16-Bit CPU
#15,R5
LABEL
; Jump is taken if R5 ≥ 15
; Continue here if R5 < 15
Instruction Set
JEQ, JZ
Jump if equal, jump if zero
Syntax
JEQ
Operation
If Z = 1: PC + 2 × offset −> PC
If Z = 0: execute following instruction
Description
The status register zero bit (Z) is tested. If it is set, the 10-bit signed offset
contained in the instruction LSBs is added to the program counter. If Z is not
set, the instruction following the jump is executed.
Status Bits
Status bits are not affected.
Example
Jump to address TONI if R7 contains zero.
TST
JZ
Example
Example
label,
JZ
R7
TONI
label
; Test R7
; if zero: JUMP
Jump to address LEO if R6 is equal to the table contents.
CMP
R6,Table(R5)
JEQ
......
LEO
; Compare content of R6 with content of
; MEM (table address + content of R5)
; Jump if both data are equal
; No, data are not equal, continue here
Branch to LABEL if R5 is 0.
TST
JZ
......
R5
LABEL
RISC 16-Bit CPU
3-45
Instruction Set
JGE
Jump if greater or equal
Syntax
JGE
Operation
If (N .XOR. V) = 0 then jump to label: PC + 2 × offset −> PC
If (N .XOR. V) = 1 then execute the following instruction
Description
The status register negative bit (N) and overflow bit (V) are tested. If both N
and V are set or reset, the 10-bit signed offset contained in the instruction LSBs
is added to the program counter. If only one is set, the instruction following the
jump is executed.
label
This allows comparison of signed integers.
Status Bits
Status bits are not affected.
Example
When the content of R6 is greater or equal to the memory pointed to by R7,
the program continues at label EDE.
CMP
JGE
......
......
......
3-46
RISC 16-Bit CPU
@R7,R6
EDE
; R6 ≥ (R7)?, compare on signed numbers
; Yes, R6 ≥ (R7)
; No, proceed
Instruction Set
JL
Jump if less
Syntax
JL
Operation
If (N .XOR. V) = 1 then jump to label: PC + 2 × offset −> PC
If (N .XOR. V) = 0 then execute following instruction
Description
The status register negative bit (N) and overflow bit (V) are tested. If only one
is set, the 10-bit signed offset contained in the instruction LSBs is added to the
program counter. If both N and V are set or reset, the instruction following the
jump is executed.
label
This allows comparison of signed integers.
Status Bits
Status bits are not affected.
Example
When the content of R6 is less than the memory pointed to by R7, the program
continues at label EDE.
CMP
JL
......
......
......
@R7,R6
EDE
; R6 < (R7)?, compare on signed numbers
; Yes, R6 < (R7)
; No, proceed
RISC 16-Bit CPU
3-47
Instruction Set
JMP
Jump unconditionally
Syntax
JMP
Operation
PC + 2 × offset −> PC
Description
The 10-bit signed offset contained in the instruction LSBs is added to the
program counter.
Status Bits
Status bits are not affected.
Hint:
This one-word instruction replaces the BRANCH instruction in the range of
−511 to +512 words relative to the current program counter.
3-48
RISC 16-Bit CPU
label
Instruction Set
JN
Jump if negative
Syntax
JN
Operation
if N = 1: PC + 2 × offset −> PC
if N = 0: execute following instruction
Description
The negative bit (N) of the status register is tested. If it is set, the 10-bit signed
offset contained in the instruction LSBs is added to the program counter. If N
is reset, the next instruction following the jump is executed.
Status Bits
Status bits are not affected.
Example
The result of a computation in R5 is to be subtracted from COUNT. If the result
is negative, COUNT is to be cleared and the program continues execution in
another path.
L$1
SUB
JN
......
......
......
......
CLR
......
......
......
label
R5,COUNT
L$1
; COUNT − R5 −> COUNT
; If negative continue with COUNT=0 at PC=L$1
; Continue with COUNT≥0
COUNT
RISC 16-Bit CPU
3-49
Instruction Set
JNC
JLO
Jump if carry not set
Jump if lower
Syntax
JNC
JLO
Operation
if C = 0: PC + 2 × offset −> PC
if C = 1: execute following instruction
Description
The status register carry bit (C) is tested. If it is reset, the 10-bit signed offset
contained in the instruction LSBs is added to the program counter. If C is set,
the next instruction following the jump is executed. JNC (jump if no carry/lower)
is used for the comparison of unsigned numbers (0 to 65536).
Status Bits
Status bits are not affected.
Example
The result in R6 is added in BUFFER. If an overflow occurs, an error handling
routine at address ERROR is used.
ERROR
CONT
Example
ADD
JNC
......
......
......
......
......
......
......
R6,BUFFER
CONT
; BUFFER + R6 −> BUFFER
; No carry, jump to CONT
; Error handler start
; Continue with normal program flow
Branch to STL 2 if byte STATUS contains 1 or 0.
CMP.B
JLO
......
3-50
label
label
RISC 16-Bit CPU
#2,STATUS
STL2
; STATUS < 2
; STATUS ≥ 2, continue here
Instruction Set
JNE
JNZ
Jump if not equal
Jump if not zero
Syntax
JNE
JNZ
Operation
If Z = 0: PC + 2 × offset −> PC
If Z = 1: execute following instruction
Description
The status register zero bit (Z) is tested. If it is reset, the 10-bit signed offset
contained in the instruction LSBs is added to the program counter. If Z is set,
the next instruction following the jump is executed.
Status Bits
Status bits are not affected.
Example
Jump to address TONI if R7 and R8 have different contents.
CMP
JNE
......
label
label
R7,R8
TONI
; COMPARE R7 WITH R8
; if different: jump
; if equal, continue
RISC 16-Bit CPU
3-51
Instruction Set
MOV[.W]
MOV.B
Move source to destination
Move source to destination
Syntax
MOV
MOV.B
Operation
src −> dst
Description
The source operand is moved to the destination.
The source operand is not affected. The previous contents of the destination
are lost.
Status Bits
Status bits are not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The contents of table EDE (word data) are copied to table TOM. The length
of the tables must be 020h locations.
Loop
Example
Loop
3-52
MOV
MOV
MOV
DEC
JNZ
......
......
......
src,dst
src,dst
or
MOV.W
#EDE,R10
#020h,R9
@R10+,TOM−EDE−2(R10)
R9
Loop
src,dst
; Prepare pointer
; Prepare counter
; Use pointer in R10 for both tables
; Decrement counter
; Counter ≠ 0, continue copying
; Copying completed
The contents of table EDE (byte data) are copied to table TOM. The length of
the tables should be 020h locations
MOV #EDE,R10
; Prepare pointer
MOV #020h,R9
; Prepare counter
MOV.B @R10+,TOM−EDE−1(R10) ; Use pointer in R10 for
; both tables
DEC R9
; Decrement counter
JNZ
Loop
; Counter ≠ 0, continue
; copying
......
; Copying completed
......
......
RISC 16-Bit CPU
Instruction Set
* NOP
No operation
Syntax
NOP
Operation
None
Emulation
MOV
Description
No operation is performed. The instruction may be used for the elimination of
instructions during the software check or for defined waiting times.
Status Bits
Status bits are not affected.
#0, R3
The NOP instruction is mainly used for two purposes:
- To fill one, two, or three memory words
- To adjust software timing
Note: Emulating No-Operation Instruction
Other instructions can emulate the NOP function while providing different
numbers of instruction cycles and code words. Some examples are:
Examples:
MOV
MOV
MOV
BIC
JMP
BIC
#0,R3
0(R4),0(R4)
@R4,0(R4)
#0,EDE(R4)
$+2
#0,R5
; 1 cycle, 1 word
; 6 cycles, 3 words
; 5 cycles, 2 words
; 4 cycles, 2 words
; 2 cycles, 1 word
; 1 cycle, 1 word
However, care should be taken when using these examples to prevent
unintended results. For example, if MOV 0(R4), 0(R4) is used and the value
in R4 is 120h, then a security violation will occur with the watchdog timer
(address 120h) because the security key was not used.
RISC 16-Bit CPU
3-53
Instruction Set
* POP[.W]
* POP.B
Pop word from stack to destination
Pop byte from stack to destination
Syntax
POP
POP.B
Operation
@SP −> temp
SP + 2 −> SP
temp −> dst
Emulation
Emulation
MOV
MOV.B
Description
The stack location pointed to by the stack pointer (TOS) is moved to the
destination. The stack pointer is incremented by two afterwards.
Status Bits
Status bits are not affected.
Example
The contents of R7 and the status register are restored from the stack.
POP
POP
Example
R7
SR
or
MOV.W
@SP+,dst
; Restore R7
; Restore status register
LEO
; The low byte of the stack is moved to LEO.
The contents of R7 is restored from the stack.
POP.B
Example
@SP+,dst
@SP+,dst
The contents of RAM byte LEO is restored from the stack.
POP.B
Example
dst
dst
R7
; The low byte of the stack is moved to R7,
; the high byte of R7 is 00h
The contents of the memory pointed to by R7 and the status register are
restored from the stack.
POP.B
0(R7)
POP
SR
; The low byte of the stack is moved to the
; the byte which is pointed to by R7
: Example: R7 = 203h
;
Mem(R7) = low byte of system stack
: Example: R7 = 20Ah
;
Mem(R7) = low byte of system stack
; Last word on stack moved to the SR
Note: The System Stack Pointer
The system stack pointer (SP) is always incremented by two, independent
of the byte suffix.
3-54
RISC 16-Bit CPU
Instruction Set
PUSH[.W]
PUSH.B
Push word onto stack
Push byte onto stack
Syntax
PUSH
PUSH.B
Operation
SP − 2 → SP
src → @SP
Description
The stack pointer is decremented by two, then the source operand is moved
to the RAM word addressed by the stack pointer (TOS).
Status Bits
Status bits are not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The contents of the status register and R8 are saved on the stack.
PUSH
PUSH
Example
src
src
or
SR
R8
PUSH.W
src
; save status register
; save R8
The contents of the peripheral TCDAT is saved on the stack.
PUSH.B
&TCDAT
; save data from 8-bit peripheral module,
; address TCDAT, onto stack
Note: The System Stack Pointer
The system stack pointer (SP) is always decremented by two, independent
of the byte suffix.
RISC 16-Bit CPU
3-55
Instruction Set
* RET
Return from subroutine
Syntax
RET
Operation
@SP→ PC
SP + 2 → SP
Emulation
MOV
Description
The return address pushed onto the stack by a CALL instruction is moved to
the program counter. The program continues at the code address following the
subroutine call.
Status Bits
Status bits are not affected.
3-56
RISC 16-Bit CPU
@SP+,PC
Instruction Set
RETI
Return from interrupt
Syntax
RETI
Operation
TOS
SP + 2
TOS
SP + 2
Description
The status register is restored to the value at the beginning of the interrupt
service routine by replacing the present SR contents with the TOS contents.
The stack pointer (SP) is incremented by two.
→ SR
→ SP
→ PC
→ SP
The program counter is restored to the value at the beginning of interrupt
service. This is the consecutive step after the interrupted program flow.
Restoration is performed by replacing the present PC contents with the TOS
memory contents. The stack pointer (SP) is incremented.
Status Bits
N:
Z:
C:
V:
restored from system stack
restored from system stack
restored from system stack
restored from system stack
Mode Bits
OSCOFF, CPUOFF, and GIE are restored from system stack.
Example
Figure 3−13 illustrates the main program interrupt.
Figure 3−13. Main Program Interrupt
PC −6
PC −4
PC −2
PC
PC +2
Interrupt Request
Interrupt Accepted
PC+2 is Stored
Onto Stack
PC = PCi
PC +4
PCi +2
PC +6
PCi +4
PC +8
PCi +n−4
PCi +n−2
PCi +n
RETI
RISC 16-Bit CPU
3-57
Instruction Set
* RLA[.W]
* RLA.B
Rotate left arithmetically
Rotate left arithmetically
Syntax
RLA
RLA.B
Operation
C <− MSB <− MSB−1 .... LSB+1 <− LSB <− 0
Emulation
ADD
ADD.B
Description
The destination operand is shifted left one position as shown in Figure 3−14.
The MSB is shifted into the carry bit (C) and the LSB is filled with 0. The RLA
instruction acts as a signed multiplication by 2.
dst
dst
or
RLA.W
dst
dst,dst
dst,dst
An overflow occurs if dst ≥ 04000h and dst < 0C000h before operation is
performed: the result has changed sign.
Figure 3−14. Destination Operand—Arithmetic Shift Left
Word
15
0
0
C
Byte
7
0
An overflow occurs if dst ≥ 040h and dst < 0C0h before the operation is
performed: the result has changed sign.
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Loaded from the MSB
Set if an arithmetic overflow occurs:
the initial value is 04000h ≤ dst < 0C000h; reset otherwise
Set if an arithmetic overflow occurs:
the initial value is 040h ≤ dst < 0C0h; reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R7 is multiplied by 2.
RLA
Example
R7
; Shift left R7 (× 2)
The low byte of R7 is multiplied by 4.
RLA.B
RLA.B
R7
R7
; Shift left low byte of R7 (× 2)
; Shift left low byte of R7 (× 4)
Note: RLA Substitution
The assembler does not recognize the instruction:
RLA
@R5+,
RLA.B @R5+,
or
RLA(.B) @R5
ADD @R5+,−2(R5) ADD.B @R5+,−1(R5) or
ADD(.B) @R5
It must be substituted by:
3-58
RISC 16-Bit CPU
Instruction Set
* RLC[.W]
* RLC.B
Rotate left through carry
Rotate left through carry
Syntax
RLC
RLC.B
Operation
C <− MSB <− MSB−1 .... LSB+1 <− LSB <− C
Emulation
ADDC
Description
The destination operand is shifted left one position as shown in Figure 3−15.
The carry bit (C) is shifted into the LSB and the MSB is shifted into the carry
bit (C).
dst
dst
or
RLC.W
dst
dst,dst
Figure 3−15. Destination Operand—Carry Left Shift
Word
15
0
7
0
C
Byte
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Loaded from the MSB
Set if an arithmetic overflow occurs
the initial value is 04000h ≤ dst < 0C000h; reset otherwise
Set if an arithmetic overflow occurs:
the initial value is 040h ≤ dst < 0C0h; reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R5 is shifted left one position.
RLC
Example
The input P1IN.1 information is shifted into the LSB of R5.
BIT.B
RLC
Example
; (R5 x 2) + C −> R5
R5
; Information −> Carry
; Carry=P0in.1 −> LSB of R5
#2,&P1IN
R5
The MEM(LEO) content is shifted left one position.
RLC.B
; Mem(LEO) x 2 + C −> Mem(LEO)
LEO
Note: RLC and RLC.B Substitution
The assembler does not recognize the instruction:
RLC @R5+,
RLC.B @R5+,
or RLC(.B) @R5
It must be substituted by:
ADDC @R5+,−2(R5) ADDC.B
@R5+,−1(R5) or ADDC(.B) @R5
RISC 16-Bit CPU
3-59
Instruction Set
RRA[.W]
RRA.B
Rotate right arithmetically
Rotate right arithmetically
Syntax
RRA
RRA.B
Operation
MSB −> MSB, MSB −> MSB−1, ... LSB+1 −> LSB,
Description
The destination operand is shifted right one position as shown in Figure 3−16.
The MSB is shifted into the MSB, the MSB is shifted into the MSB−1, and the
LSB+1 is shifted into the LSB.
dst
dst
or
RRA.W
dst
LSB −> C
Figure 3−16. Destination Operand—Arithmetic Right Shift
Word
15
0
15
0
C
Byte
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Loaded from the LSB
Reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R5 is shifted right one position. The MSB retains the old value. It operates
equal to an arithmetic division by 2.
RRA
;
;
3-60
; R5/2 −> R5
The value in R5 is multiplied by 0.75 (0.5 + 0.25).
PUSH
RRA
ADD
RRA
......
Example
R5
R5
R5
@SP+,R5
R5
; Hold R5 temporarily using stack
; R5 × 0.5 −> R5
; R5 × 0.5 + R5 = 1.5 × R5 −> R5
; (1.5 × R5) × 0.5 = 0.75 × R5 −> R5
The low byte of R5 is shifted right one position. The MSB retains the old value.
It operates equal to an arithmetic division by 2.
RRA.B
R5
PUSH.B
RRA.B
ADD.B
......
R5
@SP
@SP+,R5
RISC 16-Bit CPU
; R5/2 −> R5: operation is on low byte only
; High byte of R5 is reset
; R5 × 0.5 −> TOS
; TOS × 0.5 = 0.5 × R5 × 0.5 = 0.25 × R5 −> TOS
; R5 × 0.5 + R5 × 0.25 = 0.75 × R5 −> R5
Instruction Set
RRC[.W]
RRC.B
Rotate right through carry
Rotate right through carry
Syntax
RRC
RRC
Operation
C −> MSB −> MSB−1 .... LSB+1 −> LSB −> C
Description
The destination operand is shifted right one position as shown in Figure 3−17.
The carry bit (C) is shifted into the MSB, the LSB is shifted into the carry bit (C).
dst
dst
or
RRC.W
dst
Figure 3−17. Destination Operand—Carry Right Shift
Word
15
0
7
0
C
Byte
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Loaded from the LSB
Reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R5 is shifted right one position. The MSB is loaded with 1.
SETC
RRC
Example
R5
; Prepare carry for MSB
; R5/2 + 8000h −> R5
R5 is shifted right one position. The MSB is loaded with 1.
SETC
RRC.B
R5
; Prepare carry for MSB
; R5/2 + 80h −> R5; low byte of R5 is used
RISC 16-Bit CPU
3-61
Instruction Set
* SBC[.W]
* SBC.B
Subtract source and borrow/.NOT. carry from destination
Subtract source and borrow/.NOT. carry from destination
Syntax
SBC
SBC.B
Operation
dst + 0FFFFh + C −> dst
dst + 0FFh + C −> dst
Emulation
SUBC
SUBC.B
Description
The carry bit (C) is added to the destination operand minus one. The previous
contents of the destination are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Set if there is a carry from the MSB of the result, reset otherwise.
Set to 1 if no borrow, reset if borrow.
V: Set if an arithmetic overflow occurs, reset otherwise.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 16-bit counter pointed to by R13 is subtracted from a 32-bit counter
pointed to by R12.
SUB
SBC
Example
dst
dst
or
SBC.W
dst
#0,dst
#0,dst
@R13,0(R12)
2(R12)
; Subtract LSDs
; Subtract carry from MSD
The 8-bit counter pointed to by R13 is subtracted from a 16-bit counter pointed
to by R12.
SUB.B
SBC.B
@R13,0(R12)
1(R12)
; Subtract LSDs
; Subtract carry from MSD
Note: Borrow Implementation.
The borrow is treated as a .NOT. carry :
3-62
RISC 16-Bit CPU
Borrow
Yes
No
Carry bit
0
1
Instruction Set
* SETC
Set carry bit
Syntax
SETC
Operation
1 −> C
Emulation
BIS
Description
The carry bit (C) is set.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Emulation of the decimal subtraction:
Subtract R5 from R6 decimally
Assume that R5 = 03987h and R6 = 04137h
DSUB
ADD
#06666h,R5
INV
R5
SETC
DADD
R5,R6
#1,SR
Not affected
Not affected
Set
Not affected
; Move content R5 from 0−9 to 6−0Fh
; R5 = 03987h + 06666h = 09FEDh
; Invert this (result back to 0−9)
; R5 = .NOT. R5 = 06012h
; Prepare carry = 1
; Emulate subtraction by addition of:
; (010000h − R5 − 1)
; R6 = R6 + R5 + 1
; R6 = 0150h
RISC 16-Bit CPU
3-63
Instruction Set
* SETN
Set negative bit
Syntax
SETN
Operation
1 −> N
Emulation
BIS
Description
The negative bit (N) is set.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
3-64
RISC 16-Bit CPU
#4,SR
Set
Not affected
Not affected
Not affected
Instruction Set
* SETZ
Set zero bit
Syntax
SETZ
Operation
1 −> Z
Emulation
BIS
Description
The zero bit (Z) is set.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
#2,SR
Not affected
Set
Not affected
Not affected
RISC 16-Bit CPU
3-65
Instruction Set
SUB[.W]
SUB.B
Subtract source from destination
Subtract source from destination
Syntax
SUB
SUB.B
Operation
dst + .NOT.src + 1 −> dst
or
[(dst − src −> dst)]
Description
The source operand is subtracted from the destination operand by adding the
source operand’s 1s complement and the constant 1. The source operand is
not affected. The previous contents of the destination are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Set if there is a carry from the MSB of the result, reset otherwise.
Set to 1 if no borrow, reset if borrow.
V: Set if an arithmetic overflow occurs, otherwise reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
See example at the SBC instruction.
Example
See example at the SBC.B instruction.
src,dst
src,dst
or
SUB.W
src,dst
Note: Borrow Is Treated as a .NOT.
The borrow is treated as a .NOT. carry :
3-66
RISC 16-Bit CPU
Borrow
Yes
No
Carry bit
0
1
Instruction Set
SUBC[.W]SBB[.W]
SUBC.B,SBB.B
Subtract source and borrow/.NOT. carry from destination
Subtract source and borrow/.NOT. carry from destination
Syntax
SUBC
SBB
SUBC.B
Operation
dst + .NOT.src + C −> dst
or
(dst − src − 1 + C −> dst)
Description
The source operand is subtracted from the destination operand by adding the
source operand’s 1s complement and the carry bit (C). The source operand
is not affected. The previous contents of the destination are lost.
Status Bits
N: Set if result is negative, reset if positive.
Z: Set if result is zero, reset otherwise.
C: Set if there is a carry from the MSB of the result, reset otherwise.
Set to 1 if no borrow, reset if borrow.
V: Set if an arithmetic overflow occurs, reset otherwise.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Two floating point mantissas (24 bits) are subtracted.
LSBs are in R13 and R10, MSBs are in R12 and R9.
SUB.W
SUBC.B
Example
src,dst
src,dst
src,dst
or
or
or
SUBC.W
SBB.W
SBB.B
src,dst
src,dst
src,dst
or
R13,R10 ; 16-bit part, LSBs
R12,R9 ; 8-bit part, MSBs
The 16-bit counter pointed to by R13 is subtracted from a 16-bit counter in R10
and R11(MSD).
SUB.B
SUBC.B
...
@R13+,R10
@R13,R11
; Subtract LSDs without carry
; Subtract MSDs with carry
; resulting from the LSDs
Note: Borrow Implementation
The borrow is treated as a .NOT. carry :
Borrow
Yes
No
Carry bit
0
1
RISC 16-Bit CPU
3-67
Instruction Set
SWPB
Swap bytes
Syntax
SWPB
Operation
Bits 15 to 8 <−> bits 7 to 0
Description
The destination operand high and low bytes are exchanged as shown in
Figure 3−18.
Status Bits
Status bits are not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
dst
Figure 3−18. Destination Operand Byte Swap
15
8
7
Example
MOV
SWPB
Example
; 0100000010111111 −> R7
; 1011111101000000 in R7
The value in R5 is multiplied by 256. The result is stored in R5,R4.
SWPB
MOV
BIC
BIC
3-68
#040BFh,R7
R7
RISC 16-Bit CPU
R5
R5,R4
#0FF00h,R5
#00FFh,R4
;
;Copy the swapped value to R4
;Correct the result
;Correct the result
0
Instruction Set
SXT
Extend Sign
Syntax
SXT
Operation
Bit 7 −> Bit 8 ......... Bit 15
Description
The sign of the low byte is extended into the high byte as shown in Figure 3−19.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
dst
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Set if result is not zero, reset otherwise (.NOT. Zero)
Reset
Figure 3−19. Destination Operand Sign Extension
15
Example
8
7
0
R7 is loaded with the P1IN value. The operation of the sign-extend instruction
expands bit 8 to bit 15 with the value of bit 7.
R7 is then added to R6.
MOV.B
SXT
&P1IN,R7
R7
; P1IN = 080h:
; R7 = 0FF80h:
. . . . . . . . 1000 0000
1111 1111 1000 0000
RISC 16-Bit CPU
3-69
Instruction Set
* TST[.W]
* TST.B
Test destination
Test destination
Syntax
TST
TST.B
Operation
dst + 0FFFFh + 1
dst + 0FFh + 1
Emulation
CMP
CMP.B
Description
The destination operand is compared with zero. The status bits are set according to the result. The destination is not affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R7 is tested. If it is negative, continue at R7NEG; if it is positive but not zero,
continue at R7POS.
#0,dst
#0,dst
TST
JN
JZ
......
......
......
R7
R7NEG
R7ZERO
; Test R7
; R7 is negative
; R7 is zero
; R7 is positive but not zero
; R7 is negative
; R7 is zero
The low byte of R7 is tested. If it is negative, continue at R7NEG; if it is positive
but not zero, continue at R7POS.
R7POS
R7NEG
R7ZERO
3-70
or TST.W dst
Set if destination is negative, reset if positive
Set if destination contains zero, reset otherwise
Set
Reset
R7POS
R7NEG
R7ZERO
Example
dst
dst
RISC 16-Bit CPU
TST.B
JN
JZ
......
.....
......
R7
R7NEG
R7ZERO
; Test low byte of R7
; Low byte of R7 is negative
; Low byte of R7 is zero
; Low byte of R7 is positive but not zero
; Low byte of R7 is negative
; Low byte of R7 is zero
Instruction Set
XOR[.W]
XOR.B
Exclusive OR of source with destination
Exclusive OR of source with destination
Syntax
XOR
XOR.B
Operation
src .XOR. dst −> dst
Description
The source and destination operands are exclusive ORed. The result is placed
into the destination. The source operand is not affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The bits set in R6 toggle the bits in the RAM word TONI.
XOR.W
src,dst
R6,TONI
; Toggle bits of word TONI on the bits set in R6
The bits set in R6 toggle the bits in the RAM byte TONI.
XOR.B
Example
or
Set if result MSB is set, reset if not set
Set if result is zero, reset otherwise
Set if result is not zero, reset otherwise ( = .NOT. Zero)
Set if both operands are negative
XOR
Example
src,dst
src,dst
R6,TONI
; Toggle bits of byte TONI on the bits set in
; low byte of R6
Reset to 0 those bits in low byte of R7 that are different from bits in RAM byte
EDE.
XOR.B
INV.B
EDE,R7
R7
; Set different bit to “1s”
; Invert Lowbyte, Highbyte is 0h
RISC 16-Bit CPU
3-71
Instruction Set
3.4.4
Instruction Cycles and Lengths
The number of CPU clock cycles required for an instruction depends on the
instruction format and the addressing modes used - not the instruction itself.
The number of clock cycles refers to the MCLK.
Interrupt and Reset Cycles
Table 3−14 lists the CPU cycles for interrupt overhead and reset.
Table 3−14.Interrupt and Reset Cycles
No. of
Cycles
5
Length of
Instruction
1
Interrupt accepted
6
−
WDT reset
4
−
Reset (RST/NMI)
4
−
Action
Return from interrupt (RETI)
Format-II (Single Operand) Instruction Cycles and Lengths
Table 3−15 lists the length and CPU cycles for all addressing modes of
format-II instructions.
Table 3−15.Format-II Instruction Cycles and Lengths
No. of Cycles
RRA, RRC
SWPB, SXT
PUSH
CALL
1
3
4
Length of
Instruction
1
@Rn
3
4
4
1
RRC @R9
@Rn+
3
5
5
1
SWPB @R10+
(See note)
4
5
2
CALL #0F00h
4
5
5
2
CALL 2(R7)
Addressing
Mode
Rn
#N
X(Rn)
Example
SWPB R5
EDE
4
5
5
2
PUSH EDE
&EDE
4
5
5
2
SXT &EDE
Note: Instruction Format II Immediate Mode
Do not use instructions RRA, RRC, SWPB, and SXT with the immediate
mode in the destination field. Use of these in the immediate mode results in
an unpredictable program operation.
Format-III (Jump) Instruction Cycles and Lengths
All jump instructions require one code word, and take two CPU cycles to
execute, regardless of whether the jump is taken or not.
3-72
RISC 16-Bit CPU
Instruction Set
Format-I (Double Operand) Instruction Cycles and Lengths
Table 3−16 lists the length and CPU cycles for all addressing modes of format-I
instructions.
Table 3−16.Format I Instruction Cycles and Lengths
No. of
Cycles
Length
g of
Instruction
1
1
MOV
PC
2
1
BR
R9
x(Rm)
4
2
ADD
R5,4(R6)
Addressing Mode
Src
Rn
@Rn
@
@Rn+
@
#N
x(Rn)
( )
EDE
&EDE
Dst
Rm
Example
R5,R8
EDE
4
2
XOR
R8,EDE
&EDE
4
2
MOV
R5,&EDE
Rm
2
1
AND
@R4,R5
PC
2
1
BR
@R8
x(Rm)
5
2
XOR
@R5,8(R6)
EDE
5
2
MOV
@R5,EDE
&EDE
5
2
XOR
@R5,&EDE
Rm
2
1
ADD
@R5+,R6
PC
3
1
BR
@R9+
x(Rm)
5
2
XOR
@R5,8(R6)
EDE
5
2
MOV
@R9+,EDE
&EDE
5
2
MOV
@R9+,&EDE
Rm
2
2
MOV
#20,R9
PC
3
2
BR
#2AEh
x(Rm)
5
3
MOV
#0300h,0(SP)
EDE
5
3
ADD
#33,EDE
&EDE
5
3
ADD
#33,&EDE
Rm
3
2
MOV
2(R5),R7
PC
3
2
BR
2(R6)
TONI
6
3
MOV
4(R7),TONI
x(Rm)
6
3
ADD
4(R4),6(R9)
&TONI
6
3
MOV
2(R4),&TONI
Rm
3
2
AND
EDE,R6
PC
3
2
BR
EDE
TONI
6
3
CMP
EDE,TONI
x(Rm)
6
3
MOV
EDE,0(SP)
&TONI
6
3
MOV
EDE,&TONI
Rm
3
2
MOV
&EDE,R8
PC
3
2
BRA
&EDE
TONI
6
3
MOV
&EDE,TONI
x(Rm)
6
3
MOV
&EDE,0(SP)
&TONI
6
3
MOV
&EDE,&TONI
RISC 16-Bit CPU
3-73
Instruction Set
3.4.5
Instruction Set Description
The instruction map is shown in Figure 3−20 and the complete instruction set
is summarized in Table 3−17.
Figure 3−20. Core Instruction Map
000
0xxx
4xxx
8xxx
Cxxx
1xxx
14xx
18xx
1Cxx
20xx
24xx
28xx
2Cxx
30xx
34xx
38xx
3Cxx
4xxx
5xxx
6xxx
7xxx
8xxx
9xxx
Axxx
Bxxx
Cxxx
Dxxx
Exxx
Fxxx
3-74
040
080
0C0
RRC RRC.B SWPB
100
RRA
140
180
RRA.B
SXT
1C0
200
240
PUSH
PUSH.B
JNE/JNZ
JEQ/JZ
JNC
JC
JN
JGE
JL
JMP
MOV, MOV.B
ADD, ADD.B
ADDC, ADDC.B
SUBC, SUBC.B
SUB, SUB.B
CMP, CMP.B
DADD, DADD.B
BIT, BIT.B
BIC, BIC.B
BIS, BIS.B
XOR, XOR.B
AND, AND.B
RISC 16-Bit CPU
280
CALL
2C0
300
RETI
340
380
3C0
Instruction Set
Table 3−17.MSP430 Instruction Set
Mnemonic
V
N
Z
ADC(.B)†
dst
Description
Add C to destination
dst + C → dst
*
*
*
C
*
ADD(.B)
src,dst
Add source to destination
src + dst → dst
*
*
*
*
ADDC(.B)
src,dst
Add source and C to destination
src + dst + C → dst
*
*
*
*
AND(.B)
src,dst
AND source and destination
src .and. dst → dst
0
*
*
*
BIC(.B)
src,dst
Clear bits in destination
.not.src .and. dst → dst
−
−
−
−
BIS(.B)
src,dst
Set bits in destination
src .or. dst → dst
−
−
−
−
BIT(.B)
src,dst
Test bits in destination
src .and. dst
0
*
*
*
BR†
dst
Branch to destination
dst → PC
−
−
−
−
CALL
dst
Call destination
PC+2 → stack, dst → PC
−
−
−
−
CLR(.B)†
dst
Clear destination
0 → dst
−
−
−
−
CLRC†
Clear C
0→C
−
−
−
0
CLRN†
Clear N
0→N
−
0
−
−
CLRZ†
Clear Z
0→Z
−
−
0
−
CMP(.B)
src,dst
Compare source and destination
dst − src
*
*
*
*
DADC(.B)†
dst
Add C decimally to destination
dst + C → dst (decimally)
*
*
*
*
DADD(.B)
src,dst
Add source and C decimally to dst.
src + dst + C → dst (decimally)
*
*
*
*
DEC(.B)†
dst
Decrement destination
dst − 1 → dst
*
*
*
*
DECD(.B)†
dst
Double-decrement destination
dst − 2 → dst
*
*
*
*
DINT†
Disable interrupts
0 → GIE
−
−
−
−
EINT†
Enable interrupts
1 → GIE
−
−
−
−
*
INC(.B)†
dst
Increment destination
dst +1 → dst
*
*
*
INCD(.B)†
dst
Double-increment destination
dst+2 → dst
*
*
*
*
INV(.B)†
dst
Invert destination
.not.dst → dst
*
*
*
*
JC/JHS
label
Jump if C set/Jump if higher or same
−
−
−
−
JEQ/JZ
label
Jump if equal/Jump if Z set
−
−
−
−
JGE
label
Jump if greater or equal
−
−
−
−
JL
label
Jump if less
−
−
−
−
JMP
label
Jump
−
−
−
−
JN
label
Jump if N set
−
−
−
−
JNC/JLO
label
Jump if C not set/Jump if lower
−
−
−
−
JNE/JNZ
label
Jump if not equal/Jump if Z not set
−
−
−
−
MOV(.B)
src,dst
Move source to destination
−
−
−
−
−
−
−
−
−
NOP†
PC + 2 x offset → PC
src → dst
No operation
POP(.B)†
dst
Pop item from stack to destination
@SP → dst, SP+2 → SP
−
−
−
PUSH(.B)
src
Push source onto stack
SP − 2 → SP, src → @SP
−
−
−
−
Return from subroutine
@SP → PC, SP + 2 → SP
−
−
−
−
RET†
Return from interrupt
*
*
*
*
RLA(.B)†
dst
Rotate left arithmetically
*
*
*
*
RLC(.B)†
dst
Rotate left through C
*
*
*
*
RRA(.B)
dst
Rotate right arithmetically
0
*
*
*
RRC(.B)
dst
Rotate right through C
*
*
*
*
SBC(.B)†
dst
RETI
Subtract not(C) from destination
dst + 0FFFFh + C → dst
*
*
*
*
SETC†
Set C
1→C
−
−
−
1
SETN†
Set N
1→N
−
1
−
−
SETZ†
Set Z
1→C
−
−
1
−
SUB(.B)
src,dst
Subtract source from destination
dst + .not.src + 1 → dst
*
*
*
*
SUBC(.B)
src,dst
Subtract source and not(C) from dst.
dst + .not.src + C → dst
*
*
*
*
SWPB
dst
Swap bytes
−
−
−
−
SXT
dst
Extend sign
0
*
*
*
TST(.B)†
dst
Test destination
dst + 0FFFFh + 1
0
*
*
1
XOR(.B)
src,dst
Exclusive OR source and destination
src .xor. dst → dst
*
*
*
*
†
Emulated Instruction
RISC 16-Bit CPU
3-75
3-76
RISC 16-Bit CPU
Chapter 4
16-Bit MSP430X CPU
This chapter describes the extended MSP430X 16-bit RISC CPU with 1-MB
memory access, its addressing modes, and instruction set. The MSP430X
CPU is implemented in all MSP430 devices that exceed 64-KB of address
space.
Topic
Page
4.1
CPU Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.2
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
4.3
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
4.4
Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
4.5
MSP430 and MSP430X Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-36
4.6
Instruction Set Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-58
16-Bit MSP430X CPU
4-1
CPU Introduction
4.1 CPU Introduction
The MSP430X CPU incorporates features specifically designed for modern
programming techniques such as calculated branching, table processing and
the use of high-level languages such as C. The MSP430X CPU can address
a 1-MB address range without paging. In addition, the MSP430X CPU has
fewer interrupt overhead cycles and fewer instruction cycles in some cases
than the MSP430 CPU, while maintaining the same or better code density than
the MSP430 CPU. The MSP430X CPU is completely backwards compatible
with the MSP430 CPU.
The MSP430X CPU features include:
- RISC architecture.
- Orthogonal architecture.
- Full register access including program counter, status register and stack
pointer.
- Single-cycle register operations.
- Large register file reduces fetches to memory.
- 20-bit address bus allows direct access and branching throughout the
entire memory range without paging.
- 16-bit data bus allows direct manipulation of word-wide arguments.
- Constant generator provides the six most often used immediate values
and reduces code size.
- Direct memory-to-memory transfers without intermediate register holding.
- Byte, word, and 20-bit address-word addressing
The block diagram of the MSP430X CPU is shown in Figure 4−1.
4-2
16-Bit MSP430X CPU
CPU Introduction
Figure 4−1. MSP430X CPU Block Diagram
MDB − Memory Data Bus
19
Memory Address Bus − MAB
0
16 15
R0/PC Program Counter
0
R1/SP Pointer Stack
0
R2/SR Status Register
R3/CG2 Constant Generator
R4
General Purpose
R5
General Purpose
R6
General Purpose
R7
General Purpose
R8
General Purpose
R9
General Purpose
R10
General Purpose
R11
General Purpose
R12
General Purpose
R13
General Purpose
R14
General Purpose
R15
General Purpose
20
16
Zero, Z
Carry, C
Overflow,V
Negative,N
dst
src
16/20−bit ALU
MCLK
16-Bit MSP430X CPU
4-3
Interrupts
4.2 Interrupts
The MSP430X uses the same interrupt structure as the MSP430:
- Vectored interrupts with no polling necessary
- Interrupt vectors are located downward from address 0FFFEh
Interrupt operation for both MSP430 and MSP430X CPUs is described in
Chapter 2 System Resets, Interrupts, and Operating modes, Section 2
Interrupts. The interrupt vectors contain 16-bit addresses that point into the
lower 64-KB memory. This means all interrupt handlers must start in the lower
64-KB memory − even in MSP430X devices.
During an interrupt, the program counter and the status register are pushed
onto the stack as shown in Figure 4−2. The MSP430X architecture efficiently
stores the complete 20-bit PC value by automatically appending the PC bits
19:16 to the stored SR value on the stack. When the RETI instruction is
executed, the full 20-bit PC is restored making return from interrupt to any
address in the memory range possible.
Figure 4−2. Program Counter Storage on the Stack for Interrupts
Item n−1
SPold
PC.15:0
SP
4-4
16-Bit MSP430X CPU
PC.19:16
SR.11:0
CPU Registers
4.3 CPU Registers
The CPU incorporates sixteen registers R0 to R15. Registers R0, R1, R2, and
R3 have dedicated functions. R4 to R15 are working registers for general use.
4.3.1
The Program Counter PC
The 20-bit program counter (PC/R0) points to the next instruction to be
executed. Each instruction uses an even number of bytes (two, four, six or
eight bytes), and the PC is incremented accordingly. Instruction accesses are
performed on word boundaries, and the PC is aligned to even addresses.
Figure 4−3 shows the program counter.
Figure 4−3. Program Counter PC
19
16 15
1
Program Counter Bits 19 to 1
0
0
The PC can be addressed with all instructions and addressing modes. A few
examples:
MOV.W #LABEL,PC ; Branch to address LABEL (lower 64 KB)
MOVA
#LABEL,PC ; Branch to address LABEL (1MB memory)
MOV.W LABEL,PC ; Branch to address in word LABEL
; (lower 64 KB)
MOV.W @R14,PC
; Branch indirect to address in
; R14 (lower 64 KB)
ADDA
; Skip two words (1 MB memory)
#4,PC
The BR and CALL instructions reset the upper four PC bits to 0. Only
addresses in the lower 64-KB address range can be reached with the BR or
CALL instruction. When branching or calling, addresses beyond the lower
64-KB range can only be reached using the BRA or CALLA instructions. Also,
any instruction to directly modify the PC does so according to the used
addressing mode. For example, MOV.W #value,PC will clear the upper four
bits of the PC because it is a .W instruction.
16-Bit MSP430X CPU
4-5
CPU Registers
The program counter is automatically stored on the stack with CALL, or CALLA
instructions, and during an interrupt service routine. Figure 4−4 shows the
storage of the program counter with the return address after a CALLA
instruction. A CALL instruction stores only bits 15:0 of the PC.
Figure 4−4. Program Counter Storage on the Stack for CALLA
SPold
Item n
PC.19:16
SP
PC.15:0
The RETA instruction restores bits 19:0 of the program counter and adds 4 to
the stack pointer. The RET instruction restores bits 15:0 to the program
counter and adds 2 to the stack pointer.
4-6
16-Bit MSP430X CPU
CPU Registers
4.3.2
Stack Pointer (SP)
The 20-bit stack pointer (SP/R1) is used by the CPU to store the return
addresses of subroutine calls and interrupts. It uses a predecrement,
postincrement scheme. In addition, the SP can be used by software with all
instructions and addressing modes. Figure 4−5 shows the SP. The SP is
initialized into RAM by the user, and is always aligned to even addresses.
Figure 4−6 shows the stack usage. Figure 4−7 shows the stack usage when
20-bit address-words are pushed.
Figure 4−5. Stack Pointer
19
1
Stack Pointer Bits 19 to 1
0
0
MOV.W 2(SP),R6
; Copy Item I2 to R6
MOV.W R7,0(SP)
; Overwrite TOS with R7
PUSH
#0123h
; Put 0123h on stack
POP
R8
; R8 = 0123h
Figure 4−6. Stack Usage
Address
PUSH #0123h
POP R8
0xxxh
I1
I1
I1
0xxxh − 2
I2
I2
I2
0xxxh − 4
I3
I3
I3
0xxxh − 6
SP
0123h
SP
SP
0xxxh − 8
Figure 4−7. PUSHX.A Format on the Stack
SPold
Item n−1
Item.19:16
SP
Item.15:0
16-Bit MSP430X CPU
4-7
CPU Registers
The special cases of using the SP as an argument to the PUSH and POP
instructions are described and shown in Figure 4−8.
Figure 4−8. PUSH SP - POP SP Sequence
PUSH SP
POP SP
SPold
SP1
SP1
The stack pointer is changed after
a PUSH SP instruction.
4-8
16-Bit MSP430X CPU
SP2
SP1
The stack pointer is not changed after a POP SP
instruction. The POP SP instruction places SP1 into the
stack pointer SP (SP2=SP1)
CPU Registers
4.3.3
Status Register (SR)
The 16-bit status register (SR/R2), used as a source or destination register,
can only be used in register mode addressed with word instructions. The
remaining combinations of addressing modes are used to support the
constant generator. Figure 4−9 shows the SR bits. Do not write 20-bit values
to the SR. Unpredictable operation can result.
Figure 4−9. Status Register Bits
9
15
Reserved
8
V
7
0
SCG1
OSC CPU
SCG0
GIE
OFF OFF
N
Z C
rw-0
Table 4−1 describes the status register bits.
Table 4−1. Description of Status Register Bits
Bit
Description
Reserved
Reserved
V
Overflow bit. This bit is set when the result of an arithmetic operation
overflows the signed-variable range.
ADD(.B), ADDX(.B,.A),
ADDC(.B), ADDCX(.B.A),
ADDA
Set when:
positive + positive = negative
negative + negative = positive
otherwise reset
SUB(.B), SUBX(.B,.A),
SUBC(.B),SUBCX(.B,.A),
SUBA, CMP(.B),
CMPX(.B,.A), CMPA
Set when:
positive − negative = negative
negative − positive = positive
otherwise reset
SCG1
System clock generator 1. This bit, when set, turns off the DCO dc
generator if DCOCLK is not used for MCLK or SMCLK.
SCG0
System clock generator 0. This bit, when set, turns off the FLL+ loop
control.
OSCOFF
Oscillator Off. This bit, when set, turns off the LFXT1 crystal oscillator
when LFXT1CLK is not used for MCLK or SMCLK.
CPUOFF
CPU off. This bit, when set, turns off the CPU.
GIE
General interrupt enable. This bit, when set, enables maskable interrupts. When reset, all maskable interrupts are disabled.
N
Negative bit. This bit is set when the result of an operation is negative
and cleared when the result is positive.
16-Bit MSP430X CPU
4-9
CPU Registers
4-10
Bit
Description
Z
Zero bit. This bit is set when the result of an operation is zero and
cleared when the result is not zero.
C
Carry bit. This bit is set when the result of an operation produced a
carry and cleared when no carry occurred.
16-Bit MSP430X CPU
CPU Registers
4.3.4
The Constant Generator Registers CG1 and CG2
Six commonly used constants are generated with the constant generator
registers R2 (CG1) and R3 (CG2), without requiring an additional 16-bit word
of program code. The constants are selected with the source register
addressing modes (As), as described in Table 4−2.
Table 4−2. Values of Constant Generators CG1, CG2
Register
As
Constant
Remarks
R2
00
-
Register mode
R2
01
(0)
Absolute address mode
R2
10
00004h
+4, bit processing
R2
11
00008h
+8, bit processing
R3
00
00000h
0, word processing
R3
01
00001h
+1
R3
10
00002h
+2, bit processing
R3
11
FFh, FFFFh, FFFFFh
-1, word processing
The constant generator advantages are:
- No special instructions required
- No additional code word for the six constants
- No code memory access required to retrieve the constant
The assembler uses the constant generator automatically if one of the six
constants is used as an immediate source operand. Registers R2 and R3,
used in the constant mode, cannot be addressed explicitly; they act as
source-only registers.
Constant Generator − Expanded Instruction Set
The RISC instruction set of the MSP430 has only 27 instructions. However, the
constant generator allows the MSP430 assembler to support 24 additional,
emulated instructions. For example, the single-operand instruction:
CLR
dst
is emulated by the double-operand instruction with the same length:
MOV
R3,dst
where the #0 is replaced by the assembler, and R3 is used with As=00.
INC
dst
is replaced by:
ADD
0(R3),dst
16-Bit MSP430X CPU
4-11
CPU Registers
4.3.5
The General Purpose Registers R4 to R15
The twelve CPU registers R4 to R15, contain 8-bit, 16-bit, or 20-bit values. Any
byte-write to a CPU register clears bits 19:8. Any word-write to a register clears
bits 19:16. The only exception is the SXT instruction. The SXT instruction
extends the sign through the complete 20-bit register.
The following figures show the handling of byte, word and address-word data.
Note the reset of the leading MSBs, if a register is the destination of a byte or
word instruction.
Figure 4−10 shows byte handling (8-bit data, .B suffix). The handling is shown
for a source register and a destination memory byte and for a source memory
byte and a destination register.
Figure 4−10. Register-Byte/Byte-Register Operation
Register-Byte Operation
Byte-Register Operation
High Byte Low Byte
19 16 15
0
87
UnUnused
Register
used
Memory
High Byte
Memory
19 16 15
87
UnUnused
used
Operation
16-Bit MSP430X CPU
0
Register
Operation
Memory
4-12
Low Byte
0
0
Register
CPU Registers
Figure 4−11 and Figure 4−12 show 16-bit word handling (.W suffix). The
handling is shown for a source register and a destination memory word and
for a source memory word and a destination register.
Figure 4−11. Register-Word Operation
Register-Word Operation
High Byte Low Byte
19 16 15
0
87
UnRegister
used
Memory
Operation
Memory
Figure 4−12. Word-Register Operation
Word-Register Operation
High Byte
Low Byte
Memory
19 16 15
Unused
87
0
Register
Operation
0
Register
16-Bit MSP430X CPU
4-13
CPU Registers
Figure 4−13 and Figure 4−14 show 20-bit address-word handling (.A suffix).
The handling is shown for a source register and a destination memory
address-word and for a source memory address-word and a destination
register.
Figure 4−13. Register − Address-Word Operation
Register − Address-Word Operation
High Byte Low Byte
19 16 15
0
87
Register
Memory +2
Unused
Memory
Operation
Memory +2
0
Memory
Figure 4−14. Address-Word − Register Operation
Address-Word − Register Operation
High Byte Low Byte
19 16 15
0
87
Memory +2
Unused
Memory
Register
Operation
Register
4-14
16-Bit MSP430X CPU
CPU Registers
4.4 Addressing Modes
Seven addressing modes for the source operand and four addressing modes
for the destination operand use 16-bit or 20-bit addresses. The MSP430 and
MSP430X instructions are usable throughout the entire 1-MB memory range.
Table 4−3. Source/Destination Addressing
As/Ad
Addressing Mode
Syntax
Description
00/0
Register mode
Rn
Register contents are operand
01/1
Indexed mode
X(Rn)
(Rn + X) points to the operand. X
is stored in the next word, or
stored in combination of the
preceding extension word and the
next word.
01/1
Symbolic mode
ADDR
(PC + X) points to the operand. X
is stored in the next word, or
stored in combination of the
preceding extension word and the
next word. Indexed mode X(PC) is
used.
01/1
Absolute mode
&ADDR
The word following the instruction
contains the absolute address. X
is stored in the next word, or
stored in combination of the
preceding extension word and the
next word. Indexed mode X(SR) is
used.
10/−
Indirect register
mode
@Rn
Rn is used as a pointer to the
operand.
11/−
Indirect
autoincrement
@Rn+
Rn is used as a pointer to the
operand. Rn is incremented
afterwards by 1 for .B instructions.
by 2 for .W instructions, and by 4
for .A instructions.
11/−
Immediate mode
#N
N is stored in the next word, or
stored in combination of the
preceding extension word and the
next word. Indirect autoincrement
mode @PC+ is used.
The seven addressing modes are explained in detail in the following sections.
Most of the examples show the same addressing mode for the source and
destination, but any valid combination of source and destination addressing
modes is possible in an instruction.
Note: Use of Labels EDE, TONI, TOM, and LEO
Throughout MSP430 documentation EDE, TONI, TOM, and LEO are used
as generic labels. They are only labels. They have no special meaning.
16-Bit MSP430X CPU
4-15
CPU Registers
4.4.1
Register Mode
Operation: The operand is the 8-, 16-, or 20-bit content of the used CPU
register.
Length:
One, two, or three words
Comment:
Valid for source and destination
Byte operation: Byte operation reads only the 8 LSBs of the source register
Rsrc and writes the result to the 8 LSBs of the destination
register Rdst. The bits Rdst.19:8 are cleared. The register
Rsrc is not modified.
Word operation:Word operation reads the 16 LSBs of the source register Rsrc
and writes the result to the 16 LSBs of the destination register
Rdst. The bits Rdst.19:16 are cleared. The register Rsrc is not
modified.
Address-Word operation: Address-word operation reads the 20 bits of the
source register Rsrc and writes the result to the 20 bits of the
destination register Rdst. The register Rsrc is not modified
SXT Exception: The SXT instruction is the only exception for register
operation. The sign of the low byte in bit 7 is extended to the
bits Rdst.19:8.
Example:
BIS.W
R5,R6 ;
This instruction logically ORs the 16-bit data contained in R5 with the 16-bit
contents of R6. R6.19:16 is cleared.
Before:
After:
Address
Space
21036h
xxxxh
21034h
D506h
Address
Space
Register
PC
R5
AA550h
21036h
xxxxh
R6
11111h
21034h
D506h
A550h.or.1111h = B551h
4-16
16-Bit MSP430X CPU
Register
PC
R5
AA550h
R6
0B551h
CPU Registers
Example:
BISX.A
R5,R6 ;
This instruction logically ORs the 20-bit data contained in R5 with the 20-bit
contents of R6.
The extension word contains the A/L-bit for 20-bit data. The instruction word
uses byte mode with bits A/L:B/W = 01. The result of the instruction is:
Before:
After:
Address
Space
Register
Address
Space
21036h
xxxxh
R5
AA550h
21036h
xxxxh
21034h
D546h
R6
11111h
21034h
D546h
21032h
1800h
21032h
1800h
PC
Register
PC
R5
AA550h
R6
BB551h
AA550h.or.11111h = BB551h
16-Bit MSP430X CPU
4-17
CPU Registers
4.4.2
Indexed Mode
The Indexed mode calculates the address of the operand by adding the signed
index to a CPU register. The Indexed mode has three addressing possibilities:
- Indexed mode in lower 64-KB memory
- MSP430 instruction with Indexed mode addressing memory above the
lower 64-KB memory.
- MSP430X instruction with Indexed mode
Indexed Mode in Lower 64 KB Memory
If the CPU register Rn points to an address in the lower 64 KB of the memory
range, the calculated memory address bits 19:16 are cleared after the addition
of the CPU register Rn and the signed 16-bit index. This means, the calculated
memory address is always located in the lower 64 KB and does not overflow
or underflow out of the lower 64-KB memory space. The RAM and the
peripheral registers can be accessed this way and existing MSP430 software
is usable without modifications as shown in Figure 4−15.
Figure 4−15. Indexed Mode in Lower 64 KB
Lower 64 KB.
Rn.19:16 = 0
19 16 15
FFFFF
0
CPU Register
Rn
0
Rn.19:0
00000
4-18
ÇÇÇÇÇ
ÇÇÇÇÇ
ÇÇÇÇÇ
ÇÇÇÇÇ
ÇÇÇÇÇ
Lower 64KB
10000
0FFFF
S
16-bit byte index
16-bit
signed index
16-bit signed add
0
Memory address
Length:
Two or three words
Operation:
The signed 16-bit index is located in the next word after the
instruction and is added to the CPU register Rn. The resulting
bits 19:16 are cleared giving a truncated 16-bit memory
address, which points to an operand address in the range
00000h to 0FFFFh. The operand is the content of the
addressed memory location.
Comment:
Valid for source and destination. The assembler calculates
the register index and inserts it.
16-Bit MSP430X CPU
CPU Registers
Example:
ADD.B
1000h(R5),0F000h(R6);
The previous instruction adds the 8-bit data contained in source byte
1000h(R5) and the destination byte 0F000h(R6) and places the result into the
destination byte. Source and destination bytes are both located in the lower
64 KB due to the cleared bits 19:16 of registers R5 and R6.
Source:
The byte pointed to by R5 + 1000h results in address 0479Ch
+ 1000h = 0579Ch after truncation to a 16-bit address.
Destination:
The byte pointed to by R6 + F000h results in address 01778h
+ F000h = 00778h after truncation to a 16-bit address.
Before:
After:
Address
Space
Register
Address
Space
Register
1103Ah
xxxxh
R5
0479Ch
1103Ah
xxxxh
PC R5
0479Ch
11038h
F000h
R6
01778h
11038h
F000h
R6
01778h
11036h
1000h
11036h
1000h
11034h
55D6h
11034h
55D6h
0077Ah
xxxxh
0077Ah
xxxxh
00778h
xx45h
01778h
+F000h
00778h
00778h
xx77h
0579Eh
xxxxh
0579Eh
xxxxh
0579Ch
xx32h
0479Ch
+1000h
0579Ch
0579Ch
xx32h
PC
32h
+45h
77h
16-Bit MSP430X CPU
src
dst
Sum
4-19
CPU Registers
MSP430 Instruction with Indexed Mode in Upper Memory
If the CPU register Rn points to an address above the lower 64-KB memory,
the Rn bits 19:16 are used for the address calculation of the operand. The
operand may be located in memory in the range Rn ±32 KB, because the
index, X, is a signed 16-bit value. In this case, the address of the operand can
overflow or underflow into the lower 64-KB memory space. See Figure 4−16
and Figure 4−17.
Figure 4−16. Indexed Mode in Upper Memory
Upper Memory
Rn.19:16 > 0
19
FFFFF
16 15
0
CPU Register
Rn
1 ... 15
Rn ±32 KB
S
S
16-bit byte index
Lower 64 KB
10000
0FFFF
20-bit signed add
Memory address
00000
Figure 4−17. Overflow and Underflow for the Indexed Mode
Rn.19:0
FFFFF
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
±32KB
Rn.19:0
0000C
4-20
16-Bit MSP430X CPU
Lower 64 KB
10000
0,FFFF
Rn.19:0
16-bit signed index
(sign extended to
20 bits)
Rn.19:0
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
±32KB
Rn.19:0
CPU Registers
Length:
Two or three words
Operation:
The sign-extended 16-bit index in the next word after the
instruction is added to the 20 bits of the CPU register Rn. This
delivers a 20-bit address, which points to an address in the
range 0 to FFFFFh. The operand is the content of the
addressed memory location.
Comment:
Valid for source and destination. The assembler calculates
the register index and inserts it.
Example:
ADD.W
8346h(R5),2100h(R6);
This instruction adds the 16-bit data contained in the source and the
destination addresses and places the 16-bit result into the destination. Source
and destination operand can be located in the entire address range.
Source:
The word pointed to by R5 + 8346h. The negative index
8346h is sign-extended, which results in address 23456h +
F8346h = 1B79Ch.
Destination:
The word pointed to by R6 + 2100h results in address
15678h + 2100h = 17778h.
Figure 4−18. Example for the Indexed Mode
Before:
After:
Address
Space
Register
Address
Space
Register
1103Ah
xxxxh
R5
23456h
1103Ah
xxxxh
PC R5
23456h
11038h
2100h
R6
15678h
11038h
2100h
R6
15678h
11036h
8346h
11036h
8346h
11034h
5596h
11034h
5596h
1777Ah
xxxxh
1777Ah
xxxxh
17778h
2345h
15678h
+02100h
17778h
17778h
7777h
1B79Eh
xxxxh
1B79Eh
xxxxh
1B79Ch
5432h
23456h
+F8346h
1B79Ch
1B79Ch
5432h
PC
05432h
+02345h
07777h
16-Bit MSP430X CPU
src
dst
Sum
4-21
CPU Registers
MSP430X Instruction with Indexed Mode
When using an MSP430X instruction with Indexed mode, the operand can be
located anywhere in the range of Rn ± 19 bits.
Length:
Three or four words
Operation:
The operand address is the sum of the 20-bit CPU register
content and the 20-bit index. The four MSBs of the index are
contained in the extension word, the 16 LSBs are contained
in the word following the instruction. The CPU register is not
modified.
Comment:
Valid for source and destination. The assembler calculates
the register index and inserts it.
Example:
ADDX.A
12346h(R5),32100h(R6) ;
This instruction adds the 20-bit data contained in the source and the
destination addresses and places the result into the destination.
4-22
Source:
Two words pointed to by R5 + 12346h which results in
address 23456h + 12346h = 3579Ch.
Destination:
Two words pointed to by R6 + 32100h which results in
address 45678h + 32100h = 77778h.
16-Bit MSP430X CPU
CPU Registers
The extension word contains the MSBs of the source index and of the
destination index and the A/L-bit for 20-bit data. The instruction word uses byte
mode due to the 20-bit data length with bits A/L:B/W = 01.
Before:
After:
Address
Space
Register
Address
Space
Register
2103Ah
xxxxh
R5
23456h
2103Ah
xxxxh
PC R5
23456h
21038h
2100h
R6
45678h
21038h
2100h
R6
45678h
21036h
2346h
21036h
2346h
21034h
55D6h
21034h
55D6h
21032h
1883h
21032h
1883h
7777Ah
0001h
7777Ah
0007h
77778h
2345h
77778h
7777h
3579Eh
0006h
3579Eh
0006h
3579Ch
5432h
3579Ch
5432h
PC
45678h
+32100h
77778h
23456h
+12346h
3579Ch
65432h
+12345h
77777h
16-Bit MSP430X CPU
src
dst
Sum
4-23
CPU Registers
4.4.3
Symbolic Mode
The Symbolic mode calculates the address of the operand by adding the
signed index to the program counter. The Symbolic mode has three
addressing possibilities:
- Symbolic mode in lower 64-KB memory
- MSP430 instruction with symbolic mode addressing memory above the
lower 64-KB memory.
- MSP430X instruction with symbolic mode
Symbolic Mode in Lower 64 KB
If the PC points to an address in the lower 64 KB of the memory range, the
calculated memory address bits 19:16 are cleared after the addition of the PC
and the signed 16-bit index. This means, the calculated memory address is
always located in the lower 64 KB and does not overflow or underflow out of
the lower 64-KB memory space. The RAM and the peripheral registers can be
accessed this way and existing MSP430 software is usable without
modifications as shown in Figure 4−15.
Figure 4−19. Symbolic Mode Running in Lower 64 KB
Lower 64 KB.
PC.19:16 = 0
19 16 15
FFFFF
0
Program
counter PC
0
S
ÇÇÇÇÇ
ÇÇÇÇÇ
ÇÇÇÇÇ
ÇÇÇÇÇ
ÇÇÇÇÇ
16-bit byte index
16-bit signed
PC index
PC.19:0
00000
Lower 64 KB
10000
0FFFF
16-bit signed add
0
Memory address
Operation: The signed 16-bit index in the next word after the instruction is
added temporarily to the PC. The resulting bits 19:16 are cleared giving a
truncated 16-bit memory address, which points to an operand address in the
range 00000h, to 0FFFFh. The operand is the content of the addressed
memory location.
4-24
Length:
Two or three words
Comment:
Valid for source and destination. The assembler calculates
the PC index and inserts it.
Example:
ADD.B
16-Bit MSP430X CPU
EDE,TONI ;
CPU Registers
The previous instruction adds the 8-bit data contained in source byte EDE and
destination byte TONI and places the result into the destination byte TONI.
Bytes EDE and TONI and the program are located in the lower 64 KB.
Source:
Byte EDE located at address 0,579Ch, pointed to by PC +
4766h where the PC index 4766h is the result of 0579Ch −
01036h = 04766h. Address 01036h is the location of the index
for this example.
Destination:
Byte TONI located at address 00778h, pointed to by PC +
F740h,
is
the
truncated
16-bit
result
of
00778h − 1038h = FF740h. Address 01038h is the location
of the index for this example.
Before:
After:
Address
Space
Address
Space
0103Ah
xxxxh
0103Ah
xxxxh
01038h
F740h
01038h
F740h
01036h
4766h
01036h
4766h
01034h
05D0h
01034h
50D0h
0077Ah
xxxxh
0077Ah
xxxxh
00778h
xx45h
00778h
xx77h
0579Eh
xxxxh
0579Eh
xxxxh
0579Ch
xx32h
0579Ch
xx32h
PC
01038h
+0F740h
00778h
01036h
+04766h
0579Ch
PC
32h
+45h
77h
16-Bit MSP430X CPU
src
dst
Sum
4-25
CPU Registers
MSP430 Instruction with Symbolic Mode in Upper Memory
If the PC points to an address above the lower 64-KB memory, the PC bits
19:16 are used for the address calculation of the operand. The operand may
be located in memory in the range PC ±32 KB, because the index, X, is a
signed 16-bit value. In this case, the address of the operand can overflow or
underflow into the lower 64-KB memory space as shown in Figure 4−20 and
Figure 4−21.
Figure 4−20. Symbolic Mode Running in Upper Memory
Upper Memory
PC.19:16 > 0
19
FFFFF
16 15
0
Program
counter PC
1 ... 15
PC ±32 KB
S
S
16-bit byte index
Lower 64 KB
10000
0FFFF
20-bit signed add
Memory address
00000
Figure 4−21. Overflow and Underflow for the Symbolic Mode
±32KB
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
0000C
4-26
16-Bit MSP430X CPU
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
PC.19:0
Lower 64 KB
10000
0FFFF
PC.19:0
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
PC.19:0
FFFFF
PC.19:0
16-bit signed PC
index (sign
extended to
20 bits)
±32KB
PC.19:0
CPU Registers
Length:
Two or three words
Operation:
The sign-extended 16-bit index in the next word after the
instruction is added to the 20 bits of the PC. This delivers a
20-bit address, which points to an address in the range 0 to
FFFFFh. The operand is the content of the addressed
memory location.
Comment:
Valid for source and destination. The assembler calculates
the PC index and inserts it
Example:
ADD.W
EDE,&TONI ;
This instruction adds the 16-bit data contained in source word EDE and
destination word TONI and places the 16-bit result into the destination word
TONI. For this example, the instruction is located at address 2,F034h.
Source:
Word EDE at address 3379Ch, pointed to by PC + 4766h
which is the 16-bit result of 3379Ch − 2F036h = 04766h.
Address 2F036h is the location of the index for this example.
Destination:
Word TONI located at address 00778h pointed to by the
absolute address 00778h.
Before:
After:
Address
Space
Address
Space
2F03Ah
xxxxh
2F03Ah
xxxxh
2F038h
0778h
2F038h
0778h
2F036h
4766h
2F036h
4766h
2F034h
5092h
2F034h
5092h
3379Eh
xxxxh
3379Eh
xxxxh
3379Ch
5432h
3379Ch
5432h
0077Ah
xxxxh
0077Ah
xxxxh
00778h
2345h
00778h
7777h
PC
2F036h
+04766h
3379Ch
PC
5432h
+2345h
7777h
16-Bit MSP430X CPU
src
dst
Sum
4-27
CPU Registers
MSP430X Instruction with Symbolic Mode
When using an MSP430X instruction with Symbolic mode, the operand can
be located anywhere in the range of PC ± 19 bits.
Length:
Three or four words
Operation:
The operand address is the sum of the 20-bit PC and the
20-bit index. The four MSBs of the index are contained in the
extension word, the 16 LSBs are contained in the word
following the instruction.
Comment:
Valid for source and destination. The assembler calculates
the register index and inserts it.
Example:
ADDX.B
EDE,TONI ;
The instruction adds the 8-bit data contained in source byte EDE and
destination byte TONI and places the result into the destination byte TONI.
Source:
Byte EDE located at address 3579Ch, pointed to by
PC + 14766h,
is
the
20-bit
result
of
3579Ch - 21036h = 14766h. Address 21036h is the address
of the index in this example.
Destination:
Byte TONI located at address 77778h, pointed to by
PC + 56740h,
is
the
20-bit
result
of
77778h - 21038h = 56740h. Address 21038h is the address
of the index in this example..
Before:
4-28
Address Space
After:
Address Space
2103Ah
xxxxh
2103Ah
xxxxh
21038h
6740h
21038h
6740h
21036h
4766h
21036h
4766h
21034h
50D0h
21034h
50D0h
21032h
18C5h
21032h
18C5h
7777Ah
xxxxh
7777Ah
xxxxh
77778h
xx45h
21038h
+56740h
77778h
77778h
xx77h
3579Eh
xxxxh
3579Eh
xxxxh
3579Ch
xx32h
21036h
+14766h
3579Ch
3579Ch
xx32h
16-Bit MSP430X CPU
PC
PC
32h
+45h
77h
src
dst
Sum
CPU Registers
4.4.4
Absolute Mode
The Absolute mode uses the contents of the word following the instruction as
the address of the operand. The Absolute mode has two addressing
possibilities:
- Absolute mode in lower 64-KB memory
- MSP430X instruction with Absolute mode
16-Bit MSP430X CPU
4-29
CPU Registers
Absolute Mode in Lower 64 KB
If an MSP430 instruction is used with Absolute addressing mode, the absolute
address is a 16-bit value and therefore points to an address in the lower 64 KB
of the memory range. The address is calculated as an index from 0 and is
stored in the word following the instruction The RAM and the peripheral
registers can be accessed this way and existing MSP430 software is usable
without modifications.
Length:
Two or three words
Operation:
The operand is the content of the addressed memory
location.
Comment:
Valid for source and destination. The assembler calculates
the index from 0 and inserts it
Example:
ADD.W
&EDE,&TONI ;
This instruction adds the 16-bit data contained in the absolute source and
destination addresses and places the result into the destination.
Source:
Word at address EDE
Destination:
Word at address TONI
Before: Address Space
4-30
After:
Address Space
2103Ah
xxxxh
2103Ah
xxxxh
21038h
7778h
21038h
7778h
21036h
579Ch
21036h
579Ch
21034h
5292h
21034h
5292h
0777Ah
xxxxh
0777Ah
xxxxh
07778h
2345h
07778h
7777h
0579Eh
xxxxh
0579Eh
xxxxh
0579Ch
5432h
0579Ch
5432h
16-Bit MSP430X CPU
PC
PC
5432h
+2345h
7777h
src
dst
Sum
CPU Registers
MSP430X Instruction with Absolute Mode
If an MSP430X instruction is used with Absolute addressing mode, the
absolute address is a 20-bit value and therefore points to any address in the
memory range. The address value is calculated as an index from 0. The four
MSBs of the index are contained in the extension word, and the 16 LSBs are
contained in the word following the instruction.
Length:
Three or four words
Operation:
The operand is the content of the addressed memory
location.
Comment:
Valid for source and destination. The assembler calculates
the index from 0 and inserts it
Example:
ADDX.A
&EDE,&TONI ;
This instruction adds the 20-bit data contained in the absolute source and
destination addresses and places the result into the destination.
Source:
Two words beginning with address EDE
Destination:
Two words beginning with address TONI
Before:
After:
Address
Space
Address
Space
2103Ah
xxxxh
2103Ah
xxxxh
21038h
7778h
21038h
7778h
21036h
579Ch
21036h
579Ch
21034h
52D2h
21034h
52D2h
21032h
1987h
21032h
1987h
7777Ah
0001h
7777Ah
0007h
77778h
2345h
77778h
7777h
3579Eh
0006h
3579Eh
0006h
3579Ch
5432h
3579Ch
5432h
PC
PC
65432h
+12345h
77777h
16-Bit MSP430X CPU
src
dst
Sum
4-31
CPU Registers
4.4.5
Indirect Register Mode
The Indirect Register mode uses the contents of the CPU register Rsrc as the
source operand. The Indirect Register mode always uses a 20-bit address.
Length:
One, two, or three words
Operation:
The operand is the content the addressed memory location.
The source register Rsrc is not modified.
Comment:
Valid only for the source operand. The substitute for the
destination operand is 0(Rdst).
Example:
ADDX.W
@R5,2100h(R6)
This instruction adds the two 16-bit operands contained in the source and the
destination addresses and places the result into the destination.
Source:
Word pointed to by R5. R5 contains address 3,579Ch for this
example.
Destination:
Word pointed to by R6 + 2100h which results in address
45678h + 2100h = 7778h.
Before:
After:
Address
Space
4-32
Register
Address
Space
Register
21038h
xxxxh
R5
3579Ch
21038h
xxxxh
PC R5
3579Ch
21036h
2100h
R6
45678h
21036h
2100h
R6
45678h
21034h
55A6h
21034h
55A6h
4777Ah
xxxxh
4777Ah
xxxxh
47778h
2345h
47778h
7777h
3579Eh
xxxxh
3579Eh
xxxxh
3579Ch
5432h
3579Ch
5432h
16-Bit MSP430X CPU
PC
45678h
+02100h
47778h
R5
5432h
+2345h
7777h
R5
src
dst
Sum
CPU Registers
4.4.6
Indirect, Autoincrement Mode
The Indirect Autoincrement mode uses the contents of the CPU register Rsrc
as the source operand. Rsrc is then automatically incremented by 1 for byte
instructions, by 2 for word instructions, and by 4 for address-word instructions
immediately after accessing the source operand. If the same register is used
for source and destination, it contains the incremented address for the
destination access. Indirect Autoincrement mode always uses 20-bit
addresses.
Length:
One, two, or three words
Operation:
The operand is the content of the addressed memory
location.
Comment:
Valid only for the source operand.
Example:
ADD.B
@R5+,0(R6)
This instruction adds the 8-bit data contained in the source and the destination
addresses and places the result into the destination.
Source:
Byte pointed to by R5. R5 contains address 3,579Ch for this
example.
Destination:
Byte pointed to by R6 + 0h which results in address 0778h for
this example.
Before:
After:
Address
Space
Register
Address
Space
Register
21038h
xxxxh
R5
3579Ch
21038h
xxxxh
PC R5
3579Dh
21036h
0000h
R6
00778h
21036h
0000h
R6
00778h
21034h
55F6h
21034h
55F6h
0077Ah
xxxxh
0077Ah
xxxxh
00778h
xx45h
00778h
xx77h
3579Dh
xxh
3579Dh
xxh
3579Ch
32h
3579Ch
xx32h
PC
00778h
+0000h
00778h
R5
32h
+45h
77h
src
dst
Sum
R5
16-Bit MSP430X CPU
4-33
CPU Registers
4.4.7
Immediate Mode
The Immediate mode allows accessing constants as operands by including
the constant in the memory location following the instruction. The program
counter PC is used with the Indirect Autoincrement mode. The PC points to
the immediate value contained in the next word. After the fetching of the
immediate operand, the PC is incremented by 2 for byte, word, or
address-word instructions. The Immediate mode has two addressing
possibilities:
- 8- or 16-bit constants with MSP430 instructions
- 20-bit constants with MSP430X instruction
MSP430 Instructions with Immediate Mode
If an MSP430 instruction is used with Immediate addressing mode, the
constant is an 8- or 16-bit value and is stored in the word following the
instruction.
Length:
Two or three words. One word less if a constant of the
constant generator can be used for the immediate operand.
Operation:
The 16-bit immediate source operand is used together with
the 16-bit destination operand.
Comment:
Valid only for the source operand.
Example:
ADD
#3456h,&TONI
This instruction adds the 16-bit immediate operand 3456h to the data in the
destination address TONI.
Source:
16-bit immediate value 3456h.
Destination:
Word at address TONI.
Before:
After:
Address
Space
4-34
Address
Space
2103Ah
xxxxh
2103Ah
xxxxh
21038h
0778h
21038h
0778h
21036h
3456h
21036h
3456h
21034h
50B2h
21034h
50B2h
0077Ah
xxxxh
0077Ah
xxxxh
00778h
2345h
00778h
579Bh
16-Bit MSP430X CPU
PC
PC
3456h
+2345h
579Bh
src
dst
Sum
CPU Registers
MSP430X Instructions with Immediate Mode
If an MSP430X instruction is used with immediate addressing mode, the
constant is a 20-bit value. The 4 MSBs of the constant are stored in the
extension word and the 16 LSBs of the constant are stored in the word
following the instruction.
Length:
Three or four words. One word less if a constant of the
constant generator can be used for the immediate operand.
Operation:
The 20-bit immediate source operand is used together with
the 20-bit destination operand.
Comment:
Valid only for the source operand.
Example:
ADDX.A
#23456h,&TONI ;
This instruction adds the 20-bit immediate operand 23456h to the data in the
destination address TONI.
Source:
20-bit immediate value 23456h.
Destination:
Two words beginning with address TONI.
Before:
After:
Address
Space
Address
Space
2103Ah
xxxxh
2103Ah
xxxxh
21038h
7778h
21038h
7778h
21036h
3456h
21036h
3456h
21034h
50F2h
21034h
50F2h
21032h
1907h
21032h
1907h
7777Ah
0001h
7777Ah
0003h
77778h
2345h
77778h
579Bh
PC
PC
23456h
+12345h
3579Bh
16-Bit MSP430X CPU
src
dst
Sum
4-35
MSP430 and MSP430X Instructions
4.5 MSP430 and MSP430X Instructions
MSP430 instructions are the 27 implemented instructions of the MSP430
CPU. These instructions are used throughout the 1-MB memory range unless
their 16-bit capability is exceeded. The MSP430X instructions are used when
the addressing of the operands or the data length exceeds the 16-bit capability
of the MSP430 instructions.
There are three possibilities when choosing between an MSP430 and
MSP430X instruction:
- To use only the MSP430 instructions: The only exceptions are the CALLA
and the RETA instruction. This can be done if a few, simple rules are met:
J
Placement of all constants, variables, arrays, tables, and data in the
lower 64 KB. This allows the use of MSP430 instructions with 16-bit
addressing for all data accesses. No pointers with 20-bit addresses
are needed.
J Placement of subroutine constants immediately after the subroutine
code. This allows the use of the symbolic addressing mode with its
16-bit index to reach addresses within the range of PC ±32 KB.
- To use only MSP430X instructions: The disadvantages of this method are
the reduced speed due to the additional CPU cycles and the increased
program space due to the necessary extension word for any double
operand instruction.
- Use the best fitting instruction where needed
The following sections list and describe the MSP430 and MSP430X
instructions.
4-36
16-Bit MSP430X CPU
MSP430 and MSP430X Instructions
4.5.1
MSP430 Instructions
The MSP430 instructions can be used, regardless if the program resides in the
lower 64 KB or beyond it. The only exceptions are the instructions CALL and
RET which are limited to the lower 64 KB address range. CALLA and RETA
instructions have been added to the MSP430X CPU to handle subroutines in
the entire address range with no code size overhead.
MSP430 Double Operand (Format I) Instructions
Figure 4−22 shows the format of the MSP430 double operand instructions.
Source and destination words are appended for the Indexed, Symbolic,
Absolute and Immediate modes. Table 4−4 lists the twelve MSP430 double
operand instructions.
Figure 4−22. MSP430 Double Operand Instruction Format
15
12
11
8
Op-code
Rsrc
7
6
Ad
B/W
5
4
0
As
Rdst
Source or Destination 15:0
Destination 15:0
Table 4−4. MSP430 Double Operand Instructions
Mnemonic
S-Reg,
g,
D-Reg
Operation
MOV(.B)
src,dst
ADD(.B)
Status Bits
V
N
Z
C
src → dst
−
−
−
−
src,dst
src + dst → dst
*
*
*
*
ADDC(.B)
src,dst
src + dst + C → dst
*
*
*
*
SUB(.B)
src,dst
dst + .not.src + 1 → dst
*
*
*
*
SUBC(.B)
src,dst
dst + .not.src + C → dst
*
*
*
*
CMP(.B)
src,dst
dst − src
*
*
*
*
DADD(.B)
src,dst
src + dst + C → dst (decimally)
*
*
*
*
BIT(.B)
src,dst
src .and. dst
0
*
*
Z
BIC(.B)
src,dst
.not.src .and. dst → dst
−
−
−
−
BIS(.B)
src,dst
src .or. dst → dst
−
−
−
−
XOR(.B)
src,dst
src .xor. dst → dst
*
*
*
Z
AND(.B)
src,dst
src .and. dst → dst
0
*
*
Z
*
The status bit is affected
−
The status bit is not affected
0
The status bit is cleared
1
The status bit is set
16-Bit MSP430X CPU
4-37
MSP430 and MSP430X Instructions
Single Operand (Format II) Instructions
Figure 4−23 shows the format for MSP430 single operand instructions, except
RETI. The destination word is appended for the Indexed, Symbolic, Absolute
and Immediate modes .Table 4−5 lists the seven single operand instructions.
Figure 4−23. MSP430 Single Operand Instructions
15
7
Op-code
6
5
B/W
4
0
Ad
Rdst
Destination 15:0
Table 4−5. MSP430 Single Operand Instructions
S-Reg,
D Reg
D-Reg
Operation
RRC(.B)
dst
C → MSB →.......LSB → C
*
*
*
*
RRA(.B)
dst
MSB → MSB →....LSB → C
0
*
*
*
PUSH(.B)
src
SP − 2 → SP, src → @SP
−
−
−
−
SWPB
dst
bit 15…bit 8 ⇔ bit 7…bit 0
−
−
−
−
CALL
dst
Call subroutine in lower 64 KB
−
−
−
−
TOS → SR, SP + 2 → SP
*
*
*
*
0
*
*
Z
Mnemonic
RETI
Status Bits
V
N
Z
C
TOS → PC,SP + 2 → SP
SXT
4-38
dst
Register mode:
bit 7 → bit 8 …bit 19
Other modes:
bit 7 → bit 8 …bit 15
*
The status bit is affected
−
The status bit is not affected
0
The status bit is cleared
1
The status bit is set
16-Bit MSP430X CPU
MSP430 and MSP430X Instructions
Jumps
Figure 4−24 shows the format for MSP430 and MSP430X jump instructions.
The signed 10-bit word offset of the jump instruction is multiplied by two,
sign-extended to a 20-bit address, and added to the 20-bit program counter.
This allows jumps in a range of -511 to +512 words relative to the program
counter in the full 20-bit address space Jumps do not affect the status bits.
Table 4−6 lists and describes the eight jump instructions.
Figure 4−24. Format of the Conditional Jump Instructions
15
13
Op-Code
12
10
Condition
9
8
S
0
10-Bit Signed PC Offset
Table 4−6. Conditional Jump Instructions
Mnemonic
S-Reg, D-Reg
Operation
JEQ/JZ
Label
Jump to label if zero bit is set
JNE/JNZ
Label
Jump to label if zero bit is reset
JC
Label
Jump to label if carry bit is set
JNC
Label
Jump to label if carry bit is reset
JN
Label
Jump to label if negative bit is set
JGE
Label
Jump to label if (N .XOR. V) = 0
JL
Label
Jump to label if (N .XOR. V) = 1
JMP
Label
Jump to label unconditionally
16-Bit MSP430X CPU
4-39
MSP430 and MSP430X Instructions
Emulated Instructions
In addition to the MSP430 and MSP430X instructions, emulated instructions
are instructions that make code easier to write and read, but do not have
op-codes themselves. Instead, they are replaced automatically by the
assembler with a core instruction. There is no code or performance penalty for
using emulated instructions. The emulated instructions are listed in Table 4−7.
Table 4−7. Emulated Instructions
Instruction
Explanation
ADC(.B) dst
Add Carry to dst
ADDC(.B) #0,dst
*
*
*
*
BR
Branch indirectly dst
MOV dst,PC
-
-
-
-
dst
V
N Z
C
Clear dst
MOV(.B) #0,dst
-
-
-
-
CLRC
Clear Carry bit
BIC #1,SR
-
-
-
0
CLRN
Clear Negative bit
BIC #4,SR
-
0
-
-
CLRZ
Clear Zero bit
BIC #2,SR
-
-
0
-
DADC(.B) dst
Add Carry to dst decimally
DADD(.B) #0,dst
*
*
*
*
DEC(.B) dst
Decrement dst by 1
SUB(.B) #1,dst
*
*
*
*
DECD(.B) dst
Decrement dst by 2
SUB(.B) #2,dst
*
*
*
*
DINT
Disable interrupt
BIC #8,SR
-
-
-
-
EINT
Enable interrupt
BIS #8,SR
-
-
-
-
INC(.B) dst
Increment dst by 1
ADD(.B) #1,dst
*
*
*
*
INCD(.B) dst
Increment dst by 2
ADD(.B) #2,dst
*
*
*
*
INV(.B) dst
Invert dst
XOR(.B) #-1,dst
*
*
*
*
NOP
No operation
MOV R3,R3
-
-
-
-
POP dst
Pop operand from stack
MOV @SP+,dst
-
-
-
-
RET
Return from subroutine
MOV @SP+,PC
-
-
-
-
RLA(.B) dst
Shift left dst arithmetically
ADD(.B) dst,dst
*
*
*
*
RLC(.B) dst
Shift left dst
logically through Carry
ADDC(.B) dst,dst
*
*
*
*
SBC(.B) dst
Subtract Carry from dst
SUBC(.B) #0,dst
*
*
*
*
SETC
Set Carry bit
BIS #1,SR
-
-
-
1
SETN
Set Negative bit
BIS #4,SR
-
1
-
-
SETZ
Set Zero bit
BIS #2,SR
-
-
1
-
TST(.B) dst
Test dst
(compare with 0)
CMP(.B) #0,dst
0
*
*
1
CLR(.B)
4-40
Emulation
dst
16-Bit MSP430X CPU
MSP430 and MSP430X Instructions
MSP430 Instruction Execution
The number of CPU clock cycles required for an instruction depends on the
instruction format and the addressing modes used - not the instruction itself.
The number of clock cycles refers to MCLK.
Instruction Cycles and Length for Interrupt, Reset, and Subroutines
Table 4−8 lists the length and the CPU cycles for reset, interrupts and
subroutines.
Table 4−8. Interrupt, Return and Reset Cycles and Length
Execution Time
MCLK Cycles
Length of
Instruction (Words)
Return from interrupt RETI
3†
1
Return from subroutine RET
3
1
Interrupt request service (cycles
needed before 1st instruction)
5‡
-
WDT reset
4
-
Reset (RST/NMI)
4
-
Action
†
‡
The cycle count in MSP430 CPU is 5.
The cycle count in MSP430 CPU is 6.
16-Bit MSP430X CPU
4-41
MSP430 and MSP430X Instructions
Format-II (Single Operand) Instruction Cycles and Lengths
Table 4−9 lists the length and the CPU cycles for all addressing modes of the
MSP430 single operand instructions.
Table 4−9. MSP430 Format-II Instruction Cycles and Length
Length of
Instruction
No. of Cycles
PUSH
CALL
Length of
Instruction
1
3
3†
1
SWPB R5
3
3†
4
1
RRC @R9
3
3†
4‡
1
SWPB @R10+
n.a.
3†
4‡
2
CALL #LABEL
4
4‡
4‡
2
CALL 2(R7)
EDE
4
4‡
4‡
2
PUSH EDE
&EDE
4
4‡
4‡
2
SXT &EDE
Addressing
Mode
Rn
@Rn
@Rn+
#N
X(Rn)
†
‡
Example
RRA, RRC
SWPB, SXT
Example
The cycle count in MSP430 CPU is 4.
The cycle count in MSP430 CPU is 5. Also, the cycle count is 5 for X(Rn) addressing mode, when
Rn = SP.
Jump Instructions. Cycles and Lengths
All jump instructions require one code word, and take two CPU cycles to
execute, regardless of whether the jump is taken or not.
4-42
16-Bit MSP430X CPU
MSP430 and MSP430X Instructions
Format-I (Double Operand) Instruction Cycles and Lengths
Table 4−10 lists the length and CPU cycles for all addressing modes of the
MSP430 format-I instructions.
Table 4−10.MSP430 Format-I Instructions Cycles and Length
Addressing Mode
Src
Rn
@Rn
@
@Rn+
@
#N
x(Rn)
( )
EDE
&EDE
†
Dst
Rm
No. of
Cycles
Length
g of
Instruction
1
1
MOV
Example
R5,R8
PC
2
1
BR
R9
x(Rm)
4†
2
ADD
R5,4(R6)
EDE
4†
2
XOR
R8,EDE
&EDE
4†
2
MOV
R5,&EDE
Rm
2
1
AND
@R4,R5
PC
3
1
BR
@R8
x(Rm)
5†
2
XOR
@R5,8(R6)
EDE
5†
2
MOV
@R5,EDE
&EDE
5†
2
XOR
@R5,&EDE
Rm
2
1
ADD
@R5+,R6
PC
3
1
BR
@R9+
x(Rm)
5†
2
XOR
@R5,8(R6)
EDE
5†
2
MOV
@R9+,EDE
&EDE
5†
2
MOV
@R9+,&EDE
Rm
2
2
MOV
#20,R9
PC
3
2
BR
#2AEh
x(Rm)
5†
3
MOV
#0300h,0(SP)
EDE
5†
3
ADD
#33,EDE
&EDE
5†
3
ADD
#33,&EDE
Rm
3
2
MOV
2(R5),R7
PC
3
2
BR
2(R6)
TONI
6†
3
MOV
4(R7),TONI
x(Rm)
6†
3
ADD
4(R4),6(R9)
&TONI
6†
3
MOV
2(R4),&TONI
Rm
3
2
AND
EDE,R6
PC
3
2
BR
EDE
TONI
6†
3
CMP
EDE,TONI
x(Rm)
6†
3
MOV
EDE,0(SP)
&TONI
6†
3
MOV
EDE,&TONI
Rm
3
2
MOV
&EDE,R8
PC
3
2
BR
&EDE
TONI
6†
3
MOV
&EDE,TONI
x(Rm)
6†
3
MOV
&EDE,0(SP)
&TONI
6†
3
MOV
&EDE,&TONI
MOV, BIT, and CMP instructions execute in 1 fewer cycle
16-Bit MSP430X CPU
4-43
MSP430X Extended Instructions
4.5.2
MSP430X Extended Instructions
The extended MSP430X instructions give the MSP430X CPU full access to its
20-bit address space. Most MSP430X instructions require an additional word
of op-code called the extension word. Some extended instructions do not
require an additional word and are noted in the instruction description. All
addresses, indexes and immediate numbers have 20-bit values, when
preceded by the extension word.
There are two types of extension word:
- Register/register mode for Format-I instructions and register mode for
Format-II instructions.
- Extension word for all other address mode combinations.
4-44
16-Bit MSP430X CPU
MSP430X Extended Instructions
Register Mode Extension Word
The register mode extension word is shown in Figure 4−25 and described in
Table 4−11. An example is shown in Figure 4−27.
Figure 4−25. The Extension Word for Register Modes
15
12
11
10
1
0001
9
00
8
7
6
5
4
ZC
#
A/L
0
0
3
0
(n−1)/Rn
Table 4−11. Description of the Extension Word Bits for Register Mode
Bit
Description
15:11
Extension word op-code. Op-codes 1800h to 1FFFh are extension
words.
10:9
Reserved
ZC
Zero carry bit.
#
A/L
0:
The executed instruction uses the status of the carry bit C.
1:
The executed instruction uses the carry bit as 0. The carry bit will
be defined by the result of the final operation after instruction execution.
Repetition bit.
0:
The number of instruction repetitions is set by extension-word bits
3:0.
1:
The number of instructions repetitions is defined by the value of the
four LSBs of Rn. See description for bits 3:0.
Data length extension bit. Together with the B/W-bits of the following
MSP430 instruction, the AL bit defines the used data length of the
instruction.
A/L
B/W
Comment
0
0
Reserved
0
1
20-bit address-word
1
0
16-bit word
1
1
8-bit byte
5:4
Reserved
3:0
Repetition Count.
# = 0:
These four bits set the repetition count n. These bits contain
n - 1.
# = 1:
These four bits define the CPU register whose bits 3:0 set the
number of repetitions. Rn.3:0 contain n - 1.
16-Bit MSP430X CPU
4-45
MSP430X Extended Instructions
Non-Register Mode Extension Word
The extension word for non-register modes is shown in Figure 4−26 and
described in Table 4−12. An example is shown in Figure 4−28.
Figure 4−26. The Extension Word for Non-Register Modes
15
0
0
0
12
11
1
1
10
7
Source bits 19:16
6
5
4
A/L
0
0
3
0
Destination bits 19:16
Table 4−12.Description of the Extension Word Bits for Non-Register Modes
Bit
Description
15:11
Extension word op-code. Op-codes 1800h to 1FFFh are extension words.
Source Bits
19:16
The four MSBs of the 20-bit source. Depending on the source
addressing mode, these four MSBs may belong to an immediate operand, an index or to an absolute address.
A/L
Data length extension bit. Together with the B/W-bits of the following MSP430 instruction, the AL bit defines the used data
length of the instruction.
A/L
B/W
Comment
0
0
Reserved
0
1
20 bit address-word
1
0
16 bit word
1
1
8 bit byte
5:4
Reserved
Destination Bits
19:16
The four MSBs of the 20-bit destination. Depending on the destination addressing mode, these four MSBs may belong to an
index or to an absolute address.
Note: B/W and A/L Bit Settings for SWPBX and SXTX
The B/W and A/L bit settings for SWPBX and SXTX are:
A/L
0
0
1
1
4-46
16-Bit MSP430X CPU
B/W
0
1
0
1
SWPBX.A, SXTX.A
n.a.
SWPB.W, SXTX.W
n.a.
MSP430X Extended Instructions
Figure 4−27. Example for an Extended Register/Register Instruction
15
14
13
12
11
0
0
0
1
1
Op-code
XORX.A
10
9
00
8
7
6
ZC
#
A/L
Rsvd
(n−1)/Rn
Ad
B/W
As
Rdst
Rsrc
5
4
3
2
1
0
R9,R8
1: Repetition count
in bits 3:0
0: Use Carry
0
0
0
1
1
0
14(XOR)
0
9
XORX instruction
01: Address word
0
0
0
0
0
1
0
8(R8)
Source R9
Destination R8
Destination
register mode
Source
register mode
Figure 4−28. Example for an Extended Immediate/Indexed Instruction
15
14
13
12
11
0
0
0
1
1
Op-code
10
9
8
7
6
Source 19:16
Ad
Rsrc
5
4
3
2
1
0
A/L
Rsvd
Destination 19:16
B/W
As
Rdst
Source 15:0
Destination 15:0
XORX.A #12345h, 45678h(R15)
X(Rn)
01: Address
word
18xx extension word
0
0
0
14 (XOR)
1
@PC+
12345h
1
1
0 (PC)
1
0
0
4
1
3
15 (R15)
Immediate operand LSBs: 2345h
Index destination LSBs: 5678h
16-Bit MSP430X CPU
4-47
MSP430X Extended Instructions
Extended Double Operand (Format-I) Instructions
All twelve double-operand instructions have extended versions as listed in
Table 4−13.
Table 4−13.Extended Double Operand Instructions
Status Bits
Mnemonic
Operands
Operation
V
N
Z
C
MOVX(.B,.A)
src,dst
src → dst
−
−
−
−
ADDX(.B,.A)
src,dst
src + dst → dst
*
*
*
*
ADDCX(.B,.A) src,dst
src + dst + C → dst
*
*
*
*
SUBX(.B,.A)
src,dst
dst + .not.src + 1 → dst
*
*
*
*
SUBCX(.B,.A) src,dst
dst + .not.src + C → dst
*
*
*
*
dst − src
*
*
*
*
DADDX(.B,.A) src,dst
src + dst + C → dst (decimal)
*
*
*
*
BITX(.B,.A)
src,dst
src .and. dst
0
*
*
Z
BICX(.B,.A)
src,dst
.not.src .and. dst → dst
−
−
−
−
BISX(.B,.A)
src,dst
src .or. dst → dst
−
−
−
−
XORX(.B,.A)
src,dst
src .xor. dst → dst
*
*
*
Z
ANDX(.B,.A)
src,dst
src .and. dst → dst
0
*
*
Z
CMPX(.B,.A)
4-48
src,dst
*
The status bit is affected
−
The status bit is not affected
0
The status bit is cleared
1
The status bit is set
16-Bit MSP430X CPU
MSP430X Extended Instructions
The four possible addressing combinations for the extension word for format-I
instructions are shown in Figure 4−29.
Figure 4−29. Extended Format-I Instruction Formats
15
14
13
12
11
10
9
8
7
6
5
4
0
0
0
1
1
0
0
ZC
#
A/L
0
0
n−1/Rn
0
B/W
0
0
dst
A/L
0
0
Op-code
0
0
0
src
1
1
src.19:16
Op-code
src
Ad
B/W
3
0
0
0
0
0
dst
As
src.15:0
0
0
0
1
1
0
Op-code
0
0
src
0
A/L
Ad
B/W
0
dst.19:16
0
dst
As
dst.15:0
0
0
0
1
1
src.19:16
Op-code
src
A/L
Ad
0
B/W
0
dst.19:16
dst
As
src.15:0
dst.15:0
If the 20-bit address of a source or destination operand is located in memory,
not in a CPU register, then two words are used for this operand as shown in
Figure 4−30.
Figure 4−30. 20-Bit Addresses in Memory
15
Address+2
Address
14
13
12
11
10
9
8
7
6
5
4
3
0 ....................................................................................... 0
2
1
0
19:16
Operand LSBs 15:0
16-Bit MSP430X CPU
4-49
MSP430X Extended Instructions
Extended Single Operand (Format-II) Instructions
Extended MSP430X Format-II instructions are listed in Table 4−14.
Table 4−14.Extended Single-Operand Instructions
Operation
Mnemonic
Operands
CALLA
dst
Call indirect to subroutine (20-bit address)
POPM.A
#n,Rdst
Pop n 20-bit registers from stack
POPM.W
#n,Rdst
PUSHM.A
#n,Rsrc
PUSHM.W
#n,Rsrc
Status Bits
n
V
N
Z
C
−
−
−
−
1 − 16 −
−
−
−
Pop n 16-bit registers from stack
1 − 16 −
−
−
−
Push n 20-bit registers to stack
1 − 16 −
−
−
−
Push n 16-bit registers to stack
1 − 16
−
−
−
−
PUSHX(.B,.A) src
Push 8/16/20-bit source to stack
RRCM(.A)
#n,Rdst
Rotate right Rdst n bits through carry
(16-/20-bit register)
1−4
0
*
*
*
RRUM(.A)
#n,Rdst
Rotate right Rdst n bits unsigned
(16-/20-bit register)
1−4
0
*
*
*
RRAM(.A)
#n,Rdst
Rotate right Rdst n bits arithmetically
(16-/20-bit register)
1−4
*
*
*
*
RLAM(.A)
#n,Rdst
Rotate left Rdst n bits arithmetically
(16-/20-bit register)
1−4
*
*
*
*
RRCX(.B,.A)
dst
Rotate right dst through carry
(8-/16-/20-bit data)
1
0
*
*
*
RRUX(.B,.A)
dst
Rotate right dst unsigned (8-/16-/20-bit )
1
0
*
*
*
RRAX(.B,.A)
dst
Rotate right dst arithmetically
1
*
*
*
*
SWPBX(.A)
dst
Exchange low byte with high byte
1
−
−
−
−
SXTX(.A)
Rdst
Bit7 → bit8 … bit19
1
0
*
*
*
SXTX(.A)
dst
Bit7 → bit8 … MSB
1
0
*
*
*
4-50
16-Bit MSP430X CPU
MSP430X Extended Instructions
The three possible addressing mode combinations for format-II instructions
are shown in Figure 4−31.
Figure 4−31. Extended Format-II Instruction Format
15
14
13
12
11
10
9
8
7
6
5
4
0
0
0
1
1
0
0
ZC
#
A/L
0
0
n−1/Rn
B/W
0
0
dst
A/L
0
0
B/W
1
x
dst
A/L
0
0
dst.19:16
B/W
x
1
dst
Op-code
0
0
0
1
0
1
0
0
0
Op-code
0
0
0
1
0
1
0
0
0
Op-code
3
0
0
0
0
0
dst.15:0
Extended Format II Instruction Format Exceptions
Exceptions for the Format II instruction formats are shown below.
Figure 4−32. PUSHM/POPM Instruction Format
15
8
Op-code
7
4
3
0
Rdst − n+1
n−1
Figure 4−33. RRCM, RRAM, RRUM and RLAM Instruction Format
15
12
C
11
10
n−1
9
4
Op-code
3
0
Rdst
16-Bit MSP430X CPU
4-51
MSP430X Extended Instructions
Figure 4−34. BRA Instruction Format
15
12
11
8
7
4
3
0
C
Rsrc
Op-code
0(PC)
C
#imm/abs19:16
Op-code
0(PC)
#imm15:0 / &abs15:0
C
Rsrc
Op-code
0(PC)
index15:0
Figure 4−35. CALLA Instruction Format
15
4
3
0
Op-code
Rdst
Op-code
Rdst
index15:0
Op-code
#imm15:0 / index15:0 / &abs15:0
4-52
16-Bit MSP430X CPU
#imm/ix/abs19:16
MSP430X Extended Instructions
Extended Emulated Instructions
The extended instructions together with the constant generator form the
extended Emulated instructions. Table 4−15 lists the Emulated instructions.
Table 4−15. Extended Emulated Instructions
Instruction
Explanation
Emulation
ADCX(.B,.A) dst
Add carry to dst
ADDCX(.B,.A) #0,dst
BRA dst
Branch indirect dst
MOVA dst,PC
RETA
Return from subroutine
MOVA @SP+,PC
CLRA Rdst
Clear Rdst
MOV #0,Rdst
CLRX(.B,.A) dst
Clear dst
MOVX(.B,.A) #0,dst
DADCX(.B,.A) dst
Add carry to dst decimally
DADDX(.B,.A) #0,dst
DECX(.B,.A) dst
Decrement dst by 1
SUBX(.B,.A) #1,dst
DECDA Rdst
Decrement dst by 2
SUBA #2,Rdst
DECDX(.B,.A) dst
Decrement dst by 2
SUBX(.B,.A) #2,dst
INCX(.B,.A) dst
Increment dst by 1
ADDX(.B,.A) #1,dst
INCDA Rdst
Increment Rdst by 2
ADDA #2,Rdst
INCDX(.B,.A) dst
Increment dst by 2
ADDX(.B,.A) #2,dst
INVX(.B,.A) dst
Invert dst
XORX(.B,.A) #-1,dst
RLAX(.B,.A) dst
Shift left dst arithmetically
ADDX(.B,.A) dst,dst
RLCX(.B,.A) dst
Shift left dst logically through carry
ADDCX(.B,.A) dst,dst
SBCX(.B,.A) dst
Subtract carry from dst
SUBCX(.B,.A) #0,dst
TSTA Rdst
Test Rdst (compare with 0)
CMPA #0,Rdst
TSTX(.B,.A) dst
Test dst (compare with 0)
CMPX(.B,.A) #0,dst
POPX dst
Pop to dst
MOVX(.B, .A) @SP+,dst
16-Bit MSP430X CPU
4-53
MSP430X Extended Instructions
MSP430X Address Instructions
MSP430X address instructions are instructions that support 20-bit operands
but have restricted addressing modes. The addressing modes are restricted
to the register mode and the Immediate mode, except for the MOVA instruction
as listed in Table 4−16. Restricting the addressing modes removes the need
for the additional extension-word op-code improving code density and
execution time. Address instructions should be used any time an MSP430X
instruction is needed with the corresponding restricted addressing mode.
Table 4−16.Address Instructions, Operate on 20-bit Registers Data
Status Bits
Mnemonic
Operands
ADDA
Rsrc,Rdst
#imm20,Rdst
MOVA
Rsrc,Rdst
Operation
V
N
Z
C
Add source to destination
register
*
*
*
*
Move source to destination
-
-
-
-
Compare source to destination register
*
*
*
*
Subtract source from destination register
*
*
*
*
#imm20,Rdst
z16(Rsrc),Rdst
EDE,Rdst
&abs20,Rdst
@Rsrc,Rdst
@Rsrc+,Rdst
Rsrc,z16(Rdst)
Rsrc,&abs20
CMPA
Rsrc,Rdst
#imm20,Rdst
SUBA
Rsrc,Rdst
#imm20,Rdst
4-54
16-Bit MSP430X CPU
MSP430X Extended Instructions
MSP430X Instruction Execution
The number of CPU clock cycles required for an MSP430X instruction
depends on the instruction format and the addressing modes used — not the
instruction itself. The number of clock cycles refers to MCLK.
MSP430X Format-II (Single-Operand) Instruction Cycles and Lengths
Table 4−17 lists the length and the CPU cycles for all addressing modes of the
MSP430X extended single-operand instructions.
Table 4−17.MSP430X Format II Instruction Cycles and Length
Execution Cycles/Length of Instruction (Words)
Instruction
Rn
@Rn
@Rn+
#N
X(Rn)
EDE
&EDE
RRAM
n/1
−
−
−
−
−
−
RRCM
n/1
−
−
−
−
−
−
RRUM
n/1
−
−
−
−
−
−
RLAM
n/1
−
−
−
−
−
−
PUSHM
2+n/1
−
−
−
−
−
−
PUSHM.A
2+2n/1
−
−
−
−
−
−
POPM
2+n/1
−
−
−
−
−
−
POPM.A
2+2n/1
−
−
−
−
−
−
6/2
6/2
4/1
5/1
5/1
4/2
6†/2
RRAX(.B)
1+n/2
4/2
4/2
−
5/3
5/3
5/3
RRAX.A
1+n/2
6/2
6/2
−
7/3
7/3
7/3
RRCX(.B)
1+n/2
4/2
4/2
−
5/3
5/3
5/3
RRCX.A
CALLA
†
1+n/2
6/2
6/2
−
7/3
7/3
7/3
PUSHX(.B)
4/2
4/2
4/2
4/3
5†/3
5/3
5/3
PUSHX.A
5/2
6/2
6/2
6/3
7†/3
7/3
7/3
POPX(.B)
3/2
−
−
−
5/3
5/3
5/3
POPX.A
4/2
−
−
−
7/3
7/3
7/3
Add one cycle when Rn = SP.
MSP430X Format-I (Double-Operand) Instruction Cycles and Lengths
Table 4−18 lists the length and CPU cycles for all addressing modes of the
MSP430X extended format-I instructions.
16-Bit MSP430X CPU
4-55
MSP430X Extended Instructions
Table 4−18.MSP430X Format-I Instruction Cycles and Length
Addressing Mode
Source Destination
Rn
@Rn
@Rn+
#N
X(Rn)
EDE
&EDE
†
Rm†
No. of
Cycles
.B/.W
.A
2
Length of
Instruction
.B/.W/.A
Examples
2
2
BITX.B R5,R8
PC
3
3
2
ADDX R9,PC
X(Rm)
5‡
7§
3
ANDX.A R5,4(R6)
EDE
5‡
7§
3
XORX R8,EDE
&EDE
5‡
7§
3
BITX.W R5,&EDE
Rm
3
4
2
BITX @R5,R8
PC
3
4
2
ADDX @R9,PC
X(Rm)
6‡
9§
3
ANDX.A @R5,4(R6)
EDE
6‡
9§
3
XORX @R8,EDE
&EDE
6‡
9§
3
BITX.B @R5,&EDE
Rm
3
4
2
BITX @R5+,R8
PC
4
5
2
ADDX.A @R9+,PC
X(Rm)
6‡
9§
3
ANDX @R5+,4(R6)
EDE
6‡
9§
3
XORX.B @R8+,EDE
&EDE
6‡
9§
3
BITX @R5+,&EDE
Rm
3
3
3
BITX #20,R8
PC¶
4
4
3
ADDX.A #FE000h,PC
X(Rm)
6‡
8§
4
ANDX #1234,4(R6)
EDE
6‡
8§
4
XORX #A5A5h,EDE
&EDE
6‡
8§
4
BITX.B #12,&EDE
Rm
4
5
3
BITX 2(R5),R8
PC¶
5
6
3
SUBX.A 2(R6),PC
X(Rm)
7‡
10§
4
ANDX 4(R7),4(R6)
EDE
7‡
10§
4
XORX.B 2(R6),EDE
&EDE
7‡
10§
4
BITX 8(SP),&EDE
Rm
4
5
3
BITX.B EDE,R8
PC¶
5
6
3
ADDX.A EDE,PC
X(Rm)
7‡
10§
4
ANDX EDE,4(R6)
EDE
7‡
10§
4
ANDX EDE,TONI
&TONI
7‡
10§
4
BITX EDE,&TONI
Rm
4
5
3
BITX &EDE,R8
PC¶
5
6
3
ADDX.A &EDE,PC
X(Rm)
7‡
10§
4
ANDX.B &EDE,4(R6)
TONI
7‡
10§
4
XORX &EDE,TONI
&TONI
7‡
10§
4
BITX &EDE,&TONI
Repeat instructions require n+1 cycles where n is the number of times the instruction is
executed.
‡ Reduce the cycle count by one for MOV, BIT, and CMP instructions.
§ Reduce the cycle count by two for MOV, BIT, and CMP instructions.
¶ Reduce the cycle count by one for MOV, ADD, and SUB instructions.
4-56
16-Bit MSP430X CPU
MSP430X Extended Instructions
MSP430X Address Instruction Cycles and Lengths
Table 4−19 lists the length and the CPU cycles for all addressing modes of the
MSP430X address instructions.
Table 4−19.Address Instruction Cycles and Length
Addressing Mode
Execution
Time MCLK
Cycles
MOVA
BRA
CMPA
ADDA
SUBA
Length of
Instruction
(Words)
Source
Destination
Rn
Rn
1
1
1
1
CMPA R5,R8
PC
2
2
1
1
SUBA R9,PC
x(Rm)
4
-
2
-
MOVA R5,4(R6)
EDE
4
-
2
-
MOVA R8,EDE
&EDE
4
-
2
-
MOVA R5,&EDE
Rm
3
-
1
-
MOVA @R5,R8
PC
3
-
1
-
MOVA @R9,PC
@Rn+
Rm
3
-
1
-
MOVA @R5+,R8
PC
3
-
1
-
MOVA @R9+,PC
#N
Rm
2
3
2
2
CMPA #20,R8
PC
3
3
2
2
SUBA #FE000h,PC
x(Rn)
Rm
4
-
2
-
MOVA 2(R5),R8
PC
4
-
2
-
MOVA 2(R6),PC
Rm
4
-
2
-
MOVA EDE,R8
PC
4
-
2
-
MOVA EDE,PC
Rm
4
-
2
-
MOVA &EDE,R8
PC
4
-
2
-
MOVA &EDE,PC
@Rn
EDE
&EDE
MOVA
CMPA
ADDA
SUBA
Example
16-Bit MSP430X CPU
4-57
Instruction Set Description
4.6 Instruction Set Description
The instruction map of the MSP430X shows all available instructions:
000
0xxx
10xx
14xx
18xx
1Cxx
20xx
24xx
28xx
2Cxx
30xx
34xx
38xx
3Cxx
4xxx
5xxx
6xxx
7xxx
8xxx
9xxx
Axxx
Bxxx
Cxxx
Dxxx
Exxx
Fxxx
4-58
040
080
0C0
100
140
180
1C0
200
240
280
2C0
300
340
MOVA, CMPA, ADDA, SUBA, RRCM, RRAM, RLAM, RRUM
RRC RRC.B SWPB
RRA
RRA.B SXT
PUSH PUSH.B CALL
PUSHM.A, POPM.A, PUSHM.W, POPM.W
Extension Word For Format I and Format II Instructions
JNE/JNZ
JEQ/JZ
JNC
JC
JN
JGE
JL
JMP
MOV, MOV.B
ADD, ADD.B
ADDC, ADDC.B
SUBC, SUBC.B
SUB, SUB.B
CMP, CMP.B
DADD, DADD.B
BIT, BIT.B
BIC, BIC.B
BIS, BIS.B
XOR, XOR.B
AND, AND.B
16-Bit MSP430X CPU
RETI CALLA
380
3C0
Instruction Set Description
4.6.1
Extended Instruction Binary Descriptions
Detailed MSP430X instruction binary descriptions are shown below.
Instruction
Group
Instruction
15
MOVA
0
0
0
0
0
0
0
0
0
0
src or
data.19:16
12 11
8
Instruction
Identifier
7
4
dst
3
0
src
0
0
0
0
dst
MOVA @Rsrc,Rdst
0
src
0
0
0
1
dst
MOVA @Rsrc+,Rdst
0
&abs.19:16
0
0
1
0
dst
MOVA &abs20,Rdst
0
1
1
dst
MOVA x(Rsrc),Rdst
&abs.15:0
0
0
0
0
src
0
±15-bit index x
x.15:0
0
0
0
0
src
0
1
1
0
&abs.19:16
MOVA Rsrc,&abs20
1
1
1
dst
MOVA Rsrc,X(Rdst)
&abs.15:0
0
0
0
0
src
0
±15-bit index x
x.15:0
0
0
0
0
imm.19:16
1
0
0
0
dst
MOVA #imm20,Rdst
0
0
1
dst
CMPA #imm20,Rdst
0
1
0
dst
ADDA #imm20,Rdst
0
1
1
dst
SUBA #imm20,Rdst
imm.15:0
CMPA
0
0
0
0
imm.19:16
1
imm.15:0
ADDA
0
0
0
0
imm.19:16
SUBA
0
0
0
0
imm.19:16
1
imm.15:0
1
imm.15:0
MOVA
0
0
0
0
src
1
1
0
0
dst
MOVA Rsrc,Rdst
CMPA
0
0
0
0
src
1
1
0
1
dst
CMPA Rsrc,Rdst
ADDA
0
0
0
0
src
1
1
1
0
dst
ADDA Rsrc,Rdst
SUBA
0
0
0
0
src
1
1
1
1
dst
SUBA Rsrc,Rdst
Instruction
Identifier
dst
Instruction
Group
Instruction
15
RRCM.A
0
0
RRAM.A
0
0
RLAM.A
0
RRUM.A
Bit
loc.
Inst.
ID
12 11 10 9
8
7
4
3
0
0
0
n−1
0
0
0
1
0
0
dst
RRCM.A #n,Rdst
0
0
n−1
0
1
0
1
0
0
dst
RRAM.A #n,Rdst
0
0
0
n−1
1
0
0
1
0
0
dst
RLAM.A #n,Rdst
0
0
0
0
n−1
1
1
0
1
0
0
dst
RRUM.A #n,Rdst
RRCM.W
0
0
0
0
n−1
0
0
0
1
0
1
dst
RRCM.W #n,Rdst
RRAM.W
0
0
0
0
n−1
0
1
0
1
0
1
dst
RRAM.W #n,Rdst
RLAM.W
0
0
0
0
n−1
1
0
0
1
0
1
dst
RLAM.W #n,Rdst
RRUM.W
0
0
0
0
n−1
1
1
0
1
0
1
dst
RRUM.W #n,Rdst
16-Bit MSP430X CPU
4-59
Instruction Set Description
Instruction Identifier
Instruction
15
12 11
RETI
0
0
0
1
0
0
CALLA
0
0
0
1
0
0
0
0
1
0
0
0
0
0
0
0
dst
8
7
6
5
4
3
0
1
1
0
0
0
0
0
0
1
1
0
1
0
0
dst
CALLA Rdst
0
0
1
1
0
1
0
1
dst
CALLA x(Rdst)
1
0
0
1
1
0
1
1
0
dst
CALLA @Rdst
0
1
0
0
1
1
0
1
1
1
dst
CALLA @Rdst+
0
1
0
0
1
1
1
0
0
0
&abs.19:16
CALLA &abs20
0
0
1
x.19:16
0
0
0
x.15:0
&abs.15:0
0
0
0
1
0
0
1
1
1
CALLA EDE
x.15:0
1
1
CALLA x(PC)
0
0
0
1
0
0
1
0
1
1
imm.19:16
1
0
1
0
x
x
x
x
1
1
x
x
x
x
x
x
CALLA #imm20
Reserved
0
0
0
1
0
0
1
1
Reserved
0
0
0
1
0
0
1
1
PUSHM.A
0
0
0
1
0
1
0
0
n−1
dst
PUSHM.A #n,Rdst
PUSHM.W
0
0
0
1
0
1
0
1
n−1
dst
PUSHM.W #n,Rdst
POPM.A
0
0
0
1
0
1
1
0
n−1
dst−n+1
POPM.A #n,Rdst
POPM.W
0
0
0
1
0
1
1
1
n−1
dst−n+1
POPM.W #n,Rdst
imm.15:0
4-60
16-Bit MSP430X CPU
MSP430 Instructions
4.6.2
MSP430 Instructions
The MSP430 instructions are listed and described on the following pages.
16-Bit MSP430X CPU
4-61
MSP430 Instructions
* ADC[.W]
* ADC.B
Add carry to destination
Add carry to destination
Syntax
ADC
ADC.B
Operation
dst + C −> dst
Emulation
ADDC
ADDC.B
Description
The carry bit (C) is added to the destination operand. The previous contents
of the destination are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Set if dst was incremented from 0FFFFh to 0000, reset otherwise
Set if dst was incremented from 0FFh to 00, reset otherwise
V: Set if an arithmetic overflow occurs, otherwise reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 16-bit counter pointed to by R13 is added to a 32-bit counter pointed to
by R12.
ADD
@R13,0(R12)
; Add LSDs
ADC
2(R12)
; Add carry to MSD
Example
The 8-bit counter pointed to by R13 is added to a 16-bit counter pointed to by
R12.
ADD.B
@R13,0(R12)
; Add LSDs
ADC.B
1(R12)
; Add carry to MSD
4-62
16-Bit MSP430X CPU
dst
dst
or
ADC.W
dst
#0,dst
#0,dst
MSP430 Instructions
ADD[.W]
ADD.B
Add source word to destination word
Add source byte to destination byte
Syntax
ADD
ADD.B
Operation
src + dst → dst
Description
The source operand is added to the destination operand. The previous content
of the destination is lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Ten is added to the 16-bit counter CNTR located in lower 64 K.
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if there is a carry from the MSB of the result, reset otherwise
Set if the result of two positive operands is negative, or if the result of
two negative numbers is positive, reset otherwise.
ADD.W
Example
src,dst or ADD.W src,dst
src,dst
#10,&CNTR
A table word pointed to by R5 (20-bit address in R5) is added to R6. The jump
to label TONI is performed on a carry.
ADD.W
@R5,R6
; Add table word to R6. R6.19:16 = 0
JC
TONI
; Jump if carry
...
Example
; Add 10 to 16-bit counter
; No carry
A table byte pointed to by R5 (20-bit address) is added to R6. The jump to label
TONI is performed if no carry occurs. The table pointer is auto-incremented by
1. R6.19:8 = 0
ADD.B
@R5+,R6
; Add byte to R6. R5 + 1. R6: 000xxh
JNC
TONI
; Jump if no carry
...
; Carry occurred
16-Bit MSP430X CPU
4-63
MSP430 Instructions
ADDC[.W]
ADDC.B
Add source word and carry to destination word
Add source byte and carry to destination byte
Syntax
ADDC
ADDC.B
Operation
src + dst + C → dst
Description
The source operand and the carry bit C are added to the destination operand.
The previous content of the destination is lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Constant value 15 and the carry of the previous instruction are added to the
16-bit counter CNTR located in lower 64 K.
#15,&CNTR
ADDC.W
@R5,R6
; Add table word + C to R6
JC
TONI
; Jump if carry
; No carry
A table byte pointed to by R5 (20-bit address) and the carry bit C are added to
R6. The jump to label TONI is performed if no carry occurs. The table pointer is
auto-incremented by 1. R6.19:8 = 0
ADDC.B
@R5+,R6
; Add table byte + C to R6. R5 + 1
JNC
TONI
; Jump if no carry
...
4-64
; Add 15 + C to 16-bit CNTR
A table word pointed to by R5 (20-bit address) and the carry C are added to R6.
The jump to label TONI is performed on a carry. R6.19:16 = 0
...
Example
src,dst
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if there is a carry from the MSB of the result, reset otherwise
Set if the result of two positive operands is negative, or if the result of
two negative numbers is positive, reset otherwise.
ADDC.W
Example
src,dst or ADDC.W
src,dst
16-Bit MSP430X CPU
; Carry occurred
MSP430 Instructions
AND[.W]
AND.B
Logical AND of source word with destination word
Logical AND of source byte with destination byte
Syntax
AND
AND.B
Operation
src .and. dst → dst
Description
The source operand and the destination operand are logically ANDed. The
result is placed into the destination. The source operand is not affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The bits set in R5 (16-bit data) are used as a mask (AA55h) for the word TOM
located in the lower 64 K. If the result is zero, a branch is taken to label TONI.
R5.19:16 = 0
src,dst or AND.W src,dst
src,dst
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if the result is not zero, reset otherwise. C = (.not. Z)
Reset
MOV
#AA55h,R5
; Load 16-bit mask to R5
AND
R5,&TOM
; TOM .and. R5 -> TOM
JZ
TONI
...
; Jump if result 0
; Result > 0
or shorter:
AND
JZ
Example
#AA55h,&TOM
TONI
; TOM .and. AA55h -> TOM
; Jump if result 0
A table byte pointed to by R5 (20-bit address) is logically ANDed with R6. R5 is
incremented by 1 after the fetching of the byte. R6.19:8 = 0
AND.B @R5+,R6
; AND table byte with R6. R5 + 1
16-Bit MSP430X CPU
4-65
MSP430 Instructions
BIC[.W]
BIC.B
Clear bits set in source word in destination word
Clear bits set in source byte in destination byte
Syntax
BIC
BIC.B
Operation
(.not. src) .and. dst → dst
Description
The inverted source operand and the destination operand are logically
ANDed. The result is placed into the destination. The source operand is not
affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The bits 15:14 of R5 (16-bit data) are cleared. R5.19:16 = 0
src,dst or BIC.W src,dst
src,dst
Not affected
Not affected
Not affected
Not affected
BIC
Example
#0C000h,R5
A table word pointed to by R5 (20-bit address) is used to clear bits in R7.
R7.19:16 = 0
BIC.W @R5,R7
Example
; Clear bits in R7 set in @R5
A table byte pointed to by R5 (20-bit address) is used to clear bits in Port1.
BIC.B @R5,&P1OUT
4-66
; Clear R5.19:14 bits
16-Bit MSP430X CPU
; Clear I/O port P1 bits set in @R5
MSP430 Instructions
BIS[.W]
BIS.B
Set bits set in source word in destination word
Set bits set in source byte in destination byte
Syntax
BIS
BIS.B
Operation
src .or. dst → dst
Description
The source operand and the destination operand are logically ORed. The
result is placed into the destination. The source operand is not affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Bits 15 and 13 of R5 (16-bit data) are set to one. R5.19:16 = 0
BIS
Example
src,dst or BIS.W src,dst
src,dst
Not affected
Not affected
Not affected
Not affected
#A000h,R5
A table word pointed to by R5 (20-bit address) is used to set bits in R7.
R7.19:16 = 0
BIS.W @R5,R7
Example
; Set R5 bits
; Set bits in R7
A table byte pointed to by R5 (20-bit address) is used to set bits in Port1. R5 is
incremented by 1 afterwards.
BIS.B
@R5+,&P1OUT
; Set I/O port P1 bits. R5 + 1
16-Bit MSP430X CPU
4-67
MSP430 Instructions
BIT[.W]
BIT.B
Test bits set in source word in destination word
Test bits set in source byte in destination byte
Syntax
BIT
BIT.B
Operation
src .and. dst
Description
The source operand and the destination operand are logically ANDed. The
result affects only the status bits in SR.
src,dst or BIT.W src,dst
src,dst
Register Mode: the register bits Rdst.19:16 (.W) resp. Rdst. 19:8 (.B) are not
cleared!
Status Bits
N:
Z:
C:
V:
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if the result is not zero, reset otherwise. C = (.not. Z)
Reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Test if one − or both − of bits 15 and 14 of R5 (16-bit data) is set. Jump to label
TONI if this is the case. R5.19:16 are not affected.
BIT
JNZ
#C000h,R5
TONI
...
Example
A table word pointed to by R5 (20-bit address) is used to test bits in R7. Jump to
label TONI if at least one bit is set. R7.19:16 are not affected.
BIT.W @R5,R7
; Test bits in R7
JC
; At least one bit is set
TONI
; Both are reset
A table byte pointed to by R5 (20-bit address) is used to test bits in output
Port1. Jump to label TONI if no bit is set. The next table byte is addressed.
BIT.B
@R5+,&P1OUT
JNC
TONI
...
4-68
; At least one bit is set in R5
; Both bits are reset
...
Example
; Test R5.15:14 bits
16-Bit MSP430X CPU
; Test I/O port P1 bits. R5 + 1
; No corresponding bit is set
; At least one bit is set
MSP430 Instructions
* BR, BRANCH
Branch to destination in lower 64K address space
Syntax
BR
Operation
dst −> PC
Emulation
MOV
Description
An unconditional branch is taken to an address anywhere in the lower 64K
address space. All source addressing modes can be used. The branch
instruction is a word instruction.
Status Bits
Status bits are not affected.
Example
Examples for all addressing modes are given.
dst
dst,PC
BR
#EXEC
;Branch to label EXEC or direct branch (e.g. #0A4h)
; Core instruction MOV @PC+,PC
BR
EXEC
; Branch to the address contained in EXEC
; Core instruction MOV X(PC),PC
; Indirect address
BR
&EXEC
; Branch to the address contained in absolute
; address EXEC
; Core instruction MOV X(0),PC
; Indirect address
BR
R5
; Branch to the address contained in R5
; Core instruction MOV R5,PC
; Indirect R5
BR
@R5
; Branch to the address contained in the word
; pointed to by R5.
; Core instruction MOV @R5,PC
; Indirect, indirect R5
BR
@R5+
; Branch to the address contained in the word pointed
; to by R5 and increment pointer in R5 afterwards.
; The next time—S/W flow uses R5 pointer—it can
; alter program execution due to access to
; next address in a table pointed to by R5
; Core instruction MOV @R5,PC
; Indirect, indirect R5 with autoincrement
BR
X(R5)
; Branch to the address contained in the address
; pointed to by R5 + X (e.g. table with address
; starting at X). X can be an address or a label
; Core instruction MOV X(R5),PC
; Indirect, indirect R5 + X
16-Bit MSP430X CPU
4-69
MSP430 Instructions
CALL
Call a Subroutine in lower 64 K
Syntax
CALL
Operation
dst → tmp
SP − 2 → SP
PC → @SP
tmp → PC
dst
16-bit dst is evaluated and stored
updated PC with return address to TOS
saved 16-bit dst to PC
Description
A subroutine call is made from an address in the lower 64 K to a subroutine
address in the lower 64 K. All seven source addressing modes can be used.
The call instruction is a word instruction. The return is made with the RET
instruction.
Status Bits
Not affected
PC.19:16:
Cleared (address in lower 64 K)
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Examples
Examples for all addressing modes are given.
Immediate Mode: Call a subroutine at label EXEC (lower 64 K) or call directly
to address.
CALL
#EXEC
; Start address EXEC
CALL
#0AA04h
; Start address 0AA04h
Symbolic Mode: Call a subroutine at the 16-bit address contained in address
EXEC. EXEC is located at the address (PC + X) where X is within PC±32 K.
CALL
EXEC
; Start address at @EXEC. z16(PC)
Absolute Mode: Call a subroutine at the 16-bit address contained in absolute
address EXEC in the lower 64 K.
CALL
&EXEC
; Start address at @EXEC
Register Mode: Call a subroutine at the 16-bit address contained in register
R5.15:0.
CALL
R5
; Start address at R5
Indirect Mode: Call a subroutine at the 16-bit address contained in the word
pointed to by register R5 (20-bit address).
CALL
4-70
16-Bit MSP430X CPU
@R5
; Start address at @R5
MSP430 Instructions
* CLR[.W]
* CLR.B
Clear destination
Clear destination
Syntax
CLR
CLR.B
Operation
0 −> dst
Emulation
MOV
MOV.B
Description
The destination operand is cleared.
Status Bits
Status bits are not affected.
Example
RAM word TONI is cleared.
CLR
Example
or CLR.W dst
#0,dst
#0,dst
TONI
; 0 −> TONI
Register R5 is cleared.
CLR
Example
dst
dst
R5
RAM byte TONI is cleared.
CLR.B
TONI
; 0 −> TONI
16-Bit MSP430X CPU
4-71
MSP430 Instructions
* CLRC
Clear carry bit
Syntax
CLRC
Operation
0 −> C
Emulation
BIC
Description
The carry bit (C) is cleared. The clear carry instruction is a word instruction.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 16-bit decimal counter pointed to by R13 is added to a 32-bit counter
pointed to by R12.
#1,SR
Not affected
Not affected
Cleared
Not affected
CLRC
DADD
DADC
4-72
16-Bit MSP430X CPU
; C=0: defines start
@R13,0(R12) ; add 16-bit counter to low word of 32-bit counter
2(R12)
; add carry to high word of 32-bit counter
MSP430 Instructions
* CLRN
Clear negative bit
Syntax
CLRN
Operation
0→N
or
(.NOT.src .AND. dst −> dst)
Emulation
BIC
Description
The constant 04h is inverted (0FFFBh) and is logically ANDed with the
destination operand. The result is placed into the destination. The clear
negative bit instruction is a word instruction.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The Negative bit in the status register is cleared. This avoids special treatment
with negative numbers of the subroutine called.
SUBR
SUBRET
#4,SR
Reset to 0
Not affected
Not affected
Not affected
CLRN
CALL
......
......
JN
......
......
......
RET
SUBR
SUBRET
; If input is negative: do nothing and return
16-Bit MSP430X CPU
4-73
MSP430 Instructions
* CLRZ
Clear zero bit
Syntax
CLRZ
Operation
0→Z
or
(.NOT.src .AND. dst −> dst)
Emulation
BIC
Description
The constant 02h is inverted (0FFFDh) and logically ANDed with the
destination operand. The result is placed into the destination. The clear zero
bit instruction is a word instruction.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The zero bit in the status register is cleared.
#2,SR
Not affected
Reset to 0
Not affected
Not affected
CLRZ
Indirect, Auto-Increment mode: Call a subroutine at the 16-bit address
contained in the word pointed to by register R5 (20-bit address) and increment
the 16-bit address in R5 afterwards by 2. The next time the software uses R5
as a pointer, it can alter the program execution due to access to the next word
address in the table pointed to by R5.
CALL
@R5+
; Start address at @R5. R5 + 2
Indexed mode: Call a subroutine at the 16-bit address contained in the 20-bit
address pointed to by register (R5 + X), e.g. a table with addresses starting at
X. The address is within the lower 64 KB. X is within ±32 KB.
CALL
4-74
16-Bit MSP430X CPU
X(R5)
; Start address at @(R5+X). z16(R5)
MSP430 Instructions
CMP[.W]
CMP.B
Compare source word and destination word
Compare source byte and destination byte
Syntax
CMP
CMP.B
Operation
(.not.src) + 1 + dst or dst − src
Description
The source operand is subtracted from the destination operand. This is made
by adding the 1’s complement of the source + 1 to the destination. The result
affects only the status bits in SR.
src,dst or CMP.W src,dst
src,dst
Register Mode: the register bits Rdst.19:16 (.W) resp. Rdst. 19:8 (.B) are not
cleared.
Status Bits
N:
Z:
C:
V:
Set if result is negative (src > dst), reset if positive (src = dst)
Set if result is zero (src = dst), reset otherwise (src ≠ dst)
Set if there is a carry from the MSB, reset otherwise
Set if the subtraction of a negative source operand from a positive destination operand delivers a negative result, or if the subtraction of a positive source operand from a negative destination operand delivers a
positive result, reset otherwise (no overflow).
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Compare word EDE
with a 16-bit constant 1800h. Jump to label TONI if
EDE equals the constant. The address of EDE is within PC ± 32 K.
CMP
#01800h,EDE
; Compare word EDE with 1800h
JEQ
TONI
; EDE contains 1800h
...
Example
; Not equal
A table word pointed to by (R5 + 10) is compared with R7. Jump to label TONI if
R7 contains a lower, signed 16-bit number. R7.19:16 is not cleared. The
address of the source operand is a 20-bit address in full memory range.
CMP.W 10(R5),R7
; Compare two signed numbers
JL
; R7 < 10(R5)
TONI
...
Example
; R7 >= 10(R5)
A table byte pointed to by R5 (20-bit address) is compared to the value in
output Port1. Jump to label TONI if values are equal. The next table byte is
addressed.
CMP.B @R5+,&P1OUT
JEQ
...
TONI
; Compare P1 bits with table. R5 + 1
; Equal contents
; Not equal
16-Bit MSP430X CPU
4-75
MSP430 Instructions
* DADC[.W]
* DADC.B
Add carry decimally to destination
Add carry decimally to destination
Syntax
DADC
DADC.B
Operation
dst + C −> dst (decimally)
Emulation
DADD
DADD.B
Description
The carry bit (C) is added decimally to the destination.
Status Bits
N: Set if MSB is 1
Z: Set if dst is 0, reset otherwise
C: Set if destination increments from 9999 to 0000, reset otherwise
Set if destination increments from 99 to 00, reset otherwise
V: Undefined
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The four-digit decimal number contained in R5 is added to an eight-digit decimal number pointed to by R8.
dst
dst
or
Example
R5,0(R8)
2(R8)
; Reset carry
; next instruction’s start condition is defined
; Add LSDs + C
; Add carry to MSD
The two-digit decimal number contained in R5 is added to a four-digit decimal
number pointed to by R8.
CLRC
DADD.B
DADC
4-76
src,dst
#0,dst
#0,dst
CLRC
DADD
DADC
DADC.W
16-Bit MSP430X CPU
R5,0(R8)
1(R8)
; Reset carry
; next instruction’s start condition is defined
; Add LSDs + C
; Add carry to MSDs
MSP430 Instructions
DADD[.W]
DADD.B
Add source word and carry decimally to destination word
Add source byte and carry decimally to destination byte
Syntax
DADD
DADD.B
Operation
src + dst + C → dst (decimally)
Description
The source operand and the destination operand are treated as two (.B) or four
(.W) binary coded decimals (BCD) with positive signs. The source operand
and the carry bit C are added decimally to the destination operand. The source
operand is not affected. The previous content of the destination is lost. The
result is not defined for non-BCD numbers.
Status Bits
N:
Z:
C:
V:
src,dst or DADD.W
src,dst
src,dst
Set if MSB of result is 1 (word > 7999h, byte > 79h), reset if MSB is 0.
Set if result is zero, reset otherwise
Set if the BCD result is too large (word > 9999h, byte > 99h), reset
otherwise
Undefined
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Decimal 10 is added to the 16-bit BCD counter DECCNTR.
DADD #10h,&DECCNTR ; Add 10 to 4-digit BCD counter
Example
The eight-digit BCD number contained in 16-bit RAM addresses BCD and
BCD+2 is added decimally to an eight-digit BCD number contained in R4 and
R5 (BCD+2 and R5 contain the MSDs). The carry C is added, and cleared.
CLRC
; Clear carry
DADD.W
&BCD,R4
; Add LSDs. R4.19:16 = 0
DADD.W
&BCD+2,R5
; Add MSDs with carry. R5.19:16 = 0
JC
OVERFLOW
...
Example
; Result >9999,9999: go to error
routine
; Result ok
The two-digit BCD number contained in word BCD (16-bit address) is added
decimally to a two-digit BCD number contained in R4. The carry C is added,
also. R4.19:8 = 0
CLRC
DADD.B
; Clear carry
&BCD,R4
; Add BCD to R4 decimally.
R4: 0,00ddh
16-Bit MSP430X CPU
4-77
MSP430 Instructions
* DEC[.W]
* DEC.B
Decrement destination
Decrement destination
Syntax
DEC
DEC.B
Operation
dst − 1 −> dst
Emulation
Emulation
SUB
SUB.B
Description
The destination operand is decremented by one. The original contents are
lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R10 is decremented by 1
dst
dst
or
DEC.W
dst
#1,dst
#1,dst
Set if result is negative, reset if positive
Set if dst contained 1, reset otherwise
Reset if dst contained 0, set otherwise
Set if an arithmetic overflow occurs, otherwise reset.
Set if initial value of destination was 08000h, otherwise reset.
Set if initial value of destination was 080h, otherwise reset.
DEC
R10
; Decrement R10
; Move a block of 255 bytes from memory location starting with EDE to memory location starting with
;TONI. Tables should not overlap: start of destination address TONI must not be within the range EDE
; to EDE+0FEh
;
MOV
#EDE,R6
MOV
#255,R10
L$1
MOV.B
@R6+,TONI−EDE−1(R6)
DEC
R10
JNZ
L$1
; Do not transfer tables using the routine above with the overlap shown in Figure 4−36.
Figure 4−36. Decrement Overlap
EDE
TONI
EDE+254
TONI+254
4-78
16-Bit MSP430X CPU
MSP430 Instructions
* DECD[.W]
* DECD.B
Double-decrement destination
Double-decrement destination
Syntax
DECD
DECD.B
Operation
dst − 2 −> dst
Emulation
Emulation
SUB
SUB.B
Description
The destination operand is decremented by two. The original contents are lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R10 is decremented by 2.
dst
dst
or
DECD.W
dst
#2,dst
#2,dst
Set if result is negative, reset if positive
Set if dst contained 2, reset otherwise
Reset if dst contained 0 or 1, set otherwise
Set if an arithmetic overflow occurs, otherwise reset.
Set if initial value of destination was 08001 or 08000h, otherwise reset.
Set if initial value of destination was 081 or 080h, otherwise reset.
DECD
R10
; Decrement R10 by two
; Move a block of 255 words from memory location starting with EDE to memory location
; starting with TONI
; Tables should not overlap: start of destination address TONI must not be within the
; range EDE to EDE+0FEh
;
MOV
#EDE,R6
MOV
#510,R10
L$1
MOV
@R6+,TONI−EDE−2(R6)
DECD
R10
JNZ
L$1
Example
Memory at location LEO is decremented by two.
DECD.B
LEO
; Decrement MEM(LEO)
Decrement status byte STATUS by two.
DECD.B
STATUS
16-Bit MSP430X CPU
4-79
MSP430 Instructions
* DINT
Disable (general) interrupts
Syntax
DINT
Operation
0 → GIE
or
(0FFF7h .AND. SR → SR
/
.NOT.src .AND. dst −> dst)
Emulation
BIC
Description
All interrupts are disabled.
The constant 08h is inverted and logically ANDed with the status register (SR).
The result is placed into the SR.
Status Bits
Status bits are not affected.
Mode Bits
GIE is reset. OSCOFF and CPUOFF are not affected.
Example
The general interrupt enable (GIE) bit in the status register is cleared to allow
a nondisrupted move of a 32-bit counter. This ensures that the counter is not
modified during the move by any interrupt.
DINT
NOP
MOV
MOV
EINT
#8,SR
; All interrupt events using the GIE bit are disabled
COUNTHI,R5 ; Copy counter
COUNTLO,R6
; All interrupt events using the GIE bit are enabled
Note: Disable Interrupt
If any code sequence needs to be protected from interruption, the DINT
should be executed at least one instruction before the beginning of the
uninterruptible sequence, or should be followed by a NOP instruction.
4-80
16-Bit MSP430X CPU
MSP430 Instructions
* EINT
Enable (general) interrupts
Syntax
EINT
Operation
1 → GIE
or
(0008h .OR. SR −> SR / .src .OR. dst −> dst)
Emulation
BIS
Description
All interrupts are enabled.
The constant #08h and the status register SR are logically ORed. The result
is placed into the SR.
Status Bits
Status bits are not affected.
Mode Bits
GIE is set. OSCOFF and CPUOFF are not affected.
Example
The general interrupt enable (GIE) bit in the status register is set.
#8,SR
; Interrupt routine of ports P1.2 to P1.7
; P1IN is the address of the register where all port bits are read. P1IFG is the address of
; the register where all interrupt events are latched.
;
PUSH.B &P1IN
BIC.B
@SP,&P1IFG ; Reset only accepted flags
EINT
; Preset port 1 interrupt flags stored on stack
; other interrupts are allowed
BIT
#Mask,@SP
JEQ
MaskOK
; Flags are present identically to mask: jump
......
MaskOK
BIC
#Mask,@SP
......
INCD
SP
; Housekeeping: inverse to PUSH instruction
; at the start of interrupt subroutine. Corrects
; the stack pointer.
RETI
Note: Enable Interrupt
The instruction following the enable interrupt instruction (EINT) is always
executed, even if an interrupt service request is pending when the interrupts
are enable.
16-Bit MSP430X CPU
4-81
MSP430 Instructions
* INC[.W]
* INC.B
Increment destination
Increment destination
Syntax
INC
INC.B
Operation
dst + 1 −> dst
Emulation
ADD
Description
The destination operand is incremented by one. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
C: Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
V: Set if dst contained 07FFFh, reset otherwise
Set if dst contained 07Fh, reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The status byte, STATUS, of a process is incremented. When it is equal to 11,
a branch to OVFL is taken.
dst
dst
#1,dst
INC.B
CMP.B
JEQ
4-82
16-Bit MSP430X CPU
or INC.W dst
STATUS
#11,STATUS
OVFL
MSP430 Instructions
* INCD[.W]
* INCD.B
Double-increment destination
Double-increment destination
Syntax
INCD
INCD.B
Operation
dst + 2 −> dst
Emulation
Emulation
ADD
ADD.B
Example
The destination operand is incremented by two. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFEh, reset otherwise
Set if dst contained 0FEh, reset otherwise
C: Set if dst contained 0FFFEh or 0FFFFh, reset otherwise
Set if dst contained 0FEh or 0FFh, reset otherwise
V: Set if dst contained 07FFEh or 07FFFh, reset otherwise
Set if dst contained 07Eh or 07Fh, reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The item on the top of the stack (TOS) is removed without using a register.
dst
dst
or INCD.W
dst
#2,dst
#2,dst
.......
PUSH
R5
INCD
SP
; R5 is the result of a calculation, which is stored
; in the system stack
; Remove TOS by double-increment from stack
; Do not use INCD.B, SP is a word-aligned
; register
RET
Example
The byte on the top of the stack is incremented by two.
INCD.B
0(SP)
; Byte on TOS is increment by two
16-Bit MSP430X CPU
4-83
MSP430 Instructions
* INV[.W]
* INV.B
Invert destination
Invert destination
Syntax
INV
INV.B
Operation
.NOT.dst −> dst
Emulation
Emulation
XOR
XOR.B
Description
The destination operand is inverted. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
C: Set if result is not zero, reset otherwise ( = .NOT. Zero)
Set if result is not zero, reset otherwise ( = .NOT. Zero)
V: Set if initial destination operand was negative, otherwise reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Content of R5 is negated (twos complement).
MOV
#00AEh,R5 ;
INV
R5
; Invert R5,
INC
R5
; R5 is now negated,
Example
#0FFFFh,dst
#0FFh,dst
R5 = 000AEh
R5 = 0FF51h
R5 = 0FF52h
Content of memory byte LEO is negated.
MOV.B
INV.B
INC.B
4-84
dst
dst
16-Bit MSP430X CPU
#0AEh,LEO ;
MEM(LEO) = 0AEh
LEO
; Invert LEO,
MEM(LEO) = 051h
LEO
; MEM(LEO) is negated,MEM(LEO) = 052h
MSP430 Instructions
JC
JHS
Jump if carry
Jump if Higher or Same (unsigned)
Syntax
JC
label
JHS
label
Operation
If C = 1:
If C = 0:
PC + (2 × Offset) → PC
execute the following instruction
Description
The carry bit C in the status register is tested. If it is set, the signed 10-bit word
offset contained in the instruction is multiplied by two, sign extended, and
added to the 20-bit program counter PC. This means a jump in the range -511
to +512 words relative to the PC in the full memory range. If C is reset, the
instruction after the jump is executed.
JC is used for the test of the carry bit C
JHS is used for the comparison of unsigned numbers
Status Bits
Status bits are not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected
Example
The state of the port 1 pin P1IN.1 bit defines the program flow.
BIT.B
#2,&P1IN
; Port 1, bit 1 set? Bit -> C
JC
Label1
; Yes, proceed at Label1
...
Example
; No, continue
If R5 ≥ R6 (unsigned) the program continues at Label2
CMP
R6,R5
; Is R5 ≥ R6? Info to C
JHS
Label2
; Yes, C = 1
...
Example
; No, R5 < R6. Continue
If R5 ≥ 12345h (unsigned operands) the program continues at Label2
CMPA #12345h,R5
; Is R5 ≥ 12345h? Info to C
JHS
; Yes, 12344h < R5 <= F,FFFFh. C = 1
...
Label2
; No, R5 < 12345h. Continue
16-Bit MSP430X CPU
4-85
MSP430 Instructions
JEQ,JZ
Jump if equal,Jump if zero
Syntax
JZ
label
JEQ
label
Operation
If Z = 1:
If Z = 0:
PC + (2 × Offset) → PC
execute following instruction
Description
The Zero bit Z in the status register is tested. If it is set, the signed 10-bit word
offset contained in the instruction is multiplied by two, sign extended, and
added to the 20-bit program counter PC. This means a jump in the range -511
to +512 words relative to the PC in the full memory range. If Z is reset, the
instruction after the jump is executed.
JZ is used for the test of the Zero bit Z
JEQ is used for the comparison of operands
Status Bits
Status bits are not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected
Example
The state of the P2IN.0 bit defines the program flow
BIT.B
#1,&P2IN
; Port 2, bit 0 reset?
JZ
Label1
; Yes, proceed at Label1
...
Example
; No, set, continue
If R5 = 15000h (20-bit data) the program continues at Label2
CMPA #15000h,R5
; Is R5 = 15000h? Info to SR
JEQ
; Yes, R5 = 15000h. Z = 1
Label2
; No, R5 ≠ 15000h. Continue
...
Example
R7 (20-bit counter) is incremented. If its content is zero, the program continues
at Label4.
ADDA #1,R7
; Increment R7
JZ
; Zero reached: Go to Label4
...
4-86
16-Bit MSP430X CPU
Label4
; R7 ≠ 0. Continue here.
MSP430 Instructions
JGE
Jump if Greater or Equal (signed)
Syntax
JGE
Operation
If (N .xor. V) = 0:
If (N .xor. V) = 1:
Description
The negative bit N and the overflow bit V in the status register are tested. If both
bits are set or both are reset, the signed 10-bit word offset contained in the
instruction is multiplied by two, sign extended, and added to the 20-bit program
counter PC. This means a jump in the range -511 to +512 words relative to the
PC in full Memory range. If only one bit is set, the instruction after the jump is
executed.
label
PC + (2 × Offset) → PC
execute following instruction
JGE is used for the comparison of signed operands: also for incorrect results
due to overflow, the decision made by the JGE instruction is correct.
Note: JGE emulates the non-implemented JP (jump if positive) instruction if
used after the instructions AND, BIT, RRA, SXTX and TST. These instructions
clear the V-bit.
Status Bits
Status bits are not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected
Example
If byte EDE (lower 64 K) contains positive data, go to Label1. Software can run
in the full memory range.
TST.B
&EDE
; Is EDE positive? V <- 0
JGE
Label1
; Yes, JGE emulates JP
...
Example
; No, 80h <= EDE <= FFh
If the content of R6 is greater than or equal to the memory pointed to by R7, the
program continues a Label5. Signed data. Data and program in full memory
range.
CMP
@R7,R6
; Is R6 ≥ @R7?
JGE
Label5
; Yes, go to Label5
...
Example
; No, continue here.
If R5 ≥ 12345h (signed operands) the program continues at Label2. Program
in full memory range.
CMPA
#12345h,R5
; Is R5 ≥ 12345h?
JGE
Label2
; Yes, 12344h < R5 <= 7FFFFh.
...
; No, 80000h <= R5 < 12345h.
16-Bit MSP430X CPU
4-87
MSP430 Instructions
JL
Jump if Less (signed)
Syntax
JL
Operation
If (N .xor. V) = 1:
If (N .xor. V) = 0:
Description
The negative bit N and the overflow bit V in the status register are tested. If only
one is set, the signed 10-bit word offset contained in the instruction is multiplied
by two, sign extended, and added to the 20-bit program counter PC. This
means a jump in the range -511 to +512 words relative to the PC in full memory
range. If both bits N and V are set or both are reset, the instruction after the
jump is executed.
label
PC + (2 × Offset) → PC
execute following instruction
JL is used for the comparison of signed operands: also for incorrect results due
to overflow, the decision made by the JL instruction is correct.
Status Bits
Status bits are not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected
Example
If byte EDE contains a smaller, signed operand than byte TONI, continue at
Label1. The address EDE is within PC ± 32 K.
CMP.B
&TONI,EDE
JL
Label1
...
Example
If the signed content of R6 is less than the memory pointed to by R7 (20-bit
address) the program continues at Label Label5. Data and program in full
memory range.
CMP
@R7,R6
; Is R6 < @R7?
JL
Label5
; Yes, go to Label5
; No, continue here.
If R5 < 12345h (signed operands) the program continues at Label2. Data and
program in full memory range.
CMPA
#12345h,R5
; Is R5 < 12345h?
JL
Label2
; Yes, 80000h =< R5 < 12345h.
...
4-88
; Yes
; No, TONI <= EDE
...
Example
; Is EDE < TONI
16-Bit MSP430X CPU
; No, 12344h < R5 =< 7FFFFh.
MSP430 Instructions
JMP
Jump unconditionally
Syntax
JMP
Operation
PC + (2 × Offset) → PC
Description
The signed 10-bit word offset contained in the instruction is multiplied by two,
sign extended, and added to the 20-bit program counter PC. This means an
unconditional jump in the range -511 to +512 words relative to the PC in the full
memory. The JMP instruction may be used as a BR or BRA instruction within its
limited range relative to the program counter.
Status Bits
Status bits are not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected
Example
The byte STATUS is set to 10. Then a jump to label MAINLOOP is made. Data
in lower 64 K, program in full memory range.
Example
label
MOV.B
#10,&STATUS ; Set STATUS to 10
JMP
MAINLOOP
; Go to main loop
The interrupt vector TAIV of Timer_A3 is read and used for the program flow.
Program in full memory range, but interrupt handlers always starts in lower
64K.
ADD
&TAIV,PC
RETI
; Add Timer_A interrupt vector to PC
; No Timer_A interrupt pending
JMP
IHCCR1
; Timer block 1 caused interrupt
JMP
IHCCR2
; Timer block 2 caused interrupt
RETI
; No legal interrupt, return
16-Bit MSP430X CPU
4-89
MSP430 Instructions
JN
Jump if Negative
Syntax
JN
label
Operation
If N = 1:
If N = 0:
PC + (2 × Offset) → PC
execute following instruction
Description
The negative bit N in the status register is tested. If it is set, the signed 10-bit
word offset contained in the instruction is multiplied by two, sign extended, and
added to the 20-bit program counter PC. This means a jump in the range -511
to +512 words relative to the PC in the full memory range. If N is reset, the
instruction after the jump is executed.
Status Bits
Status bits are not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected
Example
The byte COUNT is tested. If it is negative, program execution continues at
Label0. Data in lower 64 K, program in full memory range.
TST.B
&COUNT
; Is byte COUNT negative?
JN
Label0
; Yes, proceed at Label0
; COUNT ≥ 0
...
Example
R6 is subtracted from R5. If the result is negative, program continues at
Label2. Program in full memory range.
SUB
R6,R5
; R5 − R6 -> R5
JN
Label2
; R5 is negative: R6 > R5 (N = 1)
; R5 ≥ 0. Continue here.
...
Example
R7 (20-bit counter) is decremented. If its content is below zero, the program
continues at Label4. Program in full memory range.
SUBA
#1,R7
; Decrement R7
JN
Label4
; R7 < 0: Go to Label4
...
4-90
16-Bit MSP430X CPU
; R7 ≥ 0. Continue here.
MSP430 Instructions
JNC
JLO
Jump if No carry
Jump if lower (unsigned)
Syntax
JNC
JLO
label
label
Operation
If C = 0:
If C = 1:
PC + (2 × Offset) → PC
execute following instruction
Description
The carry bit C in the status register is tested. If it is reset, the signed 10-bit
word offset contained in the instruction is multiplied by two, sign extended, and
added to the 20-bit program counter PC. This means a jump in the range -511
to +512 words relative to the PC in the full memory range. If C is set, the
instruction after the jump is executed.
JNC is used for the test of the carry bit C
JLO is used for the comparison of unsigned numbers .
Status Bits
Status bits are not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected
Example
If byte EDE < 15 the program continues at Label2. Unsigned data. Data in
lower 64 K, program in full memory range.
CMP.B
#15,&EDE
; Is EDE < 15? Info to C
JLO
Label2
; Yes, EDE < 15. C = 0
; No, EDE ≥ 15. Continue
...
Example
The word TONI is added to R5. If no carry occurs, continue at Label0. The
address of TONI is within PC ± 32 K.
ADD
TONI,R5
; TONI + R5 -> R5. Carry -> C
JNC
Label0
; No carry
...
; Carry = 1: continue here
16-Bit MSP430X CPU
4-91
MSP430 Instructions
JNZ
JNE
Jump if Not Zero
Jump if Not Equal
Syntax
JNZ
JNE
label
label
Operation
If Z = 0:
If Z = 1:
PC + (2 × Offset) → PC
execute following instruction
Description
The zero bit Z in the status register is tested. If it is reset, the signed 10-bit word
offset contained in the instruction is multiplied by two, sign extended, and
added to the 20-bit program counter PC. This means a jump in the range -511
to +512 words relative to the PC in the full memory range. If Z is set, the
instruction after the jump is executed.
JNZ is used for the test of the Zero bit Z
JNE is used for the comparison of operands
Status Bits
Status bits are not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected
Example
The byte STATUS is tested. If it is not zero, the program continues at Label3.
The address of STATUS is within PC ± 32 K.
TST.B
STATUS
; Is STATUS = 0?
JNZ
Label3
; No, proceed at Label3
...
Example
; Yes, continue here
If word EDE ≠ 1500 the program continues at Label2. Data in lower 64 K,
program in full memory range.
CMP
#1500,&EDE
; Is EDE = 1500? Info to SR
JNE
Label2
; No, EDE ≠ 1500.
...
Example
R7 (20-bit counter) is decremented. If its content is not zero, the program
continues at Label4. Program in full memory range.
SUBA
#1,R7
; Decrement R7
JNZ
Label4
; Zero not reached: Go to Label4
...
4-92
; Yes, R5 = 1500. Continue
16-Bit MSP430X CPU
; Yes, R7 = 0. Continue here.
MSP430 Instructions
MOV[.W]
MOV.B
Move source word to destination word
Move source byte to destination byte
Syntax
MOV
MOV.B
Operation
src → dst
Description
The source operand is copied to the destination. The source operand is not
affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Move a 16-bit constant 1800h to absolute address-word EDE (lower 64 K).
Not affected
Not affected
Not affected
Not affected
MOV
Example
src,dst or MOV.W src,dst
src,dst
#01800h,&EDE
; Move 1800h to EDE
The contents of table EDE (word data, 16-bit addresses) are copied to table
TOM. The length of the tables is 030h words. Both tables reside in the lower
64K.
Loop
MOV
#EDE,R10
MOV
@R10+,TOM-EDE-2(R10) ; R10 points to both tables.
R10+2
CMP
#EDE+60h,R10
; End of table reached?
JLO
Loop
; Not yet
...
Example
; Prepare pointer (16-bit address)
; Copy completed
The contents of table EDE (byte data, 16-bit addresses) are copied to table
TOM. The length of the tables is 020h bytes. Both tables may reside in full
memory range, but must be within R10 ±32 K.
Loop
MOVA
#EDE,R10
; Prepare pointer (20-bit)
MOV
#20h,R9
; Prepare counter
MOV.B
@R10+,TOM-EDE-1(R10) ; R10 points to both tables.
; R10+1
DEC
R9
; Decrement counter
JNZ
Loop
; Not yet done
...
; Copy completed
16-Bit MSP430X CPU
4-93
MSP430 Instructions
* NOP
No operation
Syntax
NOP
Operation
None
Emulation
MOV
Description
No operation is performed. The instruction may be used for the elimination of
instructions during the software check or for defined waiting times.
Status Bits
Status bits are not affected.
4-94
16-Bit MSP430X CPU
#0, R3
MSP430 Instructions
* POP[.W]
* POP.B
Pop word from stack to destination
Pop byte from stack to destination
Syntax
POP
POP.B
Operation
@SP −> temp
SP + 2 −> SP
temp −> dst
Emulation
Emulation
MOV
MOV.B
Description
The stack location pointed to by the stack pointer (TOS) is moved to the
destination. The stack pointer is incremented by two afterwards.
Status Bits
Status bits are not affected.
Example
The contents of R7 and the status register are restored from the stack.
POP
POP
Example
R7
SR
or
MOV.W
@SP+,dst
; Restore R7
; Restore status register
LEO
; The low byte of the stack is moved to LEO.
The contents of R7 is restored from the stack.
POP.B
Example
@SP+,dst
@SP+,dst
The contents of RAM byte LEO is restored from the stack.
POP.B
Example
dst
dst
R7
; The low byte of the stack is moved to R7,
; the high byte of R7 is 00h
The contents of the memory pointed to by R7 and the status register are
restored from the stack.
POP.B
0(R7)
POP
SR
; The low byte of the stack is moved to the
; the byte which is pointed to by R7
: Example: R7 = 203h
;
Mem(R7) = low byte of system stack
: Example: R7 = 20Ah
;
Mem(R7) = low byte of system stack
; Last word on stack moved to the SR
Note: The System Stack Pointer
The system stack pointer (SP) is always incremented by two, independent
of the byte suffix.
16-Bit MSP430X CPU
4-95
MSP430 Instructions
PUSH[.W]
PUSH.B
Save a word on the stack
Save a byte on the stack
Syntax
PUSH
PUSH.B
Operation
SP − 2 → SP
dst
→ @SP
Description
The 20-bit stack pointer SP is decremented by two. The operand is then copied
to the RAM word addressed by the SP. A pushed byte is stored in the low byte,
the high byte is not affected.
Status Bits
Not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Save the two 16-bit registers R9 and R10 on the stack.
Example
4-96
dst or PUSH.W
dst
dst
PUSH
R9
; Save R9 and R10 XXXXh
PUSH
R10
; YYYYh
Save the two bytes EDE and TONI on the stack. The addresses EDE and TONI
are within PC ± 32 K.
PUSH.B
EDE
; Save EDE xxXXh
PUSH.B
TONI
; Save TONI
16-Bit MSP430X CPU
xxYYh
MSP430 Instructions
RET
Return from subroutine
Syntax
RET
Operation
@SP → PC.15:0
SP + 2 → SP
Description
The 16-bit return address (lower 64 K), pushed onto the stack by a CALL
instruction is restored to the PC. The program continues at the address
following the subroutine call. The four MSBs of the program counter PC.19:16
are cleared.
Status Bits
Not affected
PC.19:16:
Saved PC to PC.15:0.
PC.19:16 ← 0
Cleared
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Call a subroutine SUBR in the lower 64 K and return to the address in the lower
64K after the CALL
CALL
#SUBR
; Call subroutine starting at SUBR
...
SUBR PUSH
; Return by RET to here
R14
; Save R14 (16 bit data)
...
POP
; Subroutine code
R14
; Restore R14
RET
; Return to lower 64 K
Figure 4−37. The Stack After a RET Instruction
Item n
SP
SP
Item n
PCReturn
Stack before RET
instruction
Stack after RET
instruction
16-Bit MSP430X CPU
4-97
MSP430 Instructions
RETI
Return from interrupt
Syntax
RETI
Operation
@SP →
SP + 2 →
@SP →
SP + 2 →
Description
The status register is restored to the value at the beginning of the interrupt
service routine. This includes the four MSBs of the program counter PC.19:16.
The stack pointer is incremented by two afterwards.
SR.15:0
Restore saved status register SR with PC.19:16
SP
PC.15:0
Restore saved program counter PC.15:0
SP House keeping
The 20-bit PC is restored from PC.19:16 (from same stack location as the
status bits) and PC.15:0. The 20-bit program counter is restored to the value
at the beginning of the interrupt service routine. The program continues at the
address following the last executed instruction when the interrupt was granted.
The stack pointer is incremented by two afterwards.
Status Bits
N:
Z:
C:
V:
restored from stack
restored from stack
restored from stack
restored from stack
Mode Bits
OSCOFF, CPUOFF, and GIE are restored from stack
Example
Interrupt handler in the lower 64 K. A 20-bit return address is stored on the
stack.
INTRPT PUSHM.A
#2,R14
...
POPM.A
RETI
4-98
16-Bit MSP430X CPU
; Save R14 and R13 (20-bit data)
; Interrupt handler code
#2,R14
; Restore R13 and R14 (20-bit data)
; Return to 20-bit address in full memory range
MSP430 Instructions
* RLA[.W]
* RLA.B
Rotate left arithmetically
Rotate left arithmetically
Syntax
RLA
RLA.B
Operation
C <− MSB <− MSB−1 .... LSB+1 <− LSB <− 0
Emulation
ADD
ADD.B
Description
The destination operand is shifted left one position as shown in Figure 4−38.
The MSB is shifted into the carry bit (C) and the LSB is filled with 0. The RLA
instruction acts as a signed multiplication by 2.
dst
dst
or
RLA.W
dst
dst,dst
dst,dst
An overflow occurs if dst ≥ 04000h and dst < 0C000h before operation is
performed: the result has changed sign.
Figure 4−38. Destination Operand—Arithmetic Shift Left
Word
15
0
0
C
Byte
7
0
An overflow occurs if dst ≥ 040h and dst < 0C0h before the operation is
performed: the result has changed sign.
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Loaded from the MSB
Set if an arithmetic overflow occurs:
the initial value is 04000h ≤ dst < 0C000h; reset otherwise
Set if an arithmetic overflow occurs:
the initial value is 040h ≤ dst < 0C0h; reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R7 is multiplied by 2.
RLA
Example
R7
; Shift left R7 (× 2)
The low byte of R7 is multiplied by 4.
RLA.B
RLA.B
R7
R7
; Shift left low byte of R7 (× 2)
; Shift left low byte of R7 (× 4)
Note: RLA Substitution
The assembler does not recognize the instruction:
RLA
@R5+,
RLA.B @R5+,
or
RLA(.B) @R5
ADD @R5+,−2(R5) ADD.B @R5+,−1(R5) or
ADD(.B) @R5
It must be substituted by:
16-Bit MSP430X CPU
4-99
MSP430 Instructions
* RLC[.W]
* RLC.B
Rotate left through carry
Rotate left through carry
Syntax
RLC
RLC.B
Operation
C <− MSB <− MSB−1 .... LSB+1 <− LSB <− C
Emulation
ADDC
Description
The destination operand is shifted left one position as shown in Figure 4−39.
The carry bit (C) is shifted into the LSB and the MSB is shifted into the carry
bit (C).
dst
dst
or
RLC.W
dst
dst,dst
Figure 4−39. Destination Operand—Carry Left Shift
Word
15
0
7
0
C
Byte
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Loaded from the MSB
Set if an arithmetic overflow occurs
the initial value is 04000h ≤ dst < 0C000h; reset otherwise
Set if an arithmetic overflow occurs:
the initial value is 040h ≤ dst < 0C0h; reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R5 is shifted left one position.
RLC
Example
The input P1IN.1 information is shifted into the LSB of R5.
BIT.B
RLC
Example
; (R5 x 2) + C −> R5
R5
; Information −> Carry
; Carry=P0in.1 −> LSB of R5
#2,&P1IN
R5
The MEM(LEO) content is shifted left one position.
RLC.B
; Mem(LEO) x 2 + C −> Mem(LEO)
LEO
Note: RLC and RLC.B Substitution
The assembler does not recognize the instruction:
RLC @R5+,
RLC.B @R5+,
or RLC(.B) @R5
It must be substituted by:
ADDC @R5+,−2(R5) ADDC.B
4-100
16-Bit MSP430X CPU
@R5+,−1(R5) or ADDC(.B) @R5
MSP430 Instructions
RRA[.W]
RRA.B
Rotate Right Arithmetically destination word
Rotate Right Arithmetically destination byte
Syntax
RRA.B
Operation
MSB → MSB → MSB-1 .
Description
The destination operand is shifted right arithmetically by one bit position as
shown in Figure 4−40. The MSB retains its value (sign). RRA operates equal to
a signed division by 2. The MSB is retained and shifted into the MSB-1. The
LSB+1 is shifted into the LSB. The previous LSB is shifted into the carry bit C.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The signed 16-bit number in R5 is shifted arithmetically right one position.
dst or RRA.W dst
→C
Set if result is negative (MSB = 1), reset otherwise (MSB = 0)
Set if result is zero, reset otherwise
Loaded from the LSB
Reset
RRA
Example
→... LSB+1 → LSB
R5
; R5/2 -> R5
The signed RAM byte EDE is shifted arithmetically right one position.
RRA.B
EDE
; EDE/2 -> EDE
Figure 4−40. Rotate Right Arithmetically RRA.B and RRA.W
19
C
0
15
0
0
0
19
C
0
0
0
0
0
0
0
0
0
0
0
0
7
0
MSB
LSB
15
0
MSB
LSB
16-Bit MSP430X CPU
4-101
MSP430 Instructions
RRC[.W]
RRC.B
Rotate Right through carry destination word
Rotate Right through carry destination byte
Syntax
RRC
RRC.B
Operation
C → MSB → MSB-1 → ... LSB+1 → LSB → C
Description
The destination operand is shifted right by one bit position as shown in
Figure 4−41. The carry bit C is shifted into the MSB and the LSB is shifted into
the carry bit C.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
RAM word EDE is shifted right one bit position. The MSB is loaded with 1.
dst or RRC.W dst
dst
Set if result is negative (MSB = 1), reset otherwise (MSB = 0)
Set if result is zero, reset otherwise
Loaded from the LSB
Reset
SETC
; Prepare carry for MSB
RRC
EDE
; EDE = EDE » 1 + 8000h
Figure 4−41. Rotate Right through Carry RRC.B and RRC.W
19
C
0
15
0
0
0
19
C
4-102
16-Bit MSP430X CPU
0
0
0
0
0
0
0
0
0
0
0
0
7
0
MSB
LSB
15
0
MSB
LSB
MSP430 Instructions
* SBC[.W]
* SBC.B
Subtract source and borrow/.NOT. carry from destination
Subtract source and borrow/.NOT. carry from destination
Syntax
SBC
SBC.B
Operation
dst + 0FFFFh + C −> dst
dst + 0FFh + C −> dst
Emulation
SUBC
SUBC.B
Description
The carry bit (C) is added to the destination operand minus one. The previous
contents of the destination are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Set if there is a carry from the MSB of the result, reset otherwise.
Set to 1 if no borrow, reset if borrow.
V: Set if an arithmetic overflow occurs, reset otherwise.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 16-bit counter pointed to by R13 is subtracted from a 32-bit counter
pointed to by R12.
SUB
SBC
Example
dst
dst
or
SBC.W
dst
#0,dst
#0,dst
@R13,0(R12)
2(R12)
; Subtract LSDs
; Subtract carry from MSD
The 8-bit counter pointed to by R13 is subtracted from a 16-bit counter pointed
to by R12.
SUB.B
SBC.B
@R13,0(R12)
1(R12)
; Subtract LSDs
; Subtract carry from MSD
Note: Borrow Implementation.
The borrow is treated as a .NOT. carry :
Borrow
Yes
No
Carry bit
0
1
16-Bit MSP430X CPU
4-103
MSP430 Instructions
* SETC
Set carry bit
Syntax
SETC
Operation
1 −> C
Emulation
BIS
Description
The carry bit (C) is set.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Emulation of the decimal subtraction:
Subtract R5 from R6 decimally
Assume that R5 = 03987h and R6 = 04137h
DSUB
ADD
#06666h,R5
INV
R5
SETC
DADD
R5,R6
4-104
#1,SR
Not affected
Not affected
Set
Not affected
16-Bit MSP430X CPU
; Move content R5 from 0−9 to 6−0Fh
; R5 = 03987h + 06666h = 09FEDh
; Invert this (result back to 0−9)
; R5 = .NOT. R5 = 06012h
; Prepare carry = 1
; Emulate subtraction by addition of:
; (010000h − R5 − 1)
; R6 = R6 + R5 + 1
; R6 = 0150h
MSP430 Instructions
* SETN
Set negative bit
Syntax
SETN
Operation
1 −> N
Emulation
BIS
Description
The negative bit (N) is set.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
#4,SR
Set
Not affected
Not affected
Not affected
16-Bit MSP430X CPU
4-105
MSP430 Instructions
* SETZ
Set zero bit
Syntax
SETZ
Operation
1 −> Z
Emulation
BIS
Description
The zero bit (Z) is set.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
4-106
#2,SR
Not affected
Set
Not affected
Not affected
16-Bit MSP430X CPU
MSP430 Instructions
SUB[.W]
SUB.B
Subtract source word from destination word
Subtract source byte from destination byte
Syntax
SUB
SUB.B
Operation
(.not.src) + 1 + dst → dst
Description
The source operand is subtracted from the destination operand. This is made
by adding the 1’s complement of the source + 1 to the destination. The source
operand is not affected, the result is written to the destination operand.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
A 16-bit constant 7654h is subtracted from RAM word EDE.
#7654h,&EDE ; Subtract 7654h from EDE
A table word pointed to by R5 (20-bit address) is subtracted from R7.
Afterwards, if R7 contains zero, jump to label TONI. R5 is then
auto-incremented by 2. R7.19:16 = 0.
SUB
@R5+,R7
; Subtract table number from R7. R5 + 2
JZ
TONI
; R7 = @R5 (before subtraction)
...
Example
or dst − src → dst
Set if result is negative (src > dst), reset if positive (src <= dst)
Set if result is zero (src = dst), reset otherwise (src ≠ dst)
Set if there is a carry from the MSB, reset otherwise
Set if the subtraction of a negative source operand from a positive destination operand delivers a negative result, or if the subtraction of a positive source operand from a negative destination operand delivers a
positive result, reset otherwise (no overflow).
SUB
Example
src,dst or SUB.W src,dst
src,dst
; R7 <> @R5 (before subtraction)
Byte CNT is subtracted from byte R12 points to. The address of CNT is within
PC ± 32 K. The address R12 points to is in full memory range.
SUB.B
CNT,0(R12)
; Subtract CNT from @R12
16-Bit MSP430X CPU
4-107
MSP430 Instructions
SUBC[.W]
SUBC.B
Subtract source word with carry from destination word
Subtract source byte with carry from destination byte
Syntax
SUBC
SUBC.B
Operation
(.not.src) + C + dst → dst
Description
The source operand is subtracted from the destination operand. This is done
by adding the 1’s complement of the source + carry to the destination. The
source operand is not affected, the result is written to the destination operand.
Used for 32, 48, and 64-bit operands.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
A 16-bit constant 7654h is subtracted from R5 with the carry from the previous
instruction. R5.19:16 = 0
Example
or dst − (src − 1) + C → dst
#7654h,R5
; Subtract 7654h + C from R5
A 48-bit number (3 words) pointed to by R5 (20-bit address) is subtracted from
a 48-bit counter in RAM, pointed to by R7. R5 points to the next 48-bit number
afterwards. The address R7 points to is in full memory range.
SUB
@R5+,0(R7)
; Subtract LSBs. R5 + 2
SUBC
@R5+,2(R7)
; Subtract MIDs with C. R5 + 2
SUBC
@R5+,4(R7)
; Subtract MSBs with C. R5 + 2
Byte CNT is subtracted from the byte, R12 points to. The carry of the previous
instruction is used. The address of CNT is in lower 64 K.
SUBC.B
4-108
src,dst
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if there is a carry from the MSB, reset otherwise
Set if the subtraction of a negative source operand from a positive destination operand delivers a negative result, or if the subtraction of a positive source operand from a negative destination operand delivers a
positive result, reset otherwise (no overflow).
SUBC.W
Example
src,dst or SUBC.W
src,dst
16-Bit MSP430X CPU
&CNT,0(R12)
; Subtract byte CNT from @R12
MSP430 Instructions
SWPB
Swap bytes
Syntax
SWPB
Operation
dst.15:8 ⇔ dst.7:0
Description
The high and the low byte of the operand are exchanged. PC.19:16 bits are
cleared in register mode.
Status Bits
Not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Exchange the bytes of RAM word EDE (lower 64 K).
dst
MOV
#1234h,&EDE
; 1234h -> EDE
SWPB
&EDE
; 3412h -> EDE
Figure 4−42. Swap Bytes in Memory
Before SWPB
15
8
7
0
High Byte
Low Byte
After SWPB
15
8
7
0
Low Byte
High Byte
Figure 4−43. Swap Bytes in a Register
Before SWPB
19
16 15
x
8
7
High Byte
0
Low Byte
After SWPB
19
16
0
... 0
15
8
Low Byte
7
0
High Byte
16-Bit MSP430X CPU
4-109
MSP430 Instructions
SXT
Extend sign
Syntax
SXT
Operation
dst.7 → dst.15:8, dst.7 → dst.19:8 (Register Mode)
Description
Register Mode: the sign of the low byte of the operand is extended into the bits
Rdst.19:8
dst
Rdst.7 = 0: Rdst.19:8 = 000h afterwards.
Rdst.7 = 1: Rdst.19:8 = FFFh afterwards.
Other Modes: the sign of the low byte of the operand is extended into the high
byte.
dst.7 = 0: high byte = 00h afterwards.
dst.7 = 1: high byte = FFh afterwards.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The signed 8-bit data in EDE (lower 64 K) is sign extended and added to the
16-bit signed data in R7.
Example
4-110
Set if result is negative, reset otherwise
Set if result is zero, reset otherwise
Set if result is not zero, reset otherwise (C = .not.Z)
Reset
MOV.B
&EDE,R5
; EDE -> R5. 00XXh
SXT
R5
; Sign extend low byte to R5.19:8
ADD
R5,R7
; Add signed 16-bit values
The signed 8-bit data in EDE (PC ±32 K) is sign extended and added to the
20-bit data in R7.
MOV.B
EDE,R5
; EDE -> R5. 00XXh
SXT
R5
; Sign extend low byte to R5.19:8
ADDA
R5,R7
; Add signed 20-bit values
16-Bit MSP430X CPU
MSP430 Instructions
* TST[.W]
* TST.B
Test destination
Test destination
Syntax
TST
TST.B
Operation
dst + 0FFFFh + 1
dst + 0FFh + 1
Emulation
CMP
CMP.B
Description
The destination operand is compared with zero. The status bits are set according to the result. The destination is not affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R7 is tested. If it is negative, continue at R7NEG; if it is positive but not zero,
continue at R7POS.
or TST.W dst
#0,dst
#0,dst
Set if destination is negative, reset if positive
Set if destination contains zero, reset otherwise
Set
Reset
R7POS
R7NEG
R7ZERO
Example
dst
dst
TST
JN
JZ
......
......
......
R7
R7NEG
R7ZERO
; Test R7
; R7 is negative
; R7 is zero
; R7 is positive but not zero
; R7 is negative
; R7 is zero
The low byte of R7 is tested. If it is negative, continue at R7NEG; if it is positive
but not zero, continue at R7POS.
R7POS
R7NEG
R7ZERO
TST.B
JN
JZ
......
.....
......
R7
R7NEG
R7ZERO
; Test low byte of R7
; Low byte of R7 is negative
; Low byte of R7 is zero
; Low byte of R7 is positive but not zero
; Low byte of R7 is negative
; Low byte of R7 is zero
16-Bit MSP430X CPU
4-111
MSP430 Instructions
XOR[.W]
XOR.B
Exclusive OR source word with destination word
Exclusive OR source byte with destination byte
Syntax
XOR
XOR.B
Operation
src .xor. dst → dst
Description
The source and destination operands are exclusively ORed. The result is
placed into the destination. The source operand is not affected. The previous
content of the destination is lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Toggle bits in word CNTR (16-bit data) with information (bit = 1) in
address-word TONI. Both operands are located in lower 64 K.
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if result is not zero, reset otherwise (C = .not. Z)
Set if both operands are negative before execution, reset otherwise
XOR
Example
4-112
&TONI,&CNTR
; Toggle bits in CNTR
A table word pointed to by R5 (20-bit address) is used to toggle bits in R6.
R6.19:16 = 0.
XOR
Example
dst or XOR.W dst
dst
@R5,R6
; Toggle bits in R6
Reset to zero those bits in the low byte of R7 that are different from the bits in
byte EDE. R7.19:8 = 0. The address of EDE is within PC ± 32 K.
XOR.B
EDE,R7
; Set different bits to 1 in R7.
INV.B
R7
; Invert low byte of R7, high byte is 0h
16-Bit MSP430X CPU
Extended Instructions
4.6.3
Extended Instructions
The extended MSP430X instructions give the MSP430X CPU full access to its
20-bit address space. Some MSP430X instructions require an additional word
of op-code called the extension word. All addresses, indexes, and immediate
numbers have 20-bit values, when preceded by the extension word. The
MSP430X extended instructions are listed and described in the following
pages. For MSP430X instructions that do not require the extension word, it is
noted in the instruction description.
16-Bit MSP430X CPU
4-113
Extended Instructions
* ADCX.A
* ADCX.[W]
* ADCX.B
Add carry to destination address-word
Add carry to destination word
Add carry to destination byte
Syntax
ADCX.A
ADCX
ADCX.B
dst
dst
dst
or
ADCX.W
dst
Operation
dst + C −> dst
Emulation
ADDCX.A
ADDCX
ADDCX.B
Description
The carry bit (C) is added to the destination operand. The previous contents
of the destination are lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 40-bit counter, pointed to by R12 and R13, is incremented.
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if there is a carry from the MSB of the result, reset otherwise
Set if the result of two positive operands is negative, or if the result of
two negative numbers is positive, reset otherwise
INCX.A
ADCX.A
4-114
#0,dst
#0,dst
#0,dst
16-Bit MSP430X CPU
@R12
@R13
; Increment lower 20 bits
; Add carry to upper 20 bits
Extended Instructions
ADDX.A
ADDX[.W]
ADDX.B
Add source address-word to destination address-word
Add source word to destination word
Add source byte to destination byte
Syntax
ADDX.A
ADDX
ADDX.B
src,dst
src,dst or ADDX.W
src,dst
src,dst
Operation
src + dst → dst
Description
The source operand is added to the destination operand. The previous
contents of the destination are lost. Both operands can be located in the full
address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Ten is added to the 20-bit pointer CNTR located in two words CNTR (LSBs)
and CNTR+2 (MSBs).
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if there is a carry from the MSB of the result, reset otherwise
Set if the result of two positive operands is negative, or if the result of
two negative numbers is positive, reset otherwise
ADDX.A
Example
#10,CNTR
A table word (16-bit) pointed to by R5 (20-bit address) is added to R6. The jump
to label TONI is performed on a carry.
ADDX.W
@R5,R6
; Add table word to R6
JC
TONI
; Jump if carry
...
Example
; Add 10 to 20-bit pointer
; No carry
A table byte pointed to by R5 (20-bit address) is added to R6. The jump to label
TONI is performed if no carry occurs. The table pointer is auto-incremented
by 1.
ADDX.B
@R5+,R6
; Add table byte to R6. R5 + 1. R6: 000xxh
JNC
TONI
; Jump if no carry
...
; Carry occurred
Note: Use ADDA for the following two cases for better code density and
execution.
ADDX.A
Rsrc,Rdst or
ADDX.A
#imm20,Rdst
16-Bit MSP430X CPU
4-115
Extended Instructions
ADDCX.A
ADDCX[.W]
ADDCX.B
Add source address-word and carry to destination address-word
Add source word and carry to destination word
Add source byte and carry to destination byte
Syntax
ADDCX.A src,dst
ADDCX
src,dst or ADDCX.W src,dst
ADDCX.B src,dst
Operation
src + dst + C → dst
Description
The source operand and the carry bit C are added to the destination operand.
The previous contents of the destination are lost. Both operands may be
located in the full address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Constant 15 and the carry of the previous instruction are added to the 20-bit
counter CNTR located in two words.
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if there is a carry from the MSB of the result, reset otherwise
Set if the result of two positive operands is negative, or if the result of
two negative numbers is positive, reset otherwise
ADDCX.A
Example
#15,&CNTR
A table word pointed to by R5 (20-bit address) and the carry C are added to R6.
The jump to label TONI is performed on a carry.
ADDCX.W
@R5,R6
; Add table word + C to R6
JC
TONI
; Jump if carry
...
Example
; No carry
A table byte pointed to by R5 (20-bit address) and the carry bit C are added to
R6. The jump to label TONI is performed if no carry occurs. The table pointer is
auto-incremented by 1.
ADDCX.B
@R5+,R6
; Add table byte + C to R6. R5 + 1
JNC
TONI
; Jump if no carry
...
4-116
; Add 15 + C to 20-bit CNTR
16-Bit MSP430X CPU
; Carry occurred
Extended Instructions
ANDX.A
ANDX[.W]
ANDX.B
Logical AND of source address-word with destination address-word
Logical AND of source word with destination word
Logical AND of source byte with destination byte
Syntax
ANDX.A
ANDX
ANDX.B
src,dst
src,dst or ANDX.W
src,dst
src,dst
Operation
src .and. dst → dst
Description
The source operand and the destination operand are logically ANDed. The
result is placed into the destination. The source operand is not affected. Both
operands may be located in the full address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The bits set in R5 (20-bit data) are used as a mask (AAA55h) for the
address-word TOM located in two words. If the result is zero, a branch is taken
to label TONI.
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if the result is not zero, reset otherwise. C = (.not. Z)
Reset
MOVA
#AAA55h,R5
; Load 20-bit mask to R5
ANDX.A
R5,TOM
; TOM .and. R5 -> TOM
JZ
TONI
; Jump if result 0
...
; Result > 0
or shorter:
Example
ANDX.A
#AAA55h,TOM
; TOM .and. AAA55h -> TOM
JZ
TONI
; Jump if result 0
A table byte pointed to by R5 (20-bit address) is logically ANDed with R6.
R6.19:8 = 0. The table pointer is auto-incremented by 1.
ANDX.B
@R5+,R6
; AND table byte with R6. R5 + 1
16-Bit MSP430X CPU
4-117
Extended Instructions
BICX.A
BICX[.W]
BICX.B
Clear bits set in source address-word in destination address-word
Clear bits set in source word in destination word
Clear bits set in source byte in destination byte
Syntax
BICX.A
BICX
BICX.B
src,dst
src,dst or BICX.W
src,dst
src,dst
Operation
(.not. src) .and. dst → dst
Description
The inverted source operand and the destination operand are logically
ANDed. The result is placed into the destination. The source operand is not
affected. Both operands may be located in the full address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The bits 19:15 of R5 (20-bit data) are cleared.
Not affected
Not affected
Not affected
Not affected
BICX.A
Example
@R5,R7
; Clear bits in R7
A table byte pointed to by R5 (20-bit address) is used to clear bits in output
Port1.
BICX.B
4-118
; Clear R5.19:15 bits
A table word pointed to by R5 (20-bit address) is used to clear bits in R7.
R7.19:16 = 0
BICX.W
Example
#0F8000h,R5
16-Bit MSP430X CPU
@R5,&P1OUT
; Clear I/O port P1 bits
Extended Instructions
BISX.A
BISX[.W]
BISX.B
Set bits set in source address-word in destination address-word
Set bits set in source word in destination word
Set bits set in source byte in destination byte
Syntax
BISX.A
BISX
BISX.B
src,dst
src,dst or BISX.W
src,dst
src,dst
Operation
src .or. dst → dst
Description
The source operand and the destination operand are logically ORed. The
result is placed into the destination. The source operand is not affected. Both
operands may be located in the full address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Bits 16 and 15 of R5 (20-bit data) are set to one.
Not affected
Not affected
Not affected
Not affected
BISX.A
Example
; Set R5.16:15 bits
A table word pointed to by R5 (20-bit address) is used to set bits in R7.
BISX.W
Example
#018000h,R5
@R5,R7
; Set bits in R7
A table byte pointed to by R5 (20-bit address) is used to set bits in output Port1.
BISX.B
@R5,&P1OUT
; Set I/O port P1 bits
16-Bit MSP430X CPU
4-119
Extended Instructions
BITX.A
BITX[.W]
BITX.B
Test bits set in source address-word in destination address-word
Test bits set in source word in destination word
Test bits set in source byte in destination byte
Syntax
BITX.A
BITX
BITX.B
src,dst
src,dst or BITX.W
src,dst
src,dst
Operation
src .and. dst
Description
The source operand and the destination operand are logically ANDed. The
result affects only the status bits. Both operands may be located in the full
address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Test if bit 16 or 15 of R5 (20-bit data) is set. Jump to label TONI if so.
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if the result is not zero, reset otherwise. C = (.not. Z)
Reset
BITX.A
#018000h,R5
; Test R5.16:15 bits
JNZ
TONI
; At least one bit is set
...
Example
; Both are reset
A table word pointed to by R5 (20-bit address) is used to test bits in R7. Jump to
label TONI if at least one bit is set.
BITX.W
@R5,R7
; Test bits in R7: C = .not.Z
JC
TONI
; At least one is set
...
Example
A table byte pointed to by R5 (20-bit address) is used to test bits in input Port1.
Jump to label TONI if no bit is set. The next table byte is addressed.
BITX.B
@R5+,&P1IN
; Test input P1 bits. R5 + 1
JNC
TONI
; No corresponding input bit is set
...
4-120
; Both are reset
16-Bit MSP430X CPU
; At least one bit is set
Extended Instructions
* CLRX.A
* CLRX.[W]
* CLRX.B
Clear destination address-word
Clear destination word
Clear destination byte
Syntax
CLRX.A
CLRX
CLRX.B
dst
dst
dst
or CLRX.W
Operation
0 −> dst
Emulation
MOVX.A
MOVX
MOVX.B
Description
The destination operand is cleared.
Status Bits
Status bits are not affected.
Example
RAM address-word TONI is cleared.
CLRX.A
dst
#0,dst
#0,dst
#0,dst
TONI
; 0 −> TONI
16-Bit MSP430X CPU
4-121
Extended Instructions
CMPX.A
CMPX[.W]
CMPX.B
Compare source address-word and destination address-word
Compare source word and destination word
Compare source byte and destination byte
Syntax
CMPX.A
CMPX
CMPX.B
src,dst
src,dst or CMPX.W
src,dst
src,dst
Operation
(.not. src) + 1 + dst or dst − src
Description
The source operand is subtracted from the destination operand by adding the
1’s complement of the source + 1 to the destination. The result affects only the
status bits. Both operands may be located in the full address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Compare EDE with a 20-bit constant 18000h. Jump to label TONI if EDE
equals the constant.
Set if result is negative (src > dst), reset if positive (src <= dst)
Set if result is zero (src = dst), reset otherwise (src ≠ dst)
Set if there is a carry from the MSB, reset otherwise
Set if the subtraction of a negative source operand from a positive
destination operand delivers a negative result, or if the subtraction of
a positive source operand from a negative destination operand delivers
a positive result, reset otherwise (no overflow).
CMPX.A
#018000h,EDE
; Compare EDE with 18000h
JEQ
TONI
; EDE contains 18000h
...
Example
; Not equal
A table word pointed to by R5 (20-bit address) is compared with R7. Jump to
label TONI if R7 contains a lower, signed, 16-bit number.
CMPX.W
@R5,R7
; Compare two signed numbers
JL
TONI
; R7 < @R5
...
Example
; R7 >= @R5
A table byte pointed to by R5 (20-bit address) is compared to the input in I/O
Port1. Jump to label TONI if the values are equal. The next table byte is
addressed.
CMPX.B
@R5+,&P1IN
; Compare P1 bits with table. R5 + 1
JEQ
TONI
; Equal contents
...
; Not equal
Note: Use CMPA for the following two cases for better density and execution.
CMPA
Rsrc,Rdst or
CMPA
#imm20,Rdst
4-122
16-Bit MSP430X CPU
Extended Instructions
* DADCX.A
* DADCX[.W]
* DADCX.B
Add carry decimally to destination address-word
Add carry decimally to destination word
Add carry decimally to destination byte
Syntax
DADCX.A
DADCX
DADCX.B
dst
dst
dst
or
DADCX.W
src,dst
Operation
dst + C −> dst (decimally)
Emulation
DADDX.A
DADDX
DADDX.B
Description
The carry bit (C) is added decimally to the destination.
Status Bits
N:
Z:
C:
V:
#0,dst
#0,dst
#0,dst
Set if MSB of result is 1 (address-word > 79999h, word > 7999h,
byte > 79h), reset if MSB is 0.
Set if result is zero, reset otherwise.
Set if the BCD result is too large (address-word > 99999h,
word > 9999h, byte > 99h), reset otherwise.
Undefined.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 40-bit counter, pointed to by R12 and R13, is incremented decimally.
DADDX.A
DADCX.A
#1,0(R12)
0(R13)
; Increment lower 20 bits
; Add carry to upper 20 bits
16-Bit MSP430X CPU
4-123
Extended Instructions
DADDX.A
DADDX[.W]
DADDX.B
Add source address-word and carry decimally to destination address-word
Add source word and carry decimally to destination word
Add source byte and carry decimally to destination byte
Syntax
DADDX.A src,dst
DADDX
src,dst or DADDX.W src,dst
DADDX.B src,dst
Operation
src + dst + C → dst (decimally)
Description
The source operand and the destination operand are treated as two (.B), four
(.W), or five (.A) binary coded decimals (BCD) with positive signs. The source
operand and the carry bit C are added decimally to the destination operand.
The source operand is not affected. The previous contents of the destination
are lost. The result is not defined for non-BCD numbers. Both operands may
be located in the full address space.
Status Bits
N:
Z:
C:
V:
Set if MSB of result is 1 (address-word > 79999h, word > 7999h,
byte > 79h), reset if MSB is 0.
Set if result is zero, reset otherwise.
Set if the BCD result is too large (address-word > 99999h,
word > 9999h, byte > 99h), reset otherwise.
Undefined.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Decimal 10 is added to the 20-bit BCD counter DECCNTR located in two
words.
DADDX.A
Example
#10h,&DECCNTR ; Add 10 to 20-bit BCD counter
The eight-digit BCD number contained in 20-bit addresses BCD and BCD+2 is
added decimally to an eight-digit BCD number contained in R4 and R5
(BCD+2 and R5 contain the MSDs).
CLRC
; Clear carry
DADDX.W
BCD,R4
; Add LSDs
DADDX.W
BCD+2,R5
; Add MSDs with carry
JC
OVERFLOW
; Result >99999999: go to error routine
...
Example
;
The two-digit BCD number contained in 20-bit address BCD is added
decimally to a two-digit BCD number contained in R4.
CLRC
DADDX.B
4-124
Result ok
16-Bit MSP430X CPU
; Clear carry
BCD,R4
; Add BCD to R4 decimally.
; R4: 000ddh
Extended Instructions
* DECX.A
* DECX[.W]
* DECX.B
Decrement destination address-word
Decrement destination word
Decrement destination byte
Syntax
DECX
DECX
DECX.B
dst
dst
dst
or
DECX.W
dst
Operation
dst − 1 −> dst
Emulation
SUBX.A
SUBX
SUBX.B
Description
The destination operand is decremented by one. The original contents are
lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
RAM address-word TONI is decremented by 1
#1,dst
#1,dst
#1,dst
Set if result is negative, reset if positive
Set if dst contained 1, reset otherwise
Reset if dst contained 0, set otherwise
Set if an arithmetic overflow occurs, otherwise reset.
DECX.A
TONI
; Decrement TONI
16-Bit MSP430X CPU
4-125
Extended Instructions
* DECDX.A
* DECDX[.W]
* DECDX.B
Double-decrement destination address-word
Double-decrement destination word
Double-decrement destination byte
Syntax
DECDX.A
DECDX
DECDX.B
dst
dst
dst
or
DECDX.W
dst
Operation
dst − 2 −> dst
Emulation
SUBX.A
SUBX
SUBX.B
Description
The destination operand is decremented by two. The original contents are lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
RAM address-word TONI is decremented by 2.
Set if result is negative, reset if positive
Set if dst contained 2, reset otherwise
Reset if dst contained 0 or 1, set otherwise
Set if an arithmetic overflow occurs, otherwise reset.
DECDX.A
4-126
#2,dst
#2,dst
#2,dst
16-Bit MSP430X CPU
TONI
; Decrement TONI by two
Extended Instructions
* INCX.A
* INCX[.W]
* INCX.B
Increment destination address-word
Increment destination word
Increment destination byte
Syntax
INCX.A
INCX
INCX.B
dst
dst
dst
or INCX.W
dst
Operation
dst + 1 −> dst
Emulation
ADDX.A
ADDX
ADDX.B
Description
The destination operand is incremented by one. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFFFh, reset otherwise
Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
C: Set if dst contained 0FFFFFh, reset otherwise
Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
V: Set if dst contained 07FFFh, reset otherwise
Set if dst contained 07FFFh, reset otherwise
Set if dst contained 07Fh, reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
RAM address-word TONI is incremented by 1.
INCX.A
#1,dst
#1,dst
#1,dst
TONI
; Increment TONI (20-bits)
16-Bit MSP430X CPU
4-127
Extended Instructions
* INCDX.A
* INCDX[.W]
* INCDX.B
Double-increment destination address-word
Double-increment destination word
Double-increment destination byte
Syntax
INCDX.A
INCDX
INCDX.B
dst
dst
dst
or INCDX.W
dst
Operation
dst + 2 −> dst
Emulation
ADDX.A
ADDX
ADDX.B
Example
The destination operand is incremented by two. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFFEh, reset otherwise
Set if dst contained 0FFFEh, reset otherwise
Set if dst contained 0FEh, reset otherwise
C: Set if dst contained 0FFFFEh or 0FFFFFh, reset otherwise
Set if dst contained 0FFFEh or 0FFFFh, reset otherwise
Set if dst contained 0FEh or 0FFh, reset otherwise
V: Set if dst contained 07FFFEh or 07FFFFh, reset otherwise
Set if dst contained 07FFEh or 07FFFh, reset otherwise
Set if dst contained 07Eh or 07Fh, reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
RAM byte LEO is incremented by two; PC points to upper memory
INCDX.B
4-128
16-Bit MSP430X CPU
#2,dst
#2,dst
#2,dst
LEO
; Increment LEO by two
Extended Instructions
* INVX.A
* INVX[.W]
* INVX.B
Invert destination
Invert destination
Invert destination
Syntax
INVX.A
INVX
INVX.B
dst
dst
dst
or INVX.W
dst
Operation
.NOT.dst −> dst
Emulation
XORX.A
XORX
XORX.B
Description
The destination operand is inverted. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if dst contained 0FFFFFh, reset otherwise
Set if dst contained 0FFFFh, reset otherwise
Set if dst contained 0FFh, reset otherwise
C: Set if result is not zero, reset otherwise ( = .NOT. Zero)
V: Set if initial destination operand was negative, otherwise reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
20-bit content of R5 is negated (twos complement).
INVX.A
R5
; Invert R5
INCX.A
R5
; R5 is now negated
Example
Content of memory byte LEO is negated. PC is pointing to upper memory
INVX.B
LEO
; Invert LEO
INCX.B
LEO
; MEM(LEO) is negated
#0FFFFFh,dst
#0FFFFh,dst
#0FFh,dst
16-Bit MSP430X CPU
4-129
Extended Instructions
MOVX.A
MOVX[.W]
MOVX.B
Move source address-word to destination address-word
Move source word to destination word
Move source byte to destination byte
Syntax
MOVX.A
MOVX
MOVX.B
src,dst
src,dst or MOVX.W
src,dst
src,dst
Operation
src → dst
Description
The source operand is copied to the destination. The source operand is not
affected. Both operands may be located in the full address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Move a 20-bit constant 18000h to absolute address-word EDE.
Not affected
Not affected
Not affected
Not affected
MOVX.A
Example
#018000h,&EDE
The contents of table EDE (word data, 20-bit addresses) are copied to table
TOM. The length of the table is 030h words.
Loop
MOVA
#EDE,R10
MOVX.W
@R10+,TOM-EDE-2(R10) ; R10 points to both tables.
R10+2
CMPA
#EDE+60h,R10
; End of table reached?
JLO
Loop
; Not yet
...
Example
; Prepare pointer (20-bit address)
; Copy completed
The contents of table EDE (byte data, 20-bit addresses) are copied to table
TOM. The length of the table is 020h bytes.
Loop
MOVA
#EDE,R10
; Prepare pointer (20-bit)
MOV
#20h,R9
; Prepare counter
MOVX.B
@R10+,TOM-EDE-1(R10) ; R10 points to both tables.
; R10+1
DEC
R9
; Decrement counter
JNZ
Loop
; Not yet done
...
4-130
; Move 18000h to EDE
16-Bit MSP430X CPU
; Copy completed
Extended Instructions
Ten of the 28 possible addressing combinations of the MOVX.A instruction can
use the MOVA instruction. This saves two bytes and code cycles. Examples
for the addressing combinations are:
MOVX.A
Rsrc,Rdst
MOVA Rsrc,Rdst
; Reg/Reg
MOVX.A
#imm20,Rdst
MOVA #imm20,Rdst
; Immediate/Reg
MOVX.A
&abs20,Rdst
MOVA &abs20,Rdst
; Absolute/Reg
MOVX.A
@Rsrc,Rdst
MOVA @Rsrc,Rdst
; Indirect/Reg
MOVX.A
@Rsrc+,Rdst
MOVA @Rsrc+,Rdst
; Indirect,Auto/Reg
MOVX.A
Rsrc,&abs20
MOVA Rsrc,&abs20
; Reg/Absolute
The next four replacements are possible only if 16-bit indexes are sufficient for
the addressing.
MOVX.A
z20(Rsrc),Rdst
MOVA z16(Rsrc),Rdst ; Indexed/Reg
MOVX.A
Rsrc,z20(Rdst)
MOVA Rsrc,z16(Rdst) ; Reg/Indexed
MOVX.A
symb20,Rdst
MOVA symb16,Rdst
; Symbolic/Reg
MOVX.A
Rsrc,symb20
MOVA Rsrc,symb16
; Reg/Symbolic
16-Bit MSP430X CPU
4-131
Extended Instructions
POPM.A
POPM[.W]
Restore n CPU registers (20-bit data) from the stack
Restore n CPU registers (16-bit data) from the stack
Syntax
POPM.A
POPM.W
Operation
#n,Rdst
#n,Rdst
1 ≤ n ≤ 16
or POPM #n,Rdst
1 ≤ n ≤ 16
POPM.A: Restore the register values from stack to the specified CPU
registers. The stack pointer SP is incremented by four for each register
restored from stack. The 20-bit values from stack (2 words per register) are
restored to the registers.
POPM.W: Restore the 16-bit register values from stack to the specified CPU
registers. The stack pointer SP is incremented by two for each register
restored from stack. The 16-bit values from stack (one word per register) are
restored to the CPU registers.
Note : This does not use the extension word.
Description
POPM.A: The CPU registers pushed on the stack are moved to the extended
CPU registers, starting with the CPU register (Rdst - n + 1). The stack pointer
is incremented by (n × 4) after the operation.
POPM.W: The 16-bit registers pushed on the stack are moved back to the
CPU registers, starting with CPU register (Rdst - n + 1). The stack pointer is
incremented by (n × 2) after the instruction. The MSBs (Rdst.19:16) of the
restored CPU registers are cleared
Status Bits
Not affected, except SR is included in the operation
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected, except SR is included in the operation.
Example
Restore the 20-bit registers R9, R10, R11, R12, R13 from the stack.
POPM.A
Example
; Restore R9, R10, R11, R12, R13
Restore the 16-bit registers R9, R10, R11, R12, R13 from the stack.
POPM.W
4-132
#5,R13
16-Bit MSP430X CPU
#5,R13
; Restore R9, R10, R11, R12, R13
Extended Instructions
PUSHM.A
PUSHM[.W]
Save n CPU registers (20-bit data) on the stack
Save n CPU registers (16-bit words) on the stack
Syntax
PUSHM.A
PUSHM.W
Operation
#n,Rdst
#n,Rdst
1 ≤ n ≤ 16
or PUSHM
#n,Rdst
1 ≤ n ≤ 16
PUSHM.A: Save the 20-bit CPU register values on the stack. The stack pointer
(SP) is decremented by four for each register stored on the stack. The MSBs
are stored first (higher address).
PUSHM.W: Save the 16-bit CPU register values on the stack. The stack
pointer is decremented by two for each register stored on the stack.
Description
PUSHM.A: The n CPU registers, starting with Rdst backwards, are stored on
the stack. The stack pointer is decremented by (n × 4) after the operation. The
data (Rn.19:0) of the pushed CPU registers is not affected.
PUSHM.W: The n registers, starting with Rdst backwards, are stored on the
stack. The stack pointer is decremented by (n × 2) after the operation. The
data (Rn.19:0) of the pushed CPU registers is not affected.
Note : This instruction does not use the extension word.
Status Bits
Not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Save the five 20-bit registers R9, R10, R11, R12, R13 on the stack.
PUSHM.A
Example
#5,R13
; Save R13, R12, R11, R10, R9
Save the five 16-bit registers R9, R10, R11, R12, R13 on the stack.
PUSHM.W
#5,R13
; Save R13, R12, R11, R10, R9
16-Bit MSP430X CPU
4-133
Extended Instructions
* POPX.A
* POPX[.W]
* POPX.B
Restore single address-word from the stack
Restore single word from the stack
Restore single byte from the stack
Syntax
POPX.A
POPX
POPX.B
dst
dst or POPX.W
dst
dst
Operation
Restore the 8/16/20-bit value from the stack to the destination. 20-bit
addresses are possible. The stack pointer SP is incremented by two (byte and
word operands) and by four (address-word operand).
Emulation
MOVX(.B,.A)
Description
The item on TOS is written to the destination operand. Register Mode, Indexed
Mode, Symbolic Mode, and Absolute Mode are possible. The stack pointer is
incremented by two or four.
@SP+,dst
Note: the stack pointer is incremented by two also for byte operations.
Status Bits
Not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Write the 16-bit value on TOS to the 20-bit address &EDE.
POPX.W
Example
; Write word to address EDE
Write the 20-bit value on TOS to R9.
POPX.A
4-134
&EDE
16-Bit MSP430X CPU
R9
; Write address-word to R9
Extended Instructions
PUSHX.A
PUSHX[.W]
PUSHX.B
Save a single address-word on the stack
Save a single word on the stack
Save a single byte on the stack
Syntax
PUSHX.A
src
PUSHX
src or PUSHX.W
PUSHX.B
src
src
Operation
Save the 8/16/20-bit value of the source operand on the TOS. 20-bit addresses
are possible. The stack pointer (SP) is decremented by two (byte and word
operands) or by four (address-word operand) before the write operation.
Description
The stack pointer is decremented by two (byte and word operands) or by four
(address-word operand). Then the source operand is written to the TOS. All
seven addressing modes are possible for the source operand.
Note : This instruction does not use the extension word.
Status Bits
Not affected.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Save the byte at the 20-bit address &EDE on the stack.
PUSHX.B
Example
&EDE
; Save byte at address EDE
Save the 20-bit value in R9 on the stack.
PUSHX.A
R9
; Save address-word in R9
16-Bit MSP430X CPU
4-135
Extended Instructions
RLAM.A
RLAM[.W]
Rotate Left Arithmetically the 20-bit CPU register content
Rotate Left Arithmetically the 16-bit CPU register content
Syntax
RLAM.A
RLAM.W
1≤n≤4
or RLAM #n,Rdst
#n,Rdst
#n,Rdst
1≤n≤4
Operation
C ← MSB ← MSB-1 .... LSB+1 ← LSB ← 0
Description
The destination operand is shifted arithmetically left one, two, three, or four
positions as shown in Figure 4−44. RLAM works as a multiplication (signed
and unsigned) with 2, 4, 8, or 16. The word instruction RLAM.W clears the bits
Rdst.19:16
Note : This instruction does not use the extension word.
Status Bits
N:
Z:
C:
V:
Set if result is negative
.A: Rdst.19 = 1, reset if Rdst.19 = 0
.W: Rdst.15 = 1, reset if Rdst.15 = 0
Set if result is zero, reset otherwise
Loaded from the MSB (n = 1), MSB-1 (n = 2), MSB-2 (n = 3), MSB-3
(n = 4)
Undefined
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 20-bit operand in R5 is shifted left by three positions. It operates equal to
an arithmetic multiplication by 8.
RLAM.A
#3,R5
; R5 = R5 x 8
Figure 4−44. Rotate Left Arithmetically RLAM[.W] and RLAM.A
16
19
C
C
4-136
16-Bit MSP430X CPU
0000
15
0
MSB
LSB
19
0
MSB
LSB
0
0
Extended Instructions
* RLAX.A
* RLAX[.W]
* RLAX.B
Rotate left arithmetically address-word
Rotate left arithmetically word
Rotate left arithmetically byte
Syntax
RLAX.B
RLAX
RLAX.B
dst
dst
dst
or
RLAX.W
dst
Operation
C <− MSB <− MSB−1 .... LSB+1 <− LSB <− 0
Emulation
ADDX.A
ADDX
ADDX.B
Description
The destination operand is shifted left one position as shown in Figure 4−45.
The MSB is shifted into the carry bit (C) and the LSB is filled with 0. The RLAX
instruction acts as a signed multiplication by 2.
dst,dst
dst,dst
dst,dst
Figure 4−45. Destination Operand—Arithmetic Shift Left
MSB
0
0
C
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Loaded from the MSB
Set if an arithmetic overflow occurs:
the initial value is 040000h ≤ dst < 0C0000h; reset otherwise
Set if an arithmetic overflow occurs:
the initial value is 04000h ≤ dst < 0C000h; reset otherwise
Set if an arithmetic overflow occurs:
the initial value is 040h ≤ dst < 0C0h; reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 20-bit value in R7 is multiplied by 2.
RLAX.A
R7
; Shift left R7 (20-bit)
16-Bit MSP430X CPU
4-137
Extended Instructions
* RLCX.A
* RLCX[.W]
* RLCX.B
Rotate left through carry address-word
Rotate left through carry word
Rotate left through carry byte
Syntax
RLCX.A
RLCX
RLCX.B
dst
dst
dst
or
RLCX.W
dst
Operation
C <− MSB <− MSB−1 .... LSB+1 <− LSB <− C
Emulation
ADDCX.A
ADDCX
ADDCX.B
Description
The destination operand is shifted left one position as shown in Figure 4−46.
The carry bit (C) is shifted into the LSB and the MSB is shifted into the carry
bit (C).
dst,dst
dst,dst
dst,dst
Figure 4−46. Destination Operand—Carry Left Shift
MSB
0
C
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset if positive
Set if result is zero, reset otherwise
Loaded from the MSB
Set if an arithmetic overflow occurs
the initial value is 040000h ≤ dst < 0C0000h; reset otherwise
Set if an arithmetic overflow occurs:
the initial value is 04000h ≤ dst < 0C000h; reset otherwise
Set if an arithmetic overflow occurs:
the initial value is 040h ≤ dst < 0C0h; reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 20-bit value in R5 is shifted left one position.
RLCX.A
Example
; (R5 x 2) + C −> R5
The RAM byte LEO is shifted left one position. PC is pointing to upper memory
RLCX.B
4-138
R5
16-Bit MSP430X CPU
LEO
; RAM(LEO) x 2 + C −> RAM(LEO)
Extended Instructions
RRAM.A
RRAM[.W]
Rotate Right Arithmetically the 20-bit CPU register content
Rotate Right Arithmetically the 16-bit CPU register content
Syntax
RRAM.A
RRAM.W
1≤n≤4
or RRAM #n,Rdst
#n,Rdst
#n,Rdst
1≤n≤4
Operation
MSB → MSB → MSB-1 …. LSB+1 → LSB → C
Description
The destination operand is shifted right arithmetically by one, two, three, or
four bit positions as shown in Figure 4−47. The MSB retains its value (sign).
RRAM operates equal to a signed division by 2/4/8/16. The MSB is retained
and shifted into MSB-1. The LSB+1 is shifted into the LSB, and the LSB is
shifted into the carry bit C. The word instruction RRAM.W clears the bits
Rdst.19:16.
Note : This instruction does not use the extension word.
Status Bits
N:
Set if result is negative
.A: Rdst.19 = 1, reset if Rdst.19 = 0
.W: Rdst.15 = 1, reset if Rdst.15 = 0
Set if result is zero, reset otherwise
Loaded from the LSB (n = 1), LSB+1 (n = 2), LSB+2 (n = 3), or LSB+3
(n = 4)
Reset
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The signed 20-bit number in R5 is shifted arithmetically right two positions.
RRAM.A
Example
#2,R5
; R5/4 -> R5
The signed 20-bit value in R15 is multiplied by 0.75. (0.5 + 0.25) x R15
PUSHM.A
#1,R15
; Save extended R15 on stack
RRAM.A
#1,R15
; R15 × 0.5 -> R15
ADDX.A
@SP+,R15
; R15 × 0.5 + R15 = 1.5 × R15 -> R15
RRAM.A
#1,R15
; (1.5 × R15) × 0.5 = 0.75 × R15 -> R15
Figure 4−47. Rotate Right Arithmetically RRAM[.W] and RRAM.A
16
19
C
C
0000
15
0
MSB
LSB
19
0
MSB
LSB
16-Bit MSP430X CPU
4-139
Extended Instructions
RRAX.A
RRAX[.W]
RRAX.B
Rotate Right Arithmetically the 20-bit operand
Rotate Right Arithmetically the 16-bit operand
Rotate Right Arithmetically the 8-bit operand
Syntax
RRAX.A
RRAX.W
RRAX
RRAX.B
Rdst
Rdst
Rdst
Rdst
RRAX.A
RRAX.W
RRAX.B
dst
dst
dst
or
RRAX dst
Operation
MSB → MSB → MSB-1 . ... LSB+1 → LSB → C
Description
Register Mode for the destination: the destination operand is shifted right by
one bit position as shown in Figure 4−48. The MSB retains its value (sign). The
word instruction RRAX.W clears the bits Rdst.19:16, the byte instruction
RRAX.B clears the bits Rdst.19:8. The MSB retains its value (sign), the LSB is
shifted into the carry bit. RRAX here operates equal to a signed division by 2.
All other modes for the destination: the destination operand is shifted right
arithmetically by one bit position as shown in Figure 4−49. The MSB retains
its value (sign), the LSB is shifted into the carry bit. RRAX here operates equal
to a signed division by 2. All addressing modes − with the exception of the
Immediate Mode − are possible in the full memory.
Status Bits
N:
Z:
C:
V:
Mode Bits
4-140
Set if result is negative
.A: dst.19 = 1, reset if dst.19 = 0
.W: dst.15 = 1, reset if dst.15 = 0
.B: dst.7 = 1, reset if dst.7 = 0
Set if result is zero, reset otherwise
Loaded from LSB
Reset
OSCOFF, CPUOFF, and GIE are not affected.
16-Bit MSP430X CPU
Extended Instructions
Example
The signed 20-bit number in R5 is shifted arithmetically right four positions.
RPT
RRAX.A
Example
#4
R5
; R5/16 −> R5
The signed 8-bit value in EDE is multiplied by 0.5.
RRAX.B
&EDE
; EDE/2 -> EDE
Figure 4−48. Rotate Right Arithmetically RRAX(.B,.A). Register Mode
C
19
8
7
0
0
0
MSB
LSB
19
C
C
16
0000
15
0
MSB
LSB
19
0
MSB
LSB
Figure 4−49. Rotate Right Arithmetically RRAX(.B,.A). Non-Register Mode
C
C
C
7
0
MSB
LSB
15
0
MSB
LSB
31
20
0
0
19
0
MSB
LSB
16-Bit MSP430X CPU
4-141
Extended Instructions
RRCM.A
RRCM[.W]
Rotate Right through carry the 20-bit CPU register content
Rotate Right through carry the 16-bit CPU register content
Syntax
RRCM.A
RRCM.W
#n,Rdst
#n,Rdst
1≤n≤4
or RRCM #n,Rdst
1≤n≤4
Operation
C → MSB → MSB-1 → ... LSB+1 → LSB → C
Description
The destination operand is shifted right by one, two, three, or four bit positions
as shown in Figure 4−50. The carry bit C is shifted into the MSB, the LSB is
shifted into the carry bit. The word instruction RRCM.W clears the bits
Rdst.19:16
Note : This instruction does not use the extension word.
Status Bits
N:
Set if result is negative
.A: Rdst.19 = 1, reset if Rdst.19 = 0
.W: Rdst.15 = 1, reset if Rdst.15 = 0
Set if result is zero, reset otherwise
Loaded from the LSB (n = 1), LSB+1 (n = 2), LSB+2 (n = 3) or LSB+3
(n = 4)
Reset
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The address-word in R5 is shifted right by three positions. The MSB-2 is
loaded with 1.
SETC
; Prepare carry for MSB-2
RRCM.A
Example
#3,R5
; R5 = R5 » 3 + 20000h
The word in R6 is shifted right by two positions. The MSB is loaded with the
LSB. The MSB-1 is loaded with the contents of the carry flag.
RRCM.W
#2,R6
; R6 = R6 » 2. R6.19:16 = 0
Figure 4−50. Rotate Right Through Carry RRCM[.W] and RRCM.A
16
19
C
C
4-142
16-Bit MSP430X CPU
0
15
0
MSB
LSB
19
0
MSB
LSB
Extended Instructions
RRCX.A
RRCX[.W]
RRCX.B
Rotate Right through carry the 20-bit operand
Rotate Right through carry the 16-bit operand
Rotate Right through carry the 8-bit operand
Syntax
RRCX.A
RRCX.W
RRCX
RRCX.B
Rdst
Rdst
Rdst
Rdst
RRCX.A
RRCX.W
RRCX.B
dst
dst
dst
or
RRCX dst
Operation
C → MSB → MSB-1 → ... LSB+1 → LSB → C
Description
Register Mode for the destination: the destination operand is shifted right by
one bit position as shown in Figure 4−51. The word instruction RRCX.W clears
the bits Rdst.19:16, the byte instruction RRCX.B clears the bits Rdst.19:8. The
carry bit C is shifted into the MSB, the LSB is shifted into the carry bit.
All other modes for the destination: the destination operand is shifted right by
one bit position as shown in Figure 4−52. The carry bit C is shifted into the
MSB, the LSB is shifted into the carry bit. All addressing modes − with the
exception of the Immediate Mode − are possible in the full memory.
Status Bits
N:
Z:
C:
V:
Mode Bits
Set if result is negative
.A: dst.19 = 1, reset if dst.19 = 0
.W: dst.15 = 1, reset if dst.15 = 0
.B: dst.7 = 1, reset if dst.7 = 0
Set if result is zero, reset otherwise
Loaded from LSB
Reset
OSCOFF, CPUOFF, and GIE are not affected.
16-Bit MSP430X CPU
4-143
Extended Instructions
Example
The 20-bit operand at address EDE is shifted right by one position. The MSB is
loaded with 1.
SETC
; Prepare carry for MSB
RRCX.A
Example
EDE
; EDE = EDE » 1 + 80000h
The word in R6 is shifted right by twelve positions.
RPT
RRCX.W
#12
R6
; R6 = R6 » 12. R6.19:16 = 0
Figure 4−51. Rotate Right Through Carry RRCX(.B,.A). Register Mode
8
19
C
0−−−−−−−−−−−−−−−−−−−−0
19
C
C
16
0000
7
0
MSB
LSB
15
0
MSB
LSB
19
0
MSB
LSB
Figure 4−52. Rotate Right Through Carry RRCX(.B,.A). Non-Register Mode
C
C
C
4-144
16-Bit MSP430X CPU
7
0
MSB
LSB
15
0
MSB
LSB
31
20
0
0
19
0
MSB
LSB
Extended Instructions
RRUM.A
RRUM[.W]
Rotate Right Unsigned the 20-bit CPU register content
Rotate Right Unsigned the 16-bit CPU register content
Syntax
RRUM.A
RRUM.W
#n,Rdst
#n,Rdst
1≤n≤4
or RRUM #n,Rdst
1≤n≤4
→ MSB → MSB-1 . →... LSB+1 → LSB → C
Operation
0
Description
The destination operand is shifted right by one, two, three, or four bit positions
as shown in Figure 4−53. Zero is shifted into the MSB, the LSB is shifted into
the carry bit. RRUM works like an unsigned division by 2, 4, 8, or 16. The word
instruction RRUM.W clears the bits Rdst.19:16.
Note : This instruction does not use the extension word.
Status Bits
N:
Set if result is negative
.A: Rdst.19 = 1, reset if Rdst.19 = 0
.W: Rdst.15 = 1, reset if Rdst.15 = 0
Set if result is zero, reset otherwise
Loaded from the LSB (n = 1), LSB+1 (n = 2), LSB+2 (n = 3) or LSB+3
(n = 4)
Reset
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The unsigned address-word in R5 is divided by 16.
RRUM.A
Example
#4,R5
; R5 = R5 » 4. R5/16
The word in R6 is shifted right by one bit. The MSB R6.15 is loaded with 0.
RRUM.W
#1,R6
; R6 = R6/2. R6.19:15 = 0
Figure 4−53. Rotate Right Unsigned RRUM[.W] and RRUM.A
16
19
C
0000
15
0
MSB
LSB
0
C 0
19
0
MSB
LSB
16-Bit MSP430X CPU
4-145
Extended Instructions
RRUX.A
RRUX[.W]
RRUX.B
Rotate Right unsigned the 20-bit operand
Rotate Right unsigned the 16-bit operand
Rotate Right unsigned the 8-bit operand
Syntax
RRUX.A
RRUX.W
RRUX
RRUX.B
Rdst
Rdst
Rdst
Rdst
Operation
C=0 → MSB → MSB-1 → ... LSB+1 → LSB → C
Description
RRUX is valid for register Mode only: the destination operand is shifted right by
one bit position as shown in Figure 4−54. The word instruction RRUX.W clears
the bits Rdst.19:16. The byte instruction RRUX.B clears the bits Rdst.19:8.
Zero is shifted into the MSB, the LSB is shifted into the carry bit.
Status Bits
N:
Set if result is negative
.A: dst.19 = 1, reset if dst.19 = 0
.W: dst.15 = 1, reset if dst.15 = 0
.B: dst.7 = 1, reset if dst.7 = 0
Set if result is zero, reset otherwise
Loaded from LSB
Reset
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The word in R6 is shifted right by twelve positions.
RPT
RRUX.W
#12
R6
; R6 = R6 » 12. R6.19:16 = 0
Figure 4−54. Rotate Right Unsigned RRUX(.B,.A). Register Mode
8
19
C
0−−−−−−−−−−−−−−−−−−−−0
7
0
MSB
LSB
0
19
C
16
0000
15
0
MSB
LSB
0
C 0
4-146
19
0
MSB
LSB
16-Bit MSP430X CPU
Extended Instructions
* SBCX.A
* SBCX[.W]
* SBCX.B
Subtract source and borrow/.NOT. carry from destination address-word
Subtract source and borrow/.NOT. carry from destination word
Subtract source and borrow/.NOT. carry from destination byte
Syntax
SBCX.A
SBCX
SBCX.B
dst
dst
dst
or
SBCX.W dst
Operation
dst + 0FFFFFh + C −> dst
dst + 0FFFFh + C −> dst
dst + 0FFh + C −> dst
Emulation
SUBCX.A
SUBCX
SUBCX.B
Description
The carry bit (C) is added to the destination operand minus one. The previous
contents of the destination are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Set if there is a carry from the MSB of the result, reset otherwise.
Set to 1 if no borrow, reset if borrow.
V: Set if an arithmetic overflow occurs, reset otherwise.
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 8-bit counter pointed to by R13 is subtracted from a 16-bit counter pointed
to by R12.
SUBX.B
SBCX.B
#0,dst
#0,dst
#0,dst
@R13,0(R12)
1(R12)
; Subtract LSDs
; Subtract carry from MSD
Note: Borrow Implementation.
The borrow is treated as a .NOT. carry :
Borrow
Yes
No
Carry bit
0
1
16-Bit MSP430X CPU
4-147
Extended Instructions
SUBX.A
SUBX[.W]
SUBX.B
Subtract source address-word from destination address-word
Subtract source word from destination word
Subtract source byte from destination byte
Syntax
SUBX.A
SUBX
SUBX.B
src,dst
src,dst or SUBX.W
src,dst
src,dst
or dst − src → dst
Operation
(.not. src) + 1 + dst → dst
Description
The source operand is subtracted from the destination operand. This is made
by adding the 1’s complement of the source + 1 to the destination. The source
operand is not affected. The result is written to the destination operand. Both
operands may be located in the full address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
A 20-bit constant 87654h is subtracted from EDE (LSBs) and EDE+2 (MSBs).
Set if result is negative (src > dst), reset if positive (src <= dst)
Set if result is zero (src = dst), reset otherwise (src ≠ dst)
Set if there is a carry from the MSB, reset otherwise
Set if the subtraction of a negative source operand from a positive destination operand delivers a negative result, or if the subtraction of a positive source operand from a negative destination operand delivers a
positive result, reset otherwise (no overflow).
SUBX.A
Example
#87654h,EDE ; Subtract 87654h from EDE+2|EDE
A table word pointed to by R5 (20-bit address) is subtracted from R7. Jump to
label TONI if R7 contains zero after the instruction. R5 is auto-incremented by
2. R7.19:16 = 0
SUBX.W
@R5+,R7
; Subtract table number from R7. R5 + 2
JZ
TONI
; R7 = @R5 (before subtraction)
...
Example
; R7 <> @R5 (before subtraction)
Byte CNT is subtracted from the byte R12 points to in the full address space.
Address of CNT is within PC ± 512 K.
SUBX.B
CNT,0(R12)
; Subtract CNT from @R12
Note: Use SUBA for the following two cases for better density and execution.
SUBX.A
Rsrc,Rdst or
SUBX.A
#imm20,Rdst
4-148
16-Bit MSP430X CPU
Extended Instructions
SUBCX.A
SUBCX[.W]
SUBCX.B
Subtract source address-word with carry from destination address-word
Subtract source word with carry from destination word
Subtract source byte with carry from destination byte
Syntax
SUBCX.A src,dst
SUBCX
src,dst or SUBCX.W src,dst
SUBCX.B src,dst
Operation
(.not. src) + C + dst → dst
Description
The source operand is subtracted from the destination operand. This is made
by adding the 1’s complement of the source + carry to the destination. The
source operand is not affected, the result is written to the destination operand.
Both operands may be located in the full address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
A 20-bit constant 87654h is subtracted from R5 with the carry from the
previous instruction.
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if there is a carry from the MSB, reset otherwise
Set if the subtraction of a negative source operand from a positive destination operand delivers a negative result, or if the subtraction of a positive source operand from a negative destination operand delivers a
positive result, reset otherwise (no overflow).
SUBCX.A #87654h,R5
Example
; Subtract 87654h + C from R5
A 48-bit number (3 words) pointed to by R5 (20-bit address) is subtracted from
a 48-bit counter in RAM, pointed to by R7. R5 auto-increments to point to the
next 48-bit number.
SUBX.W
Example
or dst − (src − 1) + C → dst
@R5+,0(R7)
; Subtract LSBs. R5 + 2
SUBCX.W @R5+,2(R7)
; Subtract MIDs with C. R5 + 2
SUBCX.W @R5+,4(R7)
; Subtract MSBs with C. R5 + 2
Byte CNT is subtracted from the byte, R12 points to. The carry of the previous
instruction is used. 20-bit addresses.
SUBCX.B &CNT,0(R12)
; Subtract byte CNT from @R12
16-Bit MSP430X CPU
4-149
Extended Instructions
SWPBX.A
SWPBX[.W]
Swap bytes of lower word
Swap bytes of word
Syntax
SWPBX.A
SWPBX.W
dst
dst
or
SWPBX
dst
Operation
dst.15:8 à dst.7:0
Description
Register Mode: Rn.15:8 are swapped with Rn.7:0. When the .A extension is
used, Rn.19:16 are unchanged. When the .W extension is used, Rn.19:16 are
cleared.
Other Modes: When the .A extension is used, bits 31:20 of the destination
address are cleared, bits 19:16 are left unchanged, and bits 15:8 are swapped
with bits 7:0. When the .W extension is used, bits 15:8 are swapped with bits
7:0 of the addressed word.
Status Bits
Not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Exchange the bytes of RAM address-word EDE.
Example
MOVX.A
#23456h,&EDE
; 23456h −> EDE
SWPBX.A
EDE
; 25634h −> EDE
Exchange the bytes of R5.
MOVA
SWPBX.W
#23456h,R5
R5
; 23456h −> R5
; 05634h −> R5
Figure 4−55. Swap Bytes SWPBX.A Register Mode
Before SWPBX.A
19
16 15
X
8
7
High Byte
0
Low Byte
After SWPBX.A
19
16
X
4-150
16-Bit MSP430X CPU
15
8
Low Byte
7
0
High Byte
Extended Instructions
Figure 4−56. Swap Bytes SWPBX.A In Memory
Before SWPBX.A
31
20 19
16
X
X
After SWPBX.A
31
20 19
0
7
0
Low Byte
High Byte
16
X
8
15
8
15
7
0
High Byte
Low Byte
Figure 4−57. Swap Bytes SWPBX[.W] Register Mode
Before SWPBX
19
16 15
X
8
7
High Byte
0
Low Byte
After SWPBX
19
16
15
0
8
7
Low Byte
0
High Byte
Figure 4−58. Swap Bytes SWPBX[.W] In Memory
Before SWPBX
15
8
7
High Byte
0
Low Byte
After SWPBX
15
8
Low Byte
7
0
High Byte
16-Bit MSP430X CPU
4-151
Extended Instructions
SXTX.A
SXTX[.W]
Extend sign of lower byte to address-word
Extend sign of lower byte to word
Syntax
SXTX.A
SXTX.W
dst
dst
or
SXTX dst
Operation
dst.7 → dst.15:8, Rdst.7 → Rdst.19:8 (Register Mode)
Description
Register Mode:
The sign of the low byte of the operand (Rdst.7) is extended into the bits
Rdst.19:8.
Other Modes:
SXTX.A: the sign of the low byte of the operand (dst.7) is extended into
dst.19:8. The bits dst.31:20 are cleared.
SXTX[.W]: the sign of the low byte of the operand (dst.7) is extended into
dst.15:8.
Status Bits
N:
Z:
C:
V:
Set if result is negative, reset otherwise
Set if result is zero, reset otherwise
Set if result is not zero, reset otherwise (C = .not.Z)
Reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The signed 8-bit data in EDE.7:0 is sign extended to 20 bits: EDE.19:8. Bits
31:20 located in EDE+2 are cleared.
SXTX.A
; Sign extended EDE −> EDE+2/EDE
&EDE
Figure 4−59. Sign Extend SXTX.A
SXTX.A Rdst
19
16 15
8 7 6
0
S
SXTX.A dst
31
0
4-152
16-Bit MSP430X CPU
20 19
......
0
16 15
8 7 6
S
0
Extended Instructions
Figure 4−60. Sign Extend SXTX[.W]
SXTX[.W] Rdst
19
16 15
8
7
6
0
6
0
S
SXTX[.W] dst
15
8
7
S
16-Bit MSP430X CPU
4-153
Extended Instructions
* TSTX.A
* TSTX[.W]
* TSTX.B
Test destination address-word
Test destination word
Test destination byte
Syntax
TSTX.A
TSTX
TST.B
dst
dst
dst
or TST.W dst
Operation
dst + 0FFFFFh + 1
dst + 0FFFFh + 1
dst + 0FFh + 1
Emulation
CMPX.A
CMPX
CMPX.B
Description
The destination operand is compared with zero. The status bits are set
according to the result. The destination is not affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
RAM byte LEO is tested; PC is pointing to upper memory. If it is negative,
continue at LEONEG; if it is positive but not zero, continue at LEOPOS.
Set if destination is negative, reset if positive
Set if destination contains zero, reset otherwise
Set
Reset
LEOPOS
LEONEG
LEOZERO
4-154
#0,dst
#0,dst
#0,dst
16-Bit MSP430X CPU
TSTX.B
JN
JZ
......
......
......
LEO
LEONEG
LEOZERO
; Test LEO
; LEO is negative
; LEO is zero
; LEO is positive but not zero
; LEO is negative
; LEO is zero
Extended Instructions
XORX.A
XORX[.W]
XORX.B
Exclusive OR source address-word with destination address-word
Exclusive OR source word with destination word
Exclusive OR source byte with destination byte
Syntax
XORX.A
XORX
XORX.B
src,dst
src,dst or XORX.W
src,dst
src,dst
Operation
src .xor. dst → dst
Description
The source and destination operands are exclusively ORed. The result is
placed into the destination. The source operand is not affected. The previous
contents of the destination are lost. Both operands may be located in the full
address space.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Toggle bits in address-word CNTR (20-bit data) with information in
address-word TONI (20-bit address).
Set if result is negative (MSB = 1), reset if positive (MSB = 0)
Set if result is zero, reset otherwise
Set if result is not zero, reset otherwise (carry = .not. Zero)
Set if both operands are negative (before execution), reset otherwise.
XORX.A
Example
; Toggle bits in CNTR
A table word pointed to by R5 (20-bit address) is used to toggle bits in R6.
XORX.W
Example
TONI,&CNTR
@R5,R6
; Toggle bits in R6. R6.19:16 = 0
Reset to zero those bits in the low byte of R7 that are different from the bits in
byte EDE (20-bit address).
XORX.B
EDE,R7
; Set different bits to 1 in R7
INV.B
R7
; Invert low byte of R7. R7.19:8 = 0.
16-Bit MSP430X CPU
4-155
Address Instructions
4.6.4
Address Instructions
MSP430X address instructions are instructions that support 20-bit operands
but have restricted addressing modes. The addressing modes are restricted
to the Register mode and the Immediate mode, except for the MOVA
instruction. Restricting the addressing modes removes the need for the
additional extension-word op-code improving code density and execution
time. The MSP430X address instructions are listed and described in the
following pages.
4-156
16-Bit MSP430X CPU
Address Instructions
ADDA
Add 20-bit source to a 20-bit destination register
Syntax
ADDA
ADDA
Operation
src + Rdst → Rdst
Description
The 20-bit source operand is added to the 20-bit destination CPU register. The
previous contents of the destination are lost. The source operand is not
affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
R5 is increased by 0A4320h. The jump to TONI is performed if a carry occurs.
Rsrc,Rdst
#imm20,Rdst
Set if result is negative (Rdst.19 = 1), reset if positive (Rdst.19 = 0)
Set if result is zero, reset otherwise
Set if there is a carry from the 20-bit result, reset otherwise
Set if the result of two positive operands is negative, or if the result of
two negative numbers is positive, reset otherwise.
ADDA
#0A4320h,R5
; Add A4320h to 20-bit R5
JC
TONI
; Jump on carry
...
; No carry occurred
16-Bit MSP430X CPU
4-157
Address Instructions
* BRA
Branch to destination
Syntax
BRA
Operation
dst → PC
Emulation
MOVA dst,PC
Description
An unconditional branch is taken to a 20-bit address anywhere in the full
address space. All seven source addressing modes can be used. The branch
instruction is an address-word instruction. If the destination address is
contained in a memory location X, it is contained in two ascending words: X
(LSBs) and (X + 2) (MSBs).
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Examples
Examples for all addressing modes are given.
dst
Not affected
Not affected
Not affected
Not affected
Immediate Mode: Branch to label EDE located anywhere in the 20-bit address
space or branch directly to address.
BRA
#EDE
BRA
#01AA04h
; MOVA
#imm20,PC
Symbolic Mode: Branch to the 20-bit address contained in addresses EXEC
(LSBs) and EXEC+2 (MSBs). EXEC is located at the address (PC + X) where
X is within ±32 K. Indirect addressing.
BRA
EXEC
; MOVA
z16(PC),PC
Note: if the 16-bit index is not sufficient, a 20-bit index may be used with the
following instruction.
MOVX.A
EXEC,PC
; 1M byte range with 20-bit index
Absolute Mode: Branch to the 20-bit address contained in absolute addresses
EXEC (LSBs) and EXEC+2 (MSBs). Indirect addressing.
BRA
&EXEC
; MOVA
&abs20,PC
Register Mode: Branch to the 20-bit address contained in register R5. Indirect
R5.
BRA
4-158
16-Bit MSP430X CPU
R5
; MOVA
R5,PC
Address Instructions
Indirect Mode: Branch to the 20-bit address contained in the word pointed to
by register R5 (LSBs). The MSBs have the address (R5 + 2). Indirect, indirect
R5.
BRA
@R5
; MOVA
@R5,PC
Indirect, Auto-Increment Mode: Branch to the 20-bit address contained in the
words pointed to by register R5 and increment the address in R5 afterwards
by 4. The next time the S/W flow uses R5 as a pointer, it can alter the program
execution due to access to the next address in the table pointed to by R5.
Indirect, indirect R5.
BRA
@R5+
; MOVA
@R5+,PC. R5 + 4
Indexed Mode: Branch to the 20-bit address contained in the address pointed
to by register (R5 + X) (e.g. a table with addresses starting at X). (R5 + X)
points to the LSBs, (R5 + X + 2) points to the MSBs of the address. X is within
R5 ± 32 K. Indirect, indirect (R5 + X).
BRA
X(R5)
; MOVA
z16(R5),PC
Note: if the 16-bit index is not sufficient, a 20-bit index X may be used with the
following instruction:
MOVX.A
X(R5),PC
; 1M byte range with 20-bit index
16-Bit MSP430X CPU
4-159
Address Instructions
CALLA
Call a Subroutine
Syntax
CALLA
dst
Operation
dst
SP − 2
PC.19:16
SP − 2
PC.15:0
tmp
→
→
→
→
→
→
Description
A subroutine call is made to a 20-bit address anywhere in the full address
space. All seven source addressing modes can be used. The call instruction is
an address-word instruction. If the destination address is contained in a
memory location X, it is contained in two ascending words: X (LSBs) and
(X + 2) (MSBs). Two words on the stack are needed for the return address.
The return is made with the instruction RETA.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Examples
Examples for all addressing modes are given.
tmp 20-bit dst is evaluated and stored
SP
@SP updated PC with return address to TOS (MSBs)
SP
@SP updated PC to TOS (LSBs)
PC
saved 20-bit dst to PC
Not affected
Not affected
Not affected
Not affected
Immediate Mode: Call a subroutine at label EXEC or call directly an address.
CALLA
#EXEC
; Start address EXEC
CALLA
#01AA04h
; Start address 01AA04h
Symbolic Mode: Call a subroutine at the 20-bit address contained in
addresses EXEC (LSBs) and EXEC+2 (MSBs). EXEC is located at the
address (PC + X) where X is within ±32 K. Indirect addressing.
CALLA
EXEC
; Start address at @EXEC. z16(PC)
Absolute Mode: Call a subroutine at the 20-bit address contained in absolute
addresses EXEC (LSBs) and EXEC+2 (MSBs). Indirect addressing.
CALLA
&EXEC
; Start address at @EXEC
Register Mode: Call a subroutine at the 20-bit address contained in register
R5. Indirect R5.
CALLA
4-160
16-Bit MSP430X CPU
R5
; Start address at @R5
Address Instructions
Indirect Mode: Call a subroutine at the 20-bit address contained in the word
pointed to by register R5 (LSBs). The MSBs have the address (R5 + 2).
Indirect, indirect R5.
CALLA
@R5
; Start address at @R5
Indirect, Auto-Increment Mode: Call a subroutine at the 20-bit address
contained in the words pointed to by register R5 and increment the 20-bit
address in R5 afterwards by 4. The next time the S/W flow uses R5 as a
pointer, it can alter the program execution due to access to the next word
address in the table pointed to by R5. Indirect, indirect R5.
CALLA
@R5+
; Start address at @R5. R5 + 4
Indexed Mode: Call a subroutine at the 20-bit address contained in the
address pointed to by register (R5 + X) e.g. a table with addresses starting at
X. (R5 + X) points to the LSBs, (R5 + X + 2) points to the MSBs of the word
address. X is within R5 ±32 K. Indirect, indirect (R5 + X).
CALLA
X(R5)
; Start address at @(R5+X). z16(R5)
16-Bit MSP430X CPU
4-161
Address Instructions
* CLRA
Clear 20-bit destination register
Syntax
CLRA
Operation
0 −> Rdst
Emulation
MOVA
Description
The destination register is cleared.
Status Bits
Status bits are not affected.
Example
The 20-bit value in R10 is cleared.
CLRA
4-162
16-Bit MSP430X CPU
Rdst
#0,Rdst
R10
; 0 −> R10
Address Instructions
CMPA
Compare the 20-bit source with a 20-bit destination register
Syntax
CMPA
CMPA
Operation
(.not. src) + 1 + Rdst
Description
The 20-bit source operand is subtracted from the 20-bit destination CPU
register. This is made by adding the 1’s complement of the source + 1 to the
destination register. The result affects only the status bits.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
A 20-bit immediate operand and R6 are compared. If they are equal the
program continues at label EQUAL.
Rsrc,Rdst
#imm20,Rdst
Set if result is negative (src > dst), reset if positive (src <= dst)
Set if result is zero (src = dst), reset otherwise (src ≠ dst)
Set if there is a carry from the MSB, reset otherwise
Set if the subtraction of a negative source operand from a positive
destination operand delivers a negative result, or if the subtraction of
a positive source operand from a negative destination operand delivers
a positive result, reset otherwise (no overflow).
CMPA
#12345h,R6
; Compare R6 with 12345h
JEQ
EQUAL
; R5 = 12345h
...
Example
or Rdst − src
; Not equal
The 20-bit values in R5 and R6 are compared. If R5 is greater than (signed) or
equal to R6, the program continues at label GRE.
CMPA
R6,R5
; Compare R6 with R5 (R5 − R6)
JGE
GRE
; R5 >= R6
...
; R5 < R6
16-Bit MSP430X CPU
4-163
Address Instructions
* DECDA
Double-decrement 20-bit destination register
Syntax
DECDA
Operation
Rdst − 2 −> Rdst
Emulation
SUBA
Description
The destination register is decremented by two. The original contents are lost.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 20-bit value in R5 is decremented by 2
#2,Rdst
Set if result is negative, reset if positive
Set if Rdst contained 2, reset otherwise
Reset if Rdst contained 0 or 1, set otherwise
Set if an arithmetic overflow occurs, otherwise reset.
DECDA
4-164
Rdst
16-Bit MSP430X CPU
R5
; Decrement R5 by two
Address Instructions
* INCDA
Double-increment 20-bit destination register
Syntax
INCDA
Operation
dst + 2 −> dst
Emulation
ADDA
Example
The destination register is incremented by two. The original contents are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if Rdst contained 0FFFFEh, reset otherwise
Set if Rdst contained 0FFFEh, reset otherwise
Set if Rdst contained 0FEh, reset otherwise
C: Set if Rdst contained 0FFFFEh or 0FFFFFh, reset otherwise
Set if Rdst contained 0FFFEh or 0FFFFh, reset otherwise
Set if Rdst contained 0FEh or 0FFh, reset otherwise
V: Set if Rdst contained 07FFFEh or 07FFFFh, reset otherwise
Set if Rdst contained 07FFEh or 07FFFh, reset otherwise
Set if Rdst contained 07Eh or 07Fh, reset otherwise
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 20-bit value in R5 is incremented by 2
INCDA
Rdst
#2,Rdst
R5
; Increment R5 by two
16-Bit MSP430X CPU
4-165
Address Instructions
MOVA
Move the 20-bit source to the 20-bit destination
Syntax
MOVA
MOVA
MOVA
MOVA
MOVA
MOVA
MOVA
MOVA
MOVA
Operation
src
Rsrc
Description
The 20-bit source operand is moved to the 20-bit destination. The source
operand is not affected. The previous content of the destination is lost.
Status Bits
Not affected
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Examples
Copy 20-bit value in R9 to R8.
MOVA
Rsrc,Rdst
#imm20,Rdst
z16(Rsrc),Rdst
EDE,Rdst
&abs20,Rdst
@Rsrc,Rdst
@Rsrc+,Rdst
Rsrc,z16(Rdst)
Rsrc,&abs20
→ Rdst
→ dst
R9,R8
; R9 -> R8
Write 20-bit immediate value 12345h to R12.
MOVA
#12345h,R12
; 12345h -> R12
Copy 20-bit value addressed by (R9 + 100h) to R8. Source operand in
addresses (R9 + 100h) LSBs and (R9 + 102h) MSBs
MOVA
100h(R9),R8
; Index: ± 32 K. 2 words transferred
Move 20-bit value in 20-bit absolute addresses EDE (LSBs) and EDE+2
(MSBs) to R12.
MOVA
&EDE,R12
; &EDE -> R12. 2 words transferred
Move 20-bit value in 20-bit addresses EDE (LSBs) and EDE+2 (MSBs) to R12.
PC index ±32 K.
MOVA
EDE,R12
; EDE -> R12. 2 words transferred
Copy 20-bit value R9 points to (20 bit address) to R8. Source operand in
addresses @R9 LSBs and @(R9 + 2) MSBs.
MOVA
4-166
16-Bit MSP430X CPU
@R9,R8
; @R9 -> R8. 2 words transferred
Address Instructions
Copy 20-bit value R9 points to (20 bit address) to R8. R9 is incremented by
four afterwards. Source operand in addresses @R9 LSBs and @(R9 + 2)
MSBs.
MOVA
@R9+,R8
; @R9 -> R8. R9 + 4. 2 words transferred.
Copy 20-bit value in R8 to destination addressed by (R9 + 100h). Destination
operand in addresses @(R9 + 100h) LSBs and @(R9 + 102h) MSBs.
MOVA
R8,100h(R9)
; Index: +- 32 K. 2 words transferred
Move 20-bit value in R13 to 20-bit absolute addresses EDE (LSBs) and
EDE+2 (MSBs).
MOVA
R13,&EDE
; R13 -> EDE. 2 words transferred
Move 20-bit value in R13 to 20-bit addresses EDE (LSBs) and EDE+2 (MSBs).
PC index ±32 K.
MOVA
R13,EDE
; R13 -> EDE. 2 words transferred
16-Bit MSP430X CPU
4-167
Address Instructions
* RETA
Return from subroutine
Syntax
RETA
Operation
@SP
SP + 2
@SP
SP + 2
→
→
→
→
PC.15:0
SP
PC.19:16
SP
LSBs (15:0) of saved PC to PC.15:0
MSBs (19:16) of saved PC to PC.19:16
Emulation
MOVA
@SP+,PC
Description
The 20-bit return address information, pushed onto the stack by a CALLA
instruction, is restored to the program counter PC. The program continues at
the address following the subroutine call. The status register bits SR.11:0 are
not affected. This allows the transfer of information with these bits.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
Call a subroutine SUBR from anywhere in the 20-bit address space and return
to the address after the CALLA.
Not affected
Not affected
Not affected
Not affected
CALLA
#SUBR
...
; Return by RETA to here
SUBR PUSHM.A #2,R14
...
POPM.A
RETA
4-168
16-Bit MSP430X CPU
; Call subroutine starting at SUBR
; Save R14 and R13 (20 bit data)
; Subroutine code
#2,R14
; Restore R13 and R14 (20 bit data)
; Return (to full address space)
Address Instructions
* TSTA
Test 20-bit destination register
Syntax
TSTA
Operation
dst + 0FFFFFh + 1
dst + 0FFFFh + 1
dst + 0FFh + 1
Emulation
CMPA
Description
The destination register is compared with zero. The status bits are set
according to the result. The destination register is not affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 20-bit value in R7 is tested. If it is negative, continue at R7NEG; if it is
positive but not zero, continue at R7POS.
Rdst
#0,Rdst
Set if destination register is negative, reset if positive
Set if destination register contains zero, reset otherwise
Set
Reset
R7POS
R7NEG
R7ZERO
TSTA
JN
JZ
......
......
......
R7
R7NEG
R7ZERO
; Test R7
; R7 is negative
; R7 is zero
; R7 is positive but not zero
; R7 is negative
; R7 is zero
16-Bit MSP430X CPU
4-169
Address Instructions
SUBA
Subtract 20-bit source from 20-bit destination register
Syntax
SUBA
SUBA
Operation
(.not.src) + 1 + Rdst → Rdst
Description
The 20-bit source operand is subtracted from the 20-bit destination register.
This is made by adding the 1’s complement of the source + 1 to the
destination. The result is written to the destination register, the source is not
affected.
Status Bits
N:
Z:
C:
V:
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
The 20-bit value in R5 is subtracted from R6. If a carry occurs, the program
continues at label TONI.
Rsrc,Rdst
#imm20,Rdst
Set if result is negative (src > dst), reset if positive (src <= dst)
Set if result is zero (src = dst), reset otherwise (src ≠ dst)
Set if there is a carry from the MSB (Rdst.19), reset otherwise
Set if the subtraction of a negative source operand from a positive destination operand delivers a negative result, or if the subtraction of a positive source operand from a negative destination operand delivers a
positive result, reset otherwise (no overflow).
SUBA
R5,R6
; R6 − R5 -> R6
JC
TONI
; Carry occurred
...
4-170
or Rdst − src → Rdst
16-Bit MSP430X CPU
; No carry
Chapter 5
FLL+ Clock Module
The FLL+ clock module provides the clocks for MSP430x4xx devices. This
chapter discusses the FLL+ clock module. The FLL+ clock module is
implemented in all MSP430x4xx devices.
Topic
Page
5.1
FLL+ Clock Module Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.2
FLL+ Clock Module Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8
5.3
FLL+ Clock Module Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15
FLL+ Clock Module
5-1
5.1 FLL+ Clock Module Introduction
The frequency-locked loop (FLL+) clock module supports low system cost and
ultra low-power consumption. Using three internal clock signals, the user can
select the best balance of performance and low power consumption. The FLL+
features digital frequency-locked loop (FLL) hardware. The FLL operates
together with a digital modulator and stabilizes the internal digitally controlled
oscillator (DCO) frequency to a programmable multiple of the LFXT1 watch
crystal frequency. The FLL+ clock module can be configured to operate
without any external components, with one or two external crystals, or with
resonators, under full software control.
The FLL+ clock module includes two or three clock sources:
- LFXT1CLK: Low-frequency/high-frequency oscillator that can be used
either with low-frequency 32768-Hz watch crystals or standard crystals or
resonators in the 450-kHz to 8-MHz range. See the device-specific data
sheet for details.
- XT2CLK: Optional high-frequency oscillator that can be used with
standard crystals, resonators, or external clock sources in the 450-kHz to
8-MHz range. In MSP430F47x3/4 and MSP430F471xx devices the upper
limit is 16 MHz. See the device-specific data sheet for details.
- DCOCLK: Internal digitally controlled oscillator (DCO) with RC-type
characteristics, stabilized by the FLL.
- VLOCLK: Internal very low power, low frequency oscillator with 12-kHz
typical frequency.
Four clock signals are available from the FLL+ module:
- ACLK: Auxiliary clock. The ACLK is software selectable as LFXT1CLK or
VLOCLK as clock source. ACLK is software selectable for individual
peripheral modules.
- ACLK/n: Buffered output of the ACLK. The ACLK/n is ACLK divided by
1,2,4, or 8 and used externally only.
- MCLK: Master clock. MCLK is software selectable as LFXT1CLK,
VLOCLK, XT2CLK (if available), or DCOCLK. MCLK can be divided by 1,
2, 4, or 8 within the FLL block. MCLK is used by the CPU and system.
- SMCLK: Sub-main clock. SMCLK is software selectable as XT2CLK (if
available) or DCOCLK. SMCLK is software selectable for individual
peripheral modules.
5-2
FLL+ Clock Module
The block diagrams of the FLL+ clock module are shown in Figure 5−1 to
Figure 5−4.
- Figure 5−1 shows the block diagram for MSP430x43x, MSP430x44x,
MSP430FG47x, MSP430F47x, and MSP430x461x devices.
- Figure 5−2 shows the block diagram for MSP430x42x and MSP430x41x
devices.
- Figure 5−3
shows the block diagram for MSP430x47x3/4 and
MSP430F471xx devices.
- Figure 5−4 shows the block diagram for MSP430x41x2 devices.
FLL+ Clock Module
5-3
Figure 5−1. MSP430x43x, MSP430x44x, MSP430FG47x, MSP430F47x, and
MSP430x461x Frequency-Locked Loop
FLL_DIVx
Divider
/1/2/4/8
ACLK/n
fCrystal
XIN
ACLK
XTS_FLL
OSCOFF
0V
LF
SCG0
XT
PUC
LFOff
XOUT
Enable Reset
+
10−bit
Frequency
Integrator
0V
XT1Off
LFXT1 Oscillator
XCAPxPF
SELMx
CPUOFF
00
−
/(N+1)
01
01
10
10
10
SCG1
FNx
0
1
11
11
M
MCLK
4
off
DC
Generator
DCO
+
Modulator
fDCOCLK
FLLDx
Divider
/1/2/4/8
fDCO
fDCO/D
DCOPLUS
1
SELS
SMCLKOFF
0
0
1
XT20FF
XT2IN
XT2OUT
5-4
XT2 Oscillator
FLL+ Clock Module
0
1
SMCLK
Figure 5−2. MSP430x42x and MSP430x41x Frequency-Locked Loop
FLL_DIVx
Divider
/1/2/4/8
ACLK/n
fCrystal
XIN
ACLK
XTS_FLL
OSCOFF
0V
LF
SCG0
XT
PUC
LFOff
XOUT
Enable Reset
+
10−bit
Frequency
Integrator
0V
XT1Off
LFXT1 Oscillator
XCAPxPF
CPUOFF
−
/(N+1)
0
10
SCG1
FNx
1
M
MCLK to CPU
4
off
DC
Generator
DCO
+
Modulator
MCLK to Peripherals
FLLDx
Divider
/1/2/4/8
fDCOCLK
fDCO
fDCO/D
DCOPLUS
1
0
FLL+ Clock Module
SMCLK
5-5
Figure 5−3. MSP430x47x3/4 and MSP430F471xx Frequency-Locked Loop
FLL_DIVx
Divider
/1/2/4/8
ACLK/n
fCrystal
XIN
ACLK
XTS_FLL
OSCOFF
0V
LF
SCG0
XT
PUC
LFOff
XOUT
Enable Reset
+
10−bit
Frequency
Integrator
0V
XT1Off
LFXT1 Oscillator
XCAPxPF
SELMx
CPUOFF
00
−
/(N+1)
01
01
10
10
10
SCG1
FNx
0
1
11
11
M
MCLK
4
off
DC
Generator
DCO
+
Modulator
fDCOCLK
FLLDx
Divider
/1/2/4/8
fDCO
fDCO/D
DCOPLUS
1
SELS
SMCLKOFF
0
0
1
XT20FF XT2Sx
XT2IN
XT2OUT
5-6
XT2 Oscillator
(supporting upto 16MHz)
FLL+ Clock Module
0
1
SMCLK
Figure 5--4. MSP430x41x2 Frequency-Locked Loop
FLL_DIVx
Internal
LP/LF
Oscillator
VLOCLK
Divider
/1/2/4/8
ACLK/n
10
LFXT1CLK
ACLK
else
OSCOFF
XTS_FLL
XIN
LFXT1Sx
0V
SCG0
LF
XOUT
0V
SELM
Enable Reset
+
10-bit
Frequency
Integrator
-
XT1Off
LFXT1 Oscillator
XCAPxPF
PUC
XT
/(N+1)
00
CPUOFF
01
0
10
1
MCLK
11
SCG1
FNx
4
off
DC
Generator
10
DCO
+
Modulator
DCOPLUS
Divider
/1/2/4/8
fDCO
SMCLKOFF
0
fDCO/D
0
1
SMCLK
1
FLL+ Clock Module
5-7
FLL+ Clock Module Operation
5.2 FLL+ Clock Module Operation
After a PUC, MCLK and SMCLK are sourced from DCOCLK at 32 times the
ACLK frequency. When a 32 768-Hz crystal is used for ACLK, MCLK and
SMCLK stabilize to 1.048576 MHz.
Status register control bits SCG0, SCG1, OSCOFF, and CPUOFF configure
the MSP430 operating modes and enable or disable components of the FLL+
clock module. See Chapter System Resets, Interrupts and Operating Modes.
The SCFQCTL, SCFI0, SCFI1, FLL_CTL0, and FLL_CTL1 registers configure
the FLL+ clock module. The FLL+ can be configured or reconfigured by
software at any time during program execution.
Example, MCLK = 64 × ACLK = 2097152
BIC
MOV.B
MOV.B
BIS
5.2.1
#GIE,SR
#(64−1),&SCFQCTL
#FN_2,&SCFI0
#GIE,SR
;
;
;
;
Disable interrupts
MCLK = 64 * ACLK, DCOPLUS=0
Select DCO range
Enable interrupts
FLL+ Clock features for Low-Power Applications
Conflicting requirements typically exist in battery-powered MSP430x4xx
applications:
- Low clock frequency for energy conservation and time keeping
- High clock frequency for fast reaction to events and fast burst processing
capability
- Clock stability over operating temperature and supply voltage
The FLL+ clock module addresses the above conflicting requirements by
allowing the user to select from the three available clock signals: ACLK, MCLK,
and SMCLK. For optimal low-power performance, the ACLK can be
configured to oscillate with a low-power 32 786-Hz watch-crystal, providing a
stable time base for the system and low-power standby operation. The MCLK
can be configured to operate from the on-chip DCO, stabilized by the FLL, and
can activate when requested by interrupt events.
The digital frequency-locked loop provides decreased start-time and
stabilization delay over an analog phase-locked loop. A phase-locked loop
takes hundreds or thousands of clock cycles to start and stabilize. The FLL
starts immediately at its previous setting.
5-8
FLL+ Clock Module
FLL+ Clock Module Operation
5.2.2
Internal Very Low-Power, Low-Frequency Oscillator
The internal very low-power, low-frequency oscillator (VLO) provides a typical
frequency of 12kHz (see device-specific data sheet for parameters) without
requiring a crystal. VLOCLK source is selected by setting LFXT1Sx = 10 when
XTS_FLL = 0. The OSCOFF bit disables the VLO for LPM4. The LFXT1 crystal
oscillators are disabled when the VLO is selected reducing current
consumption. The VLO consumes no power when not being used.
5.2.3
LFXT1 Oscillator
The LFXT1 oscillator supports ultralow-current consumption using a
32,768-Hz watch crystal in LF mode (XTS_FLL = 0). A watch crystal connects
to XIN and XOUT without any external components.
The LFXT1 oscillator supports high-speed crystals or resonators when in HF
mode (XTS_FLL = 1). The high-speed crystal or resonator connects to XIN
and XOUT.
LFXT1 may be used with an external clock signal on the XIN pin when
XTS_FLL = 1. The input frequency range is ~1 Hz to 8 MHz. When the input
frequency is below 450 kHz, the XT1OF bit may be set to prevent the CPU from
being clocked from the external frequency.
The software-selectable XCAPxPF bits configure the internally provided load
capacitance for the LFXT1 crystal. The internal pin capacitance plus the
parasitic 2-pF pin capacitance combine serially to form the load capacitance.
The load capacitance can be selected as 1, 6, 8, or 10 pF. Additional external
capacitors can be added if necessary.
Software can disable LFXT1 by setting OSCOFF if this signal does not source
MCLK (SELM ≠ 3 or CPUOFF = 1 ).
Note: LFXT1 Oscillator Characteristics
Low-frequency crystals often require hundreds of milliseconds to start up,
depending on the crystal.
Ultralow-power oscillators such as the LFXT1 in LF mode should be guarded
from noise coupling from other sources. The crystal should be placed as
close as possible to the MSP430 with the crystal housing grounded and the
crystal traces guarded with ground traces.
The default value of XCAPxPF is 0, providing a crystal load capacitance of
~1 pF. Reliable crystal operation may not be achieved unless the crystal is
provided with the proper load capacitance, either by selection of XCAPxPF
values or by external capacitors.
FLL+ Clock Module
5-9
FLL+ Clock Module Operation
5.2.4
XT2 Oscillator
Some devices have a second crystal oscillator, XT2. XT2 sources XT2CLK
and its characteristics are identical to LFXT1 in HF mode, except XT2 does not
have internal load capacitors. The required load capacitance for the
high-frequency crystal or resonator must be provided externally.
The XT2OFF bit disables the XT2 oscillator if XT2CLK is unused for MCLK
(SELMx ≠ 2 or CPUOFF = 1) and SMCLK (SELS = 0 or SMCLKOFF = 1).
XT2 may be used with external clock signals on the XT2IN pin. When used with
an external signal, the external frequency must meet the data sheet
parameters for XT2.
If there is only one crystal in the system it should be connected to LFXT1. Using
only XT2 causes the LFOF fault flag to remain set, not allowing for the OFIFG
to ever be cleared.
XT2 Oscillator in MSP430x47x3/4 and MSP430F471xx Devices
The MSP430x47x3/4 and MSP430F471xx devices have a second crystal
oscillator (XT2) that supports crystals up to 16 MHz. XT2 sources XT2CLK.
The XT2Sx bits select the range of operation of XT2. The XT2OFF bit disables
the XT2 oscillator, if XT2CLK is not used for MCLK or SMCLK as described
above.
XT2 may be used with external clock signals on the XT2IN pin when
XT2Sx = 11. When used with an external signal, the external frequency must
meet the data sheet parameters for XT2. When the input frequency is below
the specified lower limit, the XT2OF bit may be set to prevent the CPU from
being clocked with XT2CLK.
If there is only one crystal with a frequency below 8 MHz in the system, it should
be connected to LFXT1. Using only XT2 causes the LFOF fault flag to remain
set, not allowing for the OFIFG to ever be cleared.
5-10
FLL+ Clock Module
FLL+ Clock Module Operation
5.2.5
Digitally Controlled Oscillator (DCO)
The DCO is an integrated ring oscillator with RC-type characteristics. The
DCO frequency is stabilized by the FLL to a multiple of ACLK as defined by
N, the lowest 7 bits of the SCFQCTL register.
The DCOPLUS bit sets the fDCOCLK frequency to fDCO or fDCO/D. The FLLDx
bits configure the divider, D, to 1, 2, 4, or 8. By default, DCOPLUS = 0 and
D = 2, providing a clock frequency of fDCO/2 on fDCOCLK.
The multiplier (N+1) and D set the frequency of DCOCLK.
DCOPLUS = 0: fDCOCLK = (N + 1) x fACLK
DCOPLUS = 1: fDCOCLK = D x (N + 1) x fACLK
DCO Frequency Range
The frequency range of fDCO is selected with the FNx bits as listed in
Table 5−1. The range control allows the DCO to operate near the center of the
available taps for a given DCOCLK frequency. The user must ensure that
MCLK does not exceed the maximum operating frequency. See the
device-specific data sheet for parameters.
Table 5−1. DCO Range Control Bits
5.2.6
FN_8
FN_4
FN_3
FN_2
Typical fDCO Range
0
0
0
0
0.65 to 6.1
0
0
0
1
1.3 to 12.1
0
0
1
X
2 to 17.9
0
1
X
X
2.8 to 26.6
1
X
X
X
4.2 to 46
Frequency Locked Loop (FLL)
The FLL continuously counts up or down a 10-bit frequency integrator. The
output of the frequency integrator that drives the DCO can be read in SCFI1
and SCFI0. The count is adjusted +1 or −1 with each ACLK crystal period.
Five of the integrator bits, SCFI1 bits 7−3, set the DCO frequency tap.
Twenty-nine taps are implemented for the DCO (28, 29, 30, and 31 are
equivalent), and each is approximately 10% higher than the previous. The
modulator mixes two adjacent DCO frequencies to produce fractional taps.
SCFI1 bits 2−0 and SCFI0 bits 1−0 are used for the modulator.
The DCO starts at the lowest tap after a PUC or when SCFI0 and SCFI1 are
cleared. Time must be allowed for the DCO to settle on the proper tap for
normal operation. 32 ACLK cycles are required between taps requiring a worst
case of 28 x 32 ACLK cycles for the DCO to settle.
FLL+ Clock Module
5-11
FLL+ Clock Module Operation
5.2.7
DCO Modulator
The modulator mixes two adjacent DCO frequencies to produce an
intermediate effective frequency and spread the clock energy, reducing
electromagnetic interference (EMI). The modulator mixes the two adjacent
frequencies across 32 DCOCLK clock cycles.
The error of the effective frequency is zero every 32 DCOCLK cycles and does
not accumulate. The modulator settings and DCO control are automatically
controlled by the FLL hardware. Figure 5−5 illustrates the modulator
operation.
Figure 5−5. Modulator Patterns
NDCOmod
31
24
16
15
5
4
3
2
Lower DCO Tap Frequency fDCO
Upper DCO Tap Frequency fDCO+1
1
0
f(DCOCLK) Cycles, Shown for f(DCOCLK)=f(ACLK) × 32
One ACLK Cycle
5-12
FLL+ Clock Module
FLL Operation from Low-Power Modes
5.2.8
Disabling the FLL Hardware and Modulator
The FLL is disabled when the status register bit SCG0 = 1. When the FLL is
disabled, the DCO runs at the previously selected tap and DCOCLK is not
automatically stabilized.
The DCO modulator is disabled when SCFQ_M = 1. When the DCO modulator
is disabled, the DCOCLK is adjusted to the nearest of the available DCO taps.
5.2.9
FLL Operation from Low-Power Modes
An interrupt service request clears SCG1, CPUOFF, and OSCOFF if set but
does not clear SCG0. This means that FLL operation from within an interrupt
service routine entered from LPM1, 3, or 4, the FLL remains disabled and the
DCO operates at the previous setting as defined in SCFI0 and SCFI1. SCG0
can be cleared by user software if FLL operation is required.
5.2.10 Buffered Clock Output
ACLK may be divided by 1, 2, 4, or 8 and buffered out of the device on P1.5.
The division rate is selected with the FLL_DIV bits.
The ACLK output is multiplexed with other pin functions. When multiplexed,
the pin must be configured for the ACLK output.
BIS.B #BIT5,&P1SEL
BIS.B #BIT5,&P1DIR
;
;
;
;
Select
output
Select
signal
ACLK/n signal as
for port P1.5
port P1.5 to ACLK/n
for output
FLL+ Clock Module
5-13
Buffered Clock Output
5.2.11 FLL+ Fail-Safe Operation
The FLL+ module incorporates an oscillator-fault fail-safe feature. This feature
detects an oscillator fault for LFXT1, DCO and XT2 as shown in Figure 5−6.
The available fault conditions are:
- Low-frequency oscillator fault (LFOF) for LFXT1 in LF mode
- High-frequency oscillator fault (XT1OF) for LFXT1 in HF mode
- High-frequency oscillator fault (XT2OF) for XT2
- DCO fault flag (DCOF) for the DCO
The crystal oscillator fault bits LFOF, XT1OF and XT2OF are set if the
corresponding crystal oscillator is turned on and not operating properly. The
fault bits remain set as long as the fault condition exists and are automatically
cleared if the enabled oscillators function normally. During a LFXT1crystal
failure, no ACLK signal is generated and the FLL+ continues to count down to
zero in an attempt to lock ACLK and MCLK/(D×[N+1]). The DCO tap moves
to the lowest position (SCFI1.7 to SCFI1.3 are cleared) and the DCOF is set.
A DCOF is also generated if the N-multiplier value is set too high for the
selected DCO frequency range resulting the DCO tap to move to the highest
position (SCFI1.7 to SCFI1.3 are set). The DCOF is cleared automatically if
the DCO tap is not in the lowest or the highest positions.
The OFIFG oscillator-fault interrupt flag is set and latched at POR or when an
oscillator fault (LFOF, XT1OF, XT2OF, or DCOF set) is detected. When OFIFG
is set, MCLK is sourced from the DCO, and if OFIE is set, the OFIFG requests
an NMI interrupt. When the interrupt is granted, the OFIE is reset
automatically. The OFIFG flag must be cleared by software. The source of the
fault can be identified by checking the individual fault bits.
When OFIFG is set and MCLK is automatically switched to the DCO, the
SELMx bit settings are not changed. This condition must be handled by user
software.
Note: DCO Active During Oscillator Fault
DCOCLK is active even at the lowest DCO tap. The clock signal is available
for the CPU to execute code and service an NMI during an oscillator fault.
Figure 5−6. Oscillator Fault Logic
Oscillator Fault
DCO Fault
LF_OscFault
DCOF
LFOF
Set OFIFG Flag
XTS_FLL
XT1OF
XT1_OscFault
XT2_OscFault
5-14
FLL+ Clock Module
XT2OF
FLL+ Clock Module Registers
5.3 FLL+ Clock Module Registers
The FLL+ registers are listed in Table 5−2.
Table 5−2. FLL+ Registers
†
Register
Short Form
Register Type Address
Initial State
System clock control
SCFQCTL
Read/write
052h
01Fh with PUC
System clock frequency integrator 0
SCFI0
Read/write
050h
040h with PUC
System clock frequency integrator 1
SCFI1
Read/write
051h
Reset with PUC
FLL+ control register 0
FLL_CTL0
Read/write
053h
003h with PUC
FLL+ control register 1
FLL_CTL1
Read/write
054h
Reset with PUC
FLL+ control register 2†
FLL_CTL2
Read/write
055h
Reset with PUC
SFR interrupt enable register 1
IE1
Read/write
000h
Reset with PUC
SFR interrupt flag register 1
IFG1
Read/write
002h
Reset with PUC
MSP430F41x2, MSP430F47x3/4, and MSP430F471xx devices only.
FLL+ Clock Module
5-15
FLL+ Clock Module Registers
SCFQCTL, System Clock Control Register
7
6
5
4
3
SCFQ_M
2
1
0
rw−1
rw−1
rw−1
N
rw−0
rw−0
rw−0
rw−1
rw−1
SCFQ_M
Bit 7
Modulation. This enables or disables modulation.
0
Modulation enabled
1
Modulation disabled
N
Bits
6-0
Multiplier. These bits set the multiplier value for the DCO. N must be > 0 or
unpredictable operation results.
When DCOPLUS = 0: fDCOCLK = (N + 1) ⋅ fcrystal
When DCOPLUS = 1: fDCOCLK = D x (N + 1) ⋅ fcrystal
SCFI0, System Clock Frequency Integrator Register 0
7
6
5
4
FLLDx
rw−0
3
2
FN_x
rw−1
rw−0
rw−0
1
0
MODx (LSBs)
rw−0
rw−0
rw−0
rw−0
FLLDx
Bits
7-6
FLL+ loop divider. These bits divide fDCOCLK in the FLL+ feedback loop.
This results in an additional multiplier for the multiplier bits. See also
multiplier bits.
00 /1
01 /2
10 /4
11 /8
FN_x
Bits
5-2
DCO range control. These bits select the fDCO operating range.
0000 0.65 to 6.1 MHz
0001 1.3 to 12.1 MHz
001x 2 to 17.9 MHz
01xx 2.8 to 26.6 MHz
1xxx 4.2 to 46 MHz
MODx
Bits
1−0
Least significant modulator bits. Bit 0 is the modulator LSB. These bits
affect the modulator pattern. All MODx bits are modified automatically by
the FLL+.
5-16
FLL+ Clock Module
FLL+ Clock Module Registers
SCFI1, System Clock Frequency Integrator Register 1
7
6
5
4
3
2
DCOx
rw−0
rw−0
rw−0
1
0
MODx (MSBs)
rw−0
rw−0
rw−0
rw−0
rw−0
DCOx
Bits
7-3
These bits select the DCO tap and are modified automatically by the FLL+.
MODx
Bit 2
Most significant modulator bits. Bit 2 is the modulator MSB. These bits
affect the modulator pattern. All MODx bits are modified automatically by
the FLL+.
FLL+ Clock Module
5-17
FLL+ Clock Module Registers
FLL_CTL0, FLL+ Control Register 0
†
7
6
DCOPLUS
XTS_FLL
rw−0
rw−0
5
4
XCAPxPF
rw−0
rw−0
3
2
1
0
XT2OF†
XT1OF
LFOF
DCOF
r−0
r−0
r−(1)
r−1
Not present in MSP430x41x, MSP430x42x devices
DCOPLUS
Bit 7
DCO output pre-divider. This bit selects if the DCO output is pre-divided
before sourcing MCLK or SMCLK. The division rate is selected with the
FLL_D bits
0
DCO output is divided
1
DCO output is not divided
XTS_FLL
Bit 6
LFTX1 mode select
0
Low frequency mode
1
High frequency mode
XCAPxPF
Bits
5−4
Oscillator capacitor selection. These bits select the effective capacitance
seen by the LFXT1 crystal or resonator. Should be set to 00 if the
high-frequency mode is selected for LFXT1 with XTS_FLL = 1.
00 ~1 pF
01 ~6 pF
10 ~8 pF
11 ~10 pF
XT2OF
Bit 3
XT2 oscillator fault. Not present in MSP430x41x, and MSP430x42x
devices.
0
No fault condition present
1
Fault condition present
XT1OF
Bit 2
LFXT1 high-frequency oscillator fault
0
No fault condition present
1
Fault condition present
LFOF
Bit 1
LFXT1 low-frequency oscillator fault
0
No fault condition present
1
Fault condition present
DCOF
Bit 0
DCO oscillator fault
0
No fault condition present
1
Fault condition present
5-18
FLL+ Clock Module
FLL+ Clock Module Registers
FLL_CTL1, FLL+ Control Register 1
7
6
5
LFXT1DIG‡
SMCLK
OFF†
XT2OFF†
rw−0
rw−0
rw−(1)
4
3
SELMx†
rw−(0)
2
1
SELS†
rw−(0)
rw−(0)
0
FLL_DIVx
rw−(0)
rw−(0)
†
Not present in MSP430x41x, MSP430x42x devices except MSP430F41x2.
‡ Only supported by MSP430xG46x, MSP430FG47x, MSP430F47x, MSP430x47x3/4, and MSP430F471xx devices. Otherwise
unused.
LFXT1DIG
Bit 7
Select digital external clock source. This bit enables the input of an
external digital clock signal on XIN in low-frequency mode (XTS_FLL = 0).
Only supported in MSP430xG46x, MSP430FG47x, MSP430F47x,
MSP430x47x3/4, and MSP430F471xx devices.
0
Crystal input selected
1
Digital clock input selected
SMCLKOFF
Bit 6
SMCLK off. This bit turns off SMCLK. Not present in MSP430x41x and
MSPx42x devices.
0
SMCLK is on
1
SMCLK is off
XT2OFF
Bit 5
XT2 off. This bit turns off the XT2 oscillator. Not present in MSP430x41x
and MSPx42x devices.
0
XT2 is on
1
XT2 is off if it is not used for MCLK or SMCLK
SELMx
Bits
4−3
Select MCLK. These bits select the MCLK source. Not present in
MSP430x41x and MSP430x42x devices except MSP430F41x2.
00 DCOCLK
01 DCOCLK
10 XT2CLK
11 LFXT1CLK
In the MSP430F41x2 devices:
00 DCOCLK
01 DCOCLK
10 LFXT1CLK or VLO
11 LFXT1CLK or VLO
SELS
Bit 2
Select SMCLK. This bit selects the SMCLK source. Not present in
MSP430x41x and MSP430x42x devices.
0
DCOCLK
1
XT2CLK
FLL_DIVx
Bits
1−0
ACLK divider
00 /1
01 /2
10 /4
11 /8
FLL+ Clock Module
5-19
FLL+ Clock Module Registers
FLL_CTL2, FLL+ Control Register 2
(MSP430x47x3/4, and MSP430F471xx devices only)
7
6
5
4
3
XT2Sx
rw−0
2
1
0
r0
r0
r0
Reserved
rw−0
r0
r0
r0
XT2Sx
Bits
7-6
XT2 range select. These bits select the frequency range for XT2.
00 0.4 to 1-MHz crystal or resonator
01 1 to 3-MHz crystal or resonator
10 3 to 16-MHz crystal or resonator
11 Digital external 0.4 to 16-MHz clock source
Reserved
Bits
5-0
Reserved.
FLL_CTL2, FLL+ Control Register 2
(MSP430F41x2 devices only)
7
6
5
Reserved
r0
4
3
2
LFXT1Sx
r0
rw−0
1
0
r0
r0
Reserved
rw−0
r0
r0
Reserved
Bits
7-6
Reserved.
LFXT1Sx
Bits
5−4
Low−frequency clock select and LFXT1 range select. These bits select
between LFXT1 and VLO when XTS_FLL = 0.
When XTS_FLL = 0:
00 32 768-Hz crystal on LFXT1
01 Reserved
10 VLOCLK
11 Digital external clock source
When XTS_FLL = 1:
00 Reserved
01 Reserved
10 Reserved
11 Reserved
Reserved
Bits
3-0
Reserved.
5-20
FLL+ Clock Module
FLL+ Clock Module Registers
IE1, Interrupt Enable Register 1
7
6
5
4
3
2
1
0
OFIE
rw−0
OFIE
Bits
7-2
These bits may be used by other modules. See device-specific data sheet.
Bit 1
Oscillator fault interrupt enable. This bit enables the OFIFG interrupt.
Because other bits in IE1 may be used for other modules, it is recommended
to set or clear this bit using BIS.B or BIC.B instructions, rather than MOV.B
or CLR.B instructions.
0
Interrupt not enabled
1
Interrupt enabled
Bits 0
This bit may be used by other modules. See device-specific data sheet.
FLL+ Clock Module
5-21
FLL+ Clock Module Registers
IFG1, Interrupt Flag Register 1
7
6
5
4
3
2
1
0
OFIFG
rw−0
OFIFG
5-22
Bits
7-2
These bits may be used by other modules. See device-specific data sheet.
Bit 1
Oscillator fault interrupt flag. Because other bits in IFG1 may be used for other
modules, it is recommended to set or clear this bit using BIS.B or BIC.B
instructions, rather than MOV.B or CLR.B instructions.
0
No interrupt pending
1
Interrupt pending
Bits 0
This bit may be used by other modules. See device-specific data sheet.
FLL+ Clock Module
Chapter 6
Flash Memory Controller
This chapter describes the operation of the MSP430 flash memory controller.
Topic
Page
6.1
Flash Memory Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
6.2
Flash Memory Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4
6.3
Flash Memory Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
6.4
Flash Memory Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
Flash Memory Controller
6-1
Flash Memory Introduction
6.1 Flash Memory Introduction
The MSP430 flash memory is bit-, byte-, and word-addressable and
programmable. The flash memory module has an integrated controller that
controls programming and erase operations. The controller has three or four
registers (see the device-specific data sheet), a timing generator, and a
voltage generator to supply program and erase voltages.
MSP430 flash memory features include:
- Internal programming voltage generation
- Bit, byte, or word programmable
- Ultralow-power operation
- Segment erase and mass erase
- Marginal 0 and marginal 1 read mode (implemented in MSP430FG47x,
MSP430F47x, MSP430F47x3/4, and MSP430F471xx devices only (see
the device-specific data sheet).
The block diagram of the flash memory and controller is shown in Figure 6−1.
Note: Minimum VCC During Flash Write or Erase
The minimum VCC voltage during a flash write or erase operation is between
2.2 V and 2.7 V (see the device-specific data sheet). If VCC falls below the
minimum VCC during a write or erase, the result of the write or erase is
unpredictable.
6-2
Flash Memory Controller
Flash Memory Introduction
Figure 6−1. Flash Memory Module Block Diagram
MAB
MDB
Address Latch
FCTL1
Data Latch
FCTL2
Enable
Address
Latch
FCTL3
Timing
Generator
Enable
Flash
Memory
Array 1
Flash
Memory
Array 2†
Data Latch
Programming
Voltage
Generator
† MSP430FG461x devices only
Flash Memory Controller
6-3
Flash Memory Segmentation
6.2 Flash Memory Segmentation
MSP430FG461x devices have two flash memory arrays. Other MSP430x4xx
devices have one flash array. All flash memory is partitioned into segments.
Single bits, bytes, or words can be written to flash memory, but the segment
is the smallest size of flash memory that can be erased.
The flash memory is partitioned into main and information memory sections.
There is no difference in the operation of the main and information memory
sections. Code or data can be located in either section. The differences
between the two sections are the segment size and the physical addresses.
The information memory has four 64-byte segments on the MSP430FG47x,
MSP430F47x, MSP430F47x3/4, and MSP430F471xx devices or two
128-byte segments on all other MSP430x4xx devices. The main memory has
two or more 512-byte segments. See the device-specific data sheet for the
complete memory map of a device.
The segments are further divided into blocks.
Figure 6−2 shows the flash segmentation using an example of 4-KB flash that
has eight main segments and two information segments.
Figure 6−2. Flash Memory Segments, 4-KB Example
4 KB + 256 byte
FFFFh
FFFFh
4-kbyte
Flash
Main Memory
FE00h
FDFFh
FC00h
F000h
10FFh
1000h
xxFFh
Segment0
256-byte
Flash
Information Memory
Segment1
xx80h
xx7Fh
Segment2
xx40h
xx3Fh
Segment3
xx00h
Segment4
Segment5
Segment6
F000h
Segment7
10FFh
SegmentA
1000h
6-4
Flash Memory Controller
xxC0h
xxBFh
SegmentB
Block
Block
Block
Block
Flash Memory Segmentation
6.2.1 SegmentA on MSP430FG47x, MSP430F47x, MSP430F47x3/4, and
MSP430F471xx Devices
On MSP430FG47x, MSP430F47x, MSP430F47x3/4, and MSP430F471xx
devices, SegmentA of the information memory is locked separately from all
other segments with the LOCKA bit. When LOCKA = 1, SegmentA cannot be
written or erased and all information memory is protected from erasure during
a mass erase or production programming. When LOCKA = 0, SegmentA can
be erased and written as any other flash memory segment, and all information
memory is erased during a mass erase or production programming.
The state of the LOCKA bit is toggled when a 1 is written to it. Writing a 0 to
LOCKA has no effect. This allows existing flash programming routines to be
used unchanged.
; Unlock SegmentA
BIT
#LOCKA,&FCTL3
JZ
SEGA_UNLOCKED
MOV
#FWKEY+LOCKA,&FCTL3
SEGA_UNLOCKED
; SegmentA is unlocked
;
;
;
;
Test LOCKA
Already unlocked?
No, unlock SegmentA
Yes, continue
; Lock SegmentA
BIT
#LOCKA,&FCTL3
JNZ
SEGALOCKED
MOV
#FWKEY+LOCKA,&FCTL3
SEGA_LOCKED
; SegmentA is locked
;
;
;
;
Test LOCKA
Already locked?
No, lock SegmentA
Yes, continue
Flash Memory Controller
6-5
Flash Memory Operation
6.3 Flash Memory Operation
The default mode of the flash memory is read mode. In read mode, the flash
memory is not being erased or written, the flash timing generator and voltage
generator are off, and the memory operates identically to ROM.
MSP430 flash memory is in-system programmable (ISP) without the need for
additional external voltage. The CPU can program its own flash memory. The
flash memory write/erase modes are selected with the BLKWRT, WRT,
GMERAS, MERAS, and ERASE bits and are:
- Byte/word write
- Block write
- Segment erase
- Mass erase (all main memory segments)
- All erase (all segments)
Reading or writing to flash memory while it is being programmed or erased is
prohibited. If CPU execution is required during the write or erase, the code to
be executed must be in RAM. Any flash update can be initiated from within
flash memory or RAM.
6.3.1
Flash Memory Timing Generator
Write and erase operations are controlled by the flash timing generator shown
in Figure 6−3. The flash timing generator operating frequency, fFTG, must be
in the range from ~ 257 kHz to ~ 476 kHz (see device-specific data sheet).
Figure 6−3. Flash Memory Timing Generator Block Diagram
FSSELx
FN5 ...........
ACLK
00
MCLK
01
SMCLK
10
SMCLK
11
PUC
FN0
f(FTG)
Divider, 1−64
EMEX
Reset
Flash Timing Generator
BUSY
WAIT
The flash timing generator can be sourced from ACLK, SMCLK, or MCLK. The
selected clock source should be divided using the FNx bits to meet the
frequency requirements for fFTG. If the fFTG frequency deviates from the
specification during the write or erase operation, the result of the write or erase
may be unpredictable, or the flash memory may be stressed above the limits
of reliable operation.
6-6
Flash Memory Controller
Flash Memory Operation
6.3.2
Erasing Flash Memory
The erased level of a flash memory bit is 1. Each bit can be programmed from
1 to 0 individually but to reprogram from 0 to 1 requires an erase cycle. The
smallest amount of flash that can be erased is a segment. Erase modes are
selected with the GMERAS (MSP430FG461x devices), MERAS, and ERASE
bits listed in Table 6−1, Table 6−2, and Table 6−3.
Table 6−1. MSP430FG461x Erase Modes
GMERAS
MERAS
ERASE
Erase Mode
X
0
1
Segment erase
0
1
0
Mass erase (all main memory segments of
selected memory array)
0
1
1
Erase all flash memory (main and
information segments of selected memory
array)
1
1
0
Global mass erase (all main memory
segments of both memory arrays)
1
1
1
Erase main memory and information
segments of both memory arrays
Table 6−2. MSP430FG47x, MSP430F47x, MSP430F47x3/4, and F471xx Erase Modes
MERAS
ERASE
Erase Mode
0
1
Segment erase
1
0
Mass erase (all main memory segments)
1
1
LOCKA = 0: Erase main and information flash memory.
LOCKA = 1: Erase only main flash memory.
MERAS
ERASE
0
1
Segment erase
1
0
Mass erase (all main memory segments)
1
1
Erase all flash memory (main and information segments)
Table 6−3. Erase Modes
Erase Mode
Any erase is initiated by a dummy write into the address range to be erased.
The dummy write starts the flash timing generator and the erase operation.
Figure 6−4 shows the erase cycle timing. The BUSY bit is set immediately after
the dummy write and remains set throughout the erase cycle. BUSY, GMERAS
(when present), MERAS, and ERASE are automatically cleared when the
cycle completes. The erase cycle timing is not dependent on the amount of
flash memory present on a device. Erase cycle times are device-specific (see
the device-specific data sheet).
Flash Memory Controller
6-7
Flash Memory Operation
Figure 6−4. Erase Cycle Timing
Generate
Programming Voltage
Erase Operation Active
Remove
Programming Voltage
Erase Time, VCC Current Consumption is Increased
BUSY
tMass Erase, tSeg Erase, or tGlobal Mass Erase (see device-specific data sheet)
A dummy write to an address not in the range to be erased does not start the
erase cycle, does not affect the flash memory, and is not flagged in any way.
This errant dummy write is ignored.
6-8
Flash Memory Controller
Flash Memory Operation
Initiating an Erase from Within Flash Memory
Any erase cycle can be initiated from within flash memory or from RAM. When
a flash segment erase operation is initiated from within flash memory, all timing
is controlled by the flash controller, and the CPU is held while the erase cycle
completes. After the erase cycle completes, the CPU resumes code execution
with the instruction following the dummy write.
When initiating an erase cycle from within flash memory, it is possible to erase
the code needed for execution after the erase. If this occurs, CPU execution
is unpredictable after the erase cycle.
The flow to initiate an erase from flash is shown in Figure 6−5.
Figure 6−5. Erase Cycle from Within Flash Memory
Disable watchdog
Setup flash controller and erase
mode
Dummy write
Set LOCK=1, re-enable watchdog
; Segment Erase from flash. 514 kHz < SMCLK < 952 kHz
; Assumes ACCVIE = NMIIE = OFIE = 0.
MOV
#WDTPW+WDTHOLD,&WDTCTL
; Disable WDT
MOV
#FWKEY+FSSEL1+FN0,&FCTL2 ; SMCLK/2
MOV
#FWKEY,&FCTL3
; Clear LOCK
MOV
#FWKEY+ERASE,&FCTL1
; Enable segment erase
CLR
&0FC10h
; Dummy write, erase S1
MOV
#FWKEY+LOCK,&FCTL3
; Done, set LOCK
...
; Re-enable WDT?
Flash Memory Controller
6-9
Flash Memory Operation
Initiating an Erase from RAM
Any erase cycle may be initiated from RAM. In this case, the CPU is not held
and can continue to execute code from RAM. The BUSY bit must be polled to
determine the end of the erase cycle before the CPU can access any flash
address again. If a flash access occurs while BUSY = 1, it is an access
violation, ACCVIFG is set, and the erase results are unpredictable.
The flow to initiate an erase from RAM is shown in Figure 6−6.
Figure 6−6. Erase Cycle from Within RAM
Disable watchdog
yes
BUSY = 1
Setup flash controller and
erase mode
Dummy write
yes
BUSY = 1
Set LOCK = 1, re-enable
watchdog
; Segment Erase from RAM. 514 kHz
; Assumes ACCVIE = NMIIE = OFIE =
MOV
#WDTPW+WDTHOLD,&WDTCTL
L1 BIT
#BUSY,&FCTL3
JNZ
L1
MOV
#FWKEY+FSSEL1+FN0,&FCTL2
MOV
#FWKEY,&FCTL3
MOV
#FWKEY+ERASE,&FCTL1
CLR
&0FC10h
L2 BIT
#BUSY,&FCTL3
JNZ
L2
MOV
#FWKEY+LOCK,&FCTL3
...
6-10
Flash Memory Controller
< SMCLK < 952 kHz
0.
; Disable WDT
; Test BUSY
; Loop while busy
; SMCLK/2
; Clear LOCK
; Enable erase
; Dummy write, erase S1
; Test BUSY
; Loop while busy
; Done, set LOCK
; Re-enable WDT?
Flash Memory Operation
6.3.3
Writing Flash Memory
The write modes, selected by the WRT and BLKWRT bits, are listed in
Table 6−4.
Table 6−4. Write Modes
Write Mode
BLKWRT
WRT
0
1
Byte/word write
1
1
Block write
Both write modes use a sequence of individual write instructions, but using the
block write mode is approximately twice as fast as byte/word mode, because
the voltage generator remains on for the complete block write. Any instruction
that modifies a destination can be used to modify a flash location in either
byte/word mode or block-write mode. A flash word (low + high byte) must not
be written more than twice between erasures. Otherwise, damage can occur.
The BUSY bit is set while a write operation is active and cleared when the
operation completes. If the write operation is initiated from RAM, the CPU must
not access flash while BUSY = 1. Otherwise, an access violation occurs,
ACCVIFG is set, and the flash write is unpredictable.
Byte/Word Write
A byte/word write operation can be initiated from within flash memory or from
RAM. When initiating from within flash memory, all timing is controlled by the
flash controller, and the CPU is held while the write completes. After the write
completes, the CPU resumes code execution with the instruction following the
write. The byte/word write timing is shown in Figure 6−7.
Figure 6−7. Byte/Word Write Timing
ÎÎ
Generate
Programming Voltage
ÎÎ
ÎÎ
Programming Operation Active
Remove
Programming Voltage
Programming Time, VCC Current Consumption is Increased
BUSY
tWord (see device-specific data sheet)
When a byte/word write is executed from RAM, the CPU continues to execute
code from RAM. The BUSY bit must be zero before the CPU accesses flash
again, otherwise an access violation occurs, ACCVIFG is set, and the write
result is unpredictable.
Flash Memory Controller
6-11
Flash Memory Operation
In byte/word mode, the internally generated programming voltage is applied
to the complete 64-byte block each time a byte or word is written for tWORD
minus threefFTG cycles. With each byte or word write, the amount of time the
block is subjected to the programming voltage accumulates. The cumulative
programming time, tCPT, must not be exceeded for any block. If the cumulative
programming time is met, the block must be erased before performing any
further writes to any address within the block. See the device-specific data
sheet for specifications.
Initiating a Byte/Word Write from Within Flash Memory
The flow to initiate a byte/word write from flash is shown in Figure 6−8.
Figure 6−8. Initiating a Byte/Word Write from Flash
Disable watchdog
Setup flash controller
and set WRT=1
Write byte or word
Set WRT=0, LOCK=1,
re-enable watchdog
; Byte/word write from flash. 514 kHz < SMCLK < 952 kHz
; Assumes 0FF1Eh is already erased
; Assumes ACCVIE = NMIIE = OFIE = 0.
MOV
#WDTPW+WDTHOLD,&WDTCTL
; Disable WDT
MOV
#FWKEY+FSSEL1+FN0,&FCTL2 ; SMCLK/2
MOV
#FWKEY,&FCTL3
; Clear LOCK
MOV
#FWKEY+WRT,&FCTL1
; Enable write
MOV
#0123h,&0FF1Eh
; 0123h
−> 0FF1Eh
MOV
#FWKEY,&FCTL1
; Done. Clear WRT
MOV
#FWKEY+LOCK,&FCTL3
; Set LOCK
...
; Re-enable WDT?
6-12
Flash Memory Controller
Flash Memory Operation
Initiating a Byte/Word Write from RAM
The flow to initiate a byte/word write from RAM is shown in Figure 6−9.
Figure 6−9. Initiating a Byte/Word Write from RAM
Disable watchdog
yes
BUSY = 1
Setup flash controller
and set WRT=1
Write byte or word
yes
BUSY = 1
Set WRT=0, LOCK = 1
re-enable watchdog
; Byte/word write from RAM. 514 kHz < SMCLK < 952 kHz
; Assumes 0FF1Eh is already erased
; Assumes ACCVIE = NMIIE = OFIE = 0.
MOV
#WDTPW+WDTHOLD,&WDTCTL
; Disable WDT
L1 BIT
#BUSY,&FCTL3
; Test BUSY
JNZ
L1
; Loop while busy
MOV
#FWKEY+FSSEL1+FN0,&FCTL2 ; SMCLK/2
MOV
#FWKEY,&FCTL3
; Clear LOCK
MOV
#FWKEY+WRT,&FCTL1
; Enable write
MOV
#0123h,&0FF1Eh
; 0123h −> 0FF1Eh
L2 BIT
#BUSY,&FCTL3
; Test BUSY
JNZ
L2
; Loop while busy
MOV
#FWKEY,&FCTL1
; Clear WRT
MOV
#FWKEY+LOCK,&FCTL3
; Set LOCK
...
; Re-enable WDT?
Flash Memory Controller
6-13
Flash Memory Operation
Block Write
The block write can be used to accelerate the flash write process when many
sequential bytes or words need to be programmed. The flash programming
voltage remains on for the duration of writing the 64-byte block. The
cumulative programming time tCPT must not be exceeded for any block during
a block write.
A block write cannot be initiated from within flash memory. The block write
must be initiated from RAM only. The BUSY bit remains set throughout the
duration of the block write. The WAIT bit must be checked between writing
each byte or word in the block. When WAIT is set the next byte or word of the
block can be written. When writing successive blocks, the BLKWRT bit must
be cleared after the current block is complete. BLKWRT can be set initiating
the next block write after the required flash recovery time given by tEnd. BUSY
is cleared following each block write completion indicating the next block can
be written. Figure 6−10 shows the block write timing; see device-specific data
sheet for specifications.
Figure 6−10. Block-Write Cycle Timing
BLKWRT bit
Write to Flash e.g., MOV #123h, &Flash
Generate
Programming Voltage
Remove
Programming Voltage
Programming Operation Active
Cumulative Programming Time tCPT ∼=< 10ms, VCC Current Consumption is Increased
BUSY
tBlock, 0
WAIT
6-14
Flash Memory Controller
tBlock 1-63
tBlock, 1-63
tBlock,End
Flash Memory Operation
Block Write Flow and Example
A block write flow is shown in Figure 6−11 and in the following example.
Figure 6−11. Block Write Flow
Disable watchdog
yes
BUSY = 1
Setup flash controller
Set BLKWRT=WRT=1
Write byte or word
yes
WAIT=0?
no
Block Border?
Set BLKWRT=0
yes
BUSY = 1
yes
Another
Block?
Set WRT=0, LOCK=1
re-enable WDT
Flash Memory Controller
6-15
Flash Memory Operation
; Write one block starting at 0F000h.
; Must be executed from RAM, Assumes Flash is already erased.
; 514 kHz < SMCLK < 952 kHz
; Assumes ACCVIE = NMIIE = OFIE = 0.
MOV
#32,R5
; Use as write counter
MOV
#0F000h,R6
; Write pointer
MOV
L1 BIT
JNZ
MOV
MOV
MOV
L2 MOV
L3 BIT
JZ
INCD
DEC
JNZ
MOV
L4 BIT
JNZ
MOV
...
6-16
Flash Memory Controller
#WDTPW+WDTHOLD,&WDTCTL
#BUSY,&FCTL3
L1
; Disable WDT
; Test BUSY
; Loop while busy
#FWKEY+FSSEL1+FN0,&FCTL2 ; SMCLK/2
#FWKEY,&FCTL3
#FWKEY+BLKWRT+WRT,&FCTL1
Write_Value,0(R6)
#WAIT,&FCTL3
L3
R6
R5
L2
#FWKEY,&FCTL1
#BUSY,&FCTL3
L4
#FWKEY+LOCK,&FCTL3
;
;
;
;
;
;
;
;
;
;
;
;
;
Clear LOCK
Enable block write
Write location
Test WAIT
Loop while WAIT=0
Point to next word
Decrement write counter
End of block?
Clear WRT,BLKWRT
Test BUSY
Loop while busy
Set LOCK
Re-enable WDT if needed
Flash Memory Operation
6.3.4
Flash Memory Access During Write or Erase
When any write or any erase operation is initiated from RAM and while
BUSY = 1, the CPU may not read or write to or from any flash location.
Otherwise, an access violation occurs, ACCVIFG is set, and the result is
unpredictable. Also if a write to flash is attempted with WRT = 0, the ACCVIFG
interrupt flag is set, and the flash memory is unaffected.
When a byte/word write or any erase operation is initiated from within flash
memory, the flash controller returns op-code 03FFFh to the CPU at the next
instruction fetch. Op-code 03FFFh is the JMP PC instruction. This causes the
CPU to loop until the flash operation is finished. When the operation is finished
and BUSY = 0, the flash controller allows the CPU to fetch the proper op-code
and program execution resumes.
The flash access conditions while BUSY=1 are listed in Table 6−5.
Table 6−5. Flash Access While BUSY = 1
Flash
Operation
Anyy erase or
b /
byte/word
d write
i
Block write
Flash
Access
WAIT
Result
Read
0
ACCVIFG = 0. 03FFFh is the value read
Write
0
ACCVIFG = 1. Write is ignored
Instruction
fetch
0
ACCVIFG = 0. CPU fetches 03FFFh. This
is the JMP PC instruction.
Any
0
ACCVIFG = 1, LOCK = 1
Read
1
ACCVIFG = 0, 03FFFh is the value read
Write
1
ACCVIFG = 0, Flash is written
Instruction
fetch
1
ACCVIFG = 1, LOCK = 1
Interrupts are automatically disabled during any flash operation on F47x3/4
and F471xx devices when EEI = 0 and EEIEX = 0 and on all other devices
where EEI and EEIEX are not present. After the flash operation has
completed, interrupts are automatically re-enabled. Any interrupt that
occurred during the operation will have its associated flag set and will generate
an interrupt request when re-enabled.
On F47x3/4 and F471xx devices when EEIEX = 1 and GIE = 1, an interrupt
will immediately abort any flash operation and the FAIL flag will be set. When
EEI = 1, GIE = 1, and EEIEX = 0, a segment erase will be interrupted by a
pending interrupt every 32 fFTG cycles. After servicing the interrupt, the
segment erase is continued for at least 32 fFTG cycles or until it is complete.
During the servicing of the interrupt, the BUSY bit remains set, but the flash
memory can be accessed by the CPU without causing an access violation.
Nested interrupts are not supported, because the RETI instruction is decoded
to detect the return from interrupt.
The watchdog timer (in watchdog mode) should be disabled before a flash
erase cycle. A reset aborts the erase and the result is unpredictable. After the
erase cycle has completed, the watchdog may be re-enabled.
Flash Memory Controller
6-17
Flash Memory Operation
6.3.5
Stopping a Write or Erase Cycle
Any write or erase operation can be stopped before its normal completion by
setting the emergency exit bit EMEX. Setting the EMEX bit stops the active
operation immediately and stops the flash controller. All flash operations
cease, the flash returns to read mode, and all bits in the FCTL1 register are
reset. The result of the intended operation is unpredictable.
6.3.6
Marginal Read Mode
The marginal read mode can be used to verify the integrity of the flash memory
contents. This feature is implemented in MSP430FG47x, MSP430F47x,
MSP430F47x3/4, and MSP430F471xx devices; see the device-specific data
sheet for availability. During marginal read mode, the presence of an
insufficiently programmed flash memory bit location can be detected. Events
that could produce this situation include improper fFTG settings, violation of
minimum VCC during erase/program operations, and data retention
end-of-life. One method for identifying such memory locations would be to
periodically perform a checksum calculation over a section of flash memory
(for example, a flash segment) and then to repeat this procedure with the
marginal read mode enabled. If they do not match, it could indicate an
insufficiently programmed flash memory location. It is possible to refresh the
affected flash memory segment by disabling marginal read mode, copying to
RAM, erasing the flash segment, and copying back from RAM to flash.
The program checking the flash memory contents must be executed from
RAM. Executing code from flash automatically disables the marginal read
mode. The marginal read modes are controlled by the MRG0 and MRG1 bits.
Setting MRG1 is used to detect insufficiently programmed flash cells
containing a “1“ (erased bits). Setting MRG0 is used to detect insufficiently
programmed flash cells containing a “0“ (programmed bits). Only one of these
bits should be set at a time. Therefore, a full marginal read check requires two
passes of checking the flash memory content’s integrity. During marginal read
mode, the flash access speed must be limited to 1 MHz (see device-specific
data sheet).
6.3.7
Configuring and Accessing the Flash Memory Controller
The FCTLx registers are 16-bit password-protected read/write registers. Any
read or write access must use word instructions and write accesses must
include the write password 0A5h in the upper byte. Any write to any FCTLx
register with any value other than 0A5h in the upper byte is a security key
violation, sets the KEYV flag, and triggers a PUC system reset. Any read of any
FCTLx registers reads 096h in the upper byte.
Any write to FCTL1 during an erase or byte/word write operation is an access
violation and sets ACCVIFG. Writing to FCTL1 is allowed in block write mode
when WAIT = 1, but writing to FCTL1 in block write mode when WAIT = 0 is
an access violation and sets ACCVIFG.
Any write to FCTL2 when the BUSY = 1 is an access violation.
Any FCTLx register may be read when BUSY = 1. A read does not cause an
access violation.
6-18
Flash Memory Controller
Flash Memory Operation
6.3.8
Flash Memory Controller Interrupts
The flash controller has two interrupt sources, KEYV and ACCVIFG.
ACCVIFG is set when an access violation occurs. When the ACCVIE bit is
re-enabled after a flash write or erase, a set ACCVIFG flag generates an
interrupt request. ACCVIFG sources the NMI interrupt vector, so it is not
necessary for GIE to be set for ACCVIFG to request an interrupt. ACCVIFG
may also be checked by software to determine if an access violation occurred.
ACCVIFG must be reset by software.
The key violation flag KEYV is set when any of the flash control registers are
written with an incorrect password. When this occurs, a PUC is generated,
immediately resetting the device.
6.3.9
Programming Flash Memory Devices
There are three options for programming an MSP430 flash device. All options
support in-system programming:
- Program via JTAG
- Program via the bootstrap loader
- Program via a custom solution
Programming Flash Memory via JTAG
MSP430 devices can be programmed via the JTAG port. The JTAG interface
requires four signals, ground, and optionally VCC and RST/NMI.
The JTAG port is protected with a fuse. Blowing the fuse completely disables
the JTAG port and is not reversible. Further access to the device via JTAG is
not possible For more details see the application report Programming a
Flash-Based MSP430 Using the JTAG Interface (SLAA149) at
www.ti.com/msp430.
Programming Flash Memory via the Bootstrap Loader (BSL)
Every MSP430 flash device contains a bootstrap loader. The BSL enables
users to read or program the flash memory or RAM using a UART serial
interface. Access to the MSP430 flash memory via the BSL is protected by a
256-bit, user-defined password. For more details see the application report
Features of the MSP430 Bootstrap Loader (SLAA089) at
www.ti.com/msp430.
Flash Memory Controller
6-19
Flash Memory Operation
Programming Flash Memory via a Custom Solution
The ability of the MSP430 CPU to write to its own flash memory allows for
in-system and external custom programming solutions as shown in
Figure 6−12. The user can choose to provide data to the MSP430 through any
means available (UART, SPI, etc.). User-developed software can receive the
data and program the flash memory. Because this type of solution is developed
by the user, it can be completely customized to fit the application needs for
programming, erasing, or updating the flash memory.
Figure 6−12. User-Developed Programming Solution
Commands, data, etc.
Host
MSP430
UART,
Px.x,
SPI,
etc.
Flash Memory
CPU executes
user software
Read/write flash memory
6-20
Flash Memory Controller
Flash Memory Registers
6.4 Flash Memory Registers
The flash memory registers are listed in Table 6−6.
Table 6−6. Flash Memory Registers
Register
Short Form
Register Type Address
Initial State
Flash memory control register 1
FCTL1
Read/write
0128h
09600h with PUC
Flash memory control register 2
FCTL2
Read/write
012Ah
09642h with PUC
Flash memory control register 3
FCTL3
Read/write
012Ch
09618h† with PUC
FCTL4
Read/write
01BEh
0000h with PUC
IE1
Read/write
000h
Reset with PUC
Flash memory control register
Interrupt enable 1
†
‡
4‡
09658h in MSP430FG47x, MSP430F47x, MSP430F47x3/4, and MSP430F471xx devices
MSP430FG47x, MSP430F47x, MSP430F47x3/4, and MSP430F471xx devices only
Flash Memory Controller
6-21
Flash Memory Registers
FCTL1, Flash Memory Control Register
15
14
13
12
11
10
9
8
FRKEY, Read as 096h
FWKEY, Must be written as 0A5h
7
†
‡
6
5
4
3
2
1
0
MERAS
ERASE
Reserved
rw−0
rw−0
r0
BLKWRT
WRT
Reserved
EEIEX‡
GMERAS†
EEI‡
rw−0
rw−0
r0
r0
rw-0
MSP430FG461x devices only. Reserved with r0 access on all other devices.
F47x3/4 and F471xx devices only. Reserved with r0 access on all other devices.
FRKEY/
FWKEY
Bits
15-8
FCTLx password. Always read as 096h. Must be written as 0A5h or a PUC
is generated.
BLKWRT
Bit 7
Block write mode. WRT must also be set for block write mode. BLKWRT is
automatically reset when EMEX is set.
0
Block-write mode is off
1
Block-write mode is on
WRT
Bit 6
Write. This bit is used to select any write mode. WRT is automatically reset
when EMEX is set.
0
Write mode is off
1
Write mode is on
Reserved
Bit 5
Reserved. Always read as 0.
EEIEX
Bit 4
Enable emergency interrupt exit. Setting this bit enables an interrupt to cause
an emergency exit from a flash operation when GIE = 1. EEIEX is
automatically reset when EMEX is set.
0
Exit interrupt disabled
1
Exit on interrupt enabled
EEI
Bits 3
Enable erase Interrupts. Setting this bit allows a segment erase to be
interrupted by an interrupt request. After the interrupt is serviced, the erase
cycle is resumed.
0
Interrupts during segment erase disabled
1
Interrupts during segment erase enabled
6-22
Flash Memory Controller
Flash Memory Registers
GMERAS
MERAS
ERASE
Reserved
Bit 3
Bit 2
Bit 1
Bit 0
Global mass erase, mass erase, and erase. These bits are used together to
select the erase mode. GMERAS, MERAS, and ERASE are automatically
reset when EMEX is set or the erase operation completes.
GMERAS
MERAS
ERASE
Erase Cycle
0
0
0
No erase
X
0
1
Erase individual segment only
0
1
0
Erase main memory segment of selected
array
0
1
1
Erase main memory segments and information segments of selected array
1
1
0
Erase main memory segments of all
memory arrays.
1
1
1
Erase all main memory and information
segments of all memory arrays
Reserved. Always read as 0.
Flash Memory Controller
6-23
Flash Memory Registers
FCTL2, Flash Memory Control Register
15
14
13
12
11
10
9
8
2
1
0
rw−0
rw-1
rw−0
FWKEYx, Read as 096h
Must be written as 0A5h
7
6
5
4
3
FSSELx
rw−0
FNx
rw−1
rw-0
rw-0
rw-0
FWKEYx
Bits
15-8
FCTLx password. Always read as 096h. Must be written as 0A5h, or a PUC
is generated.
FSSELx
Bits
7−6
Flash controller clock source select
00 ACLK
01 MCLK
10 SMCLK
11 SMCLK
FNx
Bits
5-0
Flash controller clock divider. These six bits select the divider for the flash
controller clock. The divisor value is FNx + 1. For example, when FNx = 00h,
0the divisor is 1. When FNx = 03Fh the divisor is 64.
6-24
Flash Memory Controller
Flash Memory Registers
FCTL3, Flash Memory Control Register FCTL3
15
14
13
12
11
10
9
8
FWKEYx, Read as 096h
Must be written as 0A5h
†
7
6
5
4
3
2
1
0
FAIL†
LOCKA†
EMEX
LOCK
WAIT
ACCVIFG
KEYV
BUSY
r(w)−0
r(w)−1
rw-0
rw-1
r-1
rw−0
rw-(0)
r(w)−0
MSP430FG47x, MSP430F47x, MSP430F47x3/4, and MSP430F471xx devices only.
Reserved with r0 access on all other devices.
FWKEYx
Bits
15-8
FCTLx password. Always read as 096h. Must be written as 0A5h, or a PUC
is generated.
FAIL
Bit 7
Operation failure. This bit is set if the fFTG clock source fails or if a flash
operation is aborted from an interrupt when EEIEX = 1. FAIL must be reset
with software.
0
No failure
1
Failure
LOCKA
Bit 6
SegmentA and Info lock. Write a 1 to this bit to change its state. Writing 0 has
no effect.
0
Segment A unlocked and all information memory is erased during a
mass erase.
1
Segment A locked and all information memory is protected from erasure
during a mass erase.
EMEX
Bit 5
Emergency exit
0
No emergency exit
1
Emergency exit
LOCK
Bit 4
Lock. This bit unlocks the flash memory for writing or erasing. The LOCK bit
can be set anytime during a byte/word write or erase operation and the
operation completes normally. In the block write mode, if the LOCK bit is set
while BLKWRT=WAIT=1, then BLKWRT and WAIT are reset, and the mode
ends normally.
0
Unlocked
1
Locked
WAIT
Bit 3
Wait. Indicates the flash memory is being written.
0
The flash memory is not ready for the next byte/word write
1
The flash memory is ready for the next byte/word write
ACCVIFG
Bit 2
Access violation interrupt flag
0
No interrupt pending
1
Interrupt pending
Flash Memory Controller
6-25
Flash Memory Registers
KEYV
Bit 1
Flash security key violation. This bit indicates an incorrect FCTLx password
was written to any flash control register and generates a PUC when set. KEYV
must be reset with software.
0
FCTLx password was written correctly
1
FCTLx password was written incorrectly
BUSY
Bit 0
Busy. This bit indicates the status of the flash timing generator.
0
Not busy
1
Busy
6-26
Flash Memory Controller
Flash Memory Registers
FCTL4, Flash Memory Control Register FCTL4
(FG47x, F47x, F47x3/4, and F471xx devices only)
15
14
13
12
11
10
9
8
3
2
1
0
r-0
r-0
r-0
r-0
FWKEYx, Read as 096h
Must be written as 0A5h
7
6
r-0
r-0
5
4
MRG1
MRG0
rw-0
rw-0
FWKEYx
Bits
15-8
FCTLx password. Always read as 096h. Must be written as 0A5h or a PUC
will be generated.
Reserved
Bits
7−6
Reserved. Always read as 0.
MRG1
Bit 5
Marginal read 1 mode. This bit enables the marginal 1 read mode. The
marginal read 1 bit is cleared if the CPU starts execution from the flash
memory. If both MRG1 and MRG0 are set MRG1 is active and MRG0 is
ignored.
0
Marginal 1 read mode is disabled.
1
Marginal 1 read mode is enabled.
MRG0
Bit 4
Marginal read 0 mode. This bit enables the marginal 0 read mode. The
marginal mode 0 is cleared if the CPU starts execution from the flash memory.
If both MRG1 and MRG0 are set MRG1 is active and MRG0 is ignored.
0
Marginal 0 read mode is disabled.
1
Marginal 0 read mode is enabled.
Reserved
Bits
3−0
Reserved. Always read as 0.
Flash Memory Controller
6-27
Flash Memory Registers
IE1, Interrupt Enable Register 1
7
6
5
4
3
2
1
0
ACCVIE
rw−0
ACCVIE
6-28
Bits
7-6,
4-0
These bits may be used by other modules. See device-specific data sheet.
Bit 5
Flash memory access violation interrupt enable. This bit enables the
ACCVIFG interrupt. Because other bits in IE1 may be used for other modules,
it is recommended to set or clear this bit using BIS.B or BIC.B instructions,
rather than MOV.B or CLR.B instructions.
0
Interrupt not enabled
1
Interrupt enabled
Flash Memory Controller
Chapter 7
Supply Voltage Supervisor
This chapter describes the operation of the SVS. The SVS is implemented in
all MSP430x4xx devices.
Topic
Page
7.1
SVS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
7.2
SVS Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
7.3
SVS Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Supply Voltage Supervisor
7-1
SVS Introduction
7.1 SVS Introduction
The supply voltage supervisor (SVS) is used to monitor the AVCC supply
voltage or an external voltage. The SVS can be configured to set a flag or
generate a POR reset when the supply voltage or external voltage drops below
a user-selected threshold.
The SVS features include:
- AVCC monitoring
- Selectable generation of POR
- Output of SVS comparator accessible by software
- Low-voltage condition latched and accessible by software
- 14 selectable threshold levels
- External channel to monitor external voltage
The SVS block diagram is shown in Figure 7−1.
Note: MSP430x412 and MSP430x413 Voltage Level Detect
The MSP430x412 and MSP430x413 devices implement only one voltage
level detect setting. When VLDx = 0, the SVS is off. Any value greater than
0 for VLDx selects a voltage level detect of 1.9V.
7-2
Supply Voltage Supervisor
SVS Introduction
Figure 7−1. SVS Block Diagram
VCC
AVCC
Brownout
Reset
D
AVCC
G S
SVSIN
~ 50us
1111
−
0001
SVS_POR
+
0010
tReset ~ 50us
1011
1100
SVSOUT
1.2V
1101
D
G S
Set SVSFG
Reset
VLD
PORON
SVSON
SVSOP
SVSFG
SVSCTL Bits
Supply Voltage Supervisor
7-3
SVS Operation
7.2 SVS Operation
The SVS detects if the AVCC voltage drops below a selectable level. It can be
configured to provide a POR or set a flag when a low-voltage condition occurs.
The SVS is disabled after a brownout reset to conserve current consumption.
7.2.1
Configuring the SVS
The VLDx bits are used to enable/disable the SVS and select one of 14
threshold levels (V(SVS_IT−)) for comparison with AVCC. The SVS is off when
VLDx = 0 and on when VLDx > 0. The SVSON bit does not turn on the SVS.
Instead, it reflects the on/off state of the SVS and can be used to determine
when the SVS is on.
When VLDx = 1111, the external SVSIN channel is selected. The voltage on
SVSIN is compared to an internal level of approximately 1.2 V.
7.2.2
SVS Comparator Operation
A low-voltage condition exists when AVCC drops below the selected threshold
or when the external voltage drops below its 1.2-V threshold. Any low-voltage
condition sets the SVSFG bit.
The PORON bit enables or disables the device-reset function of the SVS. If
PORON = 1, a POR is generated when SVSFG is set. If PORON = 0, a
low-voltage condition sets SVSFG, but does not generate a POR.
The SVSFG bit is latched. This allows user software to determine if a
low-voltage condition occurred previously. The SVSFG bit must be reset by
user software. If the low-voltage condition is still present when SVSFG is reset,
it is immediately set again by the SVS.
7-4
Supply Voltage Supervisor
SVS Operation
7.2.3
Changing the VLDx Bits
When the VLDx bits are changed from zero to any non-zero value, there is an
automatic settling delay, td(SVSon), implemented that allows the SVS circuitry
to settle. The td(SVSon) delay is approximately 50 μs. During this delay, the SVS
does not flag a low-voltage condition or reset the device, and the SVSON bit
is cleared. Software can test the SVSON bit to determine when the delay has
elapsed and the SVS is monitoring the voltage properly. Writing to SVSCTL
while SVSON = 0 aborts the SVS automatic settling delay, td(SVSon), and
switch the SVS to active mode immediately. In doing so, the SVS circuitry
might not be settled, resulting in unpredictable behavior.
When the VLDx bits are changed from any non-zero value to any other
non-zero value, the circuitry requires the time tsettle to settle. The settling time
tsettle is a maximum of ~12 μs (see the device-specific data sheet). There is
no automatic delay implemented that prevents SVSFG to be set or to prevent
a reset of the device. The recommended flow to switch between levels is
shown in the following code.
; Enable SVS for the first time:
MOV.B
#080h,&SVSCTL
; Level 2.8V, do not cause POR
; ...
; Change SVS level
MOV.B
#000h,&SVSCTL
MOV.B
#018h,&SVSCTL
; ...
; Temporarily disable SVS
; Level 1.9V, cause POR
Supply Voltage Supervisor
7-5
SVS Operation
7.2.4
SVS Operating Range
Each SVS level has hysteresis to reduce sensitivity to small supply voltage
changes when AVCC is close to the threshold. The SVS operation and
SVS/Brownout interoperation are shown in Figure 7−2.
Figure 7−2. Operating Levels for SVS and Brownout/Reset Circuit
AV
CC
V(SVS_IT−)
V(SVSstart)
Software Sets VLD>0
Vhys(SVS_IT−)
Vhys(B_IT−)
V(B_IT−)
VCC(start)
Brownout
BrownOut
Region
Brownout
Region
1
0
t d(BOR)
SVSOUT
t d(BOR)
SVS Circuit Active
1
0
td(SVSon)
Set SVS_POR
1
0
undefined
7-6
Supply Voltage Supervisor
td(SVSR)
SVS Registers
7.3 SVS Registers
The SVS registers are listed in Table 7−1.
Table 7−1. SVS Registers
Register
Short Form
Register Type Address
Initial State
SVS Control Register
SVSCTL
Read/write
Reset with BOR
056h
SVSCTL, SVS Control Register
7
6
5
4
VLDx
rw−0†
†
rw−0†
rw−0†
rw−0†
3
2
1
0
PORON
SVSON
SVSOP
SVSFG
rw−0†
r†
r†
rw−0†
Reset by a brownout reset only, not by a POR or PUC.
VLDx
Bits
7-4
Voltage level detect. These bits turn on the SVS and select the nominal SVS
threshold voltage level. See the device-specific data sheet for parameters.
0000 SVS is off
0001 1.9 V
0010 2.1 V
0011 2.2 V
0100 2.3 V
0101 2.4 V
0110 2.5 V
0111 2.65 V
1000 2.8 V
1001 2.9 V
1010 3.05
1011 3.2 V
1100 3.35 V
1101 3.5 V
1110 3.7 V
1111 Compares external input voltage SVSIN to 1.2 V.
PORON
Bit 3
POR on. This bit enables the SVSFG flag to cause a POR device reset.
0
SVSFG does not cause a POR
1
SVSFG causes a POR
SVSON
Bit 2
SVS on. This bit reflects the status of SVS operation. This bit DOES NOT turn
on the SVS. The SVS is turned on by setting VLDx > 0.
0
SVS is Off
1
SVS is On
SVSOP
Bit 1
SVS output. This bit reflects the output value of the SVS comparator.
0
SVS comparator output is low
1
SVS comparator output is high
SVSFG
Bit 0
SVS flag. This bit indicates a low voltage condition. SVSFG remains set after
a low voltage condition until reset by software.
0
No low voltage condition occurred
1
A low condition is present or has occurred
Supply Voltage Supervisor
7-7
7-8
Supply Voltage Supervisor
Chapter 8
16-Bit Hardware Multiplier
This chapter describes the 16-bit hardware multiplier. The hardware multiplier
is implemented in MSP430x44x, MSP430FE42x, MSP430FE42xA,
MSP430FE42x2, and MSP430F42x, MSP430F42xA devices.
Topic
Page
8.1
Hardware Multiplier Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2
8.2
Hardware Multiplier Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3
8.3
Hardware Multiplier Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7
16-Bit Hardware Multiplier
8-1
Hardware Multiplier Introduction
8.1 Hardware Multiplier Introduction
The hardware multiplier is a peripheral and is not part of the MSP430 CPU.
This means that its activities do not interfere with the CPU activities. The
multiplier registers are peripheral registers that are loaded and read with CPU
instructions.
The hardware multiplier supports:
- Unsigned multiply
- Signed multiply
- Unsigned multiply accumulate
- Signed multiply accumulate
- 16 × 16 bits, 16 × 8 bits, 8 × 16 bits, 8 × 8 bits
The hardware multiplier block diagram is shown in Figure 8−1.
Figure 8−1. Hardware Multiplier Block Diagram
15
rw
0
MPY 130h
15
MPYS 132h
OP1
0
rw
OP2 138h
MAC 134h
MACS 136h
16 x 16 Multipiler
Accessible
Register
MPY = 0000
MACS MPYS
32−bit Adder
MAC
MPY, MPYS
Multiplexer
32−bit Multiplexer
SUMEXT 13Eh
15
8-2
r
MAC, MACS
C
0
16-Bit Hardware Multiplier
S
RESHI 13Ch
RESLO 13Ah
31
rw
rw
0
Hardware Multiplier Operation
8.2 Hardware Multiplier Operation
The hardware multiplier supports unsigned multiply, signed multiply, unsigned
multiply accumulate, and signed multiply accumulate operations. The type of
operation is selected by the address the first operand is written to.
The hardware multiplier has two 16-bit operand registers, OP1 and OP2, and
three result registers, RESLO, RESHI, and SUMEXT. RESLO stores the low
word of the result, RESHI stores the high word of the result, and SUMEXT
stores information about the result. The result is ready in three MCLK cycles
and can be read with the next instruction after writing to OP2, except when
using an indirect addressing mode to access the result. When using indirect
addressing for the result, a NOP is required before the result is ready.
8.2.1
Operand Registers
The operand one register OP1 has four addresses, shown in Table 8−1, used
to select the multiply mode. Writing the first operand to the desired address
selects the type of multiply operation but does not start any operation. Writing
the second operand to the operand two register OP2 initiates the multiply
operation. Writing OP2 starts the selected operation with the values stored in
OP1 and OP2. The result is written into the three result registers RESLO,
RESHI, and SUMEXT.
Repeated multiply operations may be performed without reloading OP1 if the
OP1 value is used for successive operations. It is not necessary to re-write the
OP1 value to perform the operations.
Table 8−1. OP1 addresses
OP1 Address
Register Name
Operation
0130h
MPY
Unsigned multiply
0132h
MPYS
Signed multiply
0134h
MAC
Unsigned multiply accumulate
0136h
MACS
Signed multiply accumulate
16-Bit Hardware Multiplier
8-3
Hardware Multiplier Operation
8.2.2
Result Registers
The result low register RESLO holds the lower 16-bits of the calculation result.
The result high register RESHI contents depend on the multiply operation and
are listed in Table 8−2.
Table 8−2. RESHI Contents
Mode
RESHI Contents
MPY
Upper 16 bits of the result
MPYS
The MSB is the sign of the result. The remaining bits are the
upper 15 bits of the result. Two’s complement notation is used
for the result.
MAC
Upper 16 bits of the result
MACS
Upper 16 bits of the result. Two’s complement notation is used
for the result.
The sum extension registers SUMEXT contents depend on the multiply
operation and are listed in Table 8−3.
Table 8−3. SUMEXT Contents
Mode
SUMEXT
MPY
SUMEXT is always 0000h
MPYS
SUMEXT contains the extended sign of the result
00000h Result was positive or zero
0FFFFh Result was negative
MAC
SUMEXT contains the carry of the result
0000h
0001h
MACS
No carry for result
Result has a carry
SUMEXT contains the extended sign of the result
00000h Result was positive or zero
0FFFFh Result was negative
MACS Underflow and Overflow
The multiplier does not automatically detect underflow or overflow in the
MACS mode. The accumulator range for positive numbers is 0 to 7FFF FFFFh
and for negative numbers is 0FFFF FFFFh to 8000 0000h. An underflow
occurs when the sum of two negative numbers yields a result that is in the
range for a positive number. An overflow occurs when the sum of two positive
numbers yields a result that is in the range for a negative number. In both of
these cases, the SUMEXT register contains the sign of the result, 0FFFFh for
overflow and 0000h for underflow. User software must detect and handle
these conditions appropriately.
8-4
16-Bit Hardware Multiplier
Hardware Multiplier Operation
8.2.3
Software Examples
Examples for all multiplier modes follow. All 8x8 modes use the absolute
address for the registers, because the assembler does not allow .B access to
word registers when using the labels from the standard definitions file.
; 16x16 Unsigned Multiply
MOV
#01234h,&MPY ; Load first operand
MOV
#05678h,&OP2 ; Load second operand
; ...
; Process results
; 8x8 Unsigned Multiply. Absolute addressing.
MOV.B #012h,&0130h ; Load first operand
MOV.B #034h,&0138h ; Load 2nd operand
; ...
; Process results
; 16x16 Signed Multiply
MOV
#01234h,&MPYS ; Load first operand
MOV
#05678h,&OP2 ; Load 2nd operand
; ...
; Process results
; 8x8 Signed Multiply. Absolute addressing.
MOV.B #012h,&0132h ; Load first operand
SXT
&MPYS
; Sign extend first operand
MOV.B #034h,&0138h ; Load 2nd operand
SXT
&OP2
; Sign extend 2nd operand
; (triggers 2nd multiplication)
; ...
; Process results
; 16x16 Unsigned Multiply Accumulate
MOV
#01234h,&MAC ; Load first operand
MOV
#05678h,&OP2 ; Load 2nd operand
; ...
; Process results
; 8x8 Unsigned Multiply
MOV.B #012h,&0134h ;
MOV.B #034h,&0138h ;
; ...
;
Accumulate. Absolute addressing
Load first operand
Load 2nd operand
Process results
; 16x16 Signed Multiply Accumulate
MOV
#01234h,&MACS ; Load first operand
MOV
#05678h,&OP2 ; Load 2nd operand
; ...
; Process results
; 8x8 Signed Multiply
MOV.B #012h,&0136h
SXT
&MACS
MOV.B #034h,R5
SXT
R5
MOV
R5,&OP2
; ...
Accumulate. Absolute addressing
; Load first operand
; Sign extend first operand
; Temp. location for 2nd operand
; Sign extend 2nd operand
; Load 2nd operand
; Process results
16-Bit Hardware Multiplier
8-5
Hardware Multiplier Operation
8.2.4
Indirect Addressing of RESLO
When using indirect or indirect autoincrement addressing mode to access the
result registers, At least one instruction is needed between loading the second
operand and accessing one of the result registers.
; Access
MOV
MOV
MOV
NOP
MOV
MOV
8.2.5
multiplier results with indirect addressing
#RESLO,R5
; RESLO address in R5 for indirect
&OPER1,&MPY ; Load 1st operand
&OPER2,&OP2 ; Load 2nd operand
; Need one cycle
@R5+,&xxx
; Move RESLO
@R5,&xxx
; Move RESHI
Using Interrupts
If an interrupt occurs after writing OP1 but before writing OP2, and the
multiplier is used in servicing that interrupt, the original multiplier mode
selection is lost and the results are unpredictable. To avoid this, disable
interrupts before using the hardware multiplier or do not use the multiplier in
interrupt service routines.
; Disable interrupts
DINT
;
NOP
;
MOV
#xxh,&MPY ;
MOV
#xxh,&OP2 ;
EINT
;
;
8-6
16-Bit Hardware Multiplier
before using the hardware multiplier
Disable interrupts
Required for DINT
Load 1st operand
Load 2nd operand
Interrupts may be enable before
Process results
Hardware Multiplier Registers
8.3 Hardware Multiplier Registers
The hardware multiplier registers are listed in Table 8−4.
Table 8−4. Hardware Multiplier Registers
Register
Short Form
Register Type Address
Initial State
Operand one - multiply
MPY
Read/write
0130h
Unchanged
Operand one - signed multiply
MPYS
Read/write
0132h
Unchanged
Operand one - multiply accumulate
MAC
Read/write
0134h
Unchanged
Operand one - signed multiply accumulate
MACS
Read/write
0136h
Unchanged
Operand two
OP2
Read/write
0138h
Unchanged
Result low word
RESLO
Read/write
013Ah
Undefined
Result high word
RESHI
Read/write
013Ch
Undefined
Sum Extension register
SUMEXT
Read
013Eh
Undefined
16-Bit Hardware Multiplier
8-7
8-8
16-Bit Hardware Multiplier
Chapter 9
32-Bit Hardware Multiplier
This chapter describes the 32-bit hardware multiplier (MPY32) of the
MSP430x4xx family. The 32-bit hardware multiplier is implemented in
MSP430F47x3/4 and MSP430F471xx devices.
Topic
Page
9.1
32-Bit Hardware Multiplier Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 9-2
9.2
32-Bit Hardware Multiplier Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4
9.3
32-Bit Hardware Multiplier Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-21
32-Bit Hardware Multiplier
9-1
32-Bit Hardware Multiplier Introduction
9.1 32-Bit Hardware Multiplier Introduction
The 32-bit hardware multiplier is a peripheral and is not part of the MSP430
CPU. This means its activities do not interfere with the CPU activities. The
multiplier registers are peripheral registers that are loaded and read with CPU
instructions.
The hardware multiplier supports:
- Unsigned multiply
- Signed multiply
- Unsigned multiply accumulate
- Signed multiply accumulate
- 8-bit, 16-bit, 24-bit and 32-bit operands
- Saturation
- Fractional numbers
- 8-bit and 16-bit operation compatible with 16-bit hardware multiplier
- 8-bit and 24-bit multiplications without requiring a “sign extend” instruction
The 32-bit hardware multiplier block diagram is shown in Figure 9−1.
9-2
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Introduction
Figure 9−1. 32-Bit Hardware Multiplier Block Diagram
Accessible
Register
MPY
MPYS
MAC
MACS
31
MPY32H
MPY32L
MPYS32H
MPYS32L
MAC32H
MAC32L
MACS32H
MACS32L
16
OP1 (high word)
15
OP2
OP2H
0
OP1 (low word)
OP2L
16
31
OP2 (high word)
16−bit Multiplexer
15
0
OP2 (low word)
16−bit Multiplexer
16 x 16 Multiplier
OP1_32
OP2_32
MPYMx
MPYSAT
MPYFRAC
MPYC
2
Control
Logic
32−bit Adder
32−bit De−Multiplexer
SUMEXT
RES3
RES2
RES1/RESHI
RES0/RESLO
32−bit Multiplexer
32-Bit Hardware Multiplier
9-3
32-Bit Hardware Multiplier Operation
9.2 32-Bit Hardware Multiplier Operation
The hardware multiplier supports 8-bit, 16-bit, 24-bit, and 32-bit operands with
unsigned multiply, signed multiply, unsigned multiply-accumulate, and signed
multiply-accumulate operations. The size of the operands are defined by the
address the operand is written to and if it is written as word or byte. The type
of operation is selected by the address the first operand is written to.
The hardware multiplier has two 32-bit operand registers, operand one OP1
and operand two OP2, and a 64-bit result register accessible via registers
RES0 to RES3. For compatibility with the 16x16 hardware multiplier the result
of a 8-bit or 16-bit operation is accessible via RESLO, RESHI, and SUMEXT,
as well. RESLO stores the low word of the 16x16-bit result, RESHI stores the
high word of the result, and SUMEXT stores information about the result.
The result of a 8-bit or 16-bit operation is ready in three MCLK cycles and can
be read with the next instruction after writing to OP2, except when using an
indirect addressing mode to access the result. When using indirect addressing
for the result, a NOP is required before the result is ready.
The result of a 24-bit or 32-bit operation can be read with successive
instructions after writing OP2 or OP2H starting with RES0, except when using
an indirect addressing mode to access the result. When using indirect
addressing for the result, a NOP is required before the result is ready.
Table 9−1 summarizes when each word of the 64-bit result is available for the
various combinations of operand sizes. With a 32-bit wide second operand
OP2L and OP2H needs to be written. Depending on when the two 16-bit parts
are written the result availability may vary thus the table shows two entries, one
for OP2L written and one for OP2H written. The worst case defines the actual
result availability.
Table 9−1. Result Availability (MPYFRAC = 0; MPYSAT = 0)
Operation
Result ready in MCLK cycles
After
(OP1 x OP2)
RES0
RES1
RES2
RES3
MPYC Bit
8/16 x 8/16
3
3
4
4
3
OP2 written
24/32 x 8/16
3
5
6
7
7
OP2 written
8/16 x 24/32
3
5
6
7
7
OP2L written
N/A
3
4
4
4
OP2H written
3
8
10
11
11
OP2L written
N/A
3
5
6
6
OP2H written
24/32 x 24/32
9-4
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Operation
9.2.1
Operand Registers
Operand one OP1 has twelve registers, shown in Table 9−2, used to load data
into the multiplier and also select the multiply mode. Writing the low-word of
the first operand to a given address selects the type of multiply operation to
be performed but does not start any operation. When writing a second word
to a high-word register with suffix “32H“ the multiplier assumes a 32-bit wide
OP1, otherwise 16-bits are assumed. The last address written prior to writing
OP2 defines the width of the first operand. For example, if MPY32L is written
first followed by MPY32H, all 32 bits are used and the data width of OP1 is set
to 32 bits. If MPY32H is written first followed by MPY32L, the multiplication will
ignore MPY32H and assume a 16−bit wide OP1 using the data written into
MPY32L.
Repeated multiply operations may be performed without reloading OP1 if the
OP1 value is used for successive operations. It is not necessary to rewrite the
OP1 value to perform the operations.
Table 9−2. OP1 registers
OP1 Register Name Operation
MPY
Unsigned Multiply − operand bits 0 up to 15
MPYS
Signed Multiply − operand bits 0 up to 15
MAC
Unsigned Multiply Accumulate − operand bits 0 up to 15
MACS
Signed Multiply Accumulate − operand bits 0 up to 15
MPY32L
Unsigned Multiply − operand bits 0 up to 15
MPY32H
Unsigned Multiply − operand bits 16 up to 31
MPYS32L
Signed Multiply − operand bits 0 up to 15
MPYS32H
Signed Multiply − operand bits 16 up to 31
MAC32L
Unsigned Multiply Accumulate − operand bits 0 up to 15
MAC32H
Unsigned Multiply Accumulate − operand bits 16 up to 31
MACS32L
Signed Multiply Accumulate − operand bits 0 up to 15
MACS32H
Signed Multiply Accumulate − operand bits 16 up to 31
Writing the second operand to the operand two register OP2 initiates the
multiply operation. Writing OP2 starts the selected operation with a 16-bit wide
second operand together with the values stored in OP1. Writing OP2L starts
the selected operation with a 32-bit wide second operand and the multiplier
expects a the high word to be written to OP2H. Writing to OP2H without a
preceding write to OP2L is ignored.
32-Bit Hardware Multiplier
9-5
32-Bit Hardware Multiplier Operation
Table 9−3. OP2 registers
OP2 Register Name Operation
OP2
Start multiplication with 16-bit wide operand two OP2
(operand bits 0 up to 15)
OP2L
Start multiplication with 32-bit wide operand two OP2
(operand bits 0 up to 15)
OP2H
Continue multiplication with 32-bit wide operand two OP2
(operand bits 16 up to 31)
For 8-bit or 24-bit operands the operand registers can be accessed with byte
instructions. Accessing the multiplier with a byte instruction during a signed
operation will automatically cause a sign extension of the byte within the
multiplier module. For 24-bit operands only the high word should be written as
byte. Whether or not the 24-bit operands are sign extended is defined by the
register that is used to write the low word, because this register defines if the
operation is unsigned or signed.
The high word of a 32-bit operand remains unchanged when changing the size
of the operand to 16 bit either by modifying the operand size bits or by writing
to the respective operand register. During the execution of the 16-bit operation
the content of the high word is ignored.
Note: Changing of First or Second Operand During Multiplication
Changing OP1 or OP2 while the selected multiply operation is being
calculated will render any results invalid that are not ready at the time the new
operand(s) are changed.
Writing OP2 or OP2L will abort any ongoing calculation and start a new
operation. Results that are not ready at that time are invalid also for following
MAC or MACS operations.
Refer to the tables “Result Availability” for the different modes on how many
CPU cycles are needed until a certain result register is ready and valid.
9-6
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Operation
9.2.2
Result Registers
The multiplication result is always 64-bits wide. It is accessible via registers
RES0 to RES3. Used with a signed operation MPYS or MACS the results are
appropriately sign extended. If the result registers are loaded with initial values
before a MACS operation the user software must take care that the written
value is properly sign extended to 64 bits.
Note: Changing of Result Registers During Multiplication
The result registers must not be modified by the user software after writing
the second operand into OP2 or OP2L until the initiated operation is
completed.
In addition to RES0 to RES3, for compatibility with the 16×16 hardware
multiplier the 32-bit result of a 8-bit or 16-bit operation is accessible via
RESLO, RESHI, and SUMEXT. In this case the result low register RESLO
holds the lower 16-bits of the calculation result and the result high register
RESHI holds the upper 16 bits. RES0 and RES1 are identical to RESLO and
RESHI, respectively, in usage and access of calculated results.
The sum extension registers SUMEXT contents depend on the multiply
operation and are listed in Table 9−4. If all operands are 16 bits wide or less
the 32-bit result is used to determine sign and carry. If one of the operands is
larger than 16 bits the 64-bit result is used.
The MPYC bit reflects the multiplier’s carry as listed in Table 9−4 and thus can
be used as 33rd or 65th bit of the result if fractional or saturation mode is not
selected. With MAC or MACS operations the MPYC bit reflects the carry of the
32-bit or 64-bit accumulation and is not taken into account for successive MAC
and MACS operations as the 33rd or 65th bit.
Table 9−4. SUMEXT Contents and MPYC Contents
Mode
SUMEXT
MPYC
MPY
SUMEXT is always 0000h
MPYC is always 0
MPYS
SUMEXT contains the extended sign of the result
MPYC contains the sign of the result
00000h Result was positive or zero
0
Result was positive or zero
0FFFFh Result was negative
1
Result was negative
SUMEXT contains the carry of the result
MPYC contains the carry of the result
0000h
No carry for result
0
No carry for result
0001h
Result has a carry
1
Result has a carry
MAC
MACS
SUMEXT contains the extended sign of the result
MPYC contains the carry of the result
00000h Result was positive or zero
0
No carry for result,
0FFFFh Result was negative
1
Result has a carry
32-Bit Hardware Multiplier
9-7
32-Bit Hardware Multiplier Operation
MACS Underflow and Overflow
The multiplier does not automatically detect underflow or overflow in MACS
mode. For example working with 16-bit input data and 32-bit results, i.e. using
just RESLO and RESHI, the available range for positive numbers is 0 to
07FFF FFFFh and for negative numbers is 0FFFF FFFFh to 08000 0000h. An
underflow occurs when the sum of two negative numbers yields a result that
is in the range for a positive number. An overflow occurs when the sum of two
positive numbers yields a result that is in the range for a negative number.
The SUMEXT register contains the sign of the result in both cases described
above, 0FFFFh for a 32-bit overflow and 0000h for a 32-bit underflow. The
MPYC bit in MPY32CTL0 can be used to detect the overflow condition. If the
carry is different than the sign reflected by the SUMEXT register an overflow
or underflow occurred. User software must handle these conditions
appropriately.
9-8
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Operation
9.2.3
Software Examples
Examples for all multiplier modes follow. All 8×8 modes use the absolute
address for the registers because the assembler will not allow .B access to
word registers when using the labels from the standard definitions file.
There is no sign extension necessary in software. Accessing the multiplier with
a byte instruction during a signed operation will automatically cause a sign
extension of the byte within the multiplier module.
; 32x32 Unsigned Multiply
MOV
#01234h,&MPY32L ;
MOV
#01234h,&MPY32H ;
MOV
#05678h,&OP2L
;
MOV
#05678h,&OP2H
;
; ...
;
Load low word of
Load high word of
Load low word of
Load high word of
Process results
1st
1st
2nd
2nd
operand
operand
operand
operand
; 16x16 Unsigned Multiply
MOV
#01234h,&MPY
; Load 1st operand
MOV
#05678h,&OP2
; Load 2nd operand
; ...
; Process results
; 8x8 Unsigned Multiply.
MOV.B #012h,&MPY_B
MOV.B #034h,&OP2_B
; ...
Absolute addressing.
; Load 1st operand
; Load 2nd operand
; Process results
; 32x32 Signed Multiply
MOV
#01234h,&MPYS32L ; Load low word of 1st operand
MOV
#01234h,&MPYS32H ; Load high word of 1st operand
MOV
#05678h,&OP2L
; Load low word of 2nd operand
MOV
#05678h,&OP2H
; Load high word of 2nd operand
; ...
; Process results
; 16x16 Signed Multiply
MOV
#01234h,&MPYS
MOV
#05678h,&OP2
; ...
; Load 1st operand
; Load 2nd operand
; Process results
; 8x8 Signed Multiply. Absolute addressing.
MOV.B #012h,&MPYS_B
; Load 1st operand
MOV.B #034h,&OP2_B
; Load 2nd operand
; ...
; Process results
32-Bit Hardware Multiplier
9-9
32-Bit Hardware Multiplier Operation
9.2.4
Fractional Numbers
The 32-bit multiplier provides support for fixed-point signal processing. In
fixed−point signal processing, fractional number are represented by using a
fixed decimal point. To classify different ranges of decimal numbers, a
Q-format is used. Different Q-formats represent different locations of the
decimal point. Figure 9−2 shows the format of a signed Q15 number using 16
bits. Every bit after the decimal point has a resolution of 1/2, the most
significant bit is used as the sign bit. The most negative number is 08000h and
the maximum positive number is 07FFFh. This gives a range from −1.0 to
0.999969482 ≅ 1.0 for the signed Q15 format with 16 bits.
Figure 9−2. Q15 Format Representation
15 bits
S
1
2
1
4
1
8
1
16
...
Decimal number equivalent
Decimal point
Sign bit
The range can be increased by shifting the decimal point to the right as shown
in Figure 9−3. The signed Q14 format with 16 bits gives a range from −2.0 to
1.999938965 ≅ 2.0.
Figure 9−3. Q14 Format Representation
14 bits
S
x
1
2
1
4
1
8
1
16
...
The benefit of using 16-bit signed Q15 or 32-bit signed Q31 numbers with
multiplication is that the product of two number in the range from −1.0 to 1.0
is always in that same range.
9-10
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Operation
Fractional Number Mode
Multiplying two fractional numbers using the default multiplication mode with
MPYFRAC = 0 and MPYSAT = 0 gives a result with 2 sign bits. For example
if two 16-bit Q15 numbers are multiplied a 32-bit result in Q30 format is
obtained. To convert the result into Q15 format manually, the first 15 trailing
bits and the extended sign bit must be removed. However, when the fractional
mode of the multiplier is used, the redundant sign bit is automatically removed
yielding a result in Q31 format for the multiplication of two 16-bit Q15 numbers.
Reading the result register RES1 gives the result as 16-bit Q15 number. The
32-bit Q31 result of a multiplication of two 32-bit Q31 numbers is accessed by
reading registers RES2 and RES3.
The fractional mode is enabled with MPYFRAC = 1 in register MPY32CTL0.
The actual content of the result register(s) is not modified when
MPYFRAC = 1. When the result is accessed using software, the value is
left−shifted 1 bit resulting in the final Q formatted result. This allows user
software to switch between reading both the shifted (fractional) and the
un-shifted result. The fractional mode should only be enabled when required
and disabled after use.
In fractional mode the SUMEXT register contains the sign extended bits 32
and 33 of the shifted result for 16x16-bit operations and bits 64 and 65 for
32x32-bit operations − not only bits 32 or 64, respectively.
The MPYC bit is not affected by the fractional mode. It always reads the carry
of the nonfractional result.
; Example using
; Fractional 16x16 multiplication
BIS
#MPYFRAC,&MPY32CTL0
; Turn
MOV
&FRACT1,&MPYS
; Load
MOV
&FRACT2,&OP2
; Load
MOV
&RES1,&PROD
; Save
BIC
#MPYFRAC,&MPY32CTL0
; Back
on fractional mode
1st operand as Q15
2nd operand as Q15
result as Q15
to normal mode
Table 9−5. Result Availability in Fractional Mode (MPYFRAC = 1; MPYSAT = 0)
Operation
Result ready in MCLK cycles
(OP1 x OP2)
RES0
RES1
RES2
RES3
MPYC Bit
8/16 x 8/16
3
3
4
4
3
OP2 written
24/32 x 8/16
3
5
6
7
7
OP2 written
8/16 x 24/32
3
5
6
7
7
OP2L written
N/A
3
4
4
4
OP2H written
3
8
10
11
11
OP2L written
N/A
3
5
6
6
OP2H written
24/32 x 24/32
After
32-Bit Hardware Multiplier
9-11
32-Bit Hardware Multiplier Operation
Saturation Mode
The multiplier prevents overflow and underflow of signed operations in
saturation mode. The saturation mode is enabled with MPYSAT = 1 in register
MPY32CTL0. If an overflow occurs the result is set to the most positive value
available. If an underflow occurs the result is set to the most negative value
available. This is useful to reduce mathematical artifacts in control systems on
overflow and underflow conditions. The saturation mode should only be
enabled when required and disabled after use.
The actual content of the result register(s) is not modified when MPYSAT = 1.
When the result is accessed using software, the value is automatically
adjusted providing the most positive or most negative result when an overflow
or underflow has occurred. The adjusted result is also used for successive
multiply−and−accumulate operations. This allows user software to switch
between reading the saturated and the non-saturated result.
With 16x16 operations the saturation mode only applies to the least significant
32 bits, i.e. the result registers RES0 and RES1. Using the saturation mode
in MAC or MACS operations that mix 16x16 operations with 32x32, 16x32 or
32x16 operations will lead to unpredictable results.
With 32x32, 16x32, and 32x16 operations the saturated result can only be
calculated when RES3 is ready. In non-5xx devices, reading RES0 to RES2
prior to the complete result being ready will deliver the nonsaturated results,
independent of the MPYSAT bit setting.
Enabling the saturation mode does not affect the content of the SUMEXT
register nor the content of the MPYC bit.
; Example using
; Fractional 16x16 multiply accumulate with Saturation
; Turn on fractional and saturation mode:
BIS
#MPYSAT+MPYFRAC,&MPY32CTL0
MOV
&A1,&MPYS
; Load A1 for 1st term
MOV
&K1,&OP2
; Load K1 to get A1*K1
MOV
&A2,&MACS
; Load A2 for 2nd term
MOV
&K2,&OP2
; Load K2 to get A2*K2
MOV
&RES1,&PROD
; Save A1*K1+A2*K2 as result
BIC
#MPYSAT+MPYFRAC,&MPY32CTL0; turn back to normal
Table 9−6. Result Availability in Saturation Mode (MPYSAT = 1)
Operation
Result ready in MCLK cycles
(OP1 x OP2)
RES0
RES1
RES2
RES3
MPYC Bit
8/16 x 8/16
3
3
N/A
N/A
3
OP2 written
24/32 x 8/16
7
7
7
7
7
OP2 written
8/16 x 24/32
7
7
7
7
7
OP2L written
4
4
4
4
4
OP2H written
11
11
11
11
11
OP2L written
6
6
6
6
6
OP2H written
24/32 x 24/32
9-12
32-Bit Hardware Multiplier
after
32-Bit Hardware Multiplier Operation
Figure 9−4 shows the flow for 32-bit saturation used for 16×16 bit
multiplications and the flow for 64-bit saturation used in all other cases.
Primarily, the saturated results depends on the carry bit MPYC and the most
significant bit of the result. Secondly, if the fractional mode is enabled it
depends also on the two most significant bits of the unshift result; i.e., the result
that is read with fractional mode disabled.
Figure 9−4. Saturation Flow Chart
32−bit Saturation
MPYC=0 and
unshifted RES1,
bit 15=1
64−bit Saturation
Yes
Overflow:
RES3 unchanged
RES2 unchanged
RES1 = 07FFFh
RES0 = 0FFFFh
MPYC=0 and
unshifted RES3,
bit 15=1
No
MPYC=1 and
unshifted RES1,
bit 15=0
Yes
Underflow:
RES3 unchanged
RES2 unchanged
RES1 = 08000h
RES0 = 00000h
MPYC=1 and
unshifted RES3,
bit 15=0
No
Underflow:
RES3 = 08000h
RES2 = 00000h
RES1 = 00000h
RES0 = 00000h
No
MPYFRAC = 1
Yes
Yes
Yes
Overflow:
RES3 unchanged
RES2 unchanged
RES1 = 07FFFh
RES0 = 0FFFFh
unshifted RES3,
bit 15=0 and
bit 14=1
No
Yes
Overflow:
RES3 = 07FFFh
RES2 = 0FFFFh
RES1 = 0FFFFh
RES0 = 0FFFFh
No
Yes
Underflow:
RES3 unchanged
RES2 unchanged
RES1 = 08000h
RES0 = 00000h
unshifted RES3,
bit 15=1 and
bit 14=0
No
32−bit Saturation
completed
Yes
No
MPYFRAC = 1
unshifted RES1,
bit 15=1 and
bit 14=0
Overflow:
RES3 = 07FFFh
RES2 = 0FFFFh
RES1 = 0FFFFh
RES0 = 0FFFFh
No
No
unshifted RES1,
bit 15=0 and
bit 14=1
Yes
Yes
Underflow:
RES3 = 08000h
RES2 = 00000h
RES1 = 00000h
RES0 = 00000h
No
64−bit Saturation
completed
Note: Saturation in Fractional Mode
In case of multiplying −1.0 x −1.0 in fractional mode, the result of +1.0 is out
of range, thus, the saturated result gives the most positive result.
32-Bit Hardware Multiplier
9-13
32-Bit Hardware Multiplier Operation
The following example illustrates a special case showing the saturation
function in fractional mode. It also uses the 8-bit functionality of the MPY32
module.
; Turn on fractional and saturation mode,
; clear all other bits in MPY32CTL0:
MOV
#MPYSAT+MPYFRAC,&MPY32CTL0
;Pre−load result registers to demonstrate overflow
MOV
#0,&RES3
;
MOV
#0,&RES2
;
MOV
#07FFFh,&RES1
;
MOV
#0FA60h,&RES0
;
MOV.B #050h,&MACS_B
; 8-bit signed MAC operation
MOV.B #012h,&OP2_B
; Start 16x16 bit operation
MOV
&RES0,R6
; R6 = 0FFFFh
MOV
&RES1,R7
; R7 = 07FFFh
The result is saturated because already the result not converted into a
fractional number shows an overflow. The multiplication of the two positive
numbers 00050h and 00012h gives 005A0h. 005A0h added to 07FFF.FA60h
results in 8000.059F without MPYC being set. Since the MSB of the
unmodified result RES1 is 1 and MPYC = 0 the result is saturated according
to the saturation flow chart in Figure 9−4.
Note: Validity of Saturated Result
The saturated result is only valid if the registers RES0 to RES3, the size of
operands 1 and 2 and MPYC are not modified.
If the saturation mode is used with a preloaded result, user software must
ensure that MPYC in the MPY32CTL0 register is loaded with the sign bit of
the written result otherwise the saturation mode erroneously saturates the
result.
9-14
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Operation
9.2.5
Putting It All Together
Figure 9−5 shows the complete multiplication flow depending on the various
selectable modes for the MPY32 module.
Figure 9−5. Multiplication Flow Chart
New Multiplication
started
Yes
No
16x16
?
No
Yes
Yes
No
MAC or MACS
?
MAC or MACS
?
Yes
Yes
MPYSAT=1
?
Clear Result:
RES1 = 00000h
RES0 = 00000h
32−bit Saturation
Perform
16x16
MPY or MPYS
Operation
No
Perform
16x16
MAC or MACS
Operation
MPYSAT=1
?
No
64−bit Saturation
Perform
MAC or MACS
Operation
Yes
Perform
MPY or MPYS
Operation
Yes
MPYFRAC=1
?
MPYFRAC=1
?
No
Shift 64−bit result.
Calculate SUMEXT based on
MPYC and bit 15 of
unshifted RES1.
Shift 64−bit result.
Calculate SUMEXT based on
MPYC and bit 15 of
unshifted RES3.
Yes
No
Yes
MPYSAT=1
?
No
Clear Result:
RES3 = 00000h
RES2 = 00000h
RES1 = 00000h
RES0 = 00000h
MPYSAT=1
?
32−bit Saturation
64−bit Saturation
No
Multiplication
completed
32-Bit Hardware Multiplier
9-15
32-Bit Hardware Multiplier Operation
Given the separation in processing of 16-bit operations (32-bit results) and
32-bit operations (64-bit results) by the module, it is important to understand
the implications when using MAC/MACS operations and mixing 16-bit
operands/results with 32-bit operands/results. User software must address
these points during usage when mixing these operations. The following code
illustrates the issue.
; Mixing 32x24 multiplication with 16x16 MACS operation
MOV
#MPYSAT,&MPY32CTL0; Saturation mode
MOV
#052C5h,&MPY32L ; Load low word of 1st operand
MOV
#06153h,&MPY32H ; Load high word of 1st operand
MOV
#001ABh,&OP2L
; Load low word of 2nd operand
MOV.B #023h,&OP2H_B
; Load high word of 2nd operand
;... 5 NOPs required
MOV
&RES0,R6
; R6 = 00E97h
MOV
&RES1,R7
; R7 = 0A6EAh
MOV
&RES2,R8
; R8 = 04F06h
MOV
&RES3,R9
; R9 = 0000Dh
; Note that MPYC = 0!
MOV
#0CCC3h,&MACS
; Signed MAC operation
MOV
#0FFB6h,&OP2
; 16x16 bit operation
MOV
&RESLO,R6
; R6 = 0FFFFh
MOV
&RESHI,R7
; R7 = 07FFFh
The second operation gives a saturated result because the 32-bit value used
for the 16x16 bit MACS operation was already saturated when the operation
was started: the carry bit MPYC was 0 from the previous operation but the most
significant bit in result register RES1 is set. As one can see in the flow chart
the content of the result registers are saturated for multiply-and-accumulate
operations after starting a new operation based on the previous results but
depending on the size of the result (32-bit or 64-bit) of the newly initiated
operation.
The saturation before the multiplication can cause issues if the MPYC bit is not
properly set as the following code example illustrates.
;Pre−load result registers to demonstrate overflow
MOV
#0,&RES3
;
MOV
#0,&RES2
;
MOV
#0,&RES1
;
MOV
#0,&RES0
;
; Saturation mode and set MPYC:
MOV
#MPYSAT+MPYC,&MPY32CTL0
MOV.B #082h,&MACS_B
; 8-bit signed MAC operation
MOV.B #04Fh,&OP2_B
; Start 16x16 bit operation
MOV
&RES0,R6
; R6 = 00000h
MOV
&RES1,R7
; R7 = 08000h
9-16
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Operation
Even though the result registers were loaded with all zeros the final result is
saturated. This is because the MPYC bit was set causing the result used for
the multiply-and-accumulate to be saturated to 08000 0000h. Adding a
negative number to it would again cause an underflow thus the final result is
also saturated to 08000 0000h.
9.2.6
Indirect Addressing of Result Registers
When using indirect or indirect autoincrement addressing mode to access the
result registers and the multiplier requires 3 cycles until result availability
according to Table 9−1, at least one instruction is needed between loading the
second operand and accessing the result registers:
; Access
MOV
MOV
MOV
NOP
MOV
MOV
multiplier 16x16 results with indirect addressing
#RES0,R5
; RES0 address in R5 for indirect
&OPER1,&MPY
; Load 1st operand
&OPER2,&OP2
; Load 2nd operand
; Need one cycle
@R5+,&xxx
; Move RES0
@R5,&xxx
; Move RES1
In case of a 32x16 multiplication there is also one instruction required between
reading the first result register RES0 and the second result register RES1:
; Access
MOV
MOV
MOV
MOV
NOP
MOV
NOP
MOV
MOV
multiplier 32x16 results with indirect addressing
#RES0,R5
; RES0 address in R5 for indirect
&OPER1L,&MPY32L ; Load low word of 1st operand
&OPER1H,&MPY32H ; Load high word of 1st operand
&OPER2,&OP2
; Load 2nd operand (16 bits)
; Need one cycle
@R5+,&xxx
; Move RES0
; Need one additional cycle
@R5,&xxx
; Move RES1
; No additional cycles required!
@R5,&xxx
; Move RES2
32-Bit Hardware Multiplier
9-17
32-Bit Hardware Multiplier Operation
9.2.7
Using Interrupts
If an interrupt occurs after writing OP1, but before writing OP2, and the
multiplier is used in servicing that interrupt, the original multiplier mode
selection is lost and the results are unpredictable. To avoid this, disable
interrupts before using the hardware multiplier, do not use the multiplier in
interrupt service routines, or use the save and restore functionality of the 32-bit
multiplier.
; Disable interrupts
DINT
;
NOP
;
MOV
#xxh,&MPY ;
MOV
#xxh,&OP2 ;
EINT
;
;
;
;
9-18
32-Bit Hardware Multiplier
before using the hardware multiplier
Disable interrupts
Required for DINT
Load 1st operand
Load 2nd operand
Interrupts may be enabled before
processing results if result
registers are stored and restored in
interrupt service routines
32-Bit Hardware Multiplier Operation
Save and Restore
If the multiplier is used in interrupt service routines its state can be saved and
restored using the MPY32CTL0 register. The following code example shows
how the complete multiplier status can be saved and restored to allow
interruptible multiplications together with the usage of the multiplier in interrupt
service routines. Since the state of the MPYSAT and MPYFRAC bits are
unknown they should be cleared before the registers are saved as shown in
the code example.
; Interrupt service routine using multiplier
MPY_USING_ISR
PUSH &MPY32CTL0
; Save multiplier mode, etc.
BIC
#MPYSAT+MPYFRAC,&MPY32CTL0
; Clear MPYSAT+MPYFRAC
PUSH &RES3
; Save result 3
PUSH &RES2
; Save result 2
PUSH &RES1
; Save result 1
PUSH &RES0
; Save result 0
PUSH &MPY32H
; Save operand 1, high word
PUSH &MPY32L
; Save operand 1, low word
PUSH &OP2H
; Save operand 2, high word
PUSH &OP2L
; Save operand 2, low word
;
...
; Main part of ISR
; Using standard MPY routines
;
POP
&OP2L
; Restore operand 2, low word
POP
&OP2H
; Restore operand 2, high word
; Starts dummy multiplication but
; result is overwritten by
; following restore operations:
POP
&MPY32L
; Restore operand 1, low word
POP
&MPY32H
; Restore operand 1, high word
POP
&RES0
; Restore result 0
POP
&RES1
; Restore result 1
POP
&RES2
; Restore result 2
POP
&RES3
; Restore result 3
POP
&MPY32CTL0
; Restore multiplier mode, etc.
reti
; End of interrupt service routine
32-Bit Hardware Multiplier
9-19
32-Bit Hardware Multiplier Operation
9.2.8
Using DMA
In devices with a DMA controller the multiplier can trigger a transfer when the
complete result is available. The DMA controller needs to start reading the
result with MPY32RES0 successively up to MPY32RES3. Not all registers
need to be read. The trigger timing is such that the DMA controller starts
reading MPY32RES0 when its ready and that the MPY32RES3 can be read
exactly in the clock cycle when it is available to allow fastest access via DMA.
The signal into the DMA controller is ’Multiplier ready’. Please refer to the DMA
user’s guide chapter for details.
9-20
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Registers
9.3 32-Bit Hardware Multiplier Registers
The 32-bit hardware multiplier registers are listed in Table 9−7.
Table 9−7. 32-bit Hardware Multiplier Registers
Register
Short Form
Register
Type
Address Initial State
16-bit operand one − multiply
MPY
Read/write
0130h
Unchanged
8-bit operand one − multiply
MPY_B
Read/write
0132h
Unchanged
16-bit operand one − signed multiply
MPYS
Read/write
0132h
Unchanged
8-bit operand one − signed multiply
MPYS_B
Read/write
0132h
Unchanged
16-bit operand one − multiply accumulate
MAC
Read/write
0134h
Unchanged
8-bit operand one − multiply accumulate
MAC_B
Read/write
0134h
Unchanged
16-bit operand one − signed multiply accumulate
MACS
Read/write
0136h
Unchanged
8-bit operand one − signed multiply accumulate
MACS_B
Read/write
0136h
Unchanged
16-bit operand two
OP2
Read/write
0138h
Unchanged
8-bit operand two
OP2_B
Read/write
0138h
Unchanged
16x16-bit result low word
RESLO
Read/write
013Ah
Undefined
16x16-bit result high word
RESHI
Read/write
013Ch
Undefined
16x16-bit sum extension register
SUMEXT
Read
013Eh
Undefined
32-bit operand 1 − multiply − low word
MPY32L
Read/write
0140h
Unchanged
32-bit operand 1 − multiply − high word
MPY32H
Read/write
0142h
Unchanged
24-bit operand 1 − multiply − high byte
MPY32H_B
Read/write
0142h
Unchanged
32-bit operand 1 − signed multiply − low word
MPYS32L
Read/write
0144h
Unchanged
32-bit operand 1 − signed multiply − high word
MPYS32H
Read/write
0146h
Unchanged
24-bit operand 1 − signed multiply − high byte
MPYS32H_B Read/write
0146h
Unchanged
32-bit operand 1 − multiply accumulate − low word
MAC32L
Read/write
0148h
Unchanged
32-bit operand 1 − multiply accumulate − high word
MAC32H
Read/write
014Ah
Unchanged
24-bit operand 1 − multiply accumulate − high byte
MAC32H_B
Read/write
014Ah
Unchanged
32-bit operand 1 − signed multiply accumulate − low
word
MACS32L
Read/write
014Ch
Unchanged
32-bit operand 1 − signed multiply accumulate − high
word
MACS32H
Read/write
014Eh
Unchanged
24-bit operand 1 − signed multiply accumulate − high
byte
MACS32H_B Read/write
014Eh
Unchanged
32-bit operand 2 − low word
OP2L
Read/write
0150h
Unchanged
32-bit operand 2 − high word
OP2H
Read/write
0152h
Unchanged
24-bit operand 2 − high byte
OP2H_B
Read/write
0152h
Unchanged
32x32-bit result 0 − least significant word
RES0
Read/write
0154h
Undefined
32x32-bit result 1
RES1
Read/write
0156h
Undefined
32x32-bit result 2
RES2
Read/write
0158h
Undefined
32x32-bit result 3 − most significant word
RES3
Read/write
015Ah
Undefined
MPY32 Control Register 0
MPY32CTL0
Read/write
015Ch
Undefined
32-Bit Hardware Multiplier
9-21
32-Bit Hardware Multiplier Registers
The registers listed in Table 9−8 are treated equally.
Table 9−8. Alternative Registers
Register
Alternative 1
Alternative 2
16-bit operand one − multiply
MPY
MPY32L
8-bit operand one − multiply
MPY_B
MPYS32L_B
16-bit operand one − signed multiply
MPYS
MPYS32L
8-bit operand one − signed multiply
MPYS_B
MPYS32L_B
16-bit operand one − multiply accumulate
MAC
MAC32L
8-bit operand one − multiply accumulate
MAC_B
MAC32L_B
16-bit operand one − signed multiply accumulate
MACS
MACS32L
8-bit operand one − signed multiply accumulate
MACS_B
MACS32L_B
16x16-bit result low word
RESLO
RES0
16x16-bit result high word
RESHI
RES1
9-22
32-Bit Hardware Multiplier
32-Bit Hardware Multiplier Registers
MPY32CTL0, 32-bit Multiplier Control Register 0
15
14
13
12
11
10
9
8
Reserved
r−0
r−0
r−0
r−0
r−0
r−0
r−0
r−0
7
6
5
4
3
2
1
0
MPY
OP2_32
MPY
OP1_32
MPYSAT
MPYFRAC
Reserved
MPYC
rw
rw
rw−0
rw−0
rw−0
rw
MPYMx
rw
rw
Reserved
Bits
15−8
Reserved
MPY
OP2_32
Bit 7
Multiplier bit-width of operand 2
0
16 bits
1
32 bits
MPY
OP1_32
Bit 6
Multiplier bit-width of operand 1.
0
16 bits
1
32 bits
MPYMx
Bits
5-4
Multiplier mode
00 MPY − Multiply
01 MPYS − Signed multiply
10 MAC − Multiply accumulate
11 MACS − Signed multiply accumulate
MPYSAT
Bit 3
Saturation mode
0
Saturation mode disabled
1
Saturation mode enabled
MPYFRAC
Bit 2
Fractional mode
0
Fractional mode disabled
1
Fractional mode enabled
Reserved
Bit 1
Reserved
MPYC
Bit 0
Carry of the multiplier. It can be considered as 33rd or 65th bit of the result
if fractional or saturation mode is not selected because the MPYC bit does not
change when switching to saturation or fractional mode.
It is used to restore the SUMEXT content in MAC mode.
0
No carry for result
1
Result has a carry
32-Bit Hardware Multiplier
9-23
9-24
32-Bit Hardware Multiplier
Chapter 10
DMA Controller
The DMA controller module transfers data from one address to another
without CPU intervention. This chapter describes the operation of the DMA
controller. One DMA channel is implemented in MSP430FG43x and three
DMA channels are implemented in the MSP430FG461x and MSP430F471xx
devices.
Topic
Page
10.1 DMA Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2
10.2 DMA Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4
10.3 DMA Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-21
DMA Controller
10-1
DMA Introduction
10.1 DMA Introduction
The direct memory access (DMA) controller transfers data from one address
to another, without CPU intervention, across the entire address range. For
example, the DMA controller can move data from the ADC12 conversion
memory to RAM.
Devices that contain a DMA controller may have one, two, or three DMA
channels available. Therefore, depending on the number of DMA channels
available, some features described in this chapter are not applicable to all
devices.
Using the DMA controller can increase the throughput of peripheral modules.
It can also reduce system power consumption by allowing the CPU to remain
in a low-power mode without having to awaken to move data to or from a
peripheral.
The DMA controller features include:
- Up to three independent transfer channels
- Configurable DMA channel priorities
- Requires only two MCLK clock cycles per transfer
- Byte or word and mixed byte/word transfer capability
- Block sizes up to 65535 bytes or words
- Configurable transfer trigger selections
- Selectable edge or level-triggered transfer
- Four addressing modes
- Single, block, or burst-block transfer modes
The DMA controller block diagram is shown in Figure 10−1.
10-2
DMA Controller
DMA Introduction
Figure 10−1. DMA Controller Block Diagram
DMA0TSELx
JTAG Active
4
DMAREQ
TACCR2_CCIFG
TBCCR2_CCIFG
Serial data received
Serial transmit ready
DAC12_0IFG
ADC12IFGx
TACCR0_CCIFG
TBCCR0_CCIFG
USART1 data received
USART1 transmit ready
Multiplier ready
Serial data received
Serial transmit ready
DMA2IFG
DMAE0
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
NMI Interrupt Request
ENNMI
Halt
ROUNDROBIN
2
DMADSTINCRx
DMADSTBYTE
DMADTx
3
DMA Channel 0
DMA0SA
DT
DMA0DA
DMA0SZ
2
DMASRSBYTE
DMASRCINCRx
DMAEN
DMA1TSELx
4
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
DMA Priority And Control
DMAREQ
TACCR2_CCIFG
TBCCR2_CCIFG
Serial data received
Serial transmit ready
DAC12_0IFG
ADC12IFGx
TACCR0_CCIFG
TBCCR0_CCIFG
USART1 data received
USART1 transmit ready
Multiplier ready
Serial data received
Serial transmit ready
DMA0IFG
DMAE0
2
DMA Channel 1
DMA1SA
DMAREQ
TACCR2_CCIFG
TBCCR2_CCIFG
Serial data received
Serial transmit ready
DAC12_0IFG
ADC12IFGx
TACCR0_CCIFG
TBCCR0_CCIFG
USART1 data received
USART1 transmit ready
Multiplier ready
Serial data received
Serial transmit ready
DMA1IFG
DMAE0
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
DT
Address
Space
DMA1DA
DMA1SZ
2
DMA2TSELx
4
DMADSTINCRx DMADTx
DMADSTBYTE
3
2
DMASRSBYTE
DMASRCINCRx
DMAEN
DMADSTINCRx DMADTx
DMADSTBYTE
3
DMA Channel 2
DMA2SA
DT
DMA2DA
DMA2SZ
2
DMASRSBYTE
DMASRCINCRx
DMAEN
DMAONFETCH
Halt CPU
DMA Controller
10-3
DMA Operation
10.2 DMA Operation
The DMA controller is configured with user software. The setup and operation
of the DMA is discussed in the following sections.
10.2.1 DMA Addressing Modes
The DMA controller has four addressing modes. The addressing mode for
each DMA channel is independently configurable. For example, channel 0
may transfer between two fixed addresses, while channel 1 transfers between
two blocks of addresses. The addressing modes are shown in Figure 10−2.
The addressing modes are:
- Fixed address to fixed address
- Fixed address to block of addresses
- Block of addresses to fixed address
- Block of addresses to block of addresses
The addressing modes are configured with the DMASRCINCRx and
DMADSTINCRx control bits. The DMASRCINCRx bits select if the source
address is incremented, decremented, or unchanged after each transfer. The
DMADSTINCRx bits select if the destination address is incremented,
decremented, or unchanged after each transfer.
Transfers may be byte-to-byte, word-to-word, byte-to-word, or word-to-byte.
When transferring word-to-byte, only the lower byte of the source-word
transfers. When transferring byte-to-word, the upper byte of the
destination-word is cleared when the transfer occurs.
Figure 10−2. DMA Addressing Modes
DMA
Controller
Address Space
Fixed Address To Fixed Address
DMA
Controller
Address Space
Block Of Addresses To Fixed Address
10-4
DMA Controller
DMA
Controller
Address Space
Fixed Address To Block Of Addresses
DMA
Controller
Address Space
Block Of Addresses To Block Of Addresses
DMA Operation
10.2.2 DMA Transfer Modes
The DMA controller has six transfer modes selected by the DMADTx bits as
listed in Table 10−1. Each channel is individually configurable for its transfer
mode. For example, channel 0 may be configured in single transfer mode,
while channel 1 is configured for burst-block transfer mode, and channel 2
operates in repeated block mode. The transfer mode is configured
independently from the addressing mode. Any addressing mode can be used
with any transfer mode.
Two types of data can be transferred selectable by the DMAxCTL DSTBYTE
and SRCBYTE fields. The source and/or destination location can be either
byte or word data. It is also possible to transfer byte to byte, word to word or
any combination.
Table 10−1. DMA Transfer Modes
DMADTx
Transfer
Mode
000
Single transfer
Each transfer requires a trigger. DMAEN is
automatically cleared when DMAxSZ transfers have
been made.
001
Block transfer
A complete block is transferred with one trigger.
DMAEN is automatically cleared at the end of the
block transfer.
Burst-block
transfer
CPU activity is interleaved with a block transfer.
DMAEN is automatically cleared at the end of the
burst-block transfer.
100
Repeated
single transfer
Each transfer requires a trigger. DMAEN remains
enabled.
101
Repeated
block transfer
A complete block is transferred with one trigger.
DMAEN remains enabled.
Repeated
burst-block
transfer
CPU activity is interleaved with a block transfer.
DMAEN remains enabled.
010, 011
110, 111
Description
DMA Controller
10-5
DMA Operation
Single Transfer
In single transfer mode, each byte/word transfer requires a separate trigger.
The single transfer state diagram is shown in Figure 10−3.
The DMAxSZ register is used to define the number of transfers to be made.
The DMADSTINCRx and DMASRCINCRx bits select if the destination
address and the source address are incremented or decremented after each
transfer. If DMAxSZ = 0, no transfers occur.
The DMAxSA, DMAxDA, and DMAxSZ registers are copied into temporary
registers. The temporary values of DMAxSA and DMAxDA are incremented
or decremented after each transfer. The DMAxSZ register is decremented
after each transfer. When the DMAxSZ register decrements to zero it is
reloaded from its temporary register and the corresponding DMAIFG flag is
set. When DMADTx = 0, the DMAEN bit is cleared automatically when
DMAxSZ decrements to zero and must be set again for another transfer to
occur.
In repeated single transfer mode, the DMA controller remains enabled with
DMAEN = 1, and a transfer occurs every time a trigger occurs.
10-6
DMA Controller
DMA Operation
Figure 10−3. DMA Single Transfer State Diagram
DMAEN = 0
Reset
DMAEN = 0
DMAREQ = 0
T_Size → DMAxSZ
DMAEN = 0
DMAEN = 1
DMAxSZ → T_Size
DMAxSA → T_SourceAdd
DMAxDA → T_DestAdd
[ DMADTx = 0
AND DMAxSZ = 0]
OR DMAEN = 0
DMAABORT = 1
Idle
DMAREQ = 0
DMAABORT=0
Wait for Trigger
2 x MCLK
DMAxSZ > 0
AND DMAEN = 1
[+Trigger AND DMALEVEL = 0 ]
OR
[Trigger=1 AND DMALEVEL=1]
Hold CPU,
Transfer one word/byte
[ENNMI = 1
AND NMI event]
OR
[DMALEVEL = 1
AND Trigger = 0]
T_Size → DMAxSZ
DMAxSA → T_SourceAdd
DMAxDA → T_DestAdd
DMADTx = 4
AND DMAxSZ = 0
AND DMAEN = 1
Decrement DMAxSZ
Modify T_SourceAdd
Modify T_DestAdd
DMA Controller
10-7
DMA Operation
Block Transfers
In block transfer mode, a transfer of a complete block of data occurs after one
trigger. When DMADTx = 1, the DMAEN bit is cleared after the completion of
the block transfer and must be set again before another block transfer can be
triggered. After a block transfer has been triggered, further trigger signals
occurring during the block transfer are ignored. The block transfer state
diagram is shown in Figure 10−4.
The DMAxSZ register is used to define the size of the block and the
DMADSTINCRx and DMASRCINCRx bits select if the destination address
and the source address are incremented or decremented after each transfer
of the block. If DMAxSZ = 0, no transfers occur.
The DMAxSA, DMAxDA, and DMAxSZ registers are copied into temporary
registers. The temporary values of DMAxSA and DMAxDA are incremented
or decremented after each transfer in the block. The DMAxSZ register is
decremented after each transfer of the block and shows the number of
transfers remaining in the block. When the DMAxSZ register decrements to
zero it is reloaded from its temporary register and the corresponding DMAIFG
flag is set.
During a block transfer, the CPU is halted until the complete block has been
transferred. The block transfer takes 2 x MCLK x DMAxSZ clock cycles to
complete. CPU execution resumes with its previous state after the block
transfer is complete.
In repeated block transfer mode, the DMAEN bit remains set after completion
of the block transfer. The next trigger after the completion of a repeated block
transfer triggers another block transfer.
10-8
DMA Controller
DMA Operation
Figure 10−4. DMA Block Transfer State Diagram
DMAEN = 0
Reset
DMAEN = 0
DMAREQ = 0
T_Size → DMAxSZ
DMAEN = 0
DMAEN = 1
DMAxSZ → T_Size
DMAxSA → T_SourceAdd
DMAxDA → T_DestAdd
[DMADTx = 1
AND DMAxSZ = 0]
OR
DMAEN = 0
DMAABORT = 1
Idle
DMAREQ = 0
T_Size → DMAxSZ
DMAxSA → T_SourceAdd
DMAxDA → T_DestAdd
DMAABORT=0
Wait for Trigger
2 x MCLK
[+Trigger AND DMALEVEL = 0 ]
OR
[Trigger=1 AND DMALEVEL=1]
DMADTx = 5
AND DMAxSZ = 0
AND DMAEN = 1
Hold CPU,
Transfer one word/byte
[ENNMI = 1
AND NMI event]
OR
[DMALEVEL = 1
AND Trigger = 0]
DMAxSZ > 0
Decrement DMAxSZ
Modify T_SourceAdd
Modify T_DestAdd
DMA Controller
10-9
DMA Operation
Burst-Block Transfers
In burst-block mode, transfers are block transfers with CPU activity
interleaved. The CPU executes 2 MCLK cycles after every four byte/word
transfers of the block resulting in 20% CPU execution capacity. After the
burst-block, CPU execution resumes at 100% capacity and the DMAEN bit is
cleared. DMAEN must be set again before another burst-block transfer can
be triggered. After a burst-block transfer has been triggered, further trigger
signals occurring during the burst-block transfer are ignored. The burst-block
transfer state diagram is shown in Figure 10−5.
The DMAxSZ register is used to define the size of the block and the
DMADSTINCRx and DMASRCINCRx bits select if the destination address
and the source address are incremented or decremented after each transfer
of the block. If DMAxSZ = 0, no transfers occur.
The DMAxSA, DMAxDA, and DMAxSZ registers are copied into temporary
registers. The temporary values of DMAxSA and DMAxDA are incremented
or decremented after each transfer in the block. The DMAxSZ register is
decremented after each transfer of the block and shows the number of
transfers remaining in the block. When the DMAxSZ register decrements to
zero it is reloaded from its temporary register and the corresponding DMAIFG
flag is set.
In repeated burst-block mode the DMAEN bit remains set after completion of
the burst-block transfer and no further trigger signals are required to initiate
another burst-block transfer. Another burst-block transfer begins immediately
after completion of a burst-block transfer. In this case, the transfers must be
stopped by clearing the DMAEN bit, or by an NMI interrupt when ENNMI is set.
In repeated burst-block mode the CPU executes at 20% capacity continuously
until the repeated burst-block transfer is stopped.
10-10
DMA Controller
DMA Operation
Figure 10−5. DMA Burst-Block Transfer State Diagram
DMAEN = 0
Reset
DMAEN = 0
DMAREQ = 0
T_Size → DMAxSZ
DMAEN = 0
DMAEN = 1
DMAxSZ → T_Size
[DMADTx = {2, 3}
DMAxSA → T_SourceAdd
AND DMAxSZ = 0]
DMAxDA → T_DestAdd
OR
DMAEN = 0
DMAABORT = 1
Idle
DMAABORT=0
Wait for Trigger
2 x MCLK
[+Trigger AND DMALEVEL = 0 ]
OR
[Trigger=1 AND DMALEVEL=1]
Hold CPU,
Transfer one word/byte
[ENNMI = 1
AND NMI event]
OR
[DMALEVEL = 1
AND Trigger = 0]
T_Size → DMAxSZ
DMAxSA → T_SourceAdd
DMAxDA → T_DestAdd
Decrement DMAxSZ
Modify T_SourceAdd
Modify T_DestAdd
DMAxSZ > 0 AND
a multiple of 4 words/bytes
were transferred
DMAxSZ > 0
DMAxSZ > 0
[DMADTx = {6, 7}
AND DMAxSZ = 0]
2 x MCLK
Burst State
(release CPU for 2xMCLK)
DMA Controller
10-11
DMA Operation
10.2.3 Initiating DMA Transfers
Each DMA channel is independently configured for its trigger source with the
DMAxTSELx bits as described in Table 10−2.The DMAxTSELx bits should be
modified only when the DMACTLx DMAEN bit is 0. Otherwise, unpredictable
DMA triggers may occur.
When selecting the trigger, the trigger must not have already occurred, or the
transfer will not take place. For example, if the TACCR2 CCIFG bit is selected
as a trigger, and it is already set, no transfer will occur until the next time the
TACCR2 CCIFG bit is set.
Edge-Sensitive Triggers
When DMALEVEL = 0, edge-sensitive triggers are used and the rising edge
of the trigger signal initiates the transfer. In single-transfer mode, each transfer
requires its own trigger. When using block or burst-block modes, only one
trigger is required to initiate the block or burst-block transfer.
Level-Sensitive Triggers
When DMALEVEL = 1, level-sensitive triggers are used. For proper operation,
level-sensitive triggers can only be used when external trigger DMAE0 is
selected as the trigger. DMA transfers are triggered as long as the trigger
signal is high and the DMAEN bit remains set.
The trigger signal must remain high for a block or burst-block transfer to
complete. If the trigger signal goes low during a block or burst-block transfer,
the DMA controller is held in its current state until the trigger goes back high
or until the DMA registers are modified by software. If the DMA registers are
not modified by software, when the trigger signal goes high again, the transfer
resumes from where it was when the trigger signal went low.
When DMALEVEL = 1, transfer modes selected when DMADTx = {0, 1, 2, 3}
are recommended because the DMAEN bit is automatically reset after the
configured transfer.
Halting Executing Instructions for DMA Transfers
The DMAONFETCH bit controls when the CPU is halted for a DMA transfer.
When DMAONFETCH = 0, the CPU is halted immediately and the transfer
begins when a trigger is received. When DMAONFETCH = 1, the CPU finishes
the currently executing instruction before the DMA controller halts the CPU
and the transfer begins.
Note: DMAONFETCH Must Be Used When The DMA Writes To Flash
If the DMA controller is used to write to flash memory, the DMAONFETCH
bit must be set. Otherwise, unpredictable operation can result.
10-12
DMA Controller
DMA Operation
Table 10−2. DMA Trigger Operation
DMAxTSELx Operation
0000
A transfer is triggered when the DMAREQ bit is set. The DMAREQ bit is automatically reset
when the transfer starts
0001
A transfer is triggered when the TACCR2 CCIFG flag is set. The TACCR2 CCIFG flag is
automatically reset when the transfer starts. If the TACCR2 CCIE bit is set, the TACCR2
CCIFG flag will not trigger a transfer.
0010
A transfer is triggered when the TBCCR2 CCIFG flag is set. The TBCCR2 CCIFG flag is
automatically reset when the transfer starts. If the TBCCR2 CCIE bit is set, the TBCCR2
CCIFG flag will not trigger a transfer.
0011
Devices with USART0: A transfer is triggered when the URXIFG0 flag is set. URXIFG0 is
automatically reset when the transfer starts. If URXIE0 is set, the URXIFG0 flag will not trigger
a transfer.
Devices with USCI_A0: A transfer is triggered when the UCA0RXIFG flag is set. UCA0RXIFG
is automatically reset when the transfer starts. If UCA0RXIE is set, the UCA0RXIFG flag will
not trigger a transfer.
0100
Devices with USART0: A transfer is triggered when the UTXIFG0 flag is set. UTXIFG0 is
automatically reset when the transfer starts. If UTXIE0 is set, the UTXIFG0 flag will not trigger
a transfer.
Devices with USCI_A0: A transfer is triggered when the UCA0TXIFG flag is set. UCA0TXIFG
is automatically reset when the transfer starts. If UCA0TXIE is set, the UCA0TXIFG flag will
not trigger a transfer.
0101
Devices with DAC12: A transfer is triggered when the DAC12_0CTL DAC12IFG flag is set.
The DAC12_0CTL DAC12IFG flag is automatically cleared when the transfer starts. If the
DAC12_0CTL DAC12IE bit is set, the DAC12_0CTL DAC12IFG flag will not trigger a transfer.
0110
Devices with ADC12: A transfer is triggered by an ADC12IFGx flag. When single-channel
conversions are performed, the corresponding ADC12IFGx is the trigger. When sequences
are used, the ADC12IFGx for the last conversion in the sequence is the trigger. A transfer is
triggered when the conversion is completed and the ADC12IFGx is set. Setting the
ADC12IFGx with software will not trigger a transfer. All ADC12IFGx flags are automatically
reset when the associated ADC12MEMx register is accessed by the DMA controller.
Devices with SD16 or SD16_A: A transfer is triggered by the SD16IFG flag of the master
channel in grouped mode or of channel 0. Setting the SD16IFG with software will not trigger a
transfer. All SD16IFG flags are automatically reset when the associated SD16MEMx register
is accessed by the DMA controller. If the SD16IE of the master channel is set, the SD16IFG
will not trigger a transfer.
0111
A transfer is triggered when the TACCR0 CCIFG flag is set. The TACCR0 CCIFG flag is
automatically reset when the transfer starts. If the TACCR0 CCIE bit is set, the TACCR0
CCIFG flag will not trigger a transfer.
1000
A transfer is triggered when the TBCCR0 CCIFG flag is set. The TBCCR0 CCIFG flag is
automatically reset when the transfer starts. If the TBCCR0 CCIE bit is set, the TBCCR0
CCIFG flag will not trigger a transfer.
1001
Devices with USART1: A transfer is triggered when the URXIFG1 flag is set. URXIFG1 is
automatically reset when the transfer starts. If URXIE1 is set, the URXIFG1 flag will not trigger a
transfer.
Devices with USCI_A1: A transfer is triggered when the UCA1RXIFG flag is set. UCA1RXIFG
is automatically reset when the transfer starts. If UCA1RXIE is set, the UCA1RXIFG flag will
not trigger a transfer.
DMA Controller
10-13
DMA Operation
Table 10−2. DMA Trigger Operation (Continued)
DMAxTSELx Operation
1010
Devices with USART1: A transfer is triggered when the UTXIFG1 flag is set. UTXIFG1 is
automatically reset when the transfer starts. If UTXIE1 is set, the UTXIFG1 flag will not trigger
a transfer.
Devices with USCI_A1: A transfer is triggered when the UCA1TXIFG flag is set. UCA1TXIFG
is automatically reset when the transfer starts. If UCA1TXIE is set, the UCA1TXIFG flag will
not trigger a transfer.
1011
A transfer is triggered when the hardware multiplier is ready for a new operand.
1100
A transfer is triggered when the UCB0RXIFG flag is set. UCB0RXIFG is automatically reset
when the transfer starts. If UCB0RXIE is set, the UCB0RXIFG flag will not trigger a transfer.
1101
A transfer is triggered when the UCB0TXIFG flag is set. UCB0TXIFG is automatically reset
when the transfer starts. If UCB0TXIE is set, the UCB0TXIFG flag will not trigger a transfer.
1110
A transfer is triggered when the DMAxIFG flag is set. DMA0IFG triggers channel 1, DMA1IFG
triggers channel 2, and DMA2IFG triggers channel 0. None of the DMAxIFG flags are
automatically reset when the transfer starts.
1111
A transfer is triggered by the external trigger DMAE0.
10-14
DMA Controller
DMA Operation
10.2.4 Stopping DMA Transfers
There are two ways to stop DMA transfers in progress:
- A single, block, or burst-block transfer may be stopped with an NMI
interrupt, if the ENNMI bit is set in register DMACTL1.
- A burst-block transfer may be stopped by clearing the DMAEN bit.
10.2.5 DMA Channel Priorities
The default DMA channel priorities are DMA0−DMA1−DMA2. If two or three
triggers happen simultaneously or are pending, the channel with the highest
priority completes its transfer (single, block or burst-block transfer) first, then
the second priority channel, then the third priority channel. Transfers in
progress are not halted if a higher priority channel is triggered. The higher
priority channel waits until the transfer in progress completes before starting.
The DMA channel priorities are configurable with the ROUNDROBIN bit.
When the ROUNDROBIN bit is set, the channel that completes a transfer
becomes the lowest priority. The order of the priority of the channels always
stays the same, DMA0−DMA1−DMA2, for example:
DMA Priority
Transfer Occurs
New DMA Priority
DMA0 − DMA1 − DMA2
DMA1
DMA2 − DMA0 − DMA1
DMA2 − DMA0 − DMA1
DMA2
DMA0 − DMA1 − DMA2
DMA0 − DMA1 − DMA2
DMA0
DMA1 − DMA2 − DMA0
When the ROUNDROBIN bit is cleared the channel priority returns to the
default priority.
DMA channel priorities are not applicable to MSP430FG43x devices.
DMA Controller
10-15
DMA Operation
10.2.6 DMA Transfer Cycle Time
The DMA controller requires one or two MCLK clock cycles to synchronize
before each single transfer or complete block or burst-block transfer. Each
byte/word transfer requires two MCLK cycles after synchronization, and one
cycle of wait time after the transfer. Because the DMA controller uses MCLK,
the DMA cycle time is dependent on the MSP430 operating mode and clock
system setup.
If the MCLK source is active, but the CPU is off, the DMA controller will use
the MCLK source for each transfer, without re-enabling the CPU. If the MCLK
source is off, the DMA controller will temporarily restart MCLK, sourced with
DCOCLK, for the single transfer or complete block or burst-block transfer. The
CPU remains off, and after the transfer completes, MCLK is turned off. The
maximum DMA cycle time for all operating modes is shown in Table 10−3.
Table 10−3. Maximum Single-Transfer DMA Cycle Time
CPU Operating Mode
Clock Source
Maximum DMA Cycle Time
Active mode
MCLK=DCOCLK
4 MCLK cycles
Active mode
MCLK=LFXT1CLK
4 MCLK cycles
Low-power mode LPM0/1 MCLK=DCOCLK
5 MCLK cycles
Low-power mode LPM3/4 MCLK=DCOCLK
5 MCLK cycles + 6 μs†
Low-power mode LPM0/1 MCLK=LFXT1CLK
5 MCLK cycles
Low-power mode LPM3
MCLK=LFXT1CLK
5 MCLK cycles
Low-power mode LPM4
MCLK=LFXT1CLK
5 MCLK cycles + 6 μs†
†
10-16
DMA Controller
The additional 6 μs are needed to start the DCOCLK. It is the t(LPMx) parameter in the data sheet.
DMA Operation
10.2.7 Using DMA with System Interrupts
DMA transfers are not interruptible by system interrupts. System interrupts
remain pending until the completion of the transfer. NMI interrupts can
interrupt the DMA controller if the ENNMI bit is set.
System interrupt service routines are interrupted by DMA transfers. If an
interrupt service routine or other routine must execute with no interruptions,
the DMA controller should be disabled prior to executing the routine.
10.2.8 DMA Controller Interrupts
Each DMA channel has its own DMAIFG flag. Each DMAIFG flag is set in any
mode when the corresponding DMAxSZ register counts to zero. If the
corresponding DMAIE and GIE bits are set, an interrupt request is generated.
All DMAIFG flags source only one DMA controller interrupt vector and the
interrupt vector may be shared with the other modules. See the device-specific
datasheet for specific interrupt assignments. In this case, software must
check the DMAIFG and other flags to determine the source of the interrupt.
The DMAIFG flags are not reset automatically and must be reset by software.
10.2.9 DMAIV, DMA Interrupt Vector Generator
MSP430FG461x and MSP430F471xx devices implement the interrupt vector
register DMAIV. In this case, all DMAIFG flags are prioritized and combined
to source a single interrupt vector. The interrupt vector register DMAIV is used
to determine which flag requested an interrupt.
The highest priority enabled interrupt generates a number in the DMAIV
register (see register description). This number can be evaluated or added to
the program counter to automatically enter the appropriate software routine.
Disabled DMA interrupts do not affect the DMAIV value.
Any access, read or write, of the DMAIV register automatically resets the
highest pending interrupt flag. If another interrupt flag is set, another interrupt
is immediately generated after servicing the initial interrupt. For example, If the
DMA0IFG and DMA2IFG flags are set when the interrupt service routine
accesses the DMAIV register, DMA0IFG is reset automatically. After the RETI
instruction of the interrupt service routine is executed, the DMA2IFG will
generate another interrupt.
DMA Controller
10-17
DMA Operation
DMAIV Software Example
The following software example shows the recommended use of DMAIV and
the handling overhead. The DMAIV value is added to the PC to automatically
jump to the appropriate routine.
The numbers at the right margin show the necessary CPU cycles for each
instruction. The software overhead for different interrupt sources includes
interrupt latency and return-from-interrupt cycles, but not the task handling
itself.
;Interrupt handler for DMA0IFG, DMA1IFG, DMA2IFG
Cycles
DMA_HND
...
; Interrupt latency
6
ADD
&DMAIV,PC ; Add offset to Jump table 3
RETI
; Vector 0: No interrupt
5
JMP
DMA0_HND ; Vector 2: DMA channel 0
2
JMP
DMA1_HND ; Vector 4: DMA channel 1
2
JMP
DMA2_HND ; Vector 6: DMA channel 2
2
RETI
; Vector 8: Reserved
5
RETI
; Vector 10: Reserved
5
RETI
; Vector 12: Reserved
5
RETI
; Vector 14: Reserved
5
DMA2_HND
...
RETI
; Vector 6: DMA channel 2
; Task starts here
; Back to main program
5
...
RETI
; Vector 4: DMA channel 1
; Task starts here
; Back to main program
5
...
RETI
; Vector 2: DMA channel 0
; Task starts here
; Back to main program
5
DMA1_HND
DMA0_HND
10-18
DMA Controller
DMA Operation
10.2.10 Using the USCI_B I2C Module with the DMA Controller
The USCI_B I2C module provides two trigger sources for the DMA controller.
The USCI_B I2C module can trigger a transfer when new I2C data is received
and when data is needed for transmit.
A transfer is triggered if UCB0RXIFG is set. The UCB0RXIFG is cleared
automatically when the DMA controller acknowledges the transfer. If
UCB0RXIE is set, UCB0RXIFG will not trigger a transfer.
A transfer is triggered if UCB0TXIFG is set. The UCB0TXIFG is cleared
automatically when the DMA controller acknowledges the transfer. If
UCB0TXIE is set, UCB0TXIFG will not trigger a transfer.
10.2.11 Using ADC12 with the DMA Controller
MSP430 devices with an integrated DMA controller can automatically move
data from any ADC12MEMx register to another location. DMA transfers are
done without CPU intervention and independently of any low-power modes.
The DMA controller increases throughput of the ADC12 module, and
enhances low-power applications allowing the CPU to remain off while data
transfers occur.
DMA transfers can be triggered from any ADC12IFGx flag. When CONSEQx
= {0,2} the ADC12IFGx flag for the ADC12MEMx used for the conversion can
trigger a DMA transfer. When CONSEQx = {1,3}, the ADC12IFGx flag for the
last ADC12MEMx in the sequence can trigger a DMA transfer. Any
ADC12IFGx flag is automatically cleared when the DMA controller accesses
the corresponding ADC12MEMx.
10.2.12 Using DAC12 With the DMA Controller
MSP430 devices with an integrated DMA controller can automatically move
data to the DAC12_xDAT register. DMA transfers are done without CPU
intervention and independently of any low-power modes. The DMA controller
increases throughput to the DAC12 module, and enhances low-power
applications allowing the CPU to remain off while data transfers occur.
Applications requiring periodic waveform generation can benefit from using
the DMA controller with the DAC12. For example, an application that produces
a sinusoidal waveform may store the sinusoid values in a table. The DMA
controller can continuously and automatically transfer the values to the
DAC12 at specific intervals creating the sinusoid with zero CPU execution.
The DAC12_xCTL DAC12IFG flag is automatically cleared when the DMA
controller accesses the DAC12_xDAT register.
DMA Controller
10-19
DMA Operation
10.2.13 Using SD16 or SD16_A With the DMA Controller
MSP430 devices with an integrated DMA controller can automatically move
data from any SD16MEMx register to another location. DMA transfers are
done without CPU intervention and independently of any low-power modes.
The DMA controller increases throughput of the SD16 or SD16_A module, and
enhances low-power applications allowing the CPU to remain off while data
transfers occur.
In Grouped mode DMA transfers can be triggered by the master channel that
controls the group (i.e. the channel with the lowest channel number and
SD16GRP = 0). Otherwise channel 0 can trigger DMA transfers. Any
SD16IFG is automatically cleared when the DMA controller accesses the
corresponding SD16MEMx register.
10.2.14 Writing to Flash With the DMA Controller
MSP430 devices with an integrated DMA controller can automatically move
data to the Flash memory. DMA transfers are done without CPU intervention
and independent of any low-power modes. The DMA controller performs the
move of the data word/byte to the Flash. The write timing control is done by
the Flash controller. Write transfers to the Flash memory succeed if the Flash
controller set−up is prior to the DMA transfer and if the Flash is not busy.
10-20
DMA Controller
DMA Registers
10.3 DMA Registers
The DMA registers for MSP430FG43x devices are listed in Table 10−4. The
DMA registers for MSP430FG461x and MSP430F471xx devices are listed in
Table 10−5.
Table 10−4. DMA Registers, MSP430FG43x devices
Register
Short Form
Register Type
Address
Initial State
DMA control 0
DMACTL0
Read/write
0122h
Reset with POR
DMA control 1
DMACTL1
Read/write
0124h
Reset with POR
DMA channel 0 control
DMA0CTL
Read/write
01E0h
Reset with POR
DMA channel 0 source address
DMA0SA
Read/write
01E2h
Unchanged
DMA channel 0 destination address
DMA0DA
Read/write
01E4h
Unchanged
DMA channel 0 transfer size
DMA0SZ
Read/write
01E6h
Unchanged
DMA channel 1 control
DMA1CTL
Read/write
01E8h
Reset with POR
DMA channel 1 source address
DMA1SA
Read/write
01EAh
Unchanged
DMA channel 1 destination address
DMA1DA
Read/write
01ECh
Unchanged
DMA channel 1 transfer size
DMA1SZ
Read/write
01EEh
Unchanged
DMA channel 2 control
DMA2CTL
Read/write
01F0h
Reset with POR
DMA channel 2 source address
DMA2SA
Read/write
01F2h
Unchanged
DMA channel 2 destination address
DMA2DA
Read/write
01F4h
Unchanged
DMA channel 2 transfer size
DMA2SZ
Read/write
01F6h
Unchanged
Table 10−5. DMA Registers, MSP430FG461x, MSP430F471xx devices
Register
Short Form
Register Type
Address
Initial State
DMA control 0
DMACTL0
Read/write
0122h
Reset with POR
DMA control 1
DMACTL1
Read/write
0124h
Reset with POR
DMA interrupt vector
DMAIV
Read only
0126h
Reset with POR
DMA channel 0 control
DMA0CTL
Read/write
01D0h
Reset with POR
DMA channel 0 source address
DMA0SA
Read/write
01D2h
Unchanged
DMA channel 0 destination address
DMA0DA
Read/write
01D6h
Unchanged
DMA channel 0 transfer size
DMA0SZ
Read/write
01DAh
Unchanged
DMA channel 1 control
DMA1CTL
Read/write
01DCh
Reset with POR
DMA channel 1 source address
DMA1SA
Read/write
01DEh
Unchanged
DMA channel 1 destination address
DMA1DA
Read/write
01E2h
Unchanged
DMA channel 1 transfer size
DMA1SZ
Read/write
01E6h
Unchanged
DMA channel 2 control
DMA2CTL
Read/write
01E8h
Reset with POR
DMA channel 2 source address
DMA2SA
Read/write
01EAh
Unchanged
DMA channel 2 destination address
DMA2DA
Read/write
01EEh
Unchanged
DMA−channel 2 transfer size
DMA2SZ
Read/write
01F2h
Unchanged
DMA Controller
10-21
DMA Registers
DMACTL0, DMA Control Register 0
15
14
13
12
11
10
9
8
DMA2TSELx
Reserved
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
rw−(0)
rw−(0)
DMA1TSELx
rw−(0)
rw−(0)
rw−(0)
DMA0TSELx
rw−(0)
rw−(0)
rw−(0)
Reserved
Bits
15−12
Reserved
DMA2
TSELx
Bits
11−8
DMA trigger select. These bits select the DMA transfer trigger.
The trigger selection is device-specific. For MSP430FG43x and
MSP430FG461x devices it is given below; for other devices, see the
device-specific data sheet.
0000 DMAREQ bit (software trigger)
0001 TACCR2 CCIFG bit
0010 TBCCR2 CCIFG bit
0011 URXIFG0 (MSP430FG43x), UCA0RXIFG (MPS430FG461x)
0100 UTXIFG0 (MSP430FG43x), UCA0TXIFG (MSP430FG461x)
0101 DAC12_0CTL DAC12IFG bit
0110 ADC12 ADC12IFGx bit
0111 TACCR0 CCIFG bit
1000 TBCCR0 CCIFG bit
1001 URXIFG1 bit
1010 UTXIFG1 bit
1011 Multiplier ready
1100 No action (MSP430FG43x), UCB0RXIFG (MSP430FG461x)
1101 No action (MSP430FG43x), UCB0TXIFG (MSP430FG461x)
1110 DMA0IFG bit triggers DMA channel 1
DMA1IFG bit triggers DMA channel 2
DMA2IFG bit triggers DMA channel 0
1111 External trigger DMAE0
DMA1
TSELx
Bits
7−4
Same as DMA2TSELx
DMA0
TSELx
Bits
3–0
Same as DMA2TSELx
10-22
DMA Controller
DMA Registers
DMACTL1, DMA Control Register 1
15
14
13
12
11
10
9
8
0
0
0
0
0
0
0
0
r0
r0
r0
r0
r0
r0
r0
r0
7
6
5
4
3
2
1
0
0
0
0
0
0
DMA
ONFETCH
ROUND
ROBIN
ENNMI
r0
r0
r0
r0
r0
rw−(0)
rw−(0)
rw−(0)
Reserved
Bits
15−3
Reserved. Read only. Always read as 0.
DMA
ONFETCH
Bit 2
DMA on fetch
0
The DMA transfer occurs immediately
1
The DMA transfer occurs on next instruction fetch after the trigger
ROUND
ROBIN
Bit 1
Round robin. This bit enables the round-robin DMA channel priorities.
0
DMA channel priority is DMA0 − DMA1 − DMA2
1
DMA channel priority changes with each transfer
ENNMI
Bit 0
Enable NMI. This bit enables the interruption of a DMA transfer by an NMI
interrupt. When an NMI interrupts a DMA transfer, the current transfer is
completed normally, further transfers are stopped, and DMAABORT is set.
0
NMI interrupt does not interrupt DMA transfer
1
NMI interrupt interrupts a DMA transfer
DMA Controller
10-23
DMA Registers
DMAxCTL, DMA Channel x Control Register
15
14
13
12
DMADTx
Reserved
11
10
DMADSTINCRx
9
8
DMASRCINCRx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
DMA
DSTBYTE
DMA
SRCBYTE
DMALEVEL
DMAEN
DMAIFG
DMAIE
DMA
ABORT
DMAREQ
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
Reserved
Bit 15
Reserved
DMADTx
Bits
14−12
DMA Transfer mode.
000 Single transfer
001 Block transfer
010 Burst-block transfer
011 Burst-block transfer
100 Repeated single transfer
101 Repeated block transfer
110 Repeated burst-block transfer
111 Repeated burst-block transfer
DMA
DSTINCRx
Bits
11−10
DMA destination increment. This bit selects automatic incrementing or
decrementing of the destination address after each byte or word transfer.
When DMADSTBYTE=1, the destination address increments/decrements by
one.
When
DMADSTBYTE=0,
the
destination
address
increments/decrements by two. The DMAxDA is copied into a temporary
register and the temporary register is incremented or decremented. DMAxDA
is not incremented or decremented.
00 Destination address is unchanged
01 Destination address is unchanged
10 Destination address is decremented
11 Destination address is incremented
DMA
SRCINCRx
Bits
9−8
DMA source increment. This bit selects automatic incrementing or
decrementing of the source address for each byte or word transfer. When
DMASRCBYTE=1, the source address increments/decrements by one.
When DMASRCBYTE=0, the source address increments/decrements by
two. The DMAxSA is copied into a temporary register and the temporary
register is incremented or decremented. DMAxSA is not incremented or
decremented.
00 Source address is unchanged
01 Source address is unchanged
10 Source address is decremented
11 Source address is incremented
DMA
DSTBYTE
Bit 7
DMA destination byte. This bit selects the destination as a byte or word.
0
Word
1
Byte
10-24
DMA Controller
DMA Registers
DMA
SRCBYTE
Bit 6
DMA source byte. This bit selects the source as a byte or word.
0
Word
1
Byte
DMA
LEVEL
Bit 5
DMA level. This bit selects between edge-sensitive and level-sensitive
triggers.
0
Edge sensitive (rising edge)
1
Level sensitive (high level)
DMAEN
Bit 4
DMA enable
0
Disabled
1
Enabled
DMAIFG
Bit 3
DMA interrupt flag
0
No interrupt pending
1
Interrupt pending
DMAIE
Bit 2
DMA interrupt enable
0
Disabled
1
Enabled
DMA
ABORT
Bit 1
DMA Abort. This bit indicates if a DMA transfer was interrupt by an NMI.
0
DMA transfer not interrupted
1
DMA transfer was interrupted by NMI
DMAREQ
Bit 0
DMA request. Software-controlled DMA start. DMAREQ is reset
automatically.
0
No DMA start
1
Start DMA
DMA Controller
10-25
DMA Registers
DMAxSA, DMA Source Address Register
31
30
29
28
27
26
25
824
Reserved
r0
r0
r0
r0
r0
r0
r0
r0
23
22
21
20
19
18
17
16
Reserved
DMAxSAx
r0
r0
r0
r0
rw
rw
rw
rw
15
14
13
12
11
10
9
8
DMAxSAx
rw
rw
rw
rw
rw
rw
rw
rw
7
6
5
4
3
2
1
0
rw
rw
rw
rw
DMAxSAx
rw
rw
rw
rw
Reserved
Bits
31−20
Reserved
DMAxSAx
Bits
19−0
DMA source address. The source address register points to the DMA source
address for single transfers or the first source address for block transfers. The
source address register remains unchanged during block and burst-block
transfers.
Devices that have addressable memory range 64−KB or below contain a
single word for the DMAxSA.
MSP430FG461x and MSP430F471xx devices implement two words for the
DMAxSA register as shown. Bits 31−20 are reserved and always read as
zero. Reading or writing bits 19-16 requires the use of extended instructions.
When writing to DMAxSA with word instructions, bits 19-16 are cleared.
10-26
DMA Controller
DMA Registers
DMAxDA, DMA Destination Address Register
31
30
29
28
27
26
25
824
Reserved
r0
r0
r0
r0
r0
r0
r0
r0
23
22
21
20
19
18
17
16
Reserved
DMAxDAx
r0
r0
r0
r0
rw
rw
rw
rw
15
14
13
12
11
10
9
8
DMAxDAx
rw
rw
rw
rw
rw
rw
rw
rw
7
6
5
4
3
2
1
0
rw
rw
rw
rw
DMAxDAx
rw
rw
rw
rw
Reserved
Bits
31−20
Reserved
DMAxDAx
Bits
19−0
DMA destination address. The destination address register points to the
destination address for single transfers or the first address for block transfers.
The DMAxDA register remains unchanged during block and burst-block
transfers.
Devices that have addressable memory range 64−KB or below contain a
single word for the DMAxDA.
MSP430FG461x and MSP430F471xx devices implement two words for the
DMAxDA register as shown. Bits 31−20 are reserved and always read as
zero. Reading or writing bits 19-16 requires the use of extended instructions.
When writing to DMAxDA with word instructions, bits 19-16 are cleared.
DMA Controller
10-27
DMA Registers
DMAxSZ, DMA Size Address Register
15
14
13
12
11
10
9
8
DMAxSZx
rw
rw
rw
rw
rw
rw
rw
rw
7
6
5
4
3
2
1
0
rw
rw
rw
rw
DMAxSZx
rw
DMAxSZx
10-28
rw
Bits
15−0
rw
rw
DMA size. The DMA size register defines the number of byte/word data per
block transfer. DMAxSZ register decrements with each word or byte transfer.
When DMAxSZ decrements to 0, it is immediately and automatically reloaded
with its previously initialized value.
00000h Transfer is disabled
00001h One byte or word to be transferred
00002h Two bytes or words have to be transferred
:
0FFFFh 65535 bytes or words have to be transferred
DMA Controller
DMA Registers
DMAIV, DMA Interrupt Vector Register
15
14
13
12
11
10
9
8
0
0
0
0
0
0
0
0
r0
r0
r0
r0
r0
r0
r0
r0
7
6
5
4
3
2
1
0
0
0
0
0
r0
r0
r0
r0
DMAIVx
Bits
15-0
DMAIVx
r−(0)
0
r−(0)
r−(0)
r0
DMA Interrupt Vector value
DMAIV Contents
Interrupt Source
Interrupt
Priority
Interrupt Flag
−
00h
No interrupt pending
02h
DMA channel 0
DMA0IFG
04h
DMA channel 1
DMA1IFG
06h
DMA channel 2
DMA2IFG
08h
Reserved
−
0Ah
Reserved
−
0Ch
Reserved
−
0Eh
Reserved
−
Highest
Lowest
DMA Controller
10-29
10-30
DMA Controller
Chapter 11
Digital I/O
This chapter describes the operation of the digital I/O ports.
Topic
Page
11.1 Digital I/O Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2
11.2 Digital I/O Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-3
11.3 Digital I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-7
Digital I/O
11-1
Digital I/O Introduction
11.1 Digital I/O Introduction
MSP430 devices have up to ten digital I/O ports implemented, P1 to P10. Each
port has eight I/O pins. Every I/O pin is individually configurable for input or
output direction, and each I/O line can be individually read from or written to.
Ports P1 and P2 have interrupt capability. Each interrupt for the P1 and P2 I/O
lines can be individually enabled and configured to provide an interrupt on a
rising edge or falling edge of an input signal. All P1 I/O lines source a single
interrupt vector, and all P2 I/O lines source a different, single interrupt vector.
The digital I/O features include:
- Independently programmable individual I/Os
- Any combination of input or output
- Individually configurable P1 and P2 interrupts
- Independent input and output data registers
11-2
Digital I/O
Digital I/O Operation
11.2 Digital I/O Operation
The digital I/O is configured with user software. The setup and operation of the
digital I/O is described in the following sections. Each port register is an 8-bit
register and is accessed with byte instructions. Registers for P7/P8 and
P9/P10 are arranged such that the two ports can be addressed at once as a
16-bit port. The P7/P8 combination is referred to as PA and the P9/P10
combination is referred to as PB in the standard definitions file. For example,
to write to P7SEL and P8SEL simultaneously, a word write to PASEL would
be used. Some examples of accessing these ports follow:
BIS.B #01h,&P7OUT
MOV.W #05555h,&PAOUT
CLR.B &P9SEL
MOV.W &PBIN,&0200h
;
;
;
;
;
;
;
Set LSB of P7OUT.
P8OUT is unchanged
P7OUT and P8OUT written
simultaneously
Clear P9SEL, P10SEL is unchanged
P9IN and P10IN read simultaneously
as 16-bit port.
11.2.1 Input Register PxIN
Each bit in each PxIN register reflects the value of the input signal at the
corresponding I/O pin when the pin is configured as I/O function.
Bit = 0: The input is low
Bit = 1: The input is high
Note: Writing to Read-Only Registers PxIN
Writing to these read-only registers results in increased current consumption
while the write attempt is active.
11.2.2 Output Registers PxOUT
Each bit in each PxOUT register is the value to be output on the corresponding
I/O pin when the pin is configured as I/O function and output direction.
Bit = 0: The output is low
Bit = 1: The output is high
11.2.3 Direction Registers PxDIR
Each bit in each PxDIR register selects the direction of the corresponding I/O
pin, regardless of the selected function for the pin. PxDIR bits for I/O pins that
are selected for other module functions must be set as required by the other
function.
Bit = 0: The port pin is switched to input direction
Bit = 1: The port pin is switched to output direction
Digital I/O
11-3
Digital I/O Operation
11.2.4 Pullup/Pulldown Resistor Enable Registers PxREN
(MSP430F47x3/4 and MSP430F471xx only)
In MSP430F47x3/4 and MSP430F471xx devices all port pins have a
programmable pullup/pulldown resistor. Each bit in each PxREN register
enables or disables the pullup/pulldown resistor of the corresponding I/O pin.
The corresponding bit in the PxOUT register selects if the pin is pulled up or
pulled down.
Bit = 0: Pullup/pulldown resistor disabled
Bit = 1: Pullup/pulldown resistor enabled
11.2.5 Function Select Registers PxSEL
Port pins are often multiplexed with other peripheral module functions. See the
device-specific data sheet to determine pin functions. Each PxSEL bit is used
to select the pin function — I/O port or peripheral module function.
Bit = 0: I/O function is selected for the pin
Bit = 1: Peripheral module function is selected for the pin
Setting PxSELx = 1 does not automatically set the pin direction. Other
peripheral module functions may require the PxDIRx bits to be configured
according to the direction needed for the module function. See the pin
schematics in the device-specific data sheet.
;Output ACLK on P1.5 on MSP430F41x
BIS.B #020h,&P1SEL ; Select ACLK function for pin
BIS.B #020h,&P1DIR ; Set direction to output *Required*
Note: P1 and P2 Interrupts Are Disabled When PxSEL = 1
When any P1SELx or P2SELx bit is set, the corresponding pin’s interrupt
function is disabled. Therefore, signals on these pins do not generate P1 or
P2 interrupts, regardless of the state of the corresponding P1IE or P2IE bit.
When a port pin is selected as an input to a peripheral, the input signal to the
peripheral is a latched representation of the signal at the device pin. While
PxSELx = 1, the internal input signal follows the signal at the pin. However, if
the PxSELx = 0, the input to the peripheral maintains the value of the input
signal at the device pin before the PxSELx bit was reset.
11-4
Digital I/O
Digital I/O Operation
11.2.6 P1 and P2 Interrupts
Each pin in ports P1 and P2 have interrupt capability, configured with the
PxIFG, PxIE, and PxIES registers. All P1 pins source a single interrupt vector,
and all P2 pins source a different single interrupt vector. The PxIFG register
can be tested to determine the source of a P1 or P2 interrupt.
Interrupt Flag Registers P1IFG, P2IFG
Each PxIFGx bit is the interrupt flag for its corresponding I/O pin and is set
when the selected input signal edge occurs at the pin. All PxIFGx interrupt
flags request an interrupt when their corresponding PxIE bit and the GIE bit
are set. Each PxIFG flag must be reset with software. Software can also set
each PxIFG flag, providing a way to generate a software-initiated interrupt.
Bit = 0: No interrupt is pending
Bit = 1: An interrupt is pending
Only transitions, not static levels, cause interrupts. If any PxIFGx flag becomes
set during a Px interrupt service routine or is set after the RETI instruction of
a Px interrupt service routine is executed, the set PxIFGx flag generates
another interrupt. This ensures that each transition is acknowledged.
Note: PxIFG Flags When Changing PxOUT or PxDIR
Writing to P1OUT, P1DIR, P2OUT, or P2DIR can result in setting the
corresponding P1IFG or P2IFG flags.
Note: Length of I/O Pin Interrupt Event
Any external interrupt event should be at least 1.5 times MCLK or longer, to
ensure that it is accepted and the corresponding interrupt flag is set.
Digital I/O
11-5
Digital I/O Operation
Interrupt Edge Select Registers P1IES, P2IES
Each PxIES bit selects the interrupt edge for the corresponding I/O pin.
Bit = 0: The PxIFGx flag is set with a low-to-high transition
Bit = 1: The PxIFGx flag is set with a high-to-low transition
Note: Writing to PxIESx
Writing to P1IES or P2IES can result in setting the corresponding interrupt
flags.
PxIESx
0→1
0→1
1→0
1→0
PxINx
0
1
0
1
PxIFGx
May be set
Unchanged
Unchanged
May be set
Interrupt Enable P1IE, P2IE
Each PxIE bit enables the associated PxIFG interrupt flag.
Bit = 0: The interrupt is disabled
Bit = 1: The interrupt is enabled
11.2.7 Configuring Unused Port Pins
Unused I/O pins should be configured as I/O function, output direction, and left
unconnected on the PC board, to reduce power consumption. The value of the
PxOUT bit is don’t care, because the pin is unconnected. See chapter System
Resets, Interrupts, and Operating Modes for termination of unused pins.
11-6
Digital I/O
Digital I/O Registers
11.3 Digital I/O Registers
The digital I/O registers are listed in Table 11−1 and Table 11−2.
Table 11−1. Digital I/O Registers, P1-P6
Port
Register
Short Form
Address
Register Type
P1
Input
P1IN
020h
Read only
Output
P1OUT
021h
Read/write
Unchanged
Direction
P1DIR
022h
Read/write
Reset with PUC
Interrupt Flag
P1IFG
023h
Read/write
Reset with PUC
Interrupt Edge Select
P1IES
024h
Read/write
Unchanged
Interrupt Enable
P1IE
025h
Read/write
Reset with PUC
Port Select
P1SEL
026h
Read/write
Reset with PUC
Reset with PUC
P2
P3
P4
P5
P6
Note:
Initial State
−
Resistor Enable
P1REN
027h
Read/write
Input
P2IN
028h
Read only
Output
P2OUT
029h
Read/write
Unchanged
Direction
P2DIR
02Ah
Read/write
Reset with PUC
Interrupt Flag
P2IFG
02Bh
Read/write
Reset with PUC
Interrupt Edge Select
P2IES
02Ch
Read/write
Unchanged
Interrupt Enable
P2IE
02Dh
Read/write
Reset with PUC
Port Select
P2SEL
02Eh
Read/write
0C0h with PUC
Resistor Enable
P2REN
02Fh
Read/write
Reset with PUC
Input
P3IN
018h
Read only
Output
P3OUT
019h
Read/write
Unchanged
Direction
P3DIR
01Ah
Read/write
Reset with PUC
Port Select
P3SEL
01Bh
Read/write
Reset with PUC
Resistor Enable
P3REN
010h
Read/write
Reset with PUC
Input
P4IN
01Ch
Read only
Output
P4OUT
01Dh
Read/write
Unchanged
Direction
P4DIR
01Eh
Read/write
Reset with PUC
Port Select
P4SEL
01Fh
Read/write
Reset with PUC
Resistor Enable
P4REN
011h
Read/write
Reset with PUC
Input
P5IN
030h
Read only
Output
P5OUT
031h
Read/write
Unchanged
Direction
P5DIR
032h
Read/write
Reset with PUC
Port Select
P5SEL
033h
Read/write
Reset with PUC
Resistor Enable
P5REN
012h
Read/write
Reset with PUC
Input
P6IN
034h
Read only
Output
P6OUT
035h
Read/write
Unchanged
Direction
P6DIR
036h
Read/write
Reset with PUC
−
−
−
−
−
Port Select
P6SEL
037h
Read/write
Reset with PUC
Resistor Enable
P6REN
013h
Read/write
Reset with PUC
Resistor enable registers RxREN only available in MSP430F47x3/4 and MSP430F471xx devices.
Digital I/O
11-7
Digital I/O Registers
Table 11−2. Digital I/O Registers, P7-P10
Port
Register
Short Form
Address
Register Type
P7
PA
Input
P7IN
038h
Read only
Output
P7OUT
03Ah
Read/write
Unchanged
Direction
P7DIR
03Ch
Read/write
Reset with PUC
Port Select
P7SEL
03Eh
Read/write
Reset with PUC
Resistor Enable
P7REN
014h
Read/write
Reset with PUC
Input
P8IN
039h
Read only
Output
P8OUT
03Bh
Read/write
Unchanged
Direction
P8DIR
03Dh
Read/write
Reset with PUC
Port Select
P8SEL
03Fh
Read/write
Reset with PUC
Reset with PUC
P8
P9
PB
P10
Note:
11-8
Initial State
−
−
Resistor Enable
P8REN
015h
Read/write
Input
P9IN
008h
Read only
Output
P9OUT
00Ah
Read/write
Unchanged
Direction
P9DIR
00Ch
Read/write
Reset with PUC
Port Select
P9SEL
00Eh
Read/write
Reset with PUC
Resistor Enable
P9REN
016h
Read/write
Reset with PUC
−
−
Input
P10IN
009h
Read only
Output
P10OUT
00Bh
Read/write
Unchanged
Direction
P10DIR
00Dh
Read/write
Reset with PUC
Port Select
P10SEL
00Fh
Read/write
Reset with PUC
Resistor Enable
P10REN
017h
Read/write
Reset with PUC
Resistor enable registers RxREN only available in MSP430F47x3/4 and MSP430F471xx devices.
Digital I/O
Chapter 12
Watchdog Timer, Watchdog Timer+
The watchdog timer is a 16-bit timer that can be used as a watchdog or as an
interval timer. This chapter describes the watchdog timer. The watchdog timer
is implemented in all MSP430x4xx devices, except those with the enhanced
watchdog timer, WDT+. The WDT+ is implemented in the MSP430F41x2,
MSP430F42x,
MSP430F42xA,
MSP430FE42x,
MSP430FE42xA,
MSP430FG461x, MSP430F47x, MSP430FG47x, MSP430F47x3/4, and
MSP430F471xx devices.
Topic
Page
12.1 Watchdog Timer Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2
12.2 Watchdog Timer Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-4
12.3 Watchdog Timer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-7
Watchdog Timer, Watchdog Timer+
12-1
Watchdog Timer Introduction
12.1 Watchdog Timer Introduction
The primary function of the watchdog timer (WDT) module is to perform a
controlled system restart after a software problem occurs. If the selected time
interval expires, a system reset is generated. If the watchdog function is not
needed in an application, the module can be configured as an interval timer
and can generate interrupts at selected time intervals.
Features of the watchdog timer module include:
- Four software-selectable time intervals
- Watchdog mode
- Interval mode
- Access to WDT control register is password protected
- Control of RST/NMI pin function
- Selectable clock source
- Can be stopped to conserve power
- Clock fail-safe feature in WDT+
The WDT block diagram is shown in Figure 12−1.
Note: Watchdog Timer Powers Up Active
After a PUC, the WDT module is automatically configured in the watchdog
mode with an initial 32768 clock cycle reset interval using the DCOCLK. The
user must setup or halt the WDT prior to the expiration of the initial reset
interval.
12-2
Watchdog Timer, Watchdog Timer+
Watchdog Timer Introduction
Figure 12−1. Watchdog Timer Block Diagram
WDTCTL
4
Int.
Flag
MSB
Q6
0
Q9
WDTQn
Y
3
2
1
Q13
0
Q15
1
Pulse
Generator
16−bit
Counter
A
B
1
Password
Compare
1
0
16−bit
1
Clear
PUC
CLK
(Asyn)
MCLK†
MDB
Fail-Safe
Logic†
0
EQU
Write Enable
Low Byte
EQU
SMCLK
1
WDTHOLD
ACLK
1
WDTNMIES
R/W
WDTNMI
A
EN
WDTTMSEL
WDTCNTCL
WDTSSEL
WDTIS1
WDTIS0
Clock
Request
Logic†
†
LSB
MCLK Active
SMCLK Active
ACLK Active
MSP430x42x, MSP430FE42x, MSP430FG461x, and MSP430F47x devices only
Watchdog Timer, Watchdog Timer+
12-3
Watchdog Timer Operation
12.2 Watchdog Timer Operation
The WDT module can be configured as either a watchdog or interval timer with
the WDTCTL register. The WDTCTL register also contains control bits to
configure the RST/NMI pin. WDTCTL is a 16-bit password-protected
read/write register. Any read or write access must use word instructions and
write accesses must include the write password 05Ah in the upper byte. Any
write to WDTCTL with any value other than 05Ah in the upper byte is a security
key violation and triggers a PUC system reset regardless of timer mode. Any
read of WDTCTL reads 069h in the upper byte. The WDT+ counter clock
should be slower than or equal to the system (MCLK) frequency.
12.2.1 Watchdog Timer Counter
The watchdog timer counter (WDTCNT) is a 16-bit up-counter that is not
directly accessible by software. The WDTCNT is controlled and time intervals
selected through the watchdog timer control register WDTCTL.
The WDTCNT can be sourced from ACLK or SMCLK. The clock source is
selected with the WDTSSEL bit.
12.2.2 Watchdog Mode
After a PUC condition, the WDT module is configured in the watchdog mode
with an initial 32768 cycle reset interval using the DCOCLK. The user must
setup, halt, or clear the WDT prior to the expiration of the initial reset interval,
or another PUC is generated. When the WDT is configured to operate in
watchdog mode, either writing to WDTCTL with an incorrect password or
expiration of the selected time interval triggers a PUC. A PUC resets the WDT
to its default condition and configures the RST/NMI pin to reset mode.
12.2.3 Interval Timer Mode
Setting the WDTTMSEL bit to 1 selects the interval timer mode. This mode can
be used to provide periodic interrupts. In interval timer mode, the WDTIFG flag
is set at the expiration of the selected time interval. A PUC is not generated
in interval timer mode at expiration of the selected timer interval and the
WDTIFG enable bit WDTIE remains unchanged.
When the WDTIE bit and the GIE bit are set, the WDTIFG flag requests an
interrupt. The WDTIFG interrupt flag is automatically reset when its interrupt
request is serviced, or may be reset by software. The interrupt vector address
in interval timer mode is different from that in watchdog mode.
12-4
Watchdog Timer, Watchdog Timer+
Watchdog Timer Operation
Note: Modifying the Watchdog Timer
The WDT interval should be changed together with WDTCNTCL = 1 in a
single instruction to avoid an unexpected immediate PUC or interrupt.
The WDT should be halted before changing the clock source to avoid a
possible incorrect interval.
12.2.4 Watchdog Timer Interrupts
The WDT uses two bits in the SFRs for interrupt control.
- The WDT interrupt flag, WDTIFG, located in IFG1.0
- The WDT interrupt enable, WDTIE, located in IE1.0
When using the WDT in the watchdog mode, the WDTIFG flag sources a reset
vector interrupt. The WDTIFG can be used by the reset interrupt service
routine to determine if the watchdog caused the device to reset. If the flag is
set, then the watchdog timer initiated the reset condition either by timing out
or by a security key violation. If WDTIFG is cleared, the reset was caused by
a different source.
When using the WDT in interval timer mode, the WDTIFG flag is set after the
selected time interval and requests a WDT interval timer interrupt if the WDTIE
and the GIE bits are set. The interval timer interrupt vector is different from the
reset vector used in watchdog mode. In interval timer mode, the WDTIFG flag
is reset automatically when the interrupt is serviced or can be reset with
software.
12.2.5 WDT+ Enhancements
The WDT+ module provides enhanced functionality over the WDT. The WDT+
provides a fail-safe clocking feature to ensure that the clock to the WDT+
cannot be disabled while in watchdog mode. This means the low-power
modes may be affected by the choice for the WDT+ clock. For example, if
ACLK is the WDT+ clock source, LPM4 is not available, because the WDT+
prevents ACLK from being disabled. Also, if ACLK or SMCLK fail while
sourcing the WDT+, the WDT+ clock source is automatically switched to
MCLK. In this case, if MCLK is sourced from a crystal and the crystal has failed,
the FLL+ fail-safe feature activates the DCO and uses it as the source for
MCLK.
When the WDT+ module is used in interval timer mode, there is no fail-safe
feature for the clock source.
Watchdog Timer, Watchdog Timer+
12-5
Watchdog Timer Operation
12.2.6 Operation in Low-Power Modes
The MSP430 devices have several low-power modes. Different clock signals
are available in different low-power modes. The requirements of the user’s
application and the type of clocking used determine how the WDT should be
configured. For example, the WDT should not be configured in watchdog
mode with SMCLK as its clock source if the user wants to use LPM3, because
SMCLK is not active in LPM3 and the WDT would not function. If WDT+ is
sourced from SMCLK, SMCLK remains enabled during LPM3, which
increases the current consumption of LPM3. When the watchdog timer is not
required, the WDTHOLD bit can be used to hold the WDTCNT, reducing power
consumption.
12.2.7 Software Examples
Any write operation to WDTCTL must be a word operation with 05Ah
(WDTPW) in the upper byte:
; Periodically clear an active watchdog
MOV #WDTPW+WDTCNTCL,&WDTCTL
;
; Change watchdog timer interval
MOV #WDTPW+WDTCNTL+WDTSSEL,&WDTCTL
;
; Stop the watchdog
MOV #WDTPW+WDTHOLD,&WDTCTL
;
; Change WDT to interval timer mode, clock/8192 interval
MOV #WDTPW+WDTCNTCL+WDTTMSEL+WDTIS0,&WDTCTL
12-6
Watchdog Timer, Watchdog Timer+
Watchdog Timer Registers
12.3 Watchdog Timer Registers
The watchdog timer module registers are listed in Table 12−1.
Table 12−1.Watchdog Timer Registers
†
Register
Short Form
Register Type Address
Initial State
Watchdog timer control register
WDTCTL
Read/write
06900h with PUC
0120h
SFR interrupt enable register 1
IE1
Read/write
0000h
Reset with PUC
SFR interrupt flag register 1
IFG1
Read/write
0002h
Reset with PUC†
WDTIFG is reset with POR
Watchdog Timer, Watchdog Timer+
12-7
Watchdog Timer Registers
WDTCTL, Watchdog Timer Control Register
15
14
13
12
11
10
9
8
1
0
WDTPW
Reads as 069h
Must be written as 05Ah
7
6
5
4
3
2
WDTHOLD
WDTNMIES
WDTNMI
WDTTMSEL
WDTCNTCL
WDTSSEL
rw−0
rw−0
rw−0
rw−0
r0(w)
rw−0
WDTISx
rw−0
rw−0
WDTPW
Bits
15-8
Watchdog timer password. Always read as 069h. Must be written as 05Ah, or
a PUC is generated.
WDTHOLD
Bit 7
Watchdog timer hold. This bit stops the watchdog timer. Setting
WDTHOLD = 1 when the WDT is not in use conserves power.
0
Watchdog timer is not stopped
1
Watchdog timer is stopped
WDTNMIES
Bit 6
Watchdog timer NMI edge select. This bit selects the interrupt edge for the
NMI interrupt when WDTNMI = 1. Modifying this bit can trigger an NMI. Modify
this bit when WDTNMI = 0 to avoid triggering an accidental NMI.
0
NMI on rising edge
1
NMI on falling edge
WDTNMI
Bit 5
Watchdog timer NMI select. This bit selects the function for the RST/NMI pin.
0
Reset function
1
NMI function
WDTTMSEL Bit 4
Watchdog timer mode select
0
Watchdog mode
1
Interval timer mode
WDTCNTCL Bit 3
Watchdog timer counter clear. Setting WDTCNTCL = 1 clears the count value
to 0000h. WDTCNTCL is automatically reset.
0
No action
1
WDTCNT = 0000h
WDTSSEL
Bit 2
Watchdog timer clock source select
0
SMCLK
1
ACLK
WDTISx
Bits
1-0
Watchdog timer interval select. These bits select the watchdog timer interval
to set the WDTIFG flag and/or generate a PUC.
00 Watchdog clock source / 32768
01 Watchdog clock source / 8192
10 Watchdog clock source / 512
11 Watchdog clock source / 64
12-8
Watchdog Timer, Watchdog Timer+
Watchdog Timer Registers
IE1, Interrupt Enable Register 1
7
NMIIE
WDTIE
6
5
4
3
2
1
0
NMIIE
WDTIE
rw−0
rw−0
Bits
7-5
These bits may be used by other modules. See device-specific data sheet.
Bit 4
NMI interrupt enable. This bit enables the NMI interrupt. Because other bits
in IE1 may be used for other modules, it is recommended to set or clear this
bit using BIS.B or BIC.B instructions, rather than MOV.B or CLR.B
instructions.
0
Interrupt not enabled
1
Interrupt enabled
Bits
3-1
These bits may be used by other modules. See device-specific data sheet.
Bit 0
Watchdog timer interrupt enable. This bit enables the WDTIFG interrupt for
interval timer mode. It is not necessary to set this bit for watchdog mode.
Because other bits in IE1 may be used for other modules, it is recommended
to set or clear this bit using BIS.B or BIC.B instructions, rather than MOV.B
or CLR.B instructions.
0
Interrupt not enabled
1
Interrupt enabled
Watchdog Timer, Watchdog Timer+
12-9
Watchdog Timer Registers
IFG1, Interrupt Flag Register 1
7
NMIIFG
WDTIFG
12-10
6
5
4
3
2
1
0
NMIIFG
WDTIFG
rw−(0)
rw−(0)
Bits
7-5
These bits may be used by other modules. See device-specific data sheet.
Bit 4
NMI interrupt flag. NMIIFG must be reset by software. Because other bits in
IFG1 may be used for other modules, it is recommended to clear NMIIFG by
using BIS.B or BIC.B instructions, rather than MOV.B or CLR.B instructions.
0
No interrupt pending
1
Interrupt pending
Bits
3-1
These bits may be used by other modules. See device-specific data sheet.
Bit 0
Watchdog timer interrupt flag. In watchdog mode, WDTIFG remains set until
reset by software. In interval mode, WDTIFG is reset automatically by
servicing the interrupt, or it can be reset by software. Because other bits in
IFG1 may be used for other modules, it is recommended to clear WDTIFG by
using BIS.B or BIC.B instructions, rather than MOV.B or CLR.B instructions.
0
No interrupt pending
1
Interrupt pending
Watchdog Timer, Watchdog Timer+
Chapter 13
Basic Timer1
The Basic Timer1 module is composed of two independent cascadable 8-bit
timers. This chapter describes the Basic Timer1. Basic Timer1 is implemented
in all MSP430x4xx devices.
Topic
Page
13.1 Basic Timer1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-2
13.2 Basic Timer1 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-4
13.3 Basic Timer1 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-6
Basic Timer1
13-1
Basic Timer1 Introduction
13.1 Basic Timer1 Introduction
The Basic Timer1 supplies LCD timing and low frequency time intervals. The
Basic Timer1 is two independent 8-bit timers that can also be cascaded to form
one 16-bit timer function.
Some uses for the Basic Timer1 include:
- Real-time clock (RTC) function
- Software time increments
Basic Timer1 features include:
- Selectable clock source
- Two independent, cascadable 8-bit timers
- Interrupt capability
- LCD control signal generation
The Basic Timer1 block diagram is shown in Figure 13−1.
Note: Basic Timer1 Initialization
The Basic Timer1 module registers have no initial condition. These registers
must be configured by user software before use.
13-2
Basic Timer1
Basic Timer1 Introduction
Figure 13−1. Basic Timer1 Block Diagram
BTDIV
BTHOLD
EN1
ACLK
CLK1
BTCNT1
Q4 Q5
BTFRFQx
Q6 Q7
11
10
01
00
BTSSEL
00
ACLK:256
SMCLK
01
10
11
fLCD
EN2
CLK2
BTCNT2
BTIPx
Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7
111
110
101
100
Set_BTIFG
011
010
001
000
Basic Timer1
13-3
Basic Timer1 Introduction
13.2 Basic Timer1 Operation
The Basic Timer1 module can be configured as two 8-bit timers or one 16-bit
timer with the BTCTL register. The BTCTL register is an 8-bit read/write
register. Any read or write access must use byte instructions. The Basic
Timer1 controls the LCD frame frequency with BTCNT1.
13.2.1 Basic Timer1 Counter One
The Basic Timer1 counter one, BTCNT1, is an 8-bit timer/counter directly
accessible by software. BTCNT1 is incremented with ACLK and provides the
frame frequency for the LCD controller. BTCNT1 can be stopped by setting the
BTHOLD and BTDIV bits.
13.2.2 Basic Timer1 Counter Two
The Basic Timer1 counter two, BTCNT2, is an 8-bit timer/counter directly
accessible by software. BTCNT2 can be sourced from ACLK or SMCLK, or
from ACLK/256 when cascaded with BTCNT1. The BTCNT2 clock source is
selected with the BTSSEL and BTDIV bits. BTCNT2 can be stopped to reduce
power consumption by setting the HOLD bit.
BTCNT2 sources the Basic Timer1 interrupt, BTIFG. The interrupt interval is
selected with the BTIPx bits
Note: Reading or Writing BTCNT1 and BTCNT2
When the CPU clock and counter clock are asynchronous, any read from
BTCNT1 or BTCNT2 may be unpredictable. Any write to BTCNT1 or
BTCNT2 takes effect immediately.
13.2.3 16-Bit Counter Mode
The 16-bit timer/counter mode is selected when control the BTDIV bit is set.
In this mode, BTCNT1 is cascaded with BTCNT2. The clock source of
BTCNT1 is ACLK, and the clock source of BTCNT2 is ACLK/256.
13-4
Basic Timer1
Basic Timer1 Introduction
13.2.4 Basic Timer1 Operation: Signal fLCD
The LCD controller (but not the LCD_A controller) uses the fLCD signal from
the BTCNT1 to generate the timing for common and segment lines. ACLK
sources BTCNT1 and is assumed to be 32768 Hz for generating fLCD. The fLCD
frequency is selected with the BTFRFQx bits and can be ACLK/256,
ACLK/128, ACLK/64, or ACLK/32. The proper fLCD frequency depends on the
LCD’s frame frequency and the LCD multiplex rate and is calculated by:
fLCD = 2 × mux × fFrame
For example, to calculate fLCD for a 3-mux LCD, with a frame frequency of
30 Hz to 100 Hz:
fFrame (from LCD data sheet) = 30 Hz to 100 Hz
fLCD = 2 × 3 × fFrame
fLCD(min) = 180 Hz
fLCD(max) = 600 Hz
select fLCD = 32768/128 = 256 Hz or 32768/64 = 512 Hz
The LCD_A controller does not use the Basic Timer1 for fLCD generation. See
the LCD Controller and LCD_A Controller chapters for more details on the LCD
controllers.
13.2.5 Basic Timer1 Interrupts
The Basic Timer1 uses two bits in the SFRs for interrupt control.
- Basic Timer1 interrupt flag, BTIFG, located in IFG2.7
- Basic Timer1 interrupt enable, BTIE, located in IE2.7
The BTIFG flag is set after the selected time interval and requests a Basic
Timer1 interrupt if the BTIE and the GIE bits are set. The BTIFG flag is reset
automatically when the interrupt is serviced, or it can be reset with software.
Basic Timer1
13-5
Basic Timer1 Introduction
13.3 Basic Timer1 Registers
The Basic Timer1 module registers are listed in Table 13−1.
Table 13−1.Basic Timer1 Registers
Register
Short Form
Register Type Address
Initial State
Basic Timer1 Control
BTCTL
Read/write
040h
Unchanged
Basic Timer1 Counter 1
BTCNT1
Read/write
046h
Unchanged
Basic Timer1 Counter 2
BTCNT2
Read/write
047h
Unchanged
SFR interrupt enable register 2
IE2
Read/write
001h
Reset with PUC
SFR interrupt flag register 2
IFG2
Read/write
003h
Reset with PUC
Note:
13-6
The Basic Timer1 registers should be configured at power-up. There is no initial state for BTCTL, BTCNT1, or BTCNT2.
Basic Timer1
Basic Timer1 Introduction
BTCTL, Basic Timer1 Control Register
7
6
5
BTSSEL
BTHOLD
BTDIV
rw
rw
rw
4
3
2
1
BTFRFQx
rw
0
BTIPx
rw
rw
rw
rw
BTSSEL
Bit 7
BTCNT2 clock select. This bit, together with the BTDIV bit, selects the
clock source for BTCNT2. See the description for BTDIV.
BTHOLD
Bit 6
Basic Timer1 hold
0
BTCNT1 and BTCNT2 are operational
1
BTCNT1 is held if BTDIV=1
BTCNT2 is held
BTDIV
Bit 5
Basic Timer1 clock divide. This bit together with the BTSSEL bit, selects
the clock source for BTCNT2.
BTSSEL
BTDIV
0
0
BTCNT2 Clock Source
ACLK
0
1
ACLK/256
1
0
SMCLK
1
1
ACLK/256
BTFRFQx
Bits
4−3
fLCD frequency. These bits control the LCD update frequency.
00 fACLK/32
01 fACLK/64
10 fACLK/128
11 fACLK/256
BTIPx
Bits
2−0
Basic Timer1 interrupt interval
000 fCLK2/2
001 fCLK2/4
010 fCLK2/8
011 fCLK2/16
100 fCLK2/32
101 fCLK2/64
110 fCLK2/128
111 fCLK2/256
Basic Timer1
13-7
Basic Timer1 Introduction
BTCNT1, Basic Timer1 Counter 1
7
6
5
4
3
2
1
0
rw
rw
rw
rw
BTCNT1x
rw
BTCNT1x
rw
Bits
7−0
rw
rw
BTCNT1 register. The BTCNT1 register is the count of BTCNT1.
BTCNT2, Basic Timer1 Counter 2
7
6
5
4
3
2
1
0
rw
rw
rw
rw
BTCNT2x
rw
BTCNT2x
13-8
rw
Bits
7−0
Basic Timer1
rw
rw
BTCNT2 register. The BTCNT2 register is the count of BTCNT2.
Basic Timer1 Introduction
IE2, Interrupt Enable Register 2
7
6
5
4
3
2
1
0
BTIE
rw−0
BTIE
Bit 7
Basic Timer1 interrupt enable. This bit enables the BTIFG interrupt. Because
other bits in IE2 may be used for other modules, it is recommended to set or
clear this bit using BIS.B or BIC.B instructions, rather than MOV.B or CLR.B
instructions.
0
Interrupt not enabled
1
Interrupt enabled
Bits
6-1
These bits may be used by other modules. See device-specific data sheet.
IFG2, Interrupt Flag Register 2
7
6
5
4
3
2
1
0
BTIFG
rw−0
BTIFG
Bit 7
Basic Timer1 interrupt flag. Because other bits in IFG2 may be used for other
modules, it is recommended to clear BTIFG automatically by servicing the
interrupt, or by using BIS.B or BIC.B instructions, rather than MOV.B or
CLR.B instructions.
0
No interrupt pending
1
Interrupt pending
Bits
6-1
These bits may be used by other modules. See device-specific data sheet.
Basic Timer1
13-9
13-10
Basic Timer1
Chapter 14
Real-Time Clock
The Real-Time Clock module is a 32-bit counter module with calendar
function. This chapter describes the Real-Time Clock (RTC) module of the
MSP430x4xx family. The RTC is implemented in MSP430F41x2,
MSP430FG461x, MSP430F47x, MSP430FG47x, MSP430F47x3/4, and
MSP430F471xx devices.
Topic
Page
14.1 Real-Time Clock Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-2
14.2 Real-Time Clock Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4
14.3 Real-Time Clock Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-7
Real Time Clock
14-1
RTC Introduction
14.1 RTC Introduction
The Real-Time Clock (RTC) module can be used as a general-purpose 32-bit
timer or as a RTC with calendar function.
RTC features include:
- Calender and clock mode
- 32-bit counter mode with selectable clock sources
- Automatic counting of seconds, minutes, hours, day of week, day of
month, month and year in calender mode.
- Interrupt capability
- Selectable BCD format
The RTC block diagram is shown in Figure 14−1.
Note: Real-Time Clock Initialization
Most RTC module registers have no initial condition. These registers must
be configured by user software before use.
14-2
Real Time Clock
RTC Introduction
Figure 14−1. Real-Time Clock
ACLK
00
Basic Timer BTCNT2.Q6
01
10
SMCLK
11
RTCMODEx
RTCHOLD
RTCBCD
Mode
BCD
31
...
24
RTCNT4/
RTCDOW
23
...
16
RTCNT3/
RTCHOUR
15
...
8
RTCNT2/
RTCMIN
7
...
0
RTCNT1/
RTCSEC
RTCTEVx
8−bit overflow / minute changed
16−bit overflow / hour changed
00
Set_RTCFG
01
24−bit overflow / RTCHOUR = Midnight
32−bit overflow / RTCHOUR = Noon
10
RTCIE
11
1
BCD
EN
Set_BTIFG from
Basic Timer
Set_BTIFG
0
Calendar
RTCYEARH
RTCYEARL
RTCMON
RTCDAY
Midnight
Real Time Clock
14-3
Real-Time Clock Operation
14.2 Real-Time Clock Operation
The Real-Time Clock module can be configured as a real-time clock with
calendar function or as a 32-bit general-purpose counter with the RTCMODEx
bits.
14.2.1 Counter Mode
Counter mode is selected when RTCMODEx < 11. In this mode, a 32-bit
counter is provided that is directly accessible by software. Switching from
calendar to counter mode resets the count value.
The clock to increment the counter can be sourced from ACLK, SMCLK, or
from the BTCNT2 input clock divided by 128 from the Basic Timer1 module,
selected by the RTCMODEx bits. The counter can be stopped by setting the
RTCHOLD bit.
Four individual 8-bit counters are cascaded to provide the 32-bit counter. This
provides interrupt triggers at 8-bit, 16-bit, 24-bit, and 32-bit overflows. Each
counter RTCNT1 - RTCNT4 is individually accessible and may be read or
written to.
Note: Accessing the RTCNTx registers
When the counter clock is asynchronous to the CPU clock, any read from any
RTCNTx register should occur while the counter is not operating. Otherwise,
the results may be unpredictable. Alternatively, the counter may be read
multiple times while operating, and a majority vote taken in software to
determine the correct reading. Any write to any RTCNTx register takes effect
immediately.
14-4
Real Time Clock
Real-Time Clock Operation
14.2.2 Calendar Mode
Calendar mode is selected when RTCMODEx = 11. In calendar mode the RTC
provides seconds, minutes, hours, day of week, day of month, month, and year
in selectable BCD or hexadecimal format. Switching from counter to calendar
mode clears the seconds, minutes, hours, day-of-week, and year counts and
sets day-of-month and month counts to 1.
When RTCBCD = 1, BCD format is selected for the calendar registers. The
format must be selected before the time is set. Changing the state of RTCBCD
clears the seconds, minutes, hours, day-of-week, and year counts and sets
day-of-month and month counts to 1.
The calendar includes a leap year algorithm that considers all years evenly
divisible by 4 as leap years. This algorithm is accurate from the year 1901
through 2099.
Note: Accessing the Real-Time Clock registers
When the counter clock is asynchronous to the CPU clock, any read from any
counting register should occur while the counter is not operating. Otherwise,
the results may be unpredictable. Alternatively, the counter may be read
multiple times while operating, and a majority vote taken in software to
determine the correct reading.
Any write to any counting register takes effect immediately. However the
clock is stopped during the write. This could result in losing up to one second
during a write. Writing of data outside the legal ranges results in
unpredictable behavior.
The RTC does not provide an alarm function. It can easily be implemented in
software if required.
14.2.3 RTC and Basic Timer1 Interaction
In calendar mode the Basic Timer1 is automatically configured as a pre-divider
for the RTC module with the two 8-bit timers cascaded and ACLK selected as
the Basic Timer1 clock source. The BTSSEL, BTHOLD and BTDIV bits are
ignored and RTCHOLD controls both the RTC and the Basic Timer1.
RTC and Basic Timer1 interrupts interact as described in Section 14.2.4,
Real-Time Clock Interrupts.
Real Time Clock
14-5
Real-Time Clock Operation
14.2.4 Real-Time Clock Interrupts
The Real-Time Clock uses two bits for interrupt control.
- Basic Timer1 interrupt flag, BTIFG, located in IFG2.7
- Real-Time Clock interrupt enable, RTCIE, located in the module
The Real-Time Clock module shares the Basic Timer1 interrupt flag and
vector. When RTCIE = 0, the Basic Timer1 controls interrupt generation with
the BTIPx bits. In this case, the RTCEVx bits select the interval for setting the
RTCFG flag, but the RTCFG flag does not generate an interrupt. The RTCFG
flag must be cleared with software when RTCIE = 0.
When RTCIE = 1, the RTC controls interrupt generation and the Basic Timer1
BTIPx bits are ignored. In this case, the RTCFG and BTIFG flags are set at the
interval selected with the RTCEVx bits, and an interrupt request is generated
if the GIE bit is set. Both the RTCFG and BTIFG flags are reset automatically
when the interrupt is serviced, or can be reset with software.
The interrupt intervals are listed in Table 14−1.
Table 14−1.RTC Interrupt Intervals
RTC Mode
RTCTEVx
Counter Mode
00
8-bit overflow
01
16-bit overflow
10
24-bit overflow
Calendar Mode
14-6
Real Time Clock
Interrupt Interval
11
32-bit overflow
00
Minute changed
01
Hour changed
10
Every day at midnight (00:00)
11
Every day at noon (12:00)
Real-Time Clock Registers
14.3 Real-Time Clock Registers
The Real-Time Clock registers are listed in Table 14−2 for byte access. They
may be accessed with word instructions as listed in Table 14−3.
Table 14−2.Real-Time Clock Registers
Register
Short Form
Register Type Address
Initial State
Real-Time Clock control register
RTCCTL
Read/write
041h
040h with POR
Real-Timer Clock second
Real-Timer Counter register 1
RTCSEC/
RTCNT1
Read/write
042h
None, not reset
Real-Time Clock minute
Real-Time Counter register 2
RTCMIN/
RTCNT2
Read/write
043h
None, not reset
Real-Time Clock hour
Real-Time Counter register 3
RTCHOUR/
RTCNT3
Read/write
044h
None, not reset
Real-Time Clock day-of-Week
Real-Time Counter register 4
RTCDOW/
RTCNT4
Read/write
045h
None, not reset
Real-Time Clock day-of-month
RTCDAY
Read/write
04Ch
None, not reset
Real-Time Clock month
RTCMON
Read/write
04Dh
None, not reset
Real-Time Clock year (low byte)
RTCYEARL
Read/write
04Eh
None, not reset
Real-Time Clock year (high byte)
RTCYEARH
Read/write
04Fh
None, not reset
SFR interrupt enable register 2
IE2
Read/write
001h
Reset with PUC
SFR interrupt flag register 2
IFG2
Read/write
003h
Reset with PUC
Note: Modifying SFR bits
To avoid modifying control bits of other modules, it is recommended to set
or clear the IEx and IFGx bits using BIS.B or BIC.B instructions, rather than
MOV.B or CLR.B instructions.
Table 14−3.Real-Time Clock Registers, Word Access
Word Register
Short Form
High-Byte
Register
Low-Byte
Register
Address
Real-Time control register
RTCTL
RTCCTL
BTCTL
040h
Real-Time Clock time 0
Real-Time Counter registers 1,2
RTCTIM0/
RTCNT12
RTCMIN/
RTCNT2
RTCSEC/
RTCNT1
042h
Real-Time Clock time 1
Real-Time Counter registers 3,4
RTCTIM1/
RTCNT34
RTCDOW/
RTCNT4
RTCHOUR/
RTCNT3
044h
Real-Time Clock date
RTCDATE
RTCMON
RTCDAY
04Ch
Real-Time Clock year
RTCYEAR
RTCYEARH
RTCYEARL
04Eh
Real Time Clock
14-7
Real-Time Clock Registers
RTCCTL, Real-Time Clock Control Register
7
6
5
RTCBCD
RTCHOLD
rw-(0)
rw-(1)
4
3
RTCMODEx
rw-(0)
2
RTCTEVx
rw-(0)
rw-(0)
rw-(0)
1
0
RTCIE
RTCFG
rw-0
rw-0
RTCBCD
Bit 7
BCD format select. This bit selects BCD format for the calendar registers
when RTCMODEx = 11.
0
Hexadecimal format
1
BCD format
RTCHOLD
Bit 6
Real-Time Clock hold
0
Real-Time Clock is operational
1
RTCMODEx < 11: The RTC module is stopped
RTCMODEx = 11: The RTC and the Basic Timer1 are stopped
RTCMODEx
Bits
5-4
Real-Time Clock mode and clock source select
RTCMODEx
RTCTEVx
Bits
3-2
Counter Mode
32-bit counter
ACLK
01
32-bit counter
BTCNT2.Q6
10
32-bit counter
SMCLK
11
Calendar mode
BTCNT2.Q6
Real-Time Clock interrupt event. These bits select the event for setting
RTCFG.
RTC Mode
RTCTEVx
Counter Mode
00
8-bit overflow
01
16-bit overflow
10
24-bit overflow
11
32-bit overflow
00
Minute changed
01
Hour changed
10
Every day at midnight (00:00)
11
Every day at noon (12:00)
Calendar Mode
RTCIE
Bit 1
Real-Time Clock interrupt enable
0
Interrupt not enabled
1
Interrupt enabled
RTCFG
Bit 0
Real-Time Clock interrupt flag
0
No time event occurred
1
Time event occurred
14-8
Clock Source
00
Real Time Clock
Interrupt Interval
Real-Time Clock Registers
RTCNT1, RTC Counter 1, Counter Mode
7
6
5
4
3
2
1
0
rw
rw
rw
rw
RTCNT1x
rw
RTCNT1x
rw
Bits
7−0
rw
rw
RTCNT1 register. The RTCNT1 register is the count of RTCNT1.
RTCNT2, RTC Counter 2, Counter Mode
7
6
5
4
3
2
1
0
rw
rw
rw
rw
RTCNT2x
rw
RTCNT2x
rw
Bits
7−0
rw
rw
RTCNT2 register. The RTCNT2 register is the count of RTCNT2.
RTCNT3, RTC Counter 3, Counter Mode
7
6
5
4
3
2
1
0
rw
rw
rw
rw
RTCNT3x
rw
RTCNT3x
rw
Bits
7−0
rw
rw
RTCNT3 register. The RTCNT3 register is the count of RTCNT3.
RTCNT4, RTC Counter 4, Counter Mode
−
7
6
5
4
3
2
1
0
rw
rw
rw
rw
RTCNT4x
rw
RTCNT4x
rw
Bits
7−0
rw
rw
RTCNT4 register. The RTCNT4 register is the count of RTCNT4.
Real Time Clock
14-9
Real-Time Clock Registers
RTCSEC, RTC Seconds Register, Calendar Mode with Hexadecimal Format
7
6
5
0
0
r-0
r-0
4
3
2
1
0
rw
rw
1
0
Seconds (0...59)
rw
rw
rw
rw
RTCSEC, RTC Seconds Register, Calendar Mode with BCD Format
7
6
0
r-0
5
4
3
Seconds - high digit (0...5)
rw
rw
2
Seconds - low digit (0...9)
rw
rw
rw
rw
rw
RTCMIN, RTC Minutes Register, Calendar Mode with Hexadecimal Format
7
6
0
0
r-0
r-0
5
4
3
2
1
0
rw
rw
1
0
Minutes (0...59)
rw
rw
rw
rw
RTCMIN, RTC Minutes Register, Calendar Mode with BCD Format
7
6
0
r-0
14-10
5
4
3
Minutes - high digit (0...5)
rw
Real Time Clock
rw
2
Minutes - low digit (0...9)
rw
rw
rw
rw
rw
Real-Time Clock Registers
RTCHOUR, RTC Hours Register, Calendar Mode with Hexadecimal Format
7
6
5
0
0
0
r-0
r-0
r-0
4
3
2
1
0
rw
rw
1
0
Hours (0...24)
rw
rw
rw
RTCHOUR, RTC Hours Register, Calendar Mode with BCD Format
7
6
0
0
r-0
r-0
5
4
3
Hours high digit (0...2)
rw
rw
2
Hours low digit (0...9)
rw
rw
rw
rw
2
1
0
RTCDOW, RTC Day-of-Week Register, Calendar Mode
7
6
5
4
3
0
0
0
0
0
r-0
r-0
r-0
r-0
r-0
Day-of-Week (0...6)
rw
rw
Real Time Clock
rw
14-11
Real-Time Clock Registers
RTCDAY, RTC Day-of-Month Register, Calendar Mode with Hexadecimal Format
7
6
5
0
0
0
r-0
r-0
r-0
4
3
2
1
0
Day-of-Month (1...28,29,30,31)
rw
rw
rw
rw
rw
RTCDAY, RTC Day-of-Month Register, Calendar Mode with BCD Format
7
6
0
0
r-0
r-0
5
4
3
Day-of-Month high digit
(0...3)
rw
rw
2
1
0
Day-of-Month low digit (0...9)
rw
rw
rw
rw
RTCMON, RTC Month Register, Calendar Mode with Hexadecimal Format
7
6
5
4
0
0
0
0
r-0
r-0
r-0
r-0
3
2
1
0
rw
rw
1
0
Month (1..12)
rw
rw
RTCMON, RTC Month Register, Calendar Mode with BCD Format
14-12
7
6
5
4
0
0
0
Month high
digit (0...3)
r-0
r-0
r-0
rw
Real Time Clock
3
2
Month low digit (0...9)
rw
rw
rw
rw
Real-Time Clock Registers
RTCYEARL, RTC Year Low-Byte Register, Calendar Mode with Hexadecimal Format
7
6
5
4
3
2
1
0
rw
rw
rw
Year Low Byte of 0...4095
rw
rw
rw
rw
rw
RTCYEARL, RTC Year Low-Byte Register, Calendar Mode with BCD Format
7
6
5
4
3
Decade (0...9)
rw
rw
rw
2
1
0
Year lowest digit (0...9)
rw
rw
rw
rw
rw
RTCYEARH, RTC Year High-Byte Register, Calendar Mode with Hexadecimal Format
7
6
5
4
0
0
0
0
r-0
r-0
r-0
r-0
3
2
1
0
Year High Byte of 0...4095
rw
rw
rw
rw
RTCYEARH, RTC Year High-Byte Register, Calendar Mode with BCD Format
7
6
0
r-0
5
4
3
Century high digit (0...4)
rw
rw
2
1
0
Century low digit (0...9)
rw
rw
rw
rw
Real Time Clock
rw
14-13
Real-Time Clock Registers
IE2, Interrupt Enable Register 2
7
6
5
4
3
2
1
0
BTIE
rw-0
BTIE
Bit 7
Basic Timer1 interrupt enable. This bit enables the BTIFG interrupt. Because
other bits in IE2 may be used for other modules, it is recommended to set or
clear this bit using BIS.B or BIC.B instructions, rather than MOV.B or CLR.B
instructions.
0
Interrupt not enabled
1
Interrupt enabled
Bits
6-1
These bits may be used by other modules. See device-specific data sheet.
IFG2, Interrupt Flag Register 2
7
6
5
4
3
2
1
0
BTIFG
rw-0
BTIFG
14-14
Bit 7
Basic Timer1 interrupt flag. Because other bits in IFG2 may be used for other
modules, it is recommended to clear BTIFG automatically by servicing the
interrupt, or by using BIS.B or BIC.B instructions, rather than MOV.B or
CLR.B instructions.
0
No interrupt pending
1
Interrupt pending
Bits
6-1
These bits may be used by other modules. See device-specific data sheet.
Real Time Clock
Chapter 15
Timer_A
Timer_A is a 16-bit timer/counter with multiple capture/compare registers. This
chapter describes Timer_A. This chapter describes the operation of the
Timer_A of the MSP430x4xx device family.
Topic
Page
15.1 Timer_A Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-2
15.2 Timer_A Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-4
15.3 Timer_A Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-19
Timer_A
15-1
Timer_A Introduction
15.1 Timer_A Introduction
Timer_A is a 16-bit timer/counter with three or five capture/compare registers.
Timer_A can support multiple capture/compares, PWM outputs, and interval
timing. Timer_A also has extensive interrupt capabilities. Interrupts may be
generated from the counter on overflow conditions and from each of the
capture/compare registers.
Timer_A features include:
- Asynchronous 16-bit timer/counter with four operating modes
- Selectable and configurable clock source
- Three or five configurable capture/compare registers
- Configurable outputs with PWM capability
- Asynchronous input and output latching
- Interrupt vector register for fast decoding of all Timer_A interrupts
The block diagram of Timer_A is shown in Figure 15−1.
Note: Use of the Word Count
Count is used throughout this chapter. It means the counter must be in the
process of counting for the action to take place. If a particular value is directly
written to the counter, then an associated action does not take place.
Note: Second Timer_A On Select Devices
MSP430x415, MSP430x417, and MSP430xW42x devices implement a
second Timer_A with five capture/compare registers. On these devices, both
Timer_A modules are identical in function, except for the additional
capture/compare registers.
15-2
Timer_A
Timer_A Introduction
Figure 15−1. Timer_A Block Diagram
TASSELx
IDx
Timer Block
Timer Clock
MCx
15
TACLK
00
ACLK
01
SMCLK
10
0
16−bit Timer
TAR
Divider
1/2/4/8
Count
Mode
RC
Clear
EQU0
Set TAIFG
11
TACLR
CCR0
CCR1
CCR2
CCR3
CCR4
CCISx
CMx
CCI4A
00
CCI4B
01
Capture
Mode
GND
10
VCC
11
logic
COV
SCS
Timer Clock
15
0
0
Sync
TACCR4
1
Compararator 4
CCI
EQU4
SCCI
Y
A
EN
CAP
0
1
Set TA1CCR4
CCIFG
OUT
EQU0
Output
Unit4
D Set Q
Timer Clock
OUT4 Signal
Reset
POR
OUTMODx
Timer_A
15-3
Timer_A Operation
15.2 Timer_A Operation
The Timer_A module is configured with user software. The setup and
operation of Timer_A is discussed in the following sections.
15.2.1 16-Bit Timer Counter
The 16-bit timer/counter register, TAR, increments or decrements (depending
on mode of operation) with each rising edge of the clock signal. TAR can be
read or written with software. Additionally, the timer can generate an interrupt
when it overflows.
TAR may be cleared by setting the TACLR bit. Setting TACLR also clears the
clock divider and count direction for up/down mode.
Note: Modifying Timer_A Registers
It is recommended to stop the timer before modifying its operation (with
exception of the interrupt enable, interrupt flag, and TACLR) to avoid errant
operating conditions.
When the timer clock is asynchronous to the CPU clock, any read from TAR
should occur while the timer is not operating or the results may be
unpredictable. Alternatively, the timer may be read multiple times while
operating, and a majority vote taken in software to determine the correct
reading. Any write to TAR takes effect immediately.
Clock Source Select and Divider
The timer clock can be sourced from ACLK, SMCLK, or externally via TACLK
or INCLK. The clock source is selected with the TASSELx bits. The selected
clock source may be passed directly to the timer or divided by 2, 4, or 8 using
the IDx bits. The clock divider is reset when TACLR is set.
15-4
Timer_A
Timer_A Operation
15.2.2 Starting the Timer
The timer may be started or restarted in the following ways:
- The timer counts when MCx > 0 and the clock source is active.
- When the timer mode is either up or up/down, the timer may be stopped
by writing 0 to TACCR0. The timer may then be restarted by writing a
nonzero value to TACCR0. In this scenario, the timer starts incrementing
in the up direction from zero.
15.2.3 Timer Mode Control
The timer has four modes of operation as described in Table 15−1: stop, up,
continuous, and up/down. The operating mode is selected with the MCx bits.
Table 15−1.Timer Modes
MCx
Mode
Description
00
Stop
The timer is halted.
01
Up
The timer repeatedly counts from zero to the value of
TACCR0.
10
Continuous
The timer repeatedly counts from zero to 0FFFFh.
11
Up/down
The timer repeatedly counts from zero up to the value of
TACCR0 and back down to zero.
Timer_A
15-5
Timer_A Operation
Up Mode
The up mode is used if the timer period must be different from 0FFFFh counts.
The timer repeatedly counts up to the value of compare register TACCR0,
which defines the period, as shown in Figure 15−2. The number of timer
counts in the period is TACCR0+1. When the timer value equals TACCR0 the
timer restarts counting from zero. If up mode is selected when the timer value
is greater than TACCR0, the timer immediately restarts counting from zero.
Figure 15−2. Up Mode
0FFFFh
TACCR0
0h
The TACCR0 CCIFG interrupt flag is set when the timer counts to the TACCR0
value. The TAIFG interrupt flag is set when the timer counts from TACCR0 to
zero. Figure 15−3 shows the flag set cycle.
Figure 15−3. Up Mode Flag Setting
Timer Clock
Timer
CCR0−1
CCR0
0h
1h
CCR0−1
CCR0
0h
Set TAIFG
Set TACCR0 CCIFG
Changing the Period Register TACCR0
When changing TACCR0 while the timer is running, if the new period is greater
than or equal to the old period or greater than the current count value, the timer
counts up to the new period. If the new period is less than the current count
value, the timer rolls to zero. However, one additional count may occur before
the counter rolls to zero.
15-6
Timer_A
Timer_A Operation
Continuous Mode
In the continuous mode, the timer repeatedly counts up to 0FFFFh and restarts
from zero as shown in Figure 15−4. The capture/compare register TACCR0
works the same way as the other capture/compare registers.
Figure 15−4. Continuous Mode
0FFFFh
0h
The TAIFG interrupt flag is set when the timer counts from 0FFFFh to zero.
Figure 15−5 shows the flag set cycle.
Figure 15−5. Continuous Mode Flag Setting
Timer Clock
Timer
FFFEh
FFFFh
0h
1h
FFFEh
FFFFh
0h
Set TAIFG
Timer_A
15-7
Timer_A Operation
Use of the Continuous Mode
The continuous mode can be used to generate independent time intervals and
output frequencies. Each time an interval is completed, an interrupt is
generated. The next time interval is added to the TACCRx register in the
interrupt service routine. Figure 15−6 shows two separate time intervals t0 and
t1 being added to the capture/compare registers. In this usage, the time
interval is controlled by hardware, not software, without impact from interrupt
latency. Up to three (Timer_A3) or five (Timer_A5) independent time intervals
or output frequencies can be generated using capture/compare registers.
Figure 15−6. Continuous Mode Time Intervals
TACCR1b
TACCR0b
TACCR1c
TACCR0c
TACCR0d
0FFFFh
TACCR1a
TACCR1d
TACCR0a
t0
t0
t1
t0
t1
t1
Time intervals can be produced with other modes as well, where TACCR0 is
used as the period register. Their handling is more complex since the sum of
the old TACCRx data and the new period can be higher than the TACCR0
value. When the previous TACCRx value plus tx is greater than the TACCR0
data, the TACCR0 value must be subtracted to obtain the correct time interval.
15-8
Timer_A
Timer_A Operation
Up/Down Mode
The up/down mode is used if the timer period must be different from 0FFFFh
counts, and if symmetrical pulse generation is needed. The timer repeatedly
counts up to the value of compare register TACCR0 and back down to zero,
as shown in Figure 15−7. The period is twice the value in TACCR0.
Figure 15−7. Up/Down Mode
0FFFFh
TACCR0
0h
The count direction is latched. This allows the timer to be stopped and then
restarted in the same direction it was counting before it was stopped. If this is
not desired, the TACLR bit must be set to clear the direction. The TACLR bit
also clears the TAR value and the clock divider.
In up/down mode, the TACCR0 CCIFG interrupt flag and the TAIFG interrupt
flag are set only once during a period, separated by 1/2 the timer period. The
TACCR0 CCIFG interrupt flag is set when the timer counts from TACCR0 − 1
to TACCR0, and TAIFG is set when the timer completes counting down from
0001h to 0000h. Figure 15−8 shows the flag set cycle.
Figure 15−8. Up/Down Mode Flag Setting
Timer Clock
Timer
CCR0−1
CCR0
CCR0−1
CCR0−2
1h
0h
Up/Down
Set TAIFG
Set TACCR0 CCIFG
Timer_A
15-9
Timer_A Operation
Changing the Period Register TACCR0
When changing TACCR0 while the timer is running and counting in the down
direction, the timer continues its descent until it reaches zero. The value in
TACCR0 is latched into TACL0 immediately; however, the new period takes
effect after the counter counts down to zero.
When the timer is counting in the up direction and the new period is greater
than or equal to the old period or greater than the current count value, the timer
counts up to the new period before counting down. When the timer is counting
in the up direction, and the new period is less than the current count value, the
timer begins counting down. However, one additional count may occur before
the counter begins counting down.
Use of the Up/Down Mode
The up/down mode supports applications that require dead times between
output signals (See section Timer_A Output Unit). For example, to avoid
overload conditions, two outputs driving an H-bridge must never be in a high
state simultaneously. In the example shown in Figure 15−9 the tdead is:
tdead = ttimer × (TACCR1 − TACCR2)
With:
tdead
Time during which both outputs need to be inactive
ttimer
Cycle time of the timer clock
TACCRx Content of capture/compare register x
The TACCRx registers are not buffered. They update immediately when
written to. Therefore, any required dead time is not maintained automatically.
Figure 15−9. Output Unit in Up/Down Mode
0FFFFh
TACCR0
TACCR1
TACCR2
0h
Dead Time
Output Mode 6: Toggle/Set
Output Mode 2: Toggle/Reset
EQU1
EQU1
EQU1
EQU1
TAIFG
EQU0
EQU0
EQU2
EQU2 EQU2
EQU2
TAIFG
15-10
Timer_A
Interrupt Events
Timer_A Operation
15.2.4 Capture/Compare Blocks
Three or five identical capture/compare blocks, TACCRx, are present in
Timer_A. Any of the blocks may be used to capture the timer data or to
generate time intervals.
Capture Mode
The capture mode is selected when CAP = 1. Capture mode is used to record
time events. It can be used for speed computations or time measurements.
The capture inputs CCIxA and CCIxB are connected to external pins or internal
signals and are selected with the CCISx bits. The CMx bits select the capture
edge of the input signal as rising, falling, or both. A capture occurs on the
selected edge of the input signal. If a capture occurs:
- The timer value is copied into the TACCRx register
- The interrupt flag CCIFG is set
The input signal level can be read at any time via the CCI bit. MSP430x4xx
family devices may have different signals connected to CCIxA and CCIxB. See
the device-specific data sheet for the connections of these signals.
The capture signal can be asynchronous to the timer clock and cause a race
condition. Setting the SCS bit synchronizes the capture with the next timer
clock. Setting the SCS bit to synchronize the capture signal with the timer clock
is recommended. This is illustrated in Figure 15−10.
Figure 15−10. Capture Signal (SCS=1)
Timer Clock
Timer
n−2
n−1
n
n+1
n+2
n+3
n+4
CCI
Capture
Set TACCRx CCIFG
Overflow logic is provided in each capture/compare register to indicate if a
second capture was performed before the value from the first capture was
read. Bit COV is set when this occurs as shown in Figure 15−11. COV must
be reset with software.
Timer_A
15-11
Timer_A Operation
Figure 15−11.Capture Cycle
Idle
Capture
No
Capture
Taken
Capture Read
Read
Taken
Capture
Capture
Taken
Capture
Capture Read and No Capture
Capture
Clear Bit COV
in Register TACCTLx
Second
Capture
Taken
COV = 1
Idle
Capture
Capture Initiated by Software
Captures can be initiated by software. The CMx bits can be set for capture on
both edges. Software then sets CCIS1 = 1 and toggles bit CCIS0 to switch the
capture signal between VCC and GND, initiating a capture each time CCIS0
changes state:
MOV
XOR
#CAP+SCS+CCIS1+CM_3,&TACCTLx ; Setup TACCTLx
#CCIS0,&TACCTLx
; TACCTLx = TAR
Compare Mode
The compare mode is selected when CAP = 0. The compare mode is used to
generate PWM output signals or interrupts at specific time intervals. When
TAR counts to the value in a TACCRx:
- Interrupt flag CCIFG is set
- Internal signal EQUx = 1
- EQUx affects the output according to the output mode
- The input signal CCI is latched into SCCI
15-12
Timer_A
Timer_A Operation
15.2.5 Output Unit
Each capture/compare block contains an output unit. The output unit is used
to generate output signals such as PWM signals. Each output unit has eight
operating modes that generate signals based on the EQU0 and EQUx signals.
Output Modes
The output modes are defined by the OUTMODx bits and are described in
Table 15−2. The OUTx signal is changed with the rising edge of the timer clock
for all modes except mode 0. Output modes 2, 3, 6, and 7 are not useful for
output unit 0, because EQUx = EQU0.
Table 15−2.Output Modes
OUTMODx
Mode
Description
000
Output
The output signal OUTx is defined by the
OUTx bit. The OUTx signal updates
immediately when OUTx is updated.
001
Set
The output is set when the timer counts to the
TACCRx value. It remains set until a reset of
the timer, or until another output mode is
selected and affects the output.
010
Toggle/Reset
The output is toggled when the timer counts
to the TACCRx value. It is reset when the
timer counts to the TACCR0 value.
011
Set/Reset
The output is set when the timer counts to the
TACCRx value. It is reset when the timer
counts to the TACCR0 value.
100
Toggle
The output is toggled when the timer counts
to the TACCRx value. The output period is
double the timer period.
101
Reset
The output is reset when the timer counts to
the TACCRx value. It remains reset until
another output mode is selected and affects
the output.
110
Toggle/Set
The output is toggled when the timer counts
to the TACCRx value. It is set when the timer
counts to the TACCR0 value.
111
Reset/Set
The output is reset when the timer counts to
the TACCRx value. It is set when the timer
counts to the TACCR0 value.
Timer_A
15-13
Timer_A Operation
Output Example—Timer in Up Mode
The OUTx signal is changed when the timer counts up to the TACCRx value,
and rolls from TACCR0 to zero, depending on the output mode. An example
is shown in Figure 15−12 using TACCR0 and TACCR1.
Figure 15−12. Output Example—Timer in Up Mode
0FFFFh
TACCR0
TACCR1
0h
Output Mode 1: Set
Output Mode 2: Toggle/Reset
Output Mode 3: Set/Reset
Output Mode 4: Toggle
Output Mode 5: Reset
Output Mode 6: Toggle/Set
Output Mode 7: Reset/Set
EQU0
TAIFG
15-14
Timer_A
EQU1
EQU0
TAIFG
EQU1
EQU0
TAIFG
Interrupt Events
Timer_A Operation
Output Example—Timer in Continuous Mode
The OUTx signal is changed when the timer reaches the TACCRx and
TACCR0 values, depending on the output mode. An example is shown in
Figure 15−13 using TACCR0 and TACCR1.
Figure 15−13. Output Example—Timer in Continuous Mode
0FFFFh
TACCR0
TACCR1
0h
Output Mode 1: Set
Output Mode 2: Toggle/Reset
Output Mode 3: Set/Reset
Output Mode 4: Toggle
Output Mode 5: Reset
Output Mode 6: Toggle/Set
Output Mode 7: Reset/Set
TAIFG
EQU1
EQU0 TAIFG
EQU1
EQU0
Interrupt Events
Timer_A
15-15
Timer_A Operation
Output Example—Timer in Up/Down Mode
The OUTx signal changes when the timer equals TACCRx in either count
direction and when the timer equals TACCR0, depending on the output mode.
An example is shown in Figure 15−14 using TACCR0 and TACCR2.
Figure 15−14. Output Example—Timer in Up/Down Mode
0FFFFh
TACCR0
TACCR2
0h
Output Mode 1: Set
Output Mode 2: Toggle/Reset
Output Mode 3: Set/Reset
Output Mode 4: Toggle
Output Mode 5: Reset
Output Mode 6: Toggle/Set
Output Mode 7: Reset/Set
TAIFG
EQU2
EQU2
EQU2
EQU2
EQU0
EQU0
TAIFG
Note:
Interrupt Events
Switching Between Output Modes
When switching between output modes, one of the OUTMODx bits should
remain set during the transition, unless switching to mode 0. Otherwise,
output glitching can occur because a NOR gate decodes output mode 0. A
safe method for switching between output modes is to use output mode 7 as
a transition state:
BIS
BIC
15-16
Timer_A
#OUTMOD_7,&TACCTLx ; Set output mode=7
#OUTMODx,&TACCTLx ; Clear unwanted bits
Timer_A Operation
15.2.6 Timer_A Interrupts
Two interrupt vectors are associated with the 16-bit Timer_A module:
- TACCR0 interrupt vector for TACCR0 CCIFG
- TAIV interrupt vector for all other CCIFG flags and TAIFG
In capture mode any CCIFG flag is set when a timer value is captured in the
associated TACCRx register. In compare mode, any CCIFG flag is set if TAR
counts to the associated TACCRx value. Software may also set or clear any
CCIFG flag. All CCIFG flags request an interrupt when their corresponding
CCIE bit and the GIE bit are set.
TACCR0 Interrupt
The TACCR0 CCIFG flag has the highest Timer_A interrupt priority and has
a dedicated interrupt vector as shown in Figure 15−15. The TACCR0 CCIFG
flag is automatically reset when the TACCR0 interrupt request is serviced.
Figure 15−15. Capture/Compare TACCR0 Interrupt Flag
Capture
EQU0
CAP
D
Timer Clock
Set
CCIE
Q
IRQ, Interrupt Service Requested
Reset
IRACC, Interrupt Request Accepted
POR
TAIV, Interrupt Vector Generator
The TACCR1 CCIFG, TACCR2 CCIFG, and TAIFG flags are prioritized and
combined to source a single interrupt vector. The interrupt vector register TAIV
is used to determine which flag requested an interrupt.
The highest priority enabled interrupt generates a number in the TAIV register
(see register description). This number can be evaluated or added to the
program counter to automatically enter the appropriate software routine.
Disabled Timer_A interrupts do not affect the TAIV value.
Any access, read or write, of the TAIV register automatically resets the highest
pending interrupt flag. If another interrupt flag is set, another interrupt is
immediately generated after servicing the initial interrupt. For example, if the
TACCR1 and TACCR2 CCIFG flags are set when the interrupt service routine
accesses the TAIV register, TACCR1 CCIFG is reset automatically. After the
RETI instruction of the interrupt service routine is executed, the TACCR2
CCIFG flag generates another interrupt.
Timer_A
15-17
Timer_A Operation
TAIV Software Example
The following software example shows the recommended use of TAIV and the
handling overhead. The TAIV value is added to the PC to automatically jump
to the appropriate routine.
The numbers at the right margin show the necessary CPU cycles for each
instruction. The software overhead for different interrupt sources includes
interrupt latency and return-from-interrupt cycles, but not the task handling
itself. The latencies are:
- Capture/compare block TACCR0
- Capture/compare blocks TACCR1, TACCR2
- Timer overflow TAIFG
11 cycles
16 cycles
14 cycles
; Interrupt handler for TACCR0 CCIFG.
Cycles
CCIFG_0_HND
;
...
; Start of handler Interrupt latency 6
RETI
5
; Interrupt handler for TAIFG, TACCR1 and TACCR2 CCIFG.
TA_HND
...
ADD
RETI
JMP
JMP
RETI
RETI
TAIFG_HND
...
RETI
15-18
Timer_A
;
&TAIV,PC
;
;
CCIFG_1_HND ;
CCIFG_2_HND ;
;
;
Interrupt latency
Add offset to Jump table
Vector 0: No interrupt
Vector 2: TACCR1
Vector 4: TACCR2
Vector 6: Reserved
Vector 8: Reserved
6
3
5
2
2
5
5
; Vector 10: TAIFG Flag
; Task starts here
5
CCIFG_2_HND
...
RETI
; Vector 4: TACCR2
; Task starts here
; Back to main program
5
CCIFG_1_HND
...
RETI
; Vector 2: TACCR1
; Task starts here
; Back to main program
5
Timer_A Registers
15.3 Timer_A Registers
The Timer_A registers are listed in Table 15−3 and Table 15−4.
Table 15−3.Timer_A3 Registers
Register
Short Form
Register Type Address
Initial State
Timer_A control
Timer0_A3 Control
TACTL/
TA0CTL
Read/write
0160h
Reset with POR
Timer_A counter
Timer0_A3 counter
TAR/
TA0R
Read/write
0170h
Reset with POR
Timer_A capture/compare control 0
Timer0_A3 capture/compare control 0
TACCTL0/
TA0CCTL
Read/write
0162h
Reset with POR
Timer_A capture/compare 0
Timer0_A3 capture/compare 0
TACCR0/
TA0CCR0
Read/write
0172h
Reset with POR
Timer_A capture/compare control 1
Timer0_A3 capture/compare control 1
TACCTL1/
TA0CCTL1
Read/write
0164h
Reset with POR
Timer_A capture/compare 1
Timer0_A3 capture/compare 1
TACCR1/
TA0CCR1
Read/write
0174h
Reset with POR
Timer_A capture/compare control 2
Timer0_A3 capture/compare control 2
TACCTL 2/
TA0CCTL2
Read/write
0166h
Reset with POR
Timer_A capture/compare 2
Timer0_A3 capture/compare 2
TACCR2/
TA0CCR2
Read/write
0176h
Reset with POR
Timer_A interrupt vector
Timer0_A3 interrupt vector
TAIV/
TA0IV
Read only
012Eh
Reset with POR
Register
Short Form
Register Type Address
Initial State
Timer1_A5 control
TA1CTL
Read/write
0180h
Reset with POR
Timer1_A5 counter
TA1R
Read/write
0190h
Reset with POR
Table 15−4.Timer1_A5 Registers
Timer1_A5 capture/compare control 0
TA1CCTL0
Read/write
0182h
Reset with POR
Timer1_A5 capture/compare 0
TA1CCR0
Read/write
0192h
Reset with POR
Timer1_A5 capture/compare control 1
TA1CCTL1
Read/write
0184h
Reset with POR
Timer1_A5 capture/compare 1
TA1CCR1
Read/write
0194h
Reset with POR
Timer1_A5 capture/compare control 2
TA1CCTL 2
Read/write
0186h
Reset with POR
Timer1_A5 capture/compare 2
TA1CCR2
Read/write
0196h
Reset with POR
Timer1_A5 capture/compare control 3
TA1CCTL3
Read/write
0188h
Reset with POR
Timer1_A5 capture/compare 3
TA1CCR3
Read/write
0198h
Reset with POR
Timer1_A5 capture/compare control 4
TA1CCTL4
Read/write
018Ah
Reset with POR
Timer1_A5 capture/compare 4
TA1CCR4
Read/write
019Ah
Reset with POR
Timer1_A5 interrupt Vector
TA1IV
Read only
011Eh
Reset with POR
Timer_A
15-19
Timer_A Registers
TACTL, Timer_A Control Register
15
14
13
12
11
10
9
Unused
8
TASSELx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
Unused
TACLR
TAIE
TAIFG
rw−(0)
w−(0)
rw−(0)
rw−(0)
IDx
rw−(0)
MCx
rw−(0)
rw−(0)
rw−(0)
Unused
Bits
15-10
Unused
TASSELx
Bits
9-8
Timer_A clock source select
00 TACLK
01 ACLK
10 SMCLK
11 Inverted TACLK
IDx
Bits
7-6
Input divider. These bits select the divider for the input clock.
00 /1
01 /2
10 /4
11 /8
MCx
Bits
5-4
Mode control. Setting MCx = 00h when Timer_A is not in use conserves
power.
00 Stop mode: the timer is halted
01 Up mode: the timer counts up to TACCR0
10 Continuous mode: the timer counts up to 0FFFFh
11 Up/down mode: the timer counts up to TACCR0 then down to 0000h
Unused
Bit 3
Unused
TACLR
Bit 2
Timer_A clear. Setting this bit resets TAR, the clock divider, and the count
direction. The TACLR bit is automatically reset and is always read as zero.
TAIE
Bit 1
Timer_A interrupt enable. This bit enables the TAIFG interrupt request.
0
Interrupt disabled
1
Interrupt enabled
TAIFG
Bit 0
Timer_A interrupt flag
0
No interrupt pending
1
Interrupt pending
15-20
Timer_A
Timer_A Registers
TAR, Timer_A Register
15
14
13
12
11
10
9
8
TARx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
TARx
rw−(0)
rw−(0)
Bits
15-0
TARx
rw−(0)
rw−(0)
Timer_A register. The TAR register is the count of Timer_A.
TACCRx, Timer_A Capture/Compare Register x
15
14
13
12
11
10
9
8
TACCRx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
TACCRx
rw−(0)
TACCRx
rw−(0)
Bits
15-0
rw−(0)
rw−(0)
Timer_A capture/compare register.
Compare mode: TACCRx holds the data for the comparison to the timer value
in the Timer_A Register, TAR.
Capture mode: The Timer_A Register, TAR, is copied into the TACCRx
register when a capture is performed.
Timer_A
15-21
Timer_A Registers
TACCTLx, Capture/Compare Control Register
15
14
13
CMx
12
CCISx
11
10
9
8
SCS
SCCI
Unused
CAP
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
r
r0
rw−(0)
7
6
5
4
3
2
1
0
CCIE
CCI
OUT
COV
CCIFG
rw−(0)
r
rw−(0)
rw−(0)
rw−(0)
OUTMODx
rw−(0)
rw−(0)
rw−(0)
CMx
Bit
15-14
Capture mode
00 No capture
01 Capture on rising edge
10 Capture on falling edge
11 Capture on both rising and falling edges
CCISx
Bit
13-12
Capture/compare input select. These bits select the TACCRx input signal.
See the device-specific data sheet for specific signal connections.
00 CCIxA
01 CCIxB
10 GND
11 VCC
SCS
Bit 11
Synchronize capture source. This bit is used to synchronize the capture input
signal with the timer clock.
0
Asynchronous capture
1
Synchronous capture
SCCI
Bit 10
Synchronized capture/compare input. The selected CCI input signal is
latched with the EQUx signal and can be read via this bit.
Unused
Bit 9
Unused. Read only. Always read as 0.
CAP
Bit 8
Capture mode
0
Compare mode
1
Capture mode
OUTMODx
Bits
7-5
Output mode. Modes 2, 3, 6, and 7 are not useful for TACCR0 because
EQUx = EQU0.
000 OUT bit value
001 Set
010 Toggle/reset
011 Set/reset
100 Toggle
101 Reset
110 Toggle/set
111 Reset/set
15-22
Timer_A
Timer_A Registers
CCIE
Bit 4
Capture/compare interrupt enable. This bit enables the interrupt request of
the corresponding CCIFG flag.
0
Interrupt disabled
1
Interrupt enabled
CCI
Bit 3
Capture/compare input. The selected input signal can be read by this bit.
OUT
Bit 2
Output. For output mode 0, this bit directly controls the state of the output.
0
Output low
1
Output high
COV
Bit 1
Capture overflow. This bit indicates a capture overflow occurred. COV must
be reset with software.
0
No capture overflow occurred
1
Capture overflow occurred
CCIFG
Bit 0
Capture/compare interrupt flag
0
No interrupt pending
1
Interrupt pending
TAIV, Timer_A Interrupt Vector Register
15
14
13
12
11
10
9
8
0
0
0
0
0
0
0
0
r0
r0
r0
r0
r0
r0
r0
r0
7
6
5
4
3
2
1
0
0
0
0
0
r0
r0
r0
r0
TAIVx
Bits
15-0
TAIVx
r−(0)
0
r−(0)
r−(0)
r0
Timer_A interrupt vector value
TAIV Contents
†
Interrupt Source
Interrupt
Priority
Interrupt Flag
−
00h
No interrupt pending
02h
Capture/compare 1
TACCR1 CCIFG
04h
Capture/compare 2
TACCR2 CCIFG
06h
Capture/compare 3†
TACCR3 CCIFG
08h
Capture/compare
4†
TACCR4 CCIFG
0Ah
Timer overflow
0Ch
Reserved
−
0Eh
Reserved
−
Highest
TAIFG
Lowest
Timer1_A5 only
Timer_A
15-23
15-24
Timer_A
Chapter 16
Timer_B
Timer_B is a 16-bit timer/counter with multiple capture/compare registers. This
chapter describes the operation of the Timer_B of the MSP430x4xx device
family.
Topic
Page
16.1 Timer_B Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-2
16.2 Timer_B Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-4
16.3 Timer_B Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-20
Timer_B
16-1
Timer_B Introduction
16.1 Timer_B Introduction
Timer_B is a 16-bit timer/counter with three or seven capture/compare
registers. Timer_B can support multiple capture/compares, PWM outputs, and
interval timing. Timer_B also has extensive interrupt capabilities. Interrupts
may be generated from the counter on overflow conditions and from each of
the capture/compare registers.
Timer_B features include :
- Asynchronous 16-bit timer/counter with four operating modes and four
selectable lengths
- Selectable and configurable clock source
- Three or seven configurable capture/compare registers
- Configurable outputs with PWM capability
- Double-buffered compare latches with synchronized loading
- Interrupt vector register for fast decoding of all Timer_B interrupts
The block diagram of Timer_B is shown in Figure 16−1.
Note: Use of the Word Count
Count is used throughout this chapter. It means the counter must be in the
process of counting for the action to take place. If a particular value is directly
written to the counter, then an associated action does not take place.
16.1.1 Similarities and Differences From Timer_A
Timer_B is identical to Timer_A with the following exceptions:
-
The length of Timer_B is programmable to be 8, 10, 12, or 16 bits.
- Timer_B TBCCRx registers are double-buffered and can be grouped.
- All Timer_B outputs can be put into a high-impedance state.
- The SCCI bit function is not implemented in Timer_B.
16-2
Timer_B
Timer_B Introduction
Figure 16−1. Timer_B Block Diagram
TBSSELx
IDx
Timer Block
Timer Clock
MCx
15
TBCLK
00
ACLK
01
SMCLK
10
Divider
1/2/4/8
0
16−bit Timer
RC
TBR
8 10 12 16
Clear
Count
Mode
EQU0
CNTLx
11
TBCLR
00
TBCLGRPx
01
Set TBIFG
10
Group
Load Logic
11
CCR0
CCR1
CCR2
CCR3
CCR4
CCR5
CCISx
CMx
logic
CCR6
COV
SCS
CCI6A
00
CCI6B
01
GND
10
VCC
11
Capture
Mode
15
Sync
Timer Clock
VCC
Load
Group
Load Logic
Compare Latch TBCL6
00
01
EQU0
UP/DOWN
TBCCR6
1
CLLDx
CCI
TBR=0
0
0
10
11
Compararator 6
CCR5
EQU6
CCR4
CAP
CCR1
0
1
Set TBCCR6
CCIFG
OUT
EQU0
Output
Unit6
D Set Q
Timer Clock
OUT6 Signal
Reset
POR
OUTMODx
Timer_B
16-3
Timer_B Operation
16.2 Timer_B Operation
The Timer_B module is configured with user software. The setup and
operation of Timer_B is discussed in the following sections.
16.2.1 16-Bit Timer Counter
The 16-bit timer/counter register, TBR, increments or decrements (depending
on mode of operation) with each rising edge of the clock signal. TBR can be
read or written with software. Additionally, the timer can generate an interrupt
when it overflows.
TBR may be cleared by setting the TBCLR bit. Setting TBCLR also clears the
clock divider and count direction for up/down mode.
Note: Modifying Timer_B Registers
It is recommended to stop the timer before modifying its operation (with
exception of the interrupt enable, interrupt flag, and TBCLR) to avoid errant
operating conditions.
When the timer clock is asynchronous to the CPU clock, any read from TBR
should occur while the timer is not operating, or the results may be
unpredictable. Alternatively, the timer may be read multiple times while
operating, and a majority vote taken in software to determine the correct
reading. Any write to TBR takes effect immediately.
TBR Length
Timer_B is configurable to operate as an 8-, 10-, 12-, or 16-bit timer with the
CNTLx bits. The maximum count value, TBR(max), for the selectable lengths
is 0FFh, 03FFh, 0FFFh, and 0FFFFh, respectively. Data written to the TBR
register in 8-, 10-, and 12-bit modes is right-justified with leading zeros.
Clock Source Select and Divider
The timer clock can be sourced from ACLK, SMCLK, or externally via TBCLK
or INCLK. The clock source is selected with the TBSSELx bits. The selected
clock source may be passed directly to the timer or divided by 2,4, or 8 using
the IDx bits. The clock divider is reset when TBCLR is set.
16-4
Timer_B
Timer_B Operation
16.2.2 Starting the Timer
The timer may be started or restarted in the following ways:
- The timer counts when MCx > 0 and the clock source is active.
- When the timer mode is either up or up/down, the timer may be stopped
by loading 0 to TBCL0. The timer may then be restarted by loading a
nonzero value to TBCL0. In this scenario, the timer starts incrementing in
the up direction from zero.
16.2.3 Timer Mode Control
The timer has four modes of operation as described in Table 16−1: stop, up,
continuous, and up/down. The operating mode is selected with the MCx bits.
Table 16−1.Timer Modes
MCx
Mode
Description
00
Stop
The timer is halted.
01
Up
The timer repeatedly counts from zero to the value of
compare register TBCL0.
10
Continuous
The timer repeatedly counts from zero to the value
selected by the CNTLx bits.
11
Up/down
The timer repeatedly counts from zero up to the value of
TBCL0 and then back down to zero.
Timer_B
16-5
Timer_B Operation
Up Mode
The up mode is used if the timer period must be different from TBR(max) counts.
The timer repeatedly counts up to the value of compare latch TBCL0, which
defines the period, as shown in Figure 16−2. The number of timer counts in
the period is TBCL0+1. When the timer value equals TBCL0 the timer restarts
counting from zero. If up mode is selected when the timer value is greater than
TBCL0, the timer immediately restarts counting from zero.
Figure 16−2. Up Mode
TBR(max)
TBCL0
0h
The TBCCR0 CCIFG interrupt flag is set when the timer counts to the TBCL0
value. The TBIFG interrupt flag is set when the timer counts from TBCL0 to
zero. Figure 15−3 shows the flag set cycle.
Figure 16−3. Up Mode Flag Setting
Timer Clock
Timer
TBCL0−1
TBCL0
0h
1h
TBCL0−1
TBCL0
0h
Set TBIFG
Set TBCCR0 CCIFG
Changing the Period Register TBCL0
When changing TBCL0 while the timer is running and when the TBCL0 load
event is immediate, CLLD0 = 00, if the new period is greater than or equal to
the old period, or greater than the current count value, the timer counts up to
the new period. If the new period is less than the current count value, the timer
rolls to zero. However, one additional count may occur before the counter rolls
to zero.
16-6
Timer_B
Timer_B Operation
Continuous Mode
In continuous mode the timer repeatedly counts up to TBR(max) and restarts
from zero as shown in Figure 16−4. The compare latch TBCL0 works the same
way as the other capture/compare registers.
Figure 16−4. Continuous Mode
TBR(max)
0h
The TBIFG interrupt flag is set when the timer counts from TBR(max) to zero.
Figure 16−5 shows the flag set cycle.
Figure 16−5. Continuous Mode Flag Setting
Timer Clock
Timer
TBR (max)−1 TBR (max)
0h
1h
TBR (max)−1 TBR (max)
0h
Set TBIFG
Timer_B
16-7
Timer_B Operation
Use of the Continuous Mode
The continuous mode can be used to generate independent time intervals and
output frequencies. Each time an interval is completed, an interrupt is
generated. The next time interval is added to the TBCLx latch in the interrupt
service routine. Figure 16−6 shows two separate time intervals t0 and t1 being
added to the capture/compare registers. The time interval is controlled by
hardware, not software, without impact from interrupt latency. Up to three
(Timer_B3) or 7 (Timer_B7) independent time intervals or output frequencies
can be generated using capture/compare registers.
Figure 16−6. Continuous Mode Time Intervals
TBCL1b
TBCL0b
TBCL1c
TBCL0c
TBCL0d
TBR(max)
TBCL1a
TBCL1d
TBCL0a
0h
EQU0 Interrupt
EQU1 Interrupt
t0
t0
t1
t0
t1
t1
Time intervals can be produced with other modes as well, where TBCL0 is
used as the period register. Their handling is more complex since the sum of
the old TBCLx data and the new period can be higher than the TBCL0 value.
When the sum of the previous TBCLx value plus tx is greater than the TBCL0
data, TBCL0 + 1 must be subtracted to obtain the correct time interval.
16-8
Timer_B
Timer_B Operation
Up/Down Mode
The up/down mode is used if the timer period must be different from TBR(max)
counts, and if a symmetrical pulse generation is needed. The timer repeatedly
counts up to the value of compare latch TBCL0, and back down to zero, as
shown in Figure 16−7. The period is twice the value in TBCL0.
Note: TBCL0 > TBR(max)
If TBCL0 > TBR(max), the counter operates as if it were configured for
continuous mode. It does not count down from TBR(max) to zero.
Figure 16−7. Up/Down Mode
TBCL0
0h
The count direction is latched. This allows the timer to be stopped and then
restarted in the same direction it was counting before it was stopped. If this is
not desired, the TBCLR bit must be used to clear the direction. The TBCLR bit
also clears the TBR value and the clock divider.
In up/down mode, the TBCCR0 CCIFG interrupt flag and the TBIFG interrupt
flag are set only once during the period, separated by 1/2 the timer period. The
TBCCR0 CCIFG interrupt flag is set when the timer counts from TBCL0−1 to
TBCL0, and TBIFG is set when the timer completes counting down from 0001h
to 0000h. Figure 16−8 shows the flag set cycle.
Figure 16−8. Up/Down Mode Flag Setting
Timer Clock
Timer
TBCL0−1
TBCL0
TBCL0−1 TBCL0−2
1h
0h
1h
Up/Down
Set TBIFG
Set TBCCR0 CCIFG
Timer_B
16-9
Timer_B Operation
Changing the Value of Period Register TBCL0
When changing TBCL0 while the timer is running and counting in the down
direction, and when the TBCL0 load event is immediate, the timer continues
its descent until it reaches zero. The value in TBCCR0 is latched into TBCL0
immediately; however, the new period takes effect after the counter counts
down to zero.
If the timer is counting in the up direction when the new period is latched into
TBCL0, and the new period is greater than or equal to the old period, or greater
than the current count value, the timer counts up to the new period before
counting down. When the timer is counting in the up direction, and the new
period is less than the current count value when TBCL0 is loaded, the timer
begins counting down. However, one additional count may occur before the
counter begins counting down.
Use of the Up/Down Mode
The up/down mode supports applications that require dead times between
output signals (see section Timer_B Output Unit). For example, to avoid
overload conditions, two outputs driving an H-bridge must never be in a high
state simultaneously. In the example shown in Figure 16−9 the tdead is:
tdead = ttimer × (TBCL1 − TBCL3)
With:
tdead
Time during which both outputs need to be inactive
ttimer
Cycle time of the timer clock
TBCLx Content of compare latch x
The ability to simultaneously load grouped compare latches assures the dead
times.
Figure 16−9. Output Unit in Up/Down Mode
TBR(max)
TBCL0
TBCL1
TBCL3
0h
Dead Time
Output Mode 6: Toggle/Set
Output Mode 2: Toggle/Reset
EQU1
EQU1
EQU1
EQU1
TBIFG
EQU0
EQU0
EQU3
EQU3 EQU3
EQU3
TBIFG
16-10
Timer_B
Interrupt Events
Timer_B Operation
16.2.4 Capture/Compare Blocks
Three or seven identical capture/compare blocks, TBCCRx, are present in
Timer_B. Any of the blocks may be used to capture the timer data or to
generate time intervals.
Capture Mode
The capture mode is selected when CAP = 1. Capture mode is used to record
time events. It can be used for speed computations or time measurements.
The capture inputs CCIxA and CCIxB are connected to external pins or internal
signals and are selected with the CCISx bits. The CMx bits select the capture
edge of the input signal as rising, falling, or both. A capture occurs on the
selected edge of the input signal. If a capture is performed:
- The timer value is copied into the TBCCRx register
- The interrupt flag CCIFG is set
The input signal level can be read at any time via the CCI bit. MSP430x4xx
family devices may have different signals connected to CCIxA and CCIxB.
Refer to the device-specific data sheet for the connections of these signals.
The capture signal can be asynchronous to the timer clock and cause a race
condition. Setting the SCS bit synchronizes the capture with the next timer
clock. Setting the SCS bit to synchronize the capture signal with the timer clock
is recommended. This is illustrated in Figure 16−10.
Figure 16−10. Capture Signal (SCS = 1)
Timer Clock
Timer
n−2
n−1
n
n+1
n+2
n+3
n+4
CCI
Capture
Set TBCCRx CCIFG
Overflow logic is provided in each capture/compare register to indicate if a
second capture was performed before the value from the first capture was
read. Bit COV is set when this occurs as shown in Figure 16−11. COV must
be reset with software.
Timer_B
16-11
Timer_B Operation
Figure 16−11.Capture Cycle
Idle
Capture
No
Capture
Taken
Capture Read
Read
Taken
Capture
Capture
Taken
Capture
Capture Read and No Capture
Capture
Clear Bit COV
in Register TBCCTLx
Second
Capture
Taken
COV = 1
Idle
Capture
Capture Initiated by Software
Captures can be initiated by software. The CMx bits can be set for capture on
both edges. Software then sets bit CCIS1 = 1 and toggles bit CCIS0 to switch
the capture signal between VCC and GND, initiating a capture each time
CCIS0 changes state:
MOV
XOR
#CAP+SCS+CCIS1+CM_3,&TBCCTLx ; Setup TBCCTLx
#CCIS0,&TBCCTLx
; TBCCTLx = TBR
Compare Mode
The compare mode is selected when CAP = 0. Compare mode is used to
generate PWM output signals or interrupts at specific time intervals. When
TBR counts to the value in a TBCLx:
- Interrupt flag CCIFG is set
- Internal signal EQUx = 1
- EQUx affects the output according to the output mode
16-12
Timer_B
Timer_B Operation
Compare Latch TBCLx
The TBCCRx compare latch, TBCLx, holds the data for the comparison to the
timer value in compare mode. TBCLx is buffered by TBCCRx. The buffered
compare latch gives the user control over when a compare period updates.
The user cannot directly access TBCLx. Compare data is written to each
TBCCRx and automatically transferred to TBCLx. The timing of the transfer
from TBCCRx to TBCLx is user-selectable with the CLLDx bits as described
in Table 16−2.
Table 16−2.TBCLx Load Events
CLLDx
Description
00
New data is transferred from TBCCRx to TBCLx immediately when
TBCCRx is written to.
01
New data is transferred from TBCCRx to TBCLx when TBR counts to 0
10
New data is transferred from TBCCRx to TBCLx when TBR counts to 0
for up and continuous modes. New data is transferred to from TBCCRx
to TBCLx when TBR counts to the old TBCL0 value or to 0 for up/down
mode
11
New data is transferred from TBCCRx to TBCLx when TBR counts to
the old TBCLx value.
Grouping Compare Latches
Multiple compare latches may be grouped together for simultaneous updates
with the TBCLGRPx bits. When using groups, the CLLDx bits of the lowest
numbered TBCCRx in the group determine the load event for each compare
latch of the group, except when TBCLGRP = 3, as shown in Table 16−3. The
CLLDx bits of the controlling TBCCRx must not be set to zero. When the
CLLDx bits of the controlling TBCCRx are set to zero, all compare latches
update immediately when their corresponding TBCCRx is written; no compare
latches are grouped.
Two conditions must exist for the compare latches to be loaded when grouped.
First, all TBCCRx registers of the group must be updated, even when new
TBCCRx data equals old TBCCRx data. Second, the load event must occur.
Table 16−3.Compare Latch Operating Modes
TBCLGRPx
Grouping
Update Control
00
None
Individual
01
TBCL1+TBCL2
TBCL3+TBCL4
TBCL5+TBCL6
TBCCR1
TBCCR3
TBCCR5
10
TBCL1+TBCL2+TBCL3
TBCL4+TBCL5+TBCL6
TBCCR1
TBCCR4
11
TBCL0+TBCL1+TBCL2+
TBCL3+TBCL4+TBCL5+TBCL6
TBCCR1
Timer_B
16-13
Timer_B Operation
16.2.5 Output Unit
Each capture/compare block contains an output unit. The output unit is used
to generate output signals such as PWM signals. Each output unit has eight
operating modes that generate signals based on the EQU0 and EQUx signals.
The TBOUTH pin function can be used to put all Timer_B outputs into a
high-impedance state. When the TBOUTH pin function is selected for the pin,
and when the pin is pulled high, all Timer_B outputs are in a high-impedance
state.
Output Modes
The output modes are defined by the OUTMODx bits and are described in
Table 16−4. The OUTx signal is changed with the rising edge of the timer clock
for all modes except mode 0. Output modes 2, 3, 6, and 7 are not useful for
output unit 0, because EQUx = EQU0.
Table 16−4.Output Modes
16-14
Timer_B
OUTMODx
Mode
Description
000
Output
The output signal OUTx is defined by the
OUTx bit. The OUTx signal updates
immediately when OUTx is updated.
001
Set
The output is set when the timer counts to the
TBCLx value. It remains set until a reset of
the timer, or until another output mode is
selected and affects the output.
010
Toggle/Reset
The output is toggled when the timer counts
to the TBCLx value. It is reset when the timer
counts to the TBCL0 value.
011
Set/Reset
The output is set when the timer counts to the
TBCLx value. It is reset when the timer
counts to the TBCL0 value.
100
Toggle
The output is toggled when the timer counts
to the TBCLx value. The output period is
double the timer period.
101
Reset
The output is reset when the timer counts to
the TBCLx value. It remains reset until
another output mode is selected and affects
the output.
110
Toggle/Set
The output is toggled when the timer counts
to the TBCLx value. It is set when the timer
counts to the TBCL0 value.
111
Reset/Set
The output is reset when the timer counts to
the TBCLx value. It is set when the timer
counts to the TBCL0 value.
Timer_B Operation
Output Example—Timer in Up Mode
The OUTx signal is changed when the timer counts up to the TBCLx value, and
rolls from TBCL0 to zero, depending on the output mode. An example is shown
in Figure 16−12 using TBCL0 and TBCL1.
Figure 16−12. Output Example—Timer in Up Mode
TBR(max)
TBCL0
TBCL1
0h
Output Mode 1: Set
Output Mode 2: Toggle/Reset
Output Mode 3: Set/Reset
Output Mode 4: Toggle
Output Mode 5: Reset
Output Mode 6: Toggle/Set
Output Mode 7: Reset/Set
EQU0
TBIFG
EQU1
EQU0
TBIFG
EQU1
EQU0
TBIFG
Interrupt Events
Timer_B
16-15
Timer_B Operation
Output Example—Timer in Continuous Mode
The OUTx signal is changed when the timer reaches the TBCLx and TBCL0
values, depending on the output mode, An example is shown in Figure 16−13
using TBCL0 and TBCL1.
Figure 16−13. Output Example—Timer in Continuous Mode
TBR(max)
TBCL0
TBCL1
0h
Output Mode 1: Set
Output Mode 2: Toggle/Reset
Output Mode 3: Set/Reset
Output Mode 4: Toggle
Output Mode 5: Reset
Output Mode 6: Toggle/Set
Output Mode 7: Reset/Set
TBIFG
16-16
Timer_B
EQU1
EQU0 TBIFG
EQU1
EQU0
Interrupt Events
Timer_B Operation
Output Example − Timer in Up/Down Mode
The OUTx signal changes when the timer equals TBCLx in either count
direction and when the timer equals TBCL0, depending on the output mode.
An example is shown in Figure 16−14 using TBCL0 and TBCL3.
Figure 16−14. Output Example—Timer in Up/Down Mode
TBR(max)
TBCL0
TBCL3
0h
Output Mode 1: Set
Output Mode 2: Toggle/Reset
Output Mode 3: Set/Reset
Output Mode 4: Toggle
Output Mode 5: Reset
Output Mode 6: Toggle/Set
Output Mode 7: Reset/Set
TBIFG
EQU3
EQU3
EQU3
EQU3
EQU0
EQU0
TBIFG
Note:
Interrupt Events
Switching Between Output Modes
When switching between output modes, one of the OUTMODx bits should
remain set during the transition, unless switching to mode 0. Otherwise,
output glitching can occur because a NOR gate decodes output mode 0. A
safe method for switching between output modes is to use output mode 7 as
a transition state:
BIS
BIC
#OUTMOD_7,&TBCCTLx ; Set output mode=7
#OUTMODx,&TBCCTLx ; Clear unwanted bits
Timer_B
16-17
Timer_B Operation
16.2.6 Timer_B Interrupts
Two interrupt vectors are associated with the 16-bit Timer_B module:
- TBCCR0 interrupt vector for TBCCR0 CCIFG
- TBIV interrupt vector for all other CCIFG flags and TBIFG
In capture mode, any CCIFG flag is set when a timer value is captured in the
associated TBCCRx register. In compare mode, any CCIFG flag is set when
TBR counts to the associated TBCLx value. Software may also set or clear any
CCIFG flag. All CCIFG flags request an interrupt when their corresponding
CCIE bit and the GIE bit are set.
TBCCR0 Interrupt Vector
The TBCCR0 CCIFG flag has the highest Timer_B interrupt priority and has
a dedicated interrupt vector as shown in Figure 16−15. The TBCCR0 CCIFG
flag is automatically reset when the TBCCR0 interrupt request is serviced.
Figure 16−15. Capture/Compare TBCCR0 Interrupt Flag
Capture
EQU0
CAP
D
Timer Clock
Set
CCIE
Q
IRQ, Interrupt Service Requested
Reset
IRACC, Interrupt Request Accepted
POR
TBIV, Interrupt Vector Generator
The TBIFG flag and TBCCRx CCIFG flags (excluding TBCCR0 CCIFG) are
prioritized and combined to source a single interrupt vector. The interrupt
vector register TBIV is used to determine which flag requested an interrupt.
The highest priority enabled interrupt (excluding TBCCR0 CCIFG) generates
a number in the TBIV register (see register description). This number can be
evaluated or added to the program counter to automatically enter the
appropriate software routine. Disabled Timer_B interrupts do not affect the
TBIV value.
Any access, read or write, of the TBIV register automatically resets the highest
pending interrupt flag. If another interrupt flag is set, another interrupt is
immediately generated after servicing the initial interrupt. For example, if the
TBCCR1 and TBCCR2 CCIFG flags are set when the interrupt service routine
accesses the TBIV register, TBCCR1 CCIFG is reset automatically. After the
RETI instruction of the interrupt service routine is executed, the TBCCR2
CCIFG flag generates another interrupt.
16-18
Timer_B
Timer_B Operation
TBIV, Interrupt Handler Examples
The following software example shows the recommended use of TBIV and the
handling overhead. The TBIV value is added to the PC to automatically jump
to the appropriate routine.
The numbers at the right margin show the necessary CPU clock cycles for
each instruction. The software overhead for different interrupt sources
includes interrupt latency and return-from-interrupt cycles, but not the task
handling itself. The latencies are:
- Capture/compare block CCR0
- Capture/compare blocks CCR1 to CCR6
- Timer overflow TBIFG
11 cycles
16 cycles
14 cycles
The following software example shows the recommended use of TBIV for
Timer_B3.
; Interrupt handler for TBCCR0 CCIFG.
Cycles
CCIFG_0_HND
...
; Start of handler Interrupt latency 6
RETI
5
; Interrupt handler for TBIFG, TBCCR1 and TBCCR2 CCIFG.
TB_HND
...
; Interrupt latency
ADD
&TBIV,PC
; Add offset to Jump table
RETI
; Vector 0: No interrupt
JMP
CCIFG_1_HND ; Vector 2: Module 1
JMP
CCIFG_2_HND ; Vector 4: Module 2
RETI
; Vector 6
RETI
; Vector 8
RETI
; Vector 10
RETI
; Vector 12
TBIFG_HND
...
RETI
CCIFG_2_HND
...
RETI
6
3
5
2
2
; Vector 14: TIMOV Flag
; Task starts here
5
; Vector 4: Module 2
; Task starts here
; Back to main program
5
; The Module 1 handler shows a way to look if any other
; interrupt is pending: 5 cycles have to be spent, but
; 9 cycles may be saved if another interrupt is pending
CCIFG_1_HND
; Vector 6: Module 3
...
; Task starts here
JMP
TB_HND
; Look for pending ints
2
Timer_B
16-19
Timer_B Registers
16.3 Timer_B Registers
The Timer_B registers are listed in Table 16−5.
Table 16−5.Timer_B Registers
Register
Short Form
Register Type Address
Initial State
Timer_B control
TBCTL
Read/write
0180h
Reset with POR
Timer_B counter
TBR
Read/write
0190h
Reset with POR
Timer_B capture/compare control 0
TBCCTL0
Read/write
0182h
Reset with POR
Timer_B capture/compare 0
TBCCR0
Read/write
0192h
Reset with POR
Timer_B capture/compare control 1
TBCCTL1
Read/write
0184h
Reset with POR
Timer_B capture/compare 1
TBCCR1
Read/write
0194h
Reset with POR
Timer_B capture/compare control 2
TBCCTL 2
Read/write
0186h
Reset with POR
Timer_B capture/compare 2
TBCCR2
Read/write
0196h
Reset with POR
Timer_B capture/compare control 3
TBCCTL3
Read/write
0188h
Reset with POR
Timer_B capture/compare 3
TBCCR3
Read/write
0198h
Reset with POR
Timer_B capture/compare control 4
TBCCTL4
Read/write
018Ah
Reset with POR
Timer_B capture/compare 4
TBCCR4
Read/write
019Ah
Reset with POR
Timer_B capture/compare control 5
TBCCTL5
Read/write
018Ch
Reset with POR
Timer_B capture/compare 5
TBCCR5
Read/write
019Ch
Reset with POR
Timer_B capture/compare control 6
TBCCTL6
Read/write
018Eh
Reset with POR
Timer_B capture/compare 6
TBCCR6
Read/write
019Eh
Reset with POR
Timer_B Interrupt Vector
TBIV
Read only
011Eh
Reset with POR
16-20
Timer_B
Timer_B Registers
Timer_B Control Register TBCTL
15
14
Unused
13
12
TBCLGRPx
11
CNTLx
10
9
Unused
8
TBSSELx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
Unused
TBCLR
TBIE
TBIFG
rw−(0)
w−(0)
rw−(0)
rw−(0)
IDx
rw−(0)
MCx
rw−(0)
rw−(0)
rw−(0)
Unused
Bit 15
Unused
TBCLGRP
Bit
14-13
TBCLx group
00 Each TBCLx latch loads independently
01 TBCL1+TBCL2 (TBCCR1 CLLDx bits control the update)
TBCL3+TBCL4 (TBCCR3 CLLDx bits control the update)
TBCL5+TBCL6 (TBCCR5 CLLDx bits control the update)
TBCL0 independent
10 TBCL1+TBCL2+TBCL3 (TBCCR1 CLLDx bits control the update)
TBCL4+TBCL5+TBCL6 (TBCCR4 CLLDx bits control the update)
TBCL0 independent
11 TBCL0+TBCL1+TBCL2+TBCL3+TBCL4+TBCL5+TBCL6
(TBCCR1 CLLDx bits control the update)
CNTLx
Bits
12-11
Counter length
00 16-bit, TBR(max) = 0FFFFh
01 12-bit, TBR(max) = 0FFFh
10 10-bit, TBR(max) = 03FFh
11 8-bit, TBR(max) = 0FFh
Unused
Bit 10
Unused
TBSSELx
Bits
9-8
Timer_B clock source select
00 TBCLK
01 ACLK
10 SMCLK
11 Inverted TBCLK
IDx
Bits
7-6
Input divider. These bits select the divider for the input clock.
00 /1
01 /2
10 /4
11 /8
MCx
Bits
5-4
Mode control. Setting MCx = 00h when Timer_B is not in use conserves
power.
00 Stop mode: the timer is halted
01 Up mode: the timer counts up to TBCL0
10 Continuous mode: the timer counts up to the value set by TBCNTLx
11 Up/down mode: the timer counts up to TBCL0 and down to 0000h
Timer_B
16-21
Timer_B Registers
Unused
Bit 3
Unused
TBCLR
Bit 2
Timer_B clear. Setting this bit resets TBR, the clock divider, and the count
direction. The TBCLR bit is automatically reset and is always read as zero.
TBIE
Bit 1
Timer_B interrupt enable. This bit enables the TBIFG interrupt request.
0
Interrupt disabled
1
Interrupt enabled
TBIFG
Bit 0
Timer_B interrupt flag.
0
No interrupt pending
1
Interrupt pending
TBR, Timer_B Register
15
14
13
12
11
10
9
8
TBRx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
TBRx
rw−(0)
TBRx
16-22
rw−(0)
Bits
15-0
Timer_B
rw−(0)
rw−(0)
Timer_B register. The TBR register is the count of Timer_B.
Timer_B Registers
TBCCRx, Timer_B Capture/Compare Register x
15
14
13
12
11
10
9
8
TBCCRx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
TBCCRx
rw−(0)
TBCCRx
rw−(0)
Bits
15-0
rw−(0)
rw−(0)
Timer_B capture/compare register
Compare mode: Compare data is written to each TBCCRx and automatically
transferred to TBCLx. TBCLx holds the data for the comparison to the timer
value in the Timer_B Register, TBR.
Capture mode: The Timer_B Register, TBR, is copied into the TBCCRx
register when a capture is performed.
Timer_B
16-23
Timer_B Registers
TBCCTLx, Capture/Compare Control Register
15
14
13
CMx
12
CCISx
11
10
SCS
9
CLLDx
8
CAP
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
CCIE
CCI
OUT
COV
CCIFG
rw−(0)
r
rw−(0)
rw−(0)
rw−(0)
OUTMODx
rw−(0)
rw−(0)
rw−(0)
CMx
Bit
15-14
Capture mode
00 No capture
01 Capture on rising edge
10 Capture on falling edge
11 Capture on both rising and falling edges
CCISx
Bit
13-12
Capture/compare input select. These bits select the TBCCRx input signal.
See the device-specific data sheet for specific signal connections.
00 CCIxA
01 CCIxB
10 GND
11 VCC
SCS
Bit 11
Synchronize capture source. This bit is used to synchronize the capture input
signal with the timer clock.
0
Asynchronous capture
1
Synchronous capture
CLLDx
Bit
10-9
Compare latch load. These bits select the compare latch load event.
00 TBCLx loads on write to TBCCRx
01 TBCLx loads when TBR counts to 0
10 TBCLx loads when TBR counts to 0 (up or continuous mode)
TBCLx loads when TBR counts to TBCL0 or to 0 (up/down mode)
11 TBCLx loads when TBR counts to TBCLx
CAP
Bit 8
Capture mode
0
Compare mode
1
Capture mode
OUTMODx
Bits
7-5
Output mode. Modes 2, 3, 6, and 7 are not useful for TBCL0, because
EQUx = EQU0.
000 OUT bit value
001 Set
010 Toggle/reset
011 Set/reset
100 Toggle
101 Reset
110 Toggle/set
111 Reset/set
16-24
Timer_B
Timer_B Registers
CCIE
Bit 4
Capture/compare interrupt enable. This bit enables the interrupt request of
the corresponding CCIFG flag.
0
Interrupt disabled
1
Interrupt enabled
CCI
Bit 3
Capture/compare input. The selected input signal can be read by this bit.
OUT
Bit 2
Output. For output mode 0, this bit directly controls the state of the output.
0
Output low
1
Output high
COV
Bit 1
Capture overflow. This bit indicates a capture overflow occurred. COV must
be reset with software.
0
No capture overflow occurred
1
Capture overflow occurred
CCIFG
Bit 0
Capture/compare interrupt flag
0
No interrupt pending
1
Interrupt pending
Timer_B
16-25
Timer_B Registers
TBIV, Timer_B Interrupt Vector Register
15
14
13
12
11
10
9
8
0
0
0
0
0
0
0
0
r0
r0
r0
r0
r0
r0
r0
r0
7
6
5
4
3
2
1
0
0
0
0
0
r0
r0
r0
r0
TBIVx
Bits
15-0
TBIVx
r−(0)
†
Timer_B
r−(0)
r−(0)
r0
Timer_B interrupt vector value
TBIV Contents
16-26
0
Interrupt Source
00h
No interrupt pending
02h
Capture/compare 1
Interrupt Flag
−
TBCCR1 CCIFG
04h
Capture/compare 2
TBCCR2 CCIFG
06h
Capture/compare 3†
TBCCR3 CCIFG
08h
Capture/compare 4†
TBCCR4 CCIFG
0Ah
Capture/compare
5†
TBCCR5 CCIFG
0Ch
Capture/compare
6†
TBCCR6 CCIFG
0Eh
Timer overflow
MSP430x4xx devices only
Interrupt
Priority
TBIFG
Highest
Lowest
Chapter 17
USART Peripheral Interface, UART Mode
The universal synchronous/asynchronous receive/transmit (USART)
peripheral interface supports two serial modes with one hardware module.
This chapter discusses the operation of the asynchronous UART mode.
USART0 is implemented on the MSP430x42x and MSP430x43x devices. In
addition to USART0, the MSP430x44x devices implement a second identical
USART module, USART1. USART1 is also implemented in MSP430FG461x
devices.
Topic
Page
17.1 USART Introduction: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-2
17.2 USART Operation: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-4
17.3 USART Registers: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-21
USART Peripheral Interface, UART Mode
17-1
USART Introduction: UART Mode
17.1 USART Introduction: UART Mode
In asynchronous mode, the USART connects the MSP430 to an external
system via two external pins, URXD and UTXD. UART mode is selected when
the SYNC bit is cleared.
UART mode features include:
- 7- or 8-bit data with odd parity, even parity, or non-parity
- Independent transmit and receive shift registers
- Separate transmit and receive buffer registers
- LSB-first data transmit and receive
- Built-in
idle-line and
multiprocessor systems
address-bit
communication
protocols
for
- Receiver start-edge detection for auto-wake up from LPMx modes
- Programmable baud rate with modulation for fractional baud rate support
- Status flags for error detection and suppression and address detection
- Independent interrupt capability for receive and transmit
Figure 17−1 shows the USART when configured for UART mode.
17-2
USART Peripheral Interface, UART Mode
USART Introduction: UART Mode
Figure 17−1. USART Block Diagram: UART Mode
SWRST URXEx* URXEIE URXWIE
SYNC= 0
URXIFGx*
Receive Control
FE PE OE BRK
Receive Status
Receiver Buffer UxRXBUF
LISTEN
0
RXERR
RXWAKE
MM
1
Receiver Shift Register
1
SSEL1 SSEL0
SPB
CHAR
PEV
0
PENA
UCLKS
UCLKI
00
ACLK
01
SMCLK
10
SMCLK
11
SYNC
1
SOMI
0
1
URXD
0
Baud−Rate Generator
STE
Prescaler/Divider UxBRx
Modulator UxMCTL
SPB
CHAR
PEV
UTXD
PENA
1
WUT
Transmit Shift Register
TXWAKE
Transmit Buffer UxTXBUF
1
SIMO
0
0
UTXIFGx*
Transmit Control
SYNC CKPH CKPL
SWRST UTXEx*
TXEPT
STC
UCLKI
UCLK
Clock Phase and Polarity
* Refer to the device-specific datasheet for SFR locations
USART Peripheral Interface, UART Mode
17-3
USART Operation: UART Mode
17.2 USART Operation: UART Mode
In UART mode, the USART transmits and receives characters at a bit rate
asynchronous to another device. Timing for each character is based on the
selected baud rate of the USART. The transmit and receive functions use the
same baud rate frequency.
17.2.1 USART Initialization and Reset
The USART is reset by a PUC or by setting the SWRST bit. After a PUC, the
SWRST bit is automatically set, keeping the USART in a reset condition. When
set, the SWRST bit resets the URXIEx, UTXIEx, URXIFGx, RXWAKE,
TXWAKE, RXERR, BRK, PE, OE, and FE bits and sets the UTXIFGx and
TXEPT bits. The receive and transmit enable flags, URXEx and UTXEx, are
not altered by SWRST. Clearing SWRST releases the USART for operation.
See also chapter USART Module, I2C mode for USART0 when reconfiguring
from I2C mode to UART mode.
Note: Initializing or Reconfiguring the USART Module
The required USART initialization/reconfiguration process is:
1) Set SWRST (BIS.B
#SWRST,&UxCTL)
2) Initialize all USART registers with SWRST = 1 (including UxCTL)
3) Enable USART module via the MEx SFRs (URXEx and/or UTXEx)
4) Clear SWRST via software (BIC.B
#SWRST,&UxCTL)
5) Enable interrupts (optional) via the IEx SFRs (URXIEx and/or UTXIEx)
Failure to follow this process may result in unpredictable USART behavior.
17.2.2 Character Format
The UART character format, shown in Figure 17−2, consists of a start bit,
seven or eight data bits, an even/odd/no parity bit, an address bit (address-bit
mode), and one or two stop bits. The bit period is defined by the selected clock
source and setup of the baud rate registers.
Figure 17−2. Character Format
Mark
ST
D0
D6
D7 AD PA
SP SP
Space
[2nd Stop Bit, SPB = 1]
[Parity Bit, PENA = 1]
[Address Bit, MM = 1]
[Optional Bit, Condition]
17-4
USART Peripheral Interface, UART Mode
[8th Data Bit, CHAR = 1]
USART Operation: UART Mode
17.2.3 Asynchronous Communication Formats
When two devices communicate asynchronously, the idle-line format is used
for the protocol. When three or more devices communicate, the USART
supports the idle-line and address-bit multiprocessor communication formats.
Idle-Line Multiprocessor Format
When MM = 0, the idle-line multiprocessor format is selected. Blocks of data
are separated by an idle time on the transmit or receive lines as shown in
Figure 17−3. An idle receive line is detected when 10 or more continuous ones
(marks) are received after the first stop bit of a character. When two stop bits
are used for the idle line the second stop bit is counted as the first mark bit of
the idle period.
The first character received after an idle period is an address character. The
RXWAKE bit is used as an address tag for each block of characters. In the
idle-line multiprocessor format, this bit is set when a received character is an
address and is transferred to UxRXBUF.
Figure 17−3. Idle-Line Format
Blocks of
Characters
UTXDx/URXDx
Idle Periods of 10 Bits or More
UTXDx/URXDx Expanded
UTXDx/URXDx
ST
Address
SP ST
First Character Within Block
Is Address. It Follows Idle
Period of 10 Bits or More
Data
SP
Character Within Block
ST
Data
SP
Character Within Block
Idle Period Less Than 10 Bits
USART Peripheral Interface, UART Mode
17-5
USART Operation: UART Mode
The URXWIE bit is used to control data reception in the idle-line
multiprocessor format. When the URXWIE bit is set, all non-address
characters are assembled but not transferred into the UxRXBUF, and
interrupts are not generated. When an address character is received, the
receiver is temporarily activated to transfer the character to UxRXBUF and
sets the URXIFGx interrupt flag. Any applicable error flag is also set. The user
can then validate the received address.
If an address is received, user software can validate the address and must
reset URXWIE to continue receiving data. If URXWIE remains set, only
address characters are received. The URXWIE bit is not modified by the
USART hardware automatically.
For address transmission in idle-line multiprocessor format, a precise idle
period can be generated by the USART to generate address character
identifiers on UTXDx. The wake-up temporary (WUT) flag is an internal flag
double-buffered with the user-accessible TXWAKE bit. When the transmitter
is loaded from UxTXBUF, WUT is also loaded from TXWAKE resetting the
TXWAKE bit.
The following procedure sends out an idle frame to indicate an address
character follows:
1) Set TXWAKE, then write any character to UxTXBUF. UxTXBUF must be
ready for new data (UTXIFGx = 1).
The TXWAKE value is shifted to WUT and the contents of UxTXBUF are
shifted to the transmit shift register when the shift register is ready for new
data. This sets WUT, which suppresses the start, data, and parity bits of a
normal transmission, then transmits an idle period of exactly 11 bits. When
two stop bits are used for the idle line, the second stop bit is counted as the
first mark bit of the idle period. TXWAKE is reset automatically.
2) Write desired address character to UxTXBUF. UxTXBUF must be ready
for new data (UTXIFGx = 1).
The new character representing the specified address is shifted out
following the address-identifying idle period on UTXDx. Writing the first
“don’t care” character to UxTXBUF is necessary in order to shift the
TXWAKE bit to WUT and generate an idle-line condition. This data is
discarded and does not appear on UTXDx.
17-6
USART Peripheral Interface, UART Mode
USART Operation: UART Mode
Address-Bit Multiprocessor Format
When MM = 1, the address-bit multiprocessor format is selected. Each
processed character contains an extra bit used as an address indicator shown
in Figure 17−4. The first character in a block of characters carries a set
address bit which indicates that the character is an address. The USART
RXWAKE bit is set when a received character is a valid address character and
is transferred to UxRXBUF.
The URXWIE bit is used to control data reception in the address-bit
multiprocessor format. If URXWIE is set, data characters (address bit = 0) are
assembled by the receiver but are not transferred to UxRXBUF and no
interrupts are generated. When a character containing a set address bit is
received, the receiver is temporarily activated to transfer the character to
UxRXBUF and set URXIFGx. All applicable error status flags are also set.
If an address is received, user software must reset URXWIE to continue
receiving data. If URXWIE remains set, only address characters (address
bit = 1) are received. The URXWIE bit is not modified by the USART hardware
automatically.
Figure 17−4. Address-Bit Multiprocessor Format
Blocks of
Characters
UTXDx/URXDx
Idle Periods of No Significance
UTXDx/URXDx
Expanded
UTXDx/URXDx
ST
Address
1 SP ST
First Character Within Block
Is an Address. AD Bit Is 1
Data
0
SP
ST
Data
0 SP
AD Bit Is 0 for
Data Within Block.
Idle Time Is of No Significance
For address transmission in address-bit multiprocessor mode, the address bit
of a character can be controlled by writing to the TXWAKE bit. The value of the
TXWAKE bit is loaded into the address bit of the character transferred from
UxTXBUF to the transmit shift register, automatically clearing the TXWAKE bit.
TXWAKE must not be cleared by software. It is cleared by USART hardware
after it is transferred to WUT or by setting SWRST.
USART Peripheral Interface, UART Mode
17-7
USART Operation: UART Mode
Automatic Error Detection
Glitch suppression prevents the USART from being accidentally started. Any
low-level on URXDx shorter than the deglitch time tτ (approximately 300 ns)
is ignored. See the device-specific data sheet for parameters.
When a low period on URXDx exceeds tτ a majority vote is taken for the start
bit. If the majority vote fails to detect a valid start bit the USART halts character
reception and waits for the next low period on URXDx. The majority vote is also
used for each bit in a character to prevent bit errors.
The USART module automatically detects framing errors, parity errors,
overrun errors, and break conditions when receiving characters. The bits FE,
PE, OE, and BRK are set when their respective condition is detected. When
any of these error flags are set, RXERR is also set. The error conditions are
described in Table 17−1.
Table 17−1.Receive Error Conditions
Error Condition
Description
Framing error
A framing error occurs when a low stop bit is detected.
When two stop bits are used, only the first stop bit is
checked for framing error. When a framing error is
detected, the FE bit is set.
Parity error
A parity error is a mismatch between the number of 1s in
a character and the value of the parity bit. When an
address bit is included in the character, it is included in
the parity calculation. When a parity error is detected, the
PE bit is set.
An overrun error occurs when a character is loaded into
Receive overrun error UxRXBUF before the prior character has been read.
When an overrun occurs, the OE bit is set.
Break condition
A break condition is a period of 10 or more low bits
received on URXDx after a missing stop bit. When a
break condition is detected, the BRK bit is set. A break
condition can also set the interrupt flag URXIFGx when
URXEIE = 0.
When URXEIE = 0 and a framing error, parity error, or break condition is
detected, no character is received into UxRXBUF. When URXEIE = 1,
characters are received into UxRXBUF and any applicable error bit is set.
When any of the FE, PE, OE, BRK, or RXERR bits are set, the bit remains set
until user software resets it or UxRXBUF is read.
17-8
USART Peripheral Interface, UART Mode
USART Operation: UART Mode
17.2.4 USART Receive Enable
The receive enable bit, URXEx, enables or disables data reception on URXDx
as shown in Figure 17−5. Disabling the USART receiver stops the receive
operation following completion of any character currently being received or
immediately if no receive operation is active. The receive-data buffer,
UxRXBUF, contains the character moved from the RX shift register after the
character is received.
Figure 17−5. State Diagram of Receiver Enable
No Valid Start Bit
URXEx = 0
URXEx = 1
Receive
Disable
URXEx = 0
Not Completed
Idle State
(Receiver
Enabled)
URXEx = 1
Valid Start Bit
URXEx = 1
Receiver
Collects
Character
Handle Interrupt
Conditions
Character
Received
URXEx = 0
Note: Re-Enabling the Receiver (Setting URXEx): UART Mode
When the receiver is disabled (URXEx = 0), re-enabling the receiver
(URXEx = 1) is asynchronous to any data stream that may be present on
URXDx at the time. Synchronization can be performed by testing for an idle
line condition before receiving a valid character (see URXWIE).
USART Peripheral Interface, UART Mode
17-9
USART Operation: UART Mode
17.2.5 USART Transmit Enable
When UTXEx is set, the UART transmitter is enabled. Transmission is initiated
by writing data to UxTXBUF. The data is then moved to the transmit shift
register on the next BITCLK after the TX shift register is empty, and
transmission begins. This process is shown in Figure 17−6.
When the UTXEx bit is reset the transmitter is stopped. Any data moved to
UxTXBUF and any active transmission of data currently in the transmit shift
register prior to clearing UTXEx continue until all data transmission is
completed.
Figure 17−6. State Diagram of Transmitter Enable
UTXEx = 0
UTXEx = 1
Transmit
Disable
UTXEx = 0
No Data Written
to Transmit Buffer
Idle State
(Transmitter
Enabled)
UTXEx = 1
Data Written to
Transmit Buffer
UTXEx = 1
Not Completed
Transmission
Active
Handle Interrupt
Conditions
Character
Transmitted
UTXEx = 0 And Last Buffer Entry Is Transmitted
When the transmitter is enabled (UTXEx = 1), data should not be written to
UxTXBUF unless it is ready for new data indicated by UTXIFGx = 1. Violation
can result in an erroneous transmission if data in UxTXBUF is modified as it
is being moved into the TX shift register.
It is recommended that the transmitter be disabled (UTXEx = 0) only after any
active transmission is complete. This is indicated by a set transmitter empty
bit (TXEPT = 1). Any data written to UxTXBUF while the transmitter is disabled
are held in the buffer but are not moved to the transmit shift register or
transmitted. Once UTXEx is set, the data in the transmit buffer is immediately
loaded into the transmit shift register and character transmission resumes.
17-10
USART Peripheral Interface, UART Mode
USART Operation: UART Mode
17.2.6 USART Baud Rate Generation
The USART baud rate generator is capable of producing standard baud rates
from non-standard source frequencies. The baud rate generator uses one
prescaler/divider and a modulator as shown in Figure 17−7. This combination
supports fractional divisors for baud rate generation. The maximum USART
baud rate is one-third the UART source clock frequency BRCLK.
Figure 17−7. MSP430 Baud Rate Generator
SSEL1 SSEL0 N = 215
28
...
27
UxBR1
UCLKI
00
ACLK
01
SMCLK
10
SMCLK
11
20
...
UxBR0
8
8
BRCLK
16−Bit Counter
............
Q15
R
Q0
Toggle
FF
R
+0 or 1 Compare (0 or 1)
BITCLK
Modulation Data Shift Register R
(LSB first)
mX
8
m7
m0
Bit Start
UxMCTL
Timing for each bit is shown in Figure 17−8. For each bit received, a majority
vote is taken to determine the bit value. These samples occur at the N/2−1,
N/2, and N/2+1 BRCLK periods, where N is the number of BRCLKs per
BITCLK.
Figure 17−8. BITCLK Baud Rate Timing
Majority Vote:
(m= 0)
(m= 1)
Bit Start
BRCLK
Counter
N/2
N/2−1 N/2−2
1
N/2
1
0
N/2−1 N/2−2
N/2
N/2−1
1
N/2
N/2−1
1
0
N/2
BITCLK
NEVEN: INT(N/2)
INT(N/2) + m(= 0)
NODD : INT(N/2) + R(= 1)
INT(N/2) + m(= 1)
Bit Period
m: corresponding modulation bit
R: Remainder from N/2 division
USART Peripheral Interface, UART Mode
17-11
USART Operation: UART Mode
Baud Rate Bit Timing
The first stage of the baud rate generator is the 16-bit counter and comparator.
At the beginning of each bit transmitted or received, the counter is loaded with
INT(N/2) where N is the value stored in the combination of UxBR0 and UxBR1.
The counter reloads INT(N/2) for each bit period half-cycle, giving a total bit
period of N BRCLKs. For a given BRCLK clock source, the baud rate used
determines the required division factor N:
N=
BRCLK
baud rate
The division factor N is often a non-integer value of which the integer portion
can be realized by the prescaler/divider. The second stage of the baud rate
generator, the modulator, is used to meet the fractional part as closely as
possible. The factor N is then defined as:
n*1
N + UxBR ) 1
n S mi
i+0
Where:
N:
UxBR:
i:
n:
mi :
Target division factor
16-bit representation of registers UxBR0 and UxBR1
Bit position in the character
Total number of bits in the character
Data of each corresponding modulation bit (1 or 0)
BRCLK
Baud rate + BRCLK +
n–1
N
UxBR ) 1 ȍ m
n
i
i+0
The BITCLK can be adjusted from bit to bit with the modulator to meet timing
requirements when a non-integer divisor is needed. Timing of each bit is
expanded by one BRCLK clock cycle if the modulator bit mi is set. Each time
a bit is received or transmitted, the next bit in the modulation control register
determines the timing for that bit. A set modulation bit increases the division
factor by one while a cleared modulation bit maintains the division factor given
by UxBR.
The timing for the start bit is determined by UxBR plus m0, the next bit is
determined by UxBR plus m1, and so on. The modulation sequence begins
with the LSB. When the character is greater than 8 bits, the modulation
sequence restarts with m0 and continues until all bits are processed.
Determining the Modulation Value
Determining the modulation value is an interactive process. Using the timing
error formula provided, beginning with the start bit , the individual bit errors are
calculated with the corresponding modulator bit set and cleared. The
modulation bit setting with the lower error is selected and the next bit error is
calculated. This process is continued until all bit errors are minimized. When
a character contains more than 8 bits, the modulation bits repeat. For example,
the ninth bit of a character uses modulation bit 0.
17-12
USART Peripheral Interface, UART Mode
USART Operation: UART Mode
Transmit Bit Timing
The timing for each character is the sum of the individual bit timings. By
modulating each bit, the cumulative bit error is reduced. The individual bit error
can be calculated by:
NJ
Error [%] + baud rate
BRCLK
ƪ( j ) 1 )
j
ƫ
UxBR ) S m i * ( j ) 1 )
i+0
Nj
100%
With:
baud rate: Desired baud rate
BRCLK: Input frequency − UCLKI, ACLK, or SMCLK
j:
Bit position - 0 for the start bit, 1 for data bit D0, and so on
UxBR:
Division factor in registers UxBR1 and UxBR0
For example, the transmit errors for the following conditions are calculated:
Baud rate =
BRCLK =
UxBR =
UxMCTL =
ǒ
2400
32,768 Hz (ACLK)
13, since the ideal division factor is 13.65
6Bh: m7 = 0, m6 = 1, m5 = 1, m4 = 0, m3 = 1, m2 = 0,
m1 = 1, and m0= 1. The LSB of UxMCTL is used first.
Ǔ
Start bit Error [%] + baud rate ((0 ) 1) UxBR ) 1)–1
100% + 2.54%
BRCLK
100% + 5.08%
Data bit D0 Error [%] + baud rate ((1 ) 1) UxBR ) 2)–2
BRCLK
ǒ
Ǔ
Data bit D1 Error [%] + ǒbaud rate ((2 ) 1) UxBR ) 2)–3Ǔ
BRCLK
Data bit D2 Error [%] + ǒbaud rate ((3 ) 1) UxBR ) 3)–4Ǔ
BRCLK
baud
rate ((4 ) 1) UxBR ) 3)–5Ǔ
Data bit D3 Error [%] + ǒ
BRCLK
Data bit D4 Error [%] + ǒbaud rate ((5 ) 1) UxBR ) 4)–6Ǔ
BRCLK
Data bit D5 Error [%] + ǒbaud rate ((6 ) 1) UxBR ) 5)–7Ǔ
BRCLK
Data bit D6 Error [%] + ǒbaud rate ((7 ) 1) UxBR ) 5)–8Ǔ
BRCLK
Data bit D7 Error [%] + ǒbaud rate ((8 ) 1) UxBR ) 6)–9Ǔ
BRCLK
Parity bit Error [%] + ǒbaud rate ((9 ) 1) UxBR ) 7)–10Ǔ
BRCLK
Stop bit 1 Error [%] + ǒbaud rate ((10 ) 1) UxBR ) 7)–11Ǔ
BRCLK
100% + 0.29%
100% + 2.83%
100% +*1.95%
100% + 0.59%
100% + 3.13%
100% + *1.66%
100% + 0.88%
100% + 3.42%
100% + *1.37%
The results show the maximum per-bit error to be 5.08% of a BITCLK period.
USART Peripheral Interface, UART Mode
17-13
USART Operation: UART Mode
Receive Bit Timing
Receive timing is subject to two error sources. The first is the bit-to-bit timing
error. The second is the error between a start edge occurring and the start
edge being accepted by the USART. Figure 17−9 shows the asynchronous
timing errors between data on the URXDx pin and the internal baud-rate clock.
Figure 17−9. Receive Error
0
i
tideal
2
1
t0
t1
1 2 3 4 5 6 7 8
9 10 11 12 13 14 1 2 3 4 5 6 7 8
9 10 11 12 13 14 1 2 3 4 5 6 7
BRCLK
URXDx
ST
D0
D1
URXDS
ST
D0
D1
tactual
Sample
URXDS
t0
Synchronization Error ± 0.5x BRCLK
Int(UxBR/2)+m0 =
Int (13/2)+1 = 6+1 = 7
t1
t2
UxBR +m1 = 13+1 = 14
Majority Vote Taken
UxBR +m2 = 13+0 = 13
Majority Vote Taken
Majority Vote Taken
The ideal start bit timing tideal(0) is half the baud-rate timing tbaudrate, because
the bit is tested in the middle of its period. The ideal baud-rate timing tideal(i)
for the remaining character bits is the baud rate timing tbaudrate. The individual
bit errors can be calculated by:
ȡ
ȧ
Ȣ
Error [%] + baud rate
BRCLK
NJ
2
Ǔƫ ) ǒ i
ƪm0 ) int ǒUxBR
2
j
UxBR ) S m i
i+1
ǓNj * 1 * j Ǔ
Where:
baud rate is the required baud rate
BRCLK is the input frequency—selected for UCLK, ACLK, or SMCLK
j = 0 for the start bit, 1 for data bit D0, and so on
UxBR is the division factor in registers UxBR1 and UxBR0
17-14
USART Peripheral Interface, UART Mode
100%
USART Operation: UART Mode
For example, the receive errors for the following conditions are calculated:
Baud rate = 2400
BRCLK =
32,768 Hz (ACLK)
UxBR =
13, since the ideal division factor is 13.65
UxMCTL = 6B:m7 = 0, m6 = 1, m5 = 1, m4 = 0, m3 = 1, m2 = 0, m1 = 1 and
m0 = 1 The LSB of UxMCTL is used first.
ǒ
Start bit Error [%] + baud rate
BRCLK
[2x(1 ) 6) ) (0
Ǔ
UxBR ) 0)] * 1 * 0
ǒ
[2x(1 ) 6) ) (1
Data bit D1 Error [%] + ǒbaud rate [2x(1 ) 6) ) (2
BRCLK
Data bit D2 Error [%] + ǒbaud rate [2x(1 ) 6) ) (3
BRCLK
Data bit D3 Error [%] + ǒbaud rate [2x(1 ) 6) ) (4
BRCLK
Data bit D4 Error [%] + ǒbaud rate [2x(1 ) 6) ) (5
BRCLK
Data bit D5 Error [%] + ǒbaud rate [2x(1 ) 6) ) (6
BRCLK
Data bit D6 Error [%] + ǒbaud rate [2x(1 ) 6) ) (7
BRCLK
baud
rate [2x(1 ) 6) ) (8
Data bit D7 Error [%] + ǒ
BRCLK
Parity bit Error [%] + ǒbaud rate [2x(1 ) 6) ) (9
BRCLK
Stop bit 1 Error [%] + ǒbaud rate [2x(1 ) 6) ) (10
BRCLK
Data bit D0 Error [%] + baud rate
BRCLK
100% + 2.54%
Ǔ 100% + 5.08%
UxBR ) 1)] * 1 * 2Ǔ 100% + 0.29%
UxBR ) 2)] * 1 * 3Ǔ 100% + 2.83%
UxBR ) 2)] * 1 * 4Ǔ 100% + −1.95%
UxBR ) 3)] * 1 * 5Ǔ 100% + 0.59%
UxBR ) 4)] * 1 * 6Ǔ 100% + 3.13%
UxBR ) 4)] * 1 * 7Ǔ 100% + −1.66%
UxBR ) 5)] * 1 * 8Ǔ 100% + 0.88%
UxBR ) 6)] * 1 * 9Ǔ 100% + 3.42%
UxBR ) 6)] * 1 * 10Ǔ 100% + −1.37%
UxBR ) 1)] * 1 * 1
The results show the maximum per-bit error to be 5.08% of a BITCLK period.
USART Peripheral Interface, UART Mode
17-15
USART Operation: UART Mode
Typical Baud Rates and Errors
Standard baud rate frequency data for UxBRx and UxMCTL are listed in
Table 17−2 for a 32,768-Hz watch crystal (ACLK) and a typical 1,048,576-Hz
SMCLK.
The receive error is the accumulated time versus the ideal scanning time in the
middle of each bit. The transmit error is the accumulated timing error versus
the ideal time of the bit period.
Table 17−2.Commonly Used Baud Rates, Baud Rate Data, and Errors
Divide by
Baud
Rate
A: BRCLK = 32,768 Hz
B: BRCLK = 1,048,576 Hz
Max.
TX
Error %
Max.
RX
Error %
Synchr.
RX
Error %
UxBR1
A:
B:
1200
27.31
873.81
0
1B
03
−4/3
− 4/3
±2
2400
13.65
436.91
0
0D
6B
− 6/3
− 6/3
±4
4800
6.83
218.45
0
06
6F
− 9/11
− 9/11
9600
3.41
109.23
0
03
4A
− 21/12
− 21/12
UxBR1
UxBR0
UxMCTL
Max.
TX
Error %
Max.
RX
Error %
UxBR0
UxMCTL
03
69
FF
0/0.3
±2
01
B4
FF
0/0.3
±2
±7
0
DA
55
0/0.4
±2
± 15
0
6D
03
−0.4/1
±2
19,200
54.61
0
36
6B
−0.2/2
±2
38,400
27.31
0
1B
03
− 4/3
±2
76,800
13.65
0
0D
6B
− 6/3
±4
115,20
0
9.1
0
09
08
− 5/7
±7
17-16
USART Peripheral Interface, UART Mode
USART Operation: UART Mode
17.2.7 USART Interrupts
The USART has one interrupt vector for transmission and one interrupt vector
for reception.
USART Transmit Interrupt Operation
The UTXIFGx interrupt flag is set by the transmitter to indicate that UxTXBUF
is ready to accept another character. An interrupt request is generated if
UTXIEx and GIE are also set. UTXIFGx is automatically reset if the interrupt
request is serviced or if a character is written to UxTXBUF.
UTXIFGx is set after a PUC or when SWRST = 1. UTXIEx is reset after a PUC
or when SWRST = 1. The operation is shown is Figure 17−10.
Figure 17−10. Transmit Interrupt Operation
Q
UTXIEx
Clear
PUC or SWRST
VCC
Character Moved From
Buffer to Shift Register
D
Set UTXIFGx
Q
Clear
Interrupt Service Requested
SWRST
Data written to UxTXBUF
IRQA
USART Peripheral Interface, UART Mode
17-17
USART Operation: UART Mode
USART Receive Interrupt Operation
The URXIFGx interrupt flag is set each time a character is received and loaded
into UxRXBUF. An interrupt request is generated if URXIEx and GIE are also
set. URXIFGx and URXIEx are reset by a system reset PUC signal or when
SWRST = 1. URXIFGx is automatically reset if the pending interrupt is served
(when URXSE = 0) or when UxRXBUF is read. The operation is shown in
Figure 17−11.
Figure 17−11.Receive Interrupt Operation
SYNC
Valid Start Bit
URXS
S
Receiver Collects Character
URXSE
From URXD
τ
Clear
Erroneous Character Rejection
PE
FE
BRK
URXIEx
URXEIE
Interrupt Service
Requested
S
URXIFGx
Clear
URXWIE
RXWAKE
Non-Address Character Rejection
Character Received
or
Break Detected
SWRST
PUC
UxRXBUF Read
URXSE
IRQA
URXEIE is used to enable or disable erroneous characters from setting
URXIFGx. When using multiprocessor addressing modes, URXWIE is used
to auto-detect valid address characters and reject unwanted data characters.
Two types of characters do not set URXIFGx:
- Erroneous characters when URXEIE = 0
- Non-address characters when URXWIE = 1
When URXEIE = 1 a break condition sets the BRK bit and the URXIFGx flag.
17-18
USART Peripheral Interface, UART Mode
USART Operation: UART Mode
Receive-Start Edge Detect Operation
The URXSE bit enables the receive start-edge detection feature. The
recommended usage of the receive-start edge feature is when BRCLK is
sourced by the DCO and when the DCO is off because of low-power mode
operation. The ultra-fast turn-on of the DCO allows character reception after
the start edge detection.
When URXSE, URXIEx and GIE are set and a start edge occurs on URXDx,
the internal signal URXS is set. When URXS is set, a receive interrupt request
is generated but URXIFGx is not set. User software in the receive interrupt
service routine can test URXIFGx to determine the source of the interrupt.
When URXIFGx = 0 a start edge was detected, and when URXIFGx = 1 a valid
character (or break) was received.
When the ISR determines the interrupt request was from a start edge, user
software toggles URXSE, and must enable the BRCLK source by returning
from the ISR to active mode or to a low-power mode where the source is active.
If the ISR returns to a low-power mode where the BRCLK source is inactive,
the character is not received. Toggling URXSE clears the URXS signal and
re-enables the start edge detect feature for future characters. See chapter
System Resets, Interrupts, and Operating Modes for information on entering
and exiting low-power modes.
The now active BRCLK allows the USART to receive the balance of the
character. After the full character is received and moved to UxRXBUF,
URXIFGx is set and an interrupt service is again requested. Upon ISR entry,
URXIFGx = 1 indicating a character was received. The URXIFGx flag is
cleared when user software reads UxRXBUF.
; Interrupt handler for start condition and
; Character receive. BRCLK = DCO.
U0RX_Int BIT.B #URXIFG0,&IFG1
JZ
ST_COND
MOV.B &UxRXBUF,dst
...
RETI
ST_COND
; Test URXIFGx to determine
; If start or character
; Read buffer
;
;
BIC.B #URXSE,&U0TCTL ; Clear URXS signal
BIS.B #URXSE,&U0TCTL ; Re-enable edge detect
BIC
#SCG0+SCG1,0(SP) ; Enable BRCLK = DCO
RETI
;
Note: Break Detect With Halted UART Clock
When using the receive start-edge detect feature, a break condition cannot
be detected when the BRCLK source is off.
USART Peripheral Interface, UART Mode
17-19
USART Operation: UART Mode
Receive-Start Edge Detect Conditions
When URXSE = 1, glitch suppression prevents the USART from being
accidentally started. Any low-level on URXDx shorter than the deglitch time tτ
(approximately 300 ns) is ignored by the USART and no interrupt request is
generated (see Figure 17−12). See the device-specific data sheet for
parameters.
Figure 17−12. Glitch Suppression, USART Receive Not Started
URXDx
URXS
tτ
When a glitch is longer than tτ or a valid start bit occurs on URXDx, the USART
receive operation is started and a majority vote is taken as shown in
Figure 17−13. If the majority vote fails to detect a start bit, the USART halts
character reception.
If character reception is halted, an active BRCLK is not necessary. A time-out
period longer than the character receive duration can be used by software to
indicate that a character was not received in the expected time, and the
software can disable BRCLK.
Figure 17−13. Glitch Suppression, USART Activated
Majority Vote Taken
URXDx
URXS
tτ
17-20
USART Peripheral Interface, UART Mode
USART Registers: UART Mode
17.3 USART Registers: UART Mode
Table 17−3 lists the registers for all devices implementing a USART module.
Table 17−4 applies only to devices with a second USART module, USART1.
Table 17−3.USART0 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USART control register
U0CTL
Read/write
070h
001h with PUC
Transmit control register
U0TCTL
Read/write
071h
001h with PUC
Receive control register
U0RCTL
Read/write
072h
000h with PUC
Modulation control register
U0MCTL
Read/write
073h
Unchanged
Baud rate control register 0
U0BR0
Read/write
074h
Unchanged
Baud rate control register 1
U0BR1
Read/write
075h
Unchanged
Receive buffer register
U0RXBUF
Read
076h
Unchanged
Transmit buffer register
U0TXBUF
Read/write
077h
Unchanged
SFR module enable register 1
ME1
Read/write
004h
000h with PUC
SFR interrupt enable register 1
IE1
Read/write
000h
000h with PUC
SFR interrupt flag register 1
IFG1
Read/write
002h
082h with PUC
Table 17−4.USART1 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USART control register
U1CTL
Read/write
078h
001h with PUC
Transmit control register
U1TCTL
Read/write
079h
001h with PUC
Receive control register
U1RCTL
Read/write
07Ah
000h with PUC
Modulation control register
U1MCTL
Read/write
07Bh
Unchanged
Baud rate control register 0
U1BR0
Read/write
07Ch
Unchanged
Baud rate control register 1
U1BR1
Read/write
07Dh
Unchanged
Receive buffer register
U1RXBUF
Read
07Eh
Unchanged
Transmit buffer register
U1TXBUF
Read/write
07Fh
Unchanged
SFR module enable register 2
ME2
Read/write
005h
000h with PUC
SFR interrupt enable register 2
IE2
Read/write
001h
000h with PUC
SFR interrupt flag register 2
IFG2
Read/write
003h
020h with PUC
Note: Modifying SFR bits
To avoid modifying control bits of other modules, it is recommended to set
or clear the IEx and IFGx bits using BIS.B or BIC.B instructions, rather than
MOV.B or CLR.B instructions.
USART Peripheral Interface, UART Mode
17-21
USART Registers: UART Mode
UxCTL, USART Control Register
7
6
5
4
3
2
1
0
PENA
PEV
SPB
CHAR
LISTEN
SYNC
MM
SWRST
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−1
PENA
Bit 7
Parity enable
0
Parity disabled
1
Parity enabled. Parity bit is generated (UTXDx) and expected
(URXDx). In address-bit multiprocessor mode, the address bit is
included in the parity calculation.
PEV
Bit 6
Parity select. PEV is not used when parity is disabled.
0
Odd parity
1
Even parity
SPB
Bit 5
Stop bit select. Number of stop bits transmitted. The receiver always
checks for one stop bit.
0
One stop bit
1
Two stop bits
CHAR
Bit 4
Character length. Selects 7-bit or 8-bit character length.
0
7-bit data
1
8-bit data
LISTEN
Bit 3
Listen enable. The LISTEN bit selects loopback mode.
0
Disabled
1
Enabled. UTXDx is internally fed back to the receiver.
SYNC
Bit 2
Synchronous mode enable
0
UART mode
1
SPI Mode
MM
Bit 1
Multiprocessor mode select
0
Idle-line multiprocessor protocol
1
Address-bit multiprocessor protocol
SWRST
Bit 0
Software reset enable
0
Disabled. USART reset released for operation
1
Enabled. USART logic held in reset state
17-22
USART Peripheral Interface, UART Mode
USART Registers: UART Mode
UxTCTL, USART Transmit Control Register
7
6
Unused
CKPL
rw−0
rw−0
5
4
SSELx
rw−0
3
2
1
0
URXSE
TXWAKE
Unused
TXEPT
rw−0
rw−0
rw−0
rw−1
rw−0
Unused
Bit 7
Unused
CKPL
Bit 6
Clock polarity select
0
UCLKI = UCLK
1
UCLKI = inverted UCLK
SSELx
Bits
5-4
Source select. These bits select the BRCLK source clock.
00 UCLKI
01 ACLK
10 SMCLK
11 SMCLK
URXSE
Bit 3
UART receive start-edge. The bit enables the UART receive start-edge
feature.
0
Disabled
1
Enabled
TXWAKE
Bit 2
Transmitter wake
0
Next frame transmitted is data
1
Next frame transmitted is an address
Unused
Bit 1
Unused
TXEPT
Bit 0
Transmitter empty flag
0
UART is transmitting data and/or data is waiting in UxTXBUF
1
Transmitter shift register and UxTXBUF are empty or SWRST = 1
USART Peripheral Interface, UART Mode
17-23
USART Registers: UART Mode
UxRCTL, USART Receive Control Register
7
6
5
4
3
2
1
0
FE
PE
OE
BRK
URXEIE
URXWIE
RXWAKE
RXERR
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
FE
Bit 7
Framing error flag
0
No error
1
Character received with low stop bit
PE
Bit 6
Parity error flag. When PENA = 0, PE is read as 0.
0
No error
1
Character received with parity error
OE
Bit 5
Overrun error flag. This bit is set when a character is transferred into
UxRXBUF before the previous character was read.
0
No error
1
Overrun error occurred
BRK
Bit 4
Break detect flag
0
No break condition
1
Break condition occurred
URXEIE
Bit 3
Receive erroneous-character interrupt-enable
0
Erroneous characters rejected and URXIFGx is not set
1
Erroneous characters received set URXIFGx
URXWIE
Bit 2
Receive wake-up interrupt-enable. This bit enables URXIFGx to be set
when an address character is received. When URXEIE = 0, an address
character does not set URXIFGx if it is received with errors.
0
All received characters set URXIFGx
1
Only received address characters set URXIFGx
RXWAKE
Bit 1
Receive wake-up flag
0
Received character is data
1
Received character is an address
RXERR
Bit 0
Receive error flag. This bit indicates a character was received with error(s).
When RXERR = 1, on or more error flags (FE,PE,OE, BRK) is also set.
RXERR is cleared when UxRXBUF is read.
0
No receive errors detected
1
Receive error detected
17-24
USART Peripheral Interface, UART Mode
USART Registers: UART Mode
UxBR0, USART Baud Rate Control Register 0
7
6
5
4
3
2
1
0
27
26
25
24
23
22
21
20
rw
rw
rw
rw
rw
rw
rw
rw
UxBR1, USART Baud Rate Control Register 1
7
6
5
4
3
2
1
0
215
214
213
212
211
210
29
28
rw
rw
rw
rw
rw
rw
rw
rw
The valid baud-rate control range is 3 ≤ UxBR < 0FFFFh, where
UxBR = {UxBR1+UxBR0}. Unpredictable receive and transmit timing
occurs if UxBR < 3.
UxBRx
UxMCTL, USART Modulation Control Register
7
6
5
4
3
2
1
0
m7
m6
m5
m4
m3
m2
m1
m0
rw
rw
rw
rw
rw
rw
rw
rw
UxMCTLx
Bits
7−0
Modulation bits. These bits select the modulation for BRCLK.
USART Peripheral Interface, UART Mode
17-25
USART Registers: UART Mode
UxRXBUF, USART Receive Buffer Register
7
6
5
4
3
2
1
0
27
26
25
24
23
22
21
20
r
r
r
r
r
r
r
r
UxRXBUFx
Bits
7−0
The receive-data buffer is user accessible and contains the last received
character from the receive shift register. Reading UxRXBUF resets the
receive-error bits, the RXWAKE bit, and URXIFGx. In 7-bit data mode,
UxRXBUF is LSB justified and the MSB is always reset.
UxTXBUF, USART Transmit Buffer Register
7
6
5
4
3
2
1
0
27
26
25
24
23
22
21
20
rw
rw
rw
rw
rw
rw
rw
rw
UxTXBUFx
17-26
Bits
7−0
The transmit data buffer is user accessible and holds the data waiting to be
moved into the transmit shift register and transmitted on UTXDx. Writing to
the transmit data buffer clears UTXIFGx. The MSB of UxTXBUF is not
used for 7-bit data and is reset.
USART Peripheral Interface, UART Mode
USART Registers: UART Mode
ME1, Module Enable Register 1
7
6
UTXE0
URXE0
rw−0
rw−0
5
4
3
2
1
0
UTXE0
Bit 7
USART0 transmit enable. This bit enables the transmitter for USART0.
0
Module not enabled
1
Module enabled
URXE0
Bit 6
USART0 receive enable. This bit enables the receiver for USART0.
0
Module not enabled
1
Module enabled
Bits
5-0
These bits may be used by other modules. See device-specific data sheet.
ME2, Module Enable Register 2
7
6
5
4
UTXE1
URXE1
rw−0
rw−0
3
2
1
0
Bits
7-6
These bits may be used by other modules. See device-specific data sheet.
UTXE1
Bit 5
USART1 transmit enable. This bit enables the transmitter for USART1.
0
Module not enabled
1
Module enabled
URXE1
Bit 4
USART1 receive enable. This bit enables the receiver for USART1.
0
Module not enabled
1
Module enabled
Bits
3-0
These bits may be used by other modules. See device-specific data sheet.
USART Peripheral Interface, UART Mode
17-27
USART Registers: UART Mode
IE1, Interrupt Enable Register 1
7
6
UTXIE0
URXIE0
rw−0
rw−0
5
4
3
2
1
0
UTXIE0
Bit 7
USART0 transmit interrupt enable. This bit enables the UTXIFG0 interrupt.
0
Interrupt not enabled
1
Interrupt enabled
URXIE0
Bit 6
USART0 receive interrupt enable. This bit enables the URXIFG0 interrupt.
0
Interrupt not enabled
1
Interrupt enabled
Bits
5-0
These bits may be used by other modules. See device-specific data sheet.
IE2, Interrupt Enable Register 2
7
6
5
4
UTXIE1
URXIE1
rw−0
rw−0
3
2
1
0
Bits
7-6
These bits may be used by other modules. See device-specific data sheet.
UTXIE1
Bit 5
USART1 transmit interrupt enable. This bit enables the UTXIFG1 interrupt.
0
Interrupt not enabled
1
Interrupt enabled
URXIE1
Bit 4
USART1 receive interrupt enable. This bit enables the URXIFG1 interrupt.
0
Interrupt not enabled
1
Interrupt enabled
Bits
3-0
These bits may be used by other modules. See device-specific data sheet.
17-28
USART Peripheral Interface, UART Mode
USART Registers: UART Mode
IFG1, Interrupt Flag Register 1
7
6
UTXIFG0
URXIFG0
rw−1
rw−0
5
4
3
2
1
0
UTXIFG0
Bit 7
USART0 transmit interrupt flag. UTXIFG0 is set when U0TXBUF is empty.
0
No interrupt pending
1
Interrupt pending
URXIFG0
Bit 6
USART0 receive interrupt flag. URXIFG0 is set when U0RXBUF has received
a complete character.
0
No interrupt pending
1
Interrupt pending
Bits
5-0
These bits may be used by other modules. See device-specific data sheet.
IFG2, Interrupt Flag Register 2
7
6
5
4
UTXIFG1
URXIFG1
rw−1
rw−0
3
2
1
0
Bits
7-6
These bits may be used by other modules. See device-specific data sheet.
UTXIFG1
Bit 5
USART1 transmit interrupt flag. UTXIFG1 is set when U1TXBUF empty.
0
No interrupt pending
1
Interrupt pending
URXIFG1
Bit 4
USART1 receive interrupt flag. URXIFG1 is set when U1RXBUF has received
a complete character.
0
No interrupt pending
1
Interrupt pending
Bits
3-0
These bits may be used by other modules. See device-specific data sheet.
USART Peripheral Interface, UART Mode
17-29
17-30
USART Peripheral Interface, UART Mode
Chapter 18
USART Peripheral Interface, SPI Mode
The universal synchronous/asynchronous receive/transmit (USART)
peripheral interface supports two serial modes with one hardware module.
This chapter discusses the operation of the synchronous peripheral interface
or SPI mode. USART0 is implemented on the MSP430x42x and MSP430x43x
devices. In addition to USART0, the MSP430x44x devices implement a
second identical USART module, USART1. USART1 is also implemented in
MSP430FG461x devices.
Topic
Page
18.1 USART Introduction: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-2
18.2 USART Operation: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-4
18.3 USART Registers: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-13
USART Peripheral Interface, SPI Mode
18-1
USART Introduction: SPI Mode
18.1 USART Introduction: SPI Mode
In synchronous mode, the USART connects the MSP430 to an external
system via three or four pins: SIMO, SOMI, UCLK, and STE. SPI mode is
selected when the SYNC bit is set and the I2C bit is cleared.
SPI mode features include:
- 7-bit or 8-bit data length
- 3-pin and 4-pin SPI operation
- Master or slave modes
- Independent transmit and receive shift registers
- Separate transmit and receive buffer registers
- Selectable UCLK polarity and phase control
- Programmable UCLK frequency in master mode
- Independent interrupt capability for receive and transmit
Figure 18−1 shows the USART when configured for SPI mode.
18-2
USART Peripheral Interface, SPI Mode
USART Introduction: SPI Mode
Figure 18−1. USART Block Diagram: SPI Mode
SWRST USPIEx* URXEIE URXWIE
SYNC= 1
URXIFGx*
Receive Control
FE PE OE BRK
Receive Status
Receiver Buffer UxRXBUF
LISTEN
0
RXERR
RXWAKE
MM
1
Receiver Shift Register
1
SSEL1 SSEL0
SPB
CHAR
PEV
0
PENA
UCLKS
UCLKI
00
ACLK
01
SMCLK
10
SMCLK
11
SYNC
1
SOMI
0
1
URXD
0
Baud−Rate Generator
STE
Prescaler/Divider UxBRx
Modulator UxMCTL
SPB
CHAR
PEV
UTXD
PENA
1
WUT
Transmit Shift Register
TXWAKE
Transmit Buffer UxTXBUF
0
1
SIMO
0
UTXIFGx*
Transmit Control
SYNC CKPH CKPL
SWRST USPIEx* TXEPT
UCLKI
STC
UCLK
Clock Phase and Polarity
* See the device-specific data sheet for SFR locations.
USART Peripheral Interface, SPI Mode
18-3
USART Operation: SPI Mode
18.2 USART Operation: SPI Mode
In SPI mode, serial data is transmitted and received by multiple devices using
a shared clock provided by the master. An additional pin, STE, is provided as
to enable a device to receive and transmit data and is controlled by the master.
Three or four signals are used for SPI data exchange:
- SIMO
Slave in, master out
Master mode: SIMO is the data output line.
Slave mode: SIMO is the data input line.
- SOMI
Slave out, master in
Master mode: SOMI is the data input line.
Slave mode: SOMI is the data output line.
- UCLK
USART SPI clock
Master mode: UCLK is an output.
Slave mode: UCLK is an input.
- STE
Slave transmit enable. Used in 4-pin mode to allow multiple
masters on a single bus. Not used in 3-pin mode.
4-Pin master mode:
When STE is high, SIMO and UCLK operate normally.
When STE is low, SIMO and UCLK are set to the input direction.
4-pin slave mode:
When STE is high, RX/TX operation of the slave is disabled and
SOMI is forced to the input direction.
When STE is low, RX/TX operation of the slave is enabled and
SOMI operates normally.
18.2.1 USART Initialization and Reset
The USART is reset by a PUC or by the SWRST bit. After a PUC, the SWRST
bit is automatically set, keeping the USART in a reset condition. When set, the
SWRST bit resets the URXIEx, UTXIEx, URXIFGx, OE, and FE bits and sets
the UTXIFGx flag. The USPIEx bit is not altered by SWRST. Clearing SWRST
releases the USART for operation. See also chapter 17.
Note: Initializing or Reconfiguring the USART Module
The required USART initialization/reconfiguration process is:
1) Set SWRST (BIS.B #SWRST,&UxCTL)
2) Initialize all USART registers with SWRST=1 (including UxCTL)
3) Enable USART module via the MEx SFRs (USPIEx)
4) Clear SWRST via software (BIC.B
#SWRST,&UxCTL)
5) Enable interrupts (optional) via the IEx SFRs (URXIEx and/or UTXIEx)
Failure to follow this process may result in unpredictable USART behavior.
18-4
USART Peripheral Interface, SPI Mode
USART Operation: SPI Mode
18.2.2 Master Mode
Figure 18−2. USART Master and External Slave
MASTER
Receive Buffer UxRXBUF
SLAVE
SIMO
Transmit Buffer UxTXBUF
Receive Shift Register
MSB
SIMO
SPI Receive Buffer
Px.x
STE
STE
SS
Port.x
SOMI
Transmit Shift Register
LSB
MSB
LSB
UCLK
MSP430 USART
SOMI
Data Shift Register (DSR)
LSB
MSB
SCLK
COMMON SPI
Figure 18−2 shows the USART as a master in both 3-pin and 4-pin
configurations. The USART initiates a data transfer when data is moved to the
transmit data buffer UxTXBUF. The UxTXBUF data is moved to the TX shift
register when the TX shift register is empty, initiating data transfer on SIMO
starting with the most significant bit. Data on SOMI is shifted into the receive
shift register on the opposite clock edge, starting with the most significant bit.
When the character is received, the receive data is moved from the RX shift
register to the received data buffer UxRXBUF and the receive interrupt flag,
URXIFGx, is set, indicating the RX/TX operation is complete.
A set transmit interrupt flag, UTXIFGx, indicates that data has moved from
UxTXBUF to the TX shift register and UxTXBUF is ready for new data. It does
not indicate RX/TX completion. In master mode, the completion of an active
transmission is indicated by a set transmitter empty bit TXEPT = 1.
To receive data into the USART in master mode, data must be written to
UxTXBUF because receive and transmit operations operate concurrently.
Four-Pin SPI Master Mode
In 4-pin master mode, STE is used to prevent conflicts with another master.
The master operates normally when STE is high. When STE is low:
- SIMO and UCLK are set to inputs and no longer drive the bus
- The error bit FE is set indicating a communication integrity violation to be
handled by the user
A low STE signal does not reset the USART module. The STE input signal is
not used in 3-pin master mode.
USART Peripheral Interface, SPI Mode
18-5
USART Operation: SPI Mode
18.2.3 Slave Mode
Figure 18−3. USART Slave and External Master
MASTER
SIMO
SPI Receive Buffer
Transmit Buffer UxTXBUF
Data Shift Register DSR
MSB
SLAVE
SIMO
Px.x
STE
STE
SS
Port.x
SOMI
SOMI
LSB
SCLK
Receive Buffer UxRXBUF
Transmit Shift Register
Receive Shift Register
MSB
MSB
LSB
LSB
UCLK
COMMON SPI
MSP430 USART
Figure 18−3 shows the USART as a slave in both 3-pin and 4-pin
configurations. UCLK is used as the input for the SPI clock and must be
supplied by the external master. The data transfer rate is determined by this
clock and not by the internal baud rate generator. Data written to UxTXBUF
and moved to the TX shift register before the start of UCLK is transmitted on
SOMI. Data on SIMO is shifted into the receive shift register on the opposite
edge of UCLK and moved to UxRXBUF when the set number of bits are
received. When data is moved from the RX shift register to UxRXBUF, the
URXIFGx interrupt flag is set, indicating that data has been received. The
overrun error bit, OE, is set when the previously received data is not read from
UxRXBUF before new data is moved to UxRXBUF.
Four-Pin SPI Slave Mode
In 4-pin slave mode, STE is used by the slave to enable the transmit and
receive operations and is provided by the SPI master. When STE is low, the
slave operates normally. When STE is high:
- Any receive operation in progress on SIMO is halted
- SOMI is set to the input direction
A high STE signal does not reset the USART module. The STE input signal
is not used in 3-pin slave mode.
18-6
USART Peripheral Interface, SPI Mode
USART Operation: SPI Mode
18.2.4 SPI Enable
The SPI transmit/receive enable bit USPIEx enables or disables the USART
in SPI mode. When USPIEx = 0, the USART stops operation after the current
transfer completes, or immediately if no operation is active. A PUC or set
SWRST bit disables the USART immediately and any active transfer is
terminated.
Transmit Enable
When USPIEx = 0, any further write to UxTXBUF does not transmit. Data
written to UxTXBUF begin to transmit when USPIEx = 1 and the BRCLK
source is active. Figure 18−4 and Figure 18−5 show the transmit enable state
diagrams.
Figure 18−4. Master Mode Transmit Enable
USPIEx = 0
USPIEx = 1
Transmit
Disable
USPIEx = 0
No Data Written
to Transfer Buffer
Idle State
(Transmitter
Enabled)
SWRST
Transmission
Active
Handle Interrupt
Conditions
Character
Transmitted
USPIEx = 1
PUC
USPIEx = 0 And Last Buffer
Entry Is Transmitted
USPIEx = 1,
Data Written to
Transmit Buffer
Not Completed
USPIEx = 0
Figure 18−5. Slave Transmit Enable State Diagram
USPIEx = 0
USPIEx = 1
Transmit
Disable
USPIEx = 0
No Clock at UCLK
Idle State
(Transmitter
Enabled)
SWRST
USPIEx = 1
External Clock
Present
USPIEx = 1
PUC
Not Completed
Transmission
Active
Handle Interrupt
Conditions
Character
Transmitted
USPIEx = 0
USART Peripheral Interface, SPI Mode
18-7
USART Operation: SPI Mode
Receive Enable
The SPI receive enable state diagrams are shown in Figure 18−6 and
Figure 18−7. When USPIEx = 0, UCLK is disabled from shifting data into the
RX shift register.
Figure 18−6. SPI Master Receive-Enable State Diagram
No Data Written
to UxTXBUF
USPIEx = 0
USPIEx = 1
Receive
Disable
USPIEx = 0
Idle State
(Receiver
Enabled)
USPIEx = 1
Data Written
to UxTXBUF
Not Completed
Receiver
Collects
Character
Handle Interrupt
Conditions
Character
Received
SWRST
USPIEx = 1
PUC
USPIEx = 0
Figure 18−7. SPI Slave Receive-Enable State Diagram
No Clock at UCLK
USPIEx = 0
USPIEx = 1
Receive
Disable
USPIEx = 0
Idle State
(Receive
Enabled)
SWRST
External Clock
Present
USPIEx = 1
PUC
USPIEx = 0
18-8
USPIEx = 1
USART Peripheral Interface, SPI Mode
Not Completed
Receiver
Collects
Character
Handle Interrupt
Conditions
Character
Received
USART Operation: SPI Mode
18.2.5 Serial Clock Control
UCLK is provided by the master on the SPI bus. When MM = 1, BITCLK is
provided by the USART baud rate generator on the UCLK pin as shown in
Figure 18−8. When MM = 0, the USART clock is provided on the UCLK pin by
the master and, the baud rate generator is not used and the SSELx bits are
“don’t care”. The SPI receiver and transmitter operate in parallel and use the
same clock source for data transfer.
Figure 18−8. SPI Baud Rate Generator
SSEL1 SSEL0 N = 215
28
...
27
UxBR1
UCLKI
00
ACLK
01
SMCLK
10
SMCLK
11
20
...
UxBR0
8
8
BRCLK
16−Bit Counter
Q15
............
R
Q0
Toggle
FF
R
Compare (0 or 1)
BITCLK
Modulation Data Shift Register R
(LSB first)
mX
m7
8
UxMCTL
m0
Bit Start
The 16-bit value of UxBR0+UxBR1 is the division factor of the USART clock
source, BRCLK. The maximum baud rate that can be generated in master
mode is BRCLK/2. The maximum baud rate that can be generated in slave
mode is BRCLK The modulator in the USART baud rate generator is not used
for SPI mode and is recommended to be set to 000h. The UCLK frequency is
given by:
Baud rate = BRCLK with UxBR= [UxBR1, UxBR0]
UxBR
USART Peripheral Interface, SPI Mode
18-9
USART Operation: SPI Mode
Serial Clock Polarity and Phase
The polarity and phase of UCLK are independently configured via the CKPL
and CKPH control bits of the USART. Timing for each case is shown in
Figure 18−9.
Figure 18−9. USART SPI Timing
CKPH CKPL
Cycle#
0
0
UCLK
0
1
UCLK
1
0
UCLK
1
1
UCLK
1
2
3
4
5
6
7
8
STE
0
X
SIMO/
SOMI
MSB
LSB
1
X
SIMO/
SOMI
MSB
LSB
Move to UxTXBUF
TX Data Shifted Out
RX Sample Points
18-10
USART Peripheral Interface, SPI Mode
USART Operation: SPI Mode
18.2.6 SPI Interrupts
The USART has one interrupt vector for transmission and one interrupt vector
for reception.
SPI Transmit Interrupt Operation
The UTXIFGx interrupt flag is set by the transmitter to indicate that UxTXBUF
is ready to accept another character. An interrupt request is generated if
UTXIEx and GIE are also set. UTXIFGx is automatically reset if the interrupt
request is serviced or if a character is written to UxTXBUF.
UTXIFGx is set after a PUC or when SWRST = 1. UTXIEx is reset after a PUC
or when SWRST = 1. The operation is shown is Figure 18−10.
Figure 18−10. Transmit Interrupt Operation
Q
UTXIEx
SYNC = 1
Clear
PUC or SWRST
VCC
Character Moved From
Buffer to Shift Register
D
Set UTXIFGx
Q
Clear
Interrupt Service Requested
SWRST
Data moved to UxTXBUF
IRQA
Note: Writing to UxTXBUF in SPI Mode
Data written to UxTXBUF when UTXIFGx = 0 and USPIEx = 1 may result in
erroneous data transmission.
USART Peripheral Interface, SPI Mode
18-11
USART Operation: SPI Mode
SPI Receive Interrupt Operation
The URXIFGx interrupt flag is set each time a character is received and loaded
into UxRXBUF as shown in Figure 18−11 and Figure 18−12. An interrupt
request is generated if URXIEx and GIE are also set. URXIFGx and URXIEx
are reset by a system reset PUC signal or when SWRST = 1. URXIFGx is
automatically reset if the pending interrupt is served or when UxRXBUF is
read.
Figure 18−11.Receive Interrupt Operation
SYNC
Valid Start Bit
SYNC = 1
URXS
Receiver Collects Character
URXSE
τ
From URXD
Clear
URXIEx
PE
FE
BRK
Interrupt Service
Requested
(S)
URXEIE
URXIFGx
URXWIE
Clear
RXWAKE
SWRST
PUC
UxRXBUF Read
URXSE
Character Received
IRQA
Figure 18−12. Receive Interrupt State Diagram
SWRST = 1
URXIFGx = 0
URXIEx = 0
Wait For Next
Start
Receive
Character
Receive
Character
Completed
USPIEx = 0
SWRST = 1
USPIEx = 0
PUC
USPIEx = 1
URXIFGx = 1
Priority
Too
Low
18-12
USART Peripheral Interface, SPI Mode
GIE = 0
USPIEx = 1 and
URXIEx = 1 and
GIE = 1 and
Priority Valid
Interrupt
Service Started,
GIE = 0
URXIFGx = 0
USART Registers: SPI Mode
18.3 USART Registers: SPI Mode
Table 18−1 lists the registers for all devices implementing a USART module.
Table 18−2 applies only to devices with a second USART module, USART1.
Table 18−1.USART0 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USART control register
U0CTL
Read/write
070h
001h with PUC
Transmit control register
U0TCTL
Read/write
071h
001h with PUC
Receive control register
U0RCTL
Read/write
072h
000h with PUC
Modulation control register
U0MCTL
Read/write
073h
Unchanged
Baud rate control register 0
U0BR0
Read/write
074h
Unchanged
Baud rate control register 1
U0BR1
Read/write
075h
Unchanged
Receive buffer register
U0RXBUF
Read
076h
Unchanged
Transmit buffer register
U0TXBUF
Read/write
077h
Unchanged
SFR module enable register 1
ME1
Read/write
004h
000h with PUC
SFR interrupt enable register 1
IE1
Read/write
000h
000h with PUC
SFR interrupt flag register 1
IFG1
Read/write
002h
082h with PUC
Table 18−2.USART1 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USART control register
U1CTL
Read/write
078h
001h with PUC
Transmit control register
U1TCTL
Read/write
079h
001h with PUC
Receive control register
U1RCTL
Read/write
07Ah
000h with PUC
Modulation control register
U1MCTL
Read/write
07Bh
Unchanged
Baud rate control register 0
U1BR0
Read/write
07Ch
Unchanged
Baud rate control register 1
U1BR1
Read/write
07Dh
Unchanged
Receive buffer register
U1RXBUF
Read
07Eh
Unchanged
Transmit buffer register
U1TXBUF
Read/write
07Fh
Unchanged
SFR module enable register 2
ME2
Read/write
005h
000h with PUC
SFR interrupt enable register 2
IE2
Read/write
001h
000h with PUC
SFR interrupt flag register 2
IFG2
Read/write
003h
020h with PUC
Note: Modifying the SFR bits
To avoid modifying control bits for other modules, it is recommended to set
or clear the IEx and IFGx bits using BIS.B or BIC.B instructions, rather than
MOV.B or CLR.B instructions.
USART Peripheral Interface, SPI Mode
18-13
USART Registers: SPI Mode
UxCTL, USART Control Register
†
7
6
5
4
3
2
1
0
Unused
Unused
I2C†
CHAR
LISTEN
SYNC
MM
SWRST
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−1
Unused
Bits
7−6
Unused
I2C†
Bit 5
I2C mode enable. This bit selects I2C or SPI operation when SYNC = 1.
0
SPI mode
1
I2C mode
CHAR
Bit 4
Character length
0
7-bit data
1
8-bit data
LISTEN
Bit 3
Listen enable. The LISTEN bit selects the loopback mode
0
Disabled
1
Enabled. The transmit signal is internally fed back to the receiver
SYNC
Bit 2
Synchronous mode enable
0
UART mode
1
SPI mode
MM
Bit 1
Master mode
0
USART is slave
1
USART is master
SWRST
Bit 0
Software reset enable
0
Disabled. USART reset released for operation
1
Enabled. USART logic held in reset state
Not implemented in 4xx devices.
18-14
USART Peripheral Interface, SPI Mode
USART Registers: SPI Mode
UxTCTL, USART Transmit Control Register
7
6
CKPH
CKPL
rw−0
rw−0
5
4
SSELx
rw−0
rw−0
3
2
1
0
Unused
Unused
STC
TXEPT
rw−0
rw−0
rw−0
rw−1
CKPH
Bit 7
Clock phase select.
0
Data is changed on the first UCLK edge and captured on the
following edge.
1
Data is captured on the first UCLK edge and changed on the
following edge.
CKPL
Bit 6
Clock polarity select
0
The inactive state is low.
1
The inactive state is high.
SSELx
Bits
5-4
Source select. These bits select the BRCLK source clock.
00 External UCLK (valid for slave mode only)
01 ACLK (valid for master mode only)
10 SMCLK (valid for master mode only)
11 SMCLK (valid for master mode only)
Unused
Bit 3
Unused
Unused
Bit 2
Unused
STC
Bit 1
Slave transmit control.
0
4-pin SPI mode: STE enabled.
1
3-pin SPI mode: STE disabled.
TXEPT
Bit 0
Transmitter empty flag. The TXEPT flag is not used in slave mode.
0
Transmission active and/or data waiting in UxTXBUF
1
UxTXBUF and TX shift register are empty
USART Peripheral Interface, SPI Mode
18-15
USART Registers: SPI Mode
UxRCTL, USART Receive Control Register
7
6
5
4
3
2
1
0
FE
Unused
OE
Unused
Unused
Unused
Unused
Unused
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
FE
Bit 7
Framing error flag. This bit indicates a bus conflict when MM = 1 and
STC = 0. FE is unused in slave mode.
0
No conflict detected
1
A negative edge occurred on STE, indicating bus conflict
Undefined
Bit 6
Unused
OE
Bit 5
Overrun error flag. This bit is set when a character is transferred into
UxRXBUF before the previous character was read. OE is automatically
reset when UxRXBUF is read, when SWRST = 1, or can be reset by
software.
0
No error
1
Overrun error occurred
Unused
Bit 4
Unused
Unused
Bit 3
Unused
Unused
Bit 2
Unused
Unused
Bit 1
Unused
Unused
Bit 0
Unused
18-16
USART Peripheral Interface, SPI Mode
USART Registers: SPI Mode
UxBR0, USART Baud Rate Control Register 0
7
6
5
4
3
2
1
0
27
26
25
24
23
22
21
20
rw
rw
rw
rw
rw
rw
rw
rw
UxBR1, USART Baud Rate Control Register 1
7
6
5
4
3
2
1
0
215
214
213
212
211
210
29
28
rw
rw
rw
rw
rw
rw
rw
rw
UxBRx
The baud-rate generator uses the content of {UxBR1+UxBR0} to set the
baud rate. Unpredictable SPI operation occurs if UxBR < 2.
UxMCTL, USART Modulation Control Register
7
6
5
4
3
2
1
0
m7
m6
m5
m4
m3
m2
m1
m0
rw
rw
rw
rw
rw
rw
rw
rw
UxMCTLx
Bits
7−0
The modulation control register is not used for SPI mode and should be set
to 000h.
USART Peripheral Interface, SPI Mode
18-17
USART Registers: SPI Mode
UxRXBUF, USART Receive Buffer Register
7
6
5
4
3
2
1
0
27
26
25
24
23
22
21
20
r
r
r
r
r
r
r
r
UxRXBUFx
Bits
7−0
The receive-data buffer is user accessible and contains the last received
character from the receive shift register. Reading UxRXBUF resets the OE
bit and URXIFGx flag. In 7-bit data mode, UxRXBUF is LSB justified and
the MSB is always reset.
UxTXBUF, USART Transmit Buffer Register
7
6
5
4
3
2
1
0
27
26
25
24
23
22
21
20
rw
rw
rw
rw
rw
rw
rw
rw
UxTXBUFx
18-18
Bits
7−0
The transmit data buffer is user accessible and contains current data to be
transmitted. When seven-bit character-length is used, the data should be
MSB justified before being moved into UxTXBUF. Data is transmitted MSB
first. Writing to UxTXBUF clears UTXIFGx.
USART Peripheral Interface, SPI Mode
USART Registers: SPI Mode
ME1, Module Enable Register 1
7
6
5
4
3
2
1
0
USPIE0
rw−0
USPIE0
Bit 7
This bit may be used by other modules. See device-specific data sheet.
Bit 6
USART0 SPI enable. This bit enables the SPI mode for USART0.
0
Module not enabled
1
Module enabled
Bits
5-0
These bits may be used by other modules. See device-specific data sheet.
ME2, Module Enable Register 2
7
6
5
4
3
2
1
0
USPIE1
rw−0
USPIE1
Bits
7-5
These bits may be used by other modules. See device-specific data sheet.
Bit 4
USART1 SPI enable. This bit enables the SPI mode for USART1.
0
Module not enabled
1
Module enabled
Bits
3-0
These bits may be used by other modules. See device-specific data sheet.
USART Peripheral Interface, SPI Mode
18-19
USART Registers: SPI Mode
IE1, Interrupt Enable Register 1
7
6
UTXIE0
URXIE0
rw−0
rw−0
5
4
3
2
1
0
UTXIE0
Bit 7
USART0 transmit interrupt enable. This bit enables the UTXIFG0 interrupt.
0
Interrupt not enabled
1
Interrupt enabled
URXIE0
Bit 6
USART0 receive interrupt enable. This bit enables the URXIFG0 interrupt.
0
Interrupt not enabled
1
Interrupt enabled
Bits
5-0
These bits may be used by other modules. See device-specific data sheet.
IE2, Interrupt Enable Register 2
7
6
5
4
UTXIE1
URXIE1
rw−0
rw−0
3
2
1
0
Bits
7-6
These bits may be used by other modules. See device-specific data sheet.
UTXIE1
Bit 5
USART1 transmit interrupt enable. This bit enables the UTXIFG1 interrupt.
0
Interrupt not enabled
1
Interrupt enabled
URXIE1
Bit 4
USART1 receive interrupt enable. This bit enables the URXIFG1 interrupt.
0
Interrupt not enabled
1
Interrupt enabled
Bits
3-0
These bits may be used by other modules. See device-specific data sheet.
18-20
USART Peripheral Interface, SPI Mode
USART Registers: SPI Mode
IFG1, Interrupt Flag Register 1
7
6
UTXIFG0
URXIFG0
rw−1
rw−0
5
4
3
2
1
0
UTXIFG0
Bit 7
USART0 transmit interrupt flag. UTXIFG0 is set when U0TXBUF is empty.
0
No interrupt pending
1
Interrupt pending
URXIFG0
Bit 6
USART0 receive interrupt flag. URXIFG0 is set when U0RXBUF has received
a complete character.
0
No interrupt pending
1
Interrupt pending
Bits
5-0
These bits may be used by other modules. See device-specific data sheet.
IFG2, Interrupt Flag Register 2
7
6
5
4
UTXIFG1
URXIFG1
rw−1
rw−0
3
2
1
0
Bits
7-6
These bits may be used by other modules. See device-specific data sheet.
UTXIFG1
Bit 5
USART1 transmit interrupt flag. UTXIFG1 is set when U1TXBUF is empty.
0
No interrupt pending
1
Interrupt pending
URXIFG1
Bit 4
USART1 receive interrupt flag. URXIFG1 is set when U1RXBUF has received
a complete character.
0
No interrupt pending
1
Interrupt pending
Bits
3-0
These bits may be used by other modules. See device-specific data sheet.
USART Peripheral Interface, SPI Mode
18-21
18-22
USART Peripheral Interface, SPI Mode
Chapter 19
Universal Serial Communication Interface,
UART Mode
The universal serial communication interface (USCI) supports multiple serial
communication modes with one hardware module. This chapter discusses the
operation of the asynchronous UART mode.
Topic
Page
19.1 USCI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-2
19.2 USCI Introduction: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-3
19.3 USCI Operation: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-5
19.4 USCI Registers: UART Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-27
Universal Serial Communication Interface, UART Mode
19-1
USCI Overview
19.1 USCI Overview
The universal serial communication interface (USCI) modules support
multiple serial communication modes. Different USCI modules support
different modes. Each different USCI module is named with a different letter.
For example, USCI_A is different from USCI_B, etc. If more than one identical
USCI module is implemented on one device, those modules are named with
incrementing numbers. For example, if one device has two USCI_A modules,
they are named USCI_A0 and USCI_A1. See the device-specific data sheet
to determine which USCI modules, if any, are implemented on which devices.
The USCI_Ax modules support:
-
UART mode
Pulse shaping for IrDA communications
Automatic baud rate detection for LIN communications
SPI mode
The USCI_Bx modules support:
- I2C mode
- SPI mode
19-2
Universal Serial Communication Interface, UART Mode
USCI Introduction: UART Mode
19.2 USCI Introduction: UART Mode
In asynchronous mode, the USCI_Ax modules connect the MSP430 to an
external system via two external pins, UCAxRXD and UCAxTXD. UART mode
is selected when the UCSYNC bit is cleared.
UART mode features include:
- 7- or 8-bit data with odd, even, or non-parity
- Independent transmit and receive shift registers
- Separate transmit and receive buffer registers
- LSB-first or MSB-first data transmit and receive
- Built-in
idle-line and
multiprocessor systems
address-bit
communication
protocols
for
- Receiver start-edge detection for auto-wake up from LPMx modes
- Programmable baud rate with modulation for fractional baud rate support
- Status flags for error detection and suppression
- Status flags for address detection
- Independent interrupt capability for receive and transmit
Figure 19−1 shows the USCI_Ax when configured for UART mode.
Universal Serial Communication Interface, UART Mode
19-3
USCI Introduction: UART Mode
Figure 19−1. USCI_Ax Block Diagram: UART Mode (UCSYNC = 0)
UCMODEx
UCSPB
UCDORM
UCRXEIE
Set Flags
UCRXERR
UCPE
UCFE
UCOE
Set RXIFG
Set UC0RXIFG
Error Flags
UCRXBRKIE
2
Receive State Machine
Set UCBRK
Set UCADDR/UCIDLE
Receive Buffer UC0RXBUF
Receive Shift Register
UCPEN UCPAR
UCIRRXPL
UCIRRXFLx
UCIRRXFE
UCIREN
6
UCLISTEN
1
IrDA Decoder
0
UC0RX
1
0
0
1
UCMSB UC7BIT
UCABEN
UCSSELx
Receive Baudrate Generator
UC0BRx
UC0CLK
00
ACLK
01
SMCLK
10
SMCLK
11
16
BRCLK
Prescaler/Divider
Receive Clock
Modulator
Transmit Clock
4
3
UCBRFx UCBRSx UCOS16
UCPEN UCPAR
UCIREN
UCMSB UC7BIT
Transmit Shift Register
0
1
IrDA Encoder
Transmit Buffer UC0TXBUF
6
UCIRTXPLx
Transmit State Machine
Set UC0TXIFG
UCTXBRK
UCTXADDR
2
UCMODEx
19-4
UCSPB
Universal Serial Communication Interface, UART Mode
UC0TX
USCI Operation: UART Mode
19.3 USCI Operation: UART Mode
In UART mode, the USCI transmits and receives characters at a bit rate
asynchronous to another device. Timing for each character is based on the
selected baud rate of the USCI. The transmit and receive functions use the
same baud rate frequency.
19.3.1 USCI Initialization and Reset
The USCI is reset by a PUC or by setting the UCSWRST bit. After a PUC, the
UCSWRST bit is automatically set, keeping the USCI in a reset condition.
When set, the UCSWRST bit resets the UCAxRXIE, UCAxTXIE, UCAxRXIFG,
UCRXERR, UCBRK, UCPE, UCOE, UCFE, UCSTOE and UCBTOE bits and
sets the UCAxTXIFG bit. Clearing UCSWRST releases the USCI for
operation.
Note: Initializing or Re-Configuring the USCI Module
The recommended USCI initialization/re-configuration process is:
1) Set UCSWRST (BIS.B #UCSWRST,&UCAxCTL1)
2) Initialize all USCI registers with UCSWRST = 1 (including UCAxCTL1)
3) Configure ports.
4) Clear UCSWRST via software (BIC.B
#UCSWRST,&UCAxCTL1)
5) Enable interrupts (optional) via UCAxRXIE and/or UCAxTXIE
19.3.2 Character Format
The UART character format, shown in Figure 19−2, consists of a start bit,
seven or eight data bits, an even/odd/no parity bit, an address bit (address-bit
mode), and one or two stop bits. The UCMSB bit controls the direction of the
transfer and selects LSB or MSB first. LSB-first is typically required for UART
communication.
Figure 19−2. Character Format
Mark
ST
D0
D6
D7 AD PA
SP SP
Space
[2nd Stop Bit, UCSPB = 1]
[Parity Bit, UCPEN = 1]
[Address Bit, UCMODEx = 10]
[Optional Bit, Condition]
[8th Data Bit, UC7BIT = 0]
Universal Serial Communication Interface, UART Mode
19-5
USCI Operation: UART Mode
19.3.3 Asynchronous Communication Formats
When two devices communicate asynchronously, no multiprocessor format is
required for the protocol. When three or more devices communicate, the USCI
supports the idle-line and address-bit multiprocessor communication formats.
Idle-Line Multiprocessor Format
When UCMODEx = 01, the idle-line multiprocessor format is selected. Blocks
of data are separated by an idle time on the transmit or receive lines as shown
in Figure 19−3. An idle receive line is detected when 10 or more continuous
ones (marks) are received after the one or two stop bits of a character. The
baud rate generator is switched off after reception of an idle line until the next
start edge is detected. When an idle line is detected the UCIDLE bit is set. The
UCIDLE bit is reset by software or by reading the UCAxRXBUF.
The first character received after an idle period is an address character. The
UCIDLE bit is used as an address tag for each block of characters. In idle-line
multiprocessor format, this bit is set when a received character is an address.
Figure 19−3. Idle-Line Format
Blocks of
Characters
UCAxTXD/RXD
Idle Periods of 10 Bits or More
UCAxTXD/RXD Expanded
UCAxTXD/RXD
ST
Address
SP ST
First Character Within Block
Is Address. It Follows Idle
Period of 10 Bits or More
19-6
Data
SP
Character Within Block
ST
Character Within Block
Idle Period Less Than 10 Bits
Universal Serial Communication Interface, UART Mode
Data
SP
USCI Operation: UART Mode
The UCDORM bit is used to control data reception in the idle-line
multiprocessor format. When UCDORM = 1, all non-address characters are
assembled but not transferred into the UCAxRXBUF, and interrupts are not
generated. When an address character is received, the character is
transferred into UCAxRXBUF, UCAxRXIFG is set, and any applicable error
flag is set when UCRXEIE = 1. When UCRXEIE = 0 and an address character
is received but has a framing error or parity error, the character is not
transferred into UCAxRXBUF and UCAxRXIFG is not set.
If an address is received, user software can validate the address and must
reset UCDORM to continue receiving data. If UCDORM remains set, only
address characters will be received. When UCDORM is cleared during the
reception of a character the receive interrupt flag will be set after the reception
completed. The UCDORM bit is not modified by the USCI hardware
automatically.
For address transmission in idle-line multiprocessor format, a precise idle
period can be generated by the USCI to generate address character identifiers
on UCAxTXD. The double-buffered UCTXADDR flag indicates if the next
character loaded into UCAxTXBUF is preceded by an idle line of 11 bits.
UCTXADDR is automatically cleared when the start bit is generated.
Transmitting an Idle Frame
The following procedure sends out an idle frame to indicate an address
character followed by associated data:
1) Set UCTXADDR, then write the address character to UCAxTXBUF.
UCAxTXBUF must be ready for new data (UCAxTXIFG = 1).
This generates an idle period of exactly 11 bits followed by the address
character. UCTXADDR is reset automatically when the address character
is transferred from UCAxTXBUF into the shift register.
2) Write desired data characters to UCAxTXBUF. UCAxTXBUF must be
ready for new data (UCAxTXIFG = 1).
The data written to UCAxTXBUF is transferred to the shift register and
transmitted as soon as the shift register is ready for new data.
The idle-line time must not be exceeded between address and data
transmission or between data transmissions. Otherwise, the transmitted
data will be misinterpreted as an address.
Universal Serial Communication Interface, UART Mode
19-7
USCI Operation: UART Mode
Address-Bit Multiprocessor Format
When UCMODEx = 10, the address-bit multiprocessor format is selected.
Each processed character contains an extra bit used as an address indicator
shown in Figure 19−4. The first character in a block of characters carries a set
address bit which indicates that the character is an address. The USCI
UCADDR bit is set when a received character has its address bit set and is
transferred to UCAxRXBUF. The UCADDR bit is reset by software or by
reading the UCAxRXBUF.
The UCDORM bit is used to control data reception in the address-bit
multiprocessor format. When UCDORM is set, data characters with address
bit = 0 are assembled by the receiver but are not transferred to UCAxRXBUF
and no interrupts are generated. When a character containing a set address
bit is received, the character is transferred into UCAxRXBUF, UCAxRXIFG is
set, and any applicable error flag is set when UCRXEIE = 1. When UCRXEIE
= 0 and a character containing a set address bit is received, but has a framing
error or parity error, the character is not transferred into UCAxRXBUF and
UCAxRXIFG is not set.
If an address is received, user software can validate the address and must
reset UCDORM to continue receiving data. If UCDORM remains set, only
address characters with address bit = 1 will be received. The UCDORM bit is
not modified by the USCI hardware automatically.
When UCDORM = 0 all received characters will set the receive interrupt flag
UCAxRXIFG. If UCDORM is cleared during the reception of a character the
receive interrupt flag will be set after the reception is completed.
For address transmission in address-bit multiprocessor mode, the address bit
of a character is controlled by the UCTXADDR bit. The value of the
UCTXADDR bit is loaded into the address bit of the character transferred from
UCAxTXBUF to the transmit shift register. UCTXADDR is automatically
cleared when the start bit is generated.
19-8
Universal Serial Communication Interface, UART Mode
USCI Operation: UART Mode
Figure 19−4. Address-Bit Multiprocessor Format
Blocks of
Characters
UCAxTXD/UCAxRXD
Idle Periods of No Significance
UCAxTXD/UCAxRXD
Expanded
UCAxTXD/UCAxRXD
ST
Address
1 SP ST
First Character Within Block
Is an Address. AD Bit Is 1
Data
AD Bit Is 0 for
Data Within Block.
0
SP
ST
Data
0 SP
Idle Time Is of No Significance
Break Reception and Generation
When UCMODEx = 00, 01, or 10 the receiver detects a break when all data,
parity, and stop bits are low, regardless of the parity, address mode, or other
character settings. When a break is detected, the UCBRK bit is set. If the break
interrupt enable bit, UCBRKIE, is set, the receive interrupt flag UCAxRXIFG
will also be set. In this case, the value in UCAxRXBUF is 0h since all data bits
were zero.
To transmit a break set the UCTXBRK bit, then write 0h to UCAxTXBUF.
UCAxTXBUF must be ready for new data (UCAxTXIFG = 1). This generates
a break with all bits low. UCTXBRK is automatically cleared when the start bit
is generated.
Universal Serial Communication Interface, UART Mode
19-9
USCI Operation: UART Mode
19.3.4 Automatic Baud Rate Detection
When UCMODEx = 11 UART mode with automatic baud rate detection is
selected. For automatic baud rate detection, a data frame is preceded by a
synchronization sequence that consists of a break and a synch field. A break
is detected when 11 or more continuous zeros (spaces) are received. If the
length of the break exceeds 21 bit times the break timeout error flag UCBTOE
is set. The synch field follows the break as shown in Figure 19−5.
Figure 19−5. Auto Baud Rate Detection − Break/Synch Sequence
Delimiter
Break
Synch
For LIN conformance the character format should be set to 8 data bits, LSB
first, no parity and one stop bit. No address bit is available.
The synch field consists of the data 055h inside a byte field as shown in
Figure 19−6. The synchronization is based on the time measurement between
the first falling edge and the last falling edge of the pattern. The transmit baud
rate generator is used for the measurement if automatic baud rate detection
is enabled by setting UCABDEN. Otherwise, the pattern is received but not
measured. The result of the measurement is transferred into the baud rate
control registers UCAxBR0, UCAxBR1, and UCAxMCTL. If the length of the
synch field exceeds the measurable time the synch timeout error flag
UCSTOE is set.
Figure 19−6. Auto Baud Rate Detection − Synch Field
Synch
8 Bit Times
Start
0
Bit
1
2
3
4
5
6
7
Stop
Bit
The UCDORM bit is used to control data reception in this mode. When
UCDORM is set, all characters are received but not transferred into the
UCAxRXBUF, and interrupts are not generated. When a break/synch field is
detected the UCBRK flag is set. The character following the break/synch field
is transferred into UCAxRXBUF and the UCAxRXIFG interrupt flag is set. Any
applicable error flag is also set. If the UCBRKIE bit is set, reception of the
break/synch sets the UCAxRXIFG. The UCBRK bit is reset by user software
or by reading the receive buffer UCAxRXBUF.
19-10
Universal Serial Communication Interface, UART Mode
USCI Operation: UART Mode
When a break/synch field is received, user software must reset UCDORM to
continue receiving data. If UCDORM remains set, only the character after the
next reception of a break/synch field will be received. The UCDORM bit is not
modified by the USCI hardware automatically.
When UCDORM = 0 all received characters will set the receive interrupt flag
UCAxRXIFG. If UCDORM is cleared during the reception of a character the
receive interrupt flag will be set after the reception is complete.
The counter used to detect the baud rate is limited to 07FFFh (32767) counts.
This means the minimum baud rate detectable is 488 Baud in oversampling
mode and 30 Baud in low-frequency mode.
The automatic baud rate detection mode can be used in a full-duplex
communication system with some restrictions. The USCI can not transmit data
while receiving the break/sync field and if a 0h byte with framing error is
received any data transmitted during this time gets corrupted. The latter case
can be discovered by checking the received data and the UCFE bit.
Transmitting a Break/Synch Field
The following procedure transmits a break/synch field:
1) Set UCTXBRK with UMODEx = 11.
2) Write 055h to UCAxTXBUF. UCAxTXBUF must be ready for new data
(UCAxTXIFG = 1).
This generates a break field of 13 bits followed by a break delimiter and the
synch character. The length of the break delimiter is controlled with the
UCDELIMx bits. UCTXBRK is reset automatically when the synch
character is transferred from UCAxTXBUF into the shift register.
3) Write desired data characters to UCAxTXBUF. UCAxTXBUF must be
ready for new data (UCAxTXIFG = 1).
The data written to UCAxTXBUF is transferred to the shift register and
transmitted as soon as the shift register is ready for new data.
Universal Serial Communication Interface, UART Mode
19-11
USCI Operation: UART Mode
19.3.5 IrDA Encoding and Decoding
When UCIREN is set the IrDA encoder and decoder are enabled and provide
hardware bit shaping for IrDA communication.
IrDA Encoding
The encoder sends a pulse for every zero bit in the transmit bit stream coming
from the UART as shown in Figure 19−7. The pulse duration is defined by
UCIRTXPLx bits specifying the number of half clock periods of the clock
selected by UCIRTXCLK.
Figure 19−7. UART vs. IrDA Data Format
Start
Bit
Data Bits
Stop
Bit
UART
IrDA
To set the pulse time of 3/16 bit period required by the IrDA standard the
BITCLK16 clock is selected with UCIRTXCLK = 1 and the pulse length is set
to 6 half clock cycles with UCIRTXPLx = 6 − 1 = 5.
When UCIRTXCLK = 0, the pulse length tPULSE is based on BRCLK and is
calculated as follows:
UCIRTXPLx + t PULSE
2
f BRCLK * 1
When the pulse length is based on BRCLK the prescaler UCBRx must to be
set to a value greater or equal to 5.
IrDA Decoding
The decoder detects high pulses when UCIRRXPL = 0. Otherwise it detects
low pulses. In addition to the analog deglitch filter an additional programmable
digital filter stage can be enabled by setting UCIRRXFE. When UCIRRXFE is
set, only pulses longer than the programmed filter length are passed. Shorter
pulses are discarded. The equation to program the filter length UCIRRXFLx
is:
UCIRRXFLx + (t PULSE * t WAKE)
2
f BRCLK * 4
where:
19-12
tPULSE:
Minimum receive pulse width
tWAKE:
Wake time from any low power mode. Zero when
MSP430 is in active mode.
Universal Serial Communication Interface, UART Mode
USCI Operation: UART Mode
19.3.6 Automatic Error Detection
Glitch suppression prevents the USCI from being accidentally started. Any
pulse on UCAxRXD shorter than the deglitch time tτ (approximately 150 ns)
will be ignored. See the device-specific data sheet for parameters.
When a low period on UCAxRXD exceeds tτ a majority vote is taken for the
start bit. If the majority vote fails to detect a valid start bit the USCI halts
character reception and waits for the next low period on UCAxRXD. The
majority vote is also used for each bit in a character to prevent bit errors.
The USCI module automatically detects framing errors, parity errors, overrun
errors, and break conditions when receiving characters. The bits UCFE,
UCPE, UCOE, and UCBRK are set when their respective condition is
detected. When the error flags UCFE, UCPE or UCOE are set, UCRXERR is
also set. The error conditions are described in Table 19−1.
Table 19−1.Receive Error Conditions
Error Condition
Framing error
Error
Flag
UCFE
Parity error
UCPE
Receive overrun
UCOE
Break condition
UCBRK
Description
A framing error occurs when a low stop bit is
detected. When two stop bits are used, both
stop bits are checked for framing error. When a
framing error is detected, the UCFE bit is set.
A parity error is a mismatch between the
number of 1s in a character and the value of
the parity bit. When an address bit is included
in the character, it is included in the parity
calculation. When a parity error is detected, the
UCPE bit is set.
An overrun error occurs when a character is
loaded into UCAxRXBUF before the prior
character has been read. When an overrun
occurs, the UCOE bit is set.
When not using automatic baud rate detection,
a break is detected when all data, parity, and
stop bits are low. When a break condition is
detected, the UCBRK bit is set. A break
condition can also set the interrupt flag
UCAxRXIFG if the break interrupt enable
UCBRKIE bit is set.
When UCRXEIE = 0 and a framing error, or parity error is detected, no
character is received into UCAxRXBUF. When UCRXEIE = 1, characters are
received into UCAxRXBUF and any applicable error bit is set.
When UCFE, UCPE, UCOE, UCBRK, or UCRXERR is set, the bit remains set
until user software resets it or UCAxRXBUF is read. UCOE must be reset by
reading UCAxRXBUF. Otherwise it will not function properly. To detect
overflows reliably the following flow is recommended. After a character was
received and UCAxRXIFG is set, first read UCAxSTAT to check the error flags
including the overflow flag UCOE. Read UCAxRXBUF next. This will clear all
Universal Serial Communication Interface, UART Mode
19-13
USCI Operation: UART Mode
error flags except UCOE if UCAxRXBUF was overwritten between the read
access to UCAxSTAT and to UCAxRXBUF. So the UCOE flag should be
checked after reading UCAxRXBUF to detect this condition. Note, in this case
the UCRXERR flag is not set.
19.3.7 USCI Receive Enable
The USCI module is enabled by clearing the UCSWRST bit and the receiver
is ready and in an idle state. The receive baud rate generator is in a ready state
but is not clocked nor producing any clocks.
The falling edge of the start bit enables the baud rate generator and the UART
state machine checks for a valid start bit. If no valid start bit is detected the
UART state machine returns to its idle state and the baud rate generator is
turned off again. If a valid start bit is detected a character will be received.
When the idle-line multiprocessor mode is selected with UCMODEx = 01 the
UART state machine checks for an idle line after receiving a character. If a start
bit is detected another character is received. Otherwise the UCIDLE flag is set
after 10 ones are received and the UART state machine returns to its idle state
and the baud rate generator is turned off.
19.3.8 Receive Data Glitch Suppression
Glitch suppression prevents the USCI from being accidentally started. Any
glitch on UCAxRXD shorter than the deglitch time tτ (approximately 150 ns)
will be ignored by the USCI and further action will be initiated as shown in
Figure 19−8. See the device-specific data sheet for parameters.
Figure 19−8. Glitch Suppression, USCI Receive Not Started
URXDx
URXS
tτ
When a glitch is longer than tτ, or a valid start bit occurs on UCAxRXD, the
USCI receive operation is started and a majority vote is taken as shown in
Figure 19−9. If the majority vote fails to detect a start bit the USCI halts
character reception.
19-14
Universal Serial Communication Interface, UART Mode
USCI Operation: UART Mode
Figure 19−9. Glitch Suppression, USCI Activated
Majority Vote Taken
URXDx
URXS
tτ
19.3.9 USCI Transmit Enable
The USCI module is enabled by clearing the UCSWRST bit and the transmitter
is ready and in an idle state. The transmit baud rate generator is ready but is
not clocked nor producing any clocks.
A transmission is initiated by writing data to UCAxTXBUF. When this occurs,
the baud rate generator is enabled and the data in UCAxTXBUF is moved to
the transmit shift register on the next BITCLK after the transmit shift register
is empty. UCAxTXIFG is set when new data can be written into UCAxTXBUF.
Transmission continues as long as new data is available in UCAxTXBUF at the
end of the previous byte transmission. If new data is not in UCAxTXBUF when
the previous byte has transmitted, the transmitter returns to its idle state and
the baud rate generator is turned off.
19.3.10 UART Baud Rate Generation
The USCI baud rate generator is capable of producing standard baud rates
from non-standard source frequencies. It provides two modes of operation
selected by the UCOS16 bit.
Low-Frequency Baud Rate Generation
The low-frequency mode is selected when UCOS16 = 0. This mode allows
generation of baud rates from low frequency clock sources (e.g. 9600 baud
from a 32768Hz crystal). By using a lower input frequency the power
consumption of the module is reduced. Using this mode with higher
frequencies and higher prescaler settings will cause the majority votes to be
taken in an increasingly smaller window and thus decrease the benefit of the
majority vote.
In low-frequency mode the baud rate generator uses one prescaler and one
modulator to generate bit clock timing. This combination supports fractional
divisors for baud rate generation. In this mode, the maximum USCI baud rate
is one-third the UART source clock frequency BRCLK.
Timing for each bit is shown in Figure 19−10. For each bit received, a majority
vote is taken to determine the bit value. These samples occur at the N/2 − 1/2,
N/2, and N/2 + 1/2 BRCLK periods, where N is the number of BRCLKs per
BITCLK.
Universal Serial Communication Interface, UART Mode
19-15
USCI Operation: UART Mode
Figure 19−10. BITCLK Baud Rate Timing with UCOS16 = 0
Majority Vote:
(m= 0)
(m= 1)
Bit Start
BRCLK
Counter
N/2
N/2−1 N/2−2
1
N/2
1
0
N/2−1 N/2−2
N/2
N/2−1
1
N/2
N/2−1
1
0
N/2
BITCLK
NEVEN: INT(N/2)
INT(N/2) + m(= 0)
NODD : INT(N/2) + R(= 1)
INT(N/2) + m(= 1)
Bit Period
m: corresponding modulation bit
R: Remainder from N/2 division
Modulation is based on the UCBRSx setting as shown in Table 19−2. A 1 in
the table indicates that m = 1 and the corresponding BITCLK period is one
BRCLK period longer than a BITCLK period with m = 0. The modulation wraps
around after 8 bits but restarts with each new start bit.
Table 19−2.BITCLK Modulation Pattern
UCBRSx
Bit 0
(Start Bit)
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
0
0
0
0
0
0
0
0
0
1
0
1
0
0
0
0
0
0
2
0
1
0
0
0
1
0
0
3
0
1
0
1
0
1
0
0
4
0
1
0
1
0
1
0
1
5
0
1
1
1
0
1
0
1
6
0
1
1
1
0
1
1
1
7
0
1
1
1
1
1
1
1
Oversampling Baud Rate Generation
The oversampling mode is selected when UCOS16 = 1. This mode supports
sampling a UART bit stream with higher input clock frequencies. This results
in majority votes that are always 1/16 of a bit clock period apart. This mode also
easily supports IrDA pulses with a 3/16 bit-time when the IrDA encoder and
decoder are enabled.
This mode uses one prescaler and one modulator to generate the BITCLK16
clock that is 16 times faster than the BITCLK. An additional divider and
modulator stage generates BITCLK from BITCLK16. This combination
supports fractional divisions of both BITCLK16 and BITCLK for baud rate
19-16
Universal Serial Communication Interface, UART Mode
USCI Operation: UART Mode
generation. In this mode, the maximum USCI baud rate is 1/16 the UART
source clock frequency BRCLK. When UCBRx is set to 0 or 1 the first prescaler
and modulator stage is bypassed and BRCLK is equal to BITCLK16.
Modulation for BITCLK16 is based on the UCBRFx setting as shown in
Table 19−3. A 1 in the table indicates that the corresponding BITCLK16 period
is one BRCLK period longer than the periods m=0. The modulation restarts
with each new bit timing.
Modulation for BITCLK is based on the UCBRSx setting as shown in
Table 19−2 as previously described.
Table 19−3.BITCLK16 Modulation Pattern
Number of BITCLK16 Clocks After Last Falling BITCLK Edge
UCBRFx
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
00h
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
01h
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
02h
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
1
03h
0
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
04h
0
1
1
0
0
0
0
0
0
0
0
0
0
0
1
1
05h
0
1
1
1
0
0
0
0
0
0
0
0
0
0
1
1
06h
0
1
1
1
0
0
0
0
0
0
0
0
0
1
1
1
07h
0
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
08h
0
1
1
1
1
0
0
0
0
0
0
0
1
1
1
1
09h
0
1
1
1
1
1
0
0
0
0
0
0
1
1
1
1
0Ah
0
1
1
1
1
1
0
0
0
0
0
1
1
1
1
1
0Bh
0
1
1
1
1
1
1
0
0
0
0
1
1
1
1
1
0Ch
0
1
1
1
1
1
1
0
0
0
1
1
1
1
1
1
0Dh
0
1
1
1
1
1
1
1
0
0
1
1
1
1
1
1
0Eh
0
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
0Fh
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Universal Serial Communication Interface, UART Mode
19-17
USCI Operation: UART Mode
19.3.11 Setting a Baud Rate
For a given BRCLK clock source, the baud rate used determines the required
division factor N:
N+
f BRCLK
Baudrate
The division factor N is often a non-integer value thus at least one divider and
one modulator stage is used to meet the factor as closely as possible.
If N is equal or greater than 16 the oversampling baud rate generation mode
can be chosen by setting UCOS16.
Low-Frequency Baud Rate Mode Setting
In the low-frequency mode, the integer portion of the divisor is realized by the
prescaler:
UCBRx = INT(N)
and the fractional portion is realized by the modulator with the following
nominal formula:
UCBRSx = round( ( N − INT(N) ) × 8 )
Incrementing or decrementing the UCBRSx setting by one count may give a
lower maximum bit error for any given bit. To determine if this is the case, a
detailed error calculation must be performed for each bit for each UCBRSx
setting.
Oversampling Baud Rate Mode Setting
In the oversampling mode the prescaler is set to:
UCBRx = INT(N/16).
and the first stage modulator is set to:
UCBRFx = round( ( (N/16) − INT(N/16) ) × 16 )
When greater accuracy is required, the UCBRSx modulator can also be
implemented with values from 0 − 7. To find the setting that gives the lowest
maximum bit error rate for any given bit, a detailed error calculation must be
performed for all settings of UCBRSx from 0 − 7 with the initial UCBRFx setting
and with the UCBRFx setting incremented and decremented by one.
19-18
Universal Serial Communication Interface, UART Mode
USCI Operation: UART Mode
19.3.12 Transmit Bit Timing
The timing for each character is the sum of the individual bit timings. Using the
modulation features of the baud rate generator reduces the cumulative bit
error. The individual bit error can be calculated using the following steps.
Low−Frequency Baud Rate Mode Bit Timing
In low-frequency mode, calculate the length of bit i Tbit,TX[i] based on the
UCBRx and UCBRSx settings:
T bit,TX[i] +
1 ǒUCBRx ) m
Ǔ
UCBRSx[i]
f BRCLK
where:
m UCBRSx[i]:
Modulation of bit i from Table 19−2
Oversampling Baud Rate Mode Bit Timing
In oversampling baud rate mode calculate the length of bit i Tbit,TX[i] based on
the baud rate generator UCBRx, UCBRFx and UCBRSx settings:
T bit,TX[i] +
f BRCLK
ǒ
[j]:
Sum of ones from the corresponding row in Table 19−3
1
ǒ16 ) m UCBRSx[i]Ǔ @ UCBRx )
ȍm
15
j+0
UCBRFx
Ǔ
[j]
where:
ȍm
15
UCBRFx
j+0
m UCBRSx[i]:
Modulation of bit i from Table 19−2
This results in an end-of-bit time tbit,TX[i] equal to the sum of all previous and
the current bit times:
ȍT
i
t bit,TX[i] +
bit,TX
[j]
j+0
To calculate bit error, this time is compared to the ideal bit time tbit,ideal,TX[i]:
t bit,ideal,TX[i] +
1
(i ) 1)
Baudrate
This results in an error normalized to one ideal bit time (1/baudrate):
Error TX[i] + ǒt bit,TX[i] * t bit,ideal,TX[i]Ǔ @ Baudrate @ 100%
Universal Serial Communication Interface, UART Mode
19-19
USCI Operation: UART Mode
19.3.13 Receive Bit Timing
Receive timing error consists of two error sources. The first is the bit-to-bit
timing error similar to the transmit bit timing error. The second is the error
between a start edge occurring and the start edge being accepted by the USCI
module. Figure 19−11 shows the asynchronous timing errors between data on
the UCAxRXD pin and the internal baud-rate clock. This results in an additional
synchronization error. The synchronization error tSYNC is between
−0.5 BRCLKs and +0.5 BRCLKs, independent of the selected baud rate
generation mode.
Figure 19−11.Receive Error
0
i
tideal
2
1
t0
t1
1 2 3 4 5 6 7 8
9 10 11 12 13 14 1 2 3 4 5 6 7 8
9 10 11 12 13 14 1 2 3 4 5 6 7
BRCLK
UCAxRXD
ST
D0
D1
RXD synch.
ST
D0
D1
tactual
t0
Synchronization Error ± 0.5x BRCLK
t1
t2
Sample
RXD synch.
Majority Vote Taken
Majority Vote Taken
Majority Vote Taken
The ideal sampling time t bit,ideal,RX[i] is in the middle of a bit period:
t bit,ideal,RX[i] +
1
(i ) 0.5)
Baudrate
The real sampling time t bit,RX[i] is equal to the sum of all previous bits according
to the formulas shown in the transmit timing section, plus one half BITCLK for
the current bit i, plus the synchronization error tSYNC.
This results in the following t bit,RX[i] for the low-frequency baud rate mode
ȍT
i*1
t bit,RX[i] + t SYNC )
j+0
bit,RX
[j] )
ǒ
where:
T bit,RX[i] +
m UCBRSx[i]:
19-20
Ǔ
1
INT(1 UCBRx) ) m UCBRSx[i]
2
f BRCLK
1 ǒUCBRx ) m
Ǔ
UCBRSx[i]
f BRCLK
Modulation of bit i from Table 19−2
Universal Serial Communication Interface, UART Mode
USCI Operation: UART Mode
For the oversampling baud rate mode the sampling time t bit,RX[i] of bit i is
calculated by:
ȍT
i*1
t bit,RX[i] + t SYNC )
)
1
f BRCLK
ǒ
where:
T bit,RX[i] +
7)m
ȍ
UCBRSx
1
f BRCLK
bit,RX
[j]
Ǔ
j+0
7)m
ǒ8 ) m UCBRSx[i]Ǔ @ UCBRx )
ǒ
ȍ
UCBRSx
[i]
m UCBRFx[j]
j+0
ǒ16 ) m UCBRSx[i]Ǔ @ UCBRx )
ȍm
15
UCBRFx
Ǔ
[j]
j+0
[i]
m UCBRFx[j]:
Sum of ones from columns 0 − 7 ) m UCBRSx[i]
j+0
from the corresponding row in Table 19−3
m UCBRSx[i]:
Modulation of bit i from Table 19−2
This results in an error normalized to one ideal bit time (1/baudrate) according
to the following formula:
Error RX[i] + ǒt bit,RX[i] * t bit,ideal,RX[i]Ǔ @ Baudrate @ 100%
19.3.14 Typical Baud Rates and Errors
Standard baud rate data for UCBRx, UCBRSx and UCBRFx are listed in
Table 19−4 and Table 19−5 for a 32,768 Hz crystal sourcing ACLK and typical
SMCLK frequencies. Please ensure that the selected BRCLK frequency does
not exceed the device specific maximum USCI input frequency. Please refer
to the device-specific data sheet.
The receive error is the accumulated time versus the ideal scanning time in the
middle of each bit. The worst case error is given for the reception of an 8-bit
character with parity and one stop bit including synchronization error.
The transmit error is the accumulated timing error versus the ideal time of the
bit period. The worst case error is given for the transmission of an 8-bit
character with parity and stop bit.
Universal Serial Communication Interface, UART Mode
19-21
USCI Operation: UART Mode
Table 19−4.Commonly Used Baud Rates, Settings, and Errors, UCOS16 = 0
BRCLK
Frequency
[Hz]
Baud
Rate
[Baud]
UCBRx
UCBRSx
UCBRFx
32,768
1200
27
2
0
32,768
2400
13
6
32,768
4800
6
7
32,768
9600
3
3
1,000,000
9600
104
1,000,000
19200
52
1,000,000
38400
26
1,000,000
57600
17
1,000,000
115200
8
1,048,576
9600
109
1,048,576
19200
54
1,048,576
38400
27
1,048,576
57600
18
1,048,576
115200
9
4,000,000
9600
416
4,000,000
19200
4,000,000
38400
Max TX Error [%]
Max RX Error [%]
−2.8
1.4
−5.9
0
−4.8
6.0
−9.7
8.3
0
−12.1
5.7
−13.4
19.0
0
−21.1
15.2
−44.3
21.3
1
0
−0.5
0.6
−0.9
1.2
0
0
−1.8
0
−2.6
0.9
0
0
−1.8
0
−3.6
1.8
3
0
−2.1
4.8
−6.8
5.8
6
0
−7.8
6.4
−9.7
16.1
2
0
−0.2
0.7
−1.0
0.8
5
0
−1.1
1.0
−1.5
2.5
2
0
−2.8
1.4
−5.9
2.0
1
0
−4.6
3.3
−6.8
6.6
1
0
−1.1
10.7
−11.5
11.3
6
0
−0.2
0.2
−0.2
0.4
208
3
0
−0.2
0.5
−0.3
0.8
104
1
0
−0.5
0.6
−0.9
1.2
2.0
4,000,000
57600
69
4
0
−0.6
0.8
−1.8
1.1
4,000,000
115200
34
6
0
−2.1
0.6
−2.5
3.1
4,000,000
230400
17
3
0
−2.1
4.8
−6.8
5.8
8,000,000
9600
833
2
0
−0.1
0
−0.2
0.1
8,000,000
19200
416
6
0
−0.2
0.2
−0.2
0.4
8,000,000
38400
208
3
0
−0.2
0.5
−0.3
0.8
8,000,000
57600
138
7
0
−0.7
0
−0.8
0.6
8,000,000
115200
69
4
0
−0.6
0.8
−1.8
1.1
8,000,000
230400
34
6
0
−2.1
0.6
−2.5
3.1
8,000,000
460800
17
3
0
−2.1
4.8
−6.8
5.8
12,000,000
9600
1250
0
0
0
0
−0.05
0.05
12,000,000
19200
625
0
0
0
0
−0.2
0
12,000,000
38400
312
4
0
−0.2
0
−0.2
0.2
12,000,000
57600
208
2
0
−0.5
0.2
−0.6
0.5
12,000,000
115200
104
1
0
−0.5
0.6
−0.9
1.2
12,000,000
230400
52
0
0
−1.8
0
−2.6
0.9
12,000,000
460800
26
0
0
−1.8
0
−3.6
1.8
19-22
Universal Serial Communication Interface, UART Mode
USCI Operation: UART Mode
Table 19−4.Commonly Used Baud Rates, Settings, and Errors, UCOS16 = 0 (Continued)
BRCLK
Frequency
[Hz]
Baud
Rate
[Baud]
UCBRx
UCBRSx
UCBRFx
16,000,000
9600
1666
6
16,000,000
19200
833
16,000,000
38400
416
16,000,000
57600
16,000,000
16,000,000
16,000,000
460800
Max TX Error [%]
Max RX Error [%]
0
−0.05
0.05
−0.05
0.1
2
0
−0.1
0.05
−0.2
0.1
6
0
−0.2
0.2
−0.2
0.4
277
7
0
−0.3
0.3
−0.5
0.4
115200
138
7
0
−0.7
0
−0.8
0.6
230400
69
4
0
−0.6
0.8
−1.8
1.1
34
6
0
−2.1
0.6
−2.5
3.1
Universal Serial Communication Interface, UART Mode
19-23
USCI Operation: UART Mode
Table 19−5.Commonly Used Baud Rates, Settings, and Errors, UCOS16 = 1
BRCLK
frequency
[Hz]
Baud
Rate
[Baud]
UCBRx
UCBRSx
UCBRFx
1,000,000
9600
6
0
8
−1.8
0
−2.2
0.4
1,000,000
19200
3
0
4
−1.8
0
−2.6
0.9
1,048,576
9600
6
0
13
−2.3
0
−2.2
0.8
1,048,576
19200
3
1
6
−4.6
3.2
−5.0
4.7
4,000,000
9600
26
0
1
0
0.9
0
1.1
4,000,000
19200
13
0
0
−1.8
0
−1.9
0.2
4,000,000
38400
6
0
8
−1.8
0
−2.2
0.4
4,000,000
57600
4
5
3
−3.5
3.2
−1.8
6.4
4,000,000
115200
2
3
2
−2.1
4.8
−2.5
7.3
8,000,000
9600
52
0
1
−0.4
0
−0.4
0.1
8,000,000
19200
26
0
1
0
0.9
0
1.1
8,000,000
38400
13
0
0
−1.8
0
−1.9
0.2
8,000,000
57600
8
0
11
0
0.88
0
1.6
8,000,000
115200
4
5
3
−3.5
3.2
−1.8
6.4
8,000,000
230400
2
3
2
−2.1
4.8
−2.5
7.3
12,000,000
9600
78
0
2
0
0
−0.05
0.05
12,000,000
19200
39
0
1
0
0
0
0.2
12,000,000
38400
19
0
8
−1.8
0
−1.8
0.1
12,000,000
57600
13
0
0
−1.8
0
−1.9
0.2
12,000,000
115200
6
0
8
−1.8
0
−2.2
0.4
12,000,000
230400
3
0
4
−1.8
0
−2.6
0.9
16,000,000
9600
104
0
3
0
0.2
0
0.3
16,000,000
19200
52
0
1
−0.4
0
−0.4
0.1
16,000,000
38400
26
0
1
0
0.9
0
1.1
16,000,000
57600
17
0
6
0
0.9
−0.1
1.0
16,000,000
115200
8
0
11
0
0.9
0
1.6
16,000,000
230400
4
5
3
−3.5
3.2
−1.8
6.4
16,000,000
460800
2
3
2
−2.1
4.8
−2.5
7.3
19-24
Max. TX Error [%]
Universal Serial Communication Interface, UART Mode
Max. RX Error [%]
USCI Operation: UART Mode
19.3.15 Using the USCI Module in UART Mode with Low-Power Modes
The USCI module provides automatic clock activation for SMCLK for use with
low-power modes. When SMCLK is the USCI clock source, and is inactive
because the device is in a low-power mode, the USCI module automatically
activates it when needed, regardless of the control-bit settings for the clock
source. The clock remains active until the USCI module returns to its idle
condition. After the USCI module returns to the idle condition, control of the
clock source reverts to the settings of its control bits. Automatic clock activation
is not provided for ACLK.
When the USCI module activates an inactive clock source, the clock source
becomes active for the whole device and any peripheral configured to use the
clock source may be affected. For example, a timer using SMCLK will
increment while the USCI module forces SMCLK active.
19.3.16 USCI Interrupts
The USCI has one interrupt vector for transmission and one interrupt vector
for reception.
USCI Transmit Interrupt Operation
The UCAxTXIFG interrupt flag is set by the transmitter to indicate that
UCAxTXBUF is ready to accept another character. An interrupt request is
generated if UCAxTXIE and GIE are also set. UCAxTXIFG is automatically
reset if a character is written to UCAxTXBUF.
UCAxTXIFG is set after a PUC or when UCSWRST = 1. UCAxTXIE is reset
after a PUC or when UCSWRST = 1.
USCI Receive Interrupt Operation
The UCAxRXIFG interrupt flag is set each time a character is received and
loaded into UCAxRXBUF. An interrupt request is generated if UCAxRXIE and
GIE are also set. UCAxRXIFG and UCAxRXIE are reset by a system reset
PUC signal or when UCSWRST = 1. UCAxRXIFG is automatically reset when
UCAxRXBUF is read.
Additional interrupt control features include:
- When UCAxRXEIE = 0 erroneous characters will not set UCAxRXIFG.
- When UCDORM = 1, non-address characters will not set UCAxRXIFG in
multiprocessor modes. In plain UART mode no characters will set
UCAxRXIFG.
- When UCBRKIE = 1 a break condition will set the UCBRK bit and the
UCAxRXIFG flag.
Universal Serial Communication Interface, UART Mode
19-25
USCI Operation: UART Mode
USCI Interrupt Usage
USCI_Ax and USCI_Bx share the same interrupt vectors. The receive
interrupt flags UCAxRXIFG and UCBxRXIFG are routed to one interrupt
vector, the transmit interrupt flags UCAxTXIFG and UCBxTXIFG share
another interrupt vector.
Shared Interrupt Vectors Software Example
The following software example shows an extract of an interrupt service
routine to handle data receive interrupts from USCI_A0 in either UART or SPI
mode and USCI_B0 in SPI mode.
USCIA0_RX_USCIB0_RX_ISR
BIT.B #UCA0RXIFG, &IFG2 ; USCI_A0 Receive Interrupt?
JNZ
USCIA0_RX_ISR
USCIB0_RX_ISR?
; Read UCB0RXBUF (clears UCB0RXIFG)
...
RETI
USCIA0_RX_ISR
; Read UCA0RXBUF (clears UCA0RXIFG)
...
RETI
The following software example shows an extract of an interrupt service
routine to handle data transmit interrupts from USCI_A0 in either UART or SPI
mode and USCI_B0 in SPI mode.
USCIA0_TX_USCIB0_TX_ISR
BIT.B #UCA0TXIFG, &IFG2 ; USCI_A0 Transmit Interrupt?
JNZ
USCIA0_TX_ISR
USCIB0_TX_ISR
; Write UCB0TXBUF (clears UCB0TXIFG)
...
RETI
USCIA0_TX_ISR
; Write UCA0TXBUF (clears UCA0TXIFG)
...
RETI
19-26
Universal Serial Communication Interface, UART Mode
USCI Registers: UART Mode
19.4 USCI Registers: UART Mode
The USCI registers applicable in UART mode are listed in Table 19−6 and
Table 19−7.
Table 19−6.USCI_A0 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USCI_A0 control register 0
UCA0CTL0
Read/write
060h
Reset with PUC
USCI_A0 control register 1
UCA0CTL1
Read/write
061h
001h with PUC
USCI_A0 Baud rate control register 0
UCA0BR0
Read/write
062h
Reset with PUC
USCI_A0 Baud rate control register 1
UCA0BR1
Read/write
063h
Reset with PUC
USCI_A0 modulation control register
UCA0MCTL
Read/write
064h
Reset with PUC
USCI_A0 status register
UCA0STAT
Read/write
065h
Reset with PUC
USCI_A0 Receive buffer register
UCA0RXBUF
Read
066h
Reset with PUC
USCI_A0 Transmit buffer register
UCA0TXBUF
Read/write
067h
Reset with PUC
USCI_A0 Auto Baud control register
UCA0ABCTL
Read/write
05Dh
Reset with PUC
USCI_A0 IrDA Transmit control register
UCA0IRTCTL
Read/write
05Eh
Reset with PUC
USCI_A0 IrDA Receive control register
UCA0IRRCTL
Read/write
05Fh
Reset with PUC
SFR interrupt enable register 2
IE2
Read/write
001h
Reset with PUC
SFR interrupt flag register 2
IFG2
Read/write
003h
00Ah with PUC
Note: Modifying SFR bits
To avoid modifying control bits of other modules, it is recommended to set
or clear the IEx and IFGx bits using BIS.B or BIC.B instructions, rather than
MOV.B or CLR.B instructions.
Table 19−7.USCI_A1 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USCI_A1 control register 0
UCA1CTL0
Read/write
0D0h
Reset with PUC
USCI_A1 control register 1
UCA1CTL1
Read/write
0D1h
001h with PUC
USCI_A1 Baud rate control register 0
UCA1BR0
Read/write
0D2h
Reset with PUC
USCI_A1 Baud rate control register 1
UCA1BR1
Read/write
0D3h
Reset with PUC
USCI_A1 modulation control register
UCA1MCTL
Read/write
0D4h
Reset with PUC
USCI_A1 status register
UCA1STAT
Read/write
0D5h
Reset with PUC
USCI_A1 Receive buffer register
UCA1RXBUF
Read
0D6h
Reset with PUC
USCI_A1 Transmit buffer register
UCA1TXBUF
Read/write
0D7h
Reset with PUC
USCI_A1 Auto Baud control register
UCA1ABCTL
Read/write
0CDh
Reset with PUC
USCI_A1 IrDA Transmit control register
UCA1IRTCTL
Read/write
0CEh
Reset with PUC
USCI_A1 IrDA Receive control register
UCA1IRRCTL
Read/write
0CFh
Reset with PUC
USCI_A1/B1 interrupt enable register
UC1IE
Read/write
006h
Reset with PUC
USCI_A1/B1 interrupt flag register
UC1IFG
Read/write
007h
00Ah with PUC
Universal Serial Communication Interface, UART Mode
19-27
USCI Registers: UART Mode
UCAxCTL0, USCI_Ax Control Register 0
7
6
5
4
3
UCPEN
UCPAR
UCMSB
UC7BIT
UCSPB
rw−0
rw−0
rw−0
rw−0
rw−0
2
1
UCMODEx
rw−0
rw−0
0
UCSYNC=0
rw−0
UCPEN
Bit 7
Parity enable
0
Parity disabled.
1
Parity enabled. Parity bit is generated (UCAxTXD) and expected
(UCAxRXD). In address-bit multiprocessor mode, the address bit is
included in the parity calculation.
UCPAR
Bit 6
Parity select. UCPAR is not used when parity is disabled.
0
Odd parity
1
Even parity
UCMSB
Bit 5
MSB first select. Controls the direction of the receive and transmit shift
register.
0
LSB first
1
MSB first
UC7BIT
Bit 4
Character length. Selects 7-bit or 8-bit character length.
0
8-bit data
1
7-bit data
UCSPB
Bit 3
Stop bit select. Number of stop bits.
0
One stop bit
1
Two stop bits
UCMODEx
Bits
2−1
USCI mode. The UCMODEx bits select the asynchronous mode when
UCSYNC = 0.
00 UART Mode.
01 Idle-Line Multiprocessor Mode.
10 Address-Bit Multiprocessor Mode.
11 UART Mode with automatic baud rate detection.
UCSYNC
Bit 0
Synchronous mode enable
0
Asynchronous mode
1
Synchronous Mode
19-28
Universal Serial Communication Interface, UART Mode
USCI Registers: UART Mode
UCAxCTL1, USCI_Ax Control Register 1
7
6
UCSSELx
rw−0
rw−0
5
4
3
2
1
0
UCRXEIE
UCBRKIE
UCDORM
UCTXADDR
UCTXBRK
UCSWRST
rw−0
rw−0
rw−0
rw−0
rw−0
rw−1
UCSSELx
Bits
7-6
USCI clock source select. These bits select the BRCLK source clock.
00 UCLK
01 ACLK
10 SMCLK
11 SMCLK
UCRXEIE
Bit 5
Receive erroneous-character interrupt-enable
0
Erroneous characters rejected and UCAxRXIFG is not set
1
Erroneous characters received will set UCAxRXIFG
UCBRKIE
Bit 4
Receive break character interrupt-enable
0
Received break characters do not set UCAxRXIFG.
1
Received break characters set UCAxRXIFG.
UCDORM
Bit 3
Dormant. Puts USCI into sleep mode.
0
Not dormant. All received characters will set UCAxRXIFG.
1
Dormant. Only characters that are preceded by an idle-line or with
address bit set will set UCAxRXIFG. In UART mode with automatic baud
rate detection only the combination of a break and synch field will set
UCAxRXIFG.
UCTXADDR
Bit 2
Transmit address. Next frame to be transmitted will be marked as address
depending on the selected multiprocessor mode.
0
Next frame transmitted is data
1
Next frame transmitted is an address
UCTXBRK
Bit 1
Transmit break. Transmits a break with the next write to the transmit buffer.
In UART mode with automatic baud rate detection 055h must be written
into UCAxTXBUF to generate the required break/synch fields. Otherwise
0h must be written into the transmit buffer.
0
Next frame transmitted is not a break
1
Next frame transmitted is a break or a break/synch
UCSWRST
Bit 0
Software reset enable
0
Disabled. USCI reset released for operation.
1
Enabled. USCI logic held in reset state.
Universal Serial Communication Interface, UART Mode
19-29
USCI Registers: UART Mode
UCAxBR0, USCI_Ax Baud Rate Control Register 0
7
6
5
4
3
2
1
0
rw
rw
rw
2
1
0
rw
rw
rw
UCBRx − low byte
rw
rw
rw
rw
rw
UCAxBR1, USCI_Ax Baud Rate Control Register 1
7
6
5
4
3
UCBRx − high byte
rw
rw
UCBRx
rw
rw
rw
Clock prescaler setting of the Baud rate generator. The 16-bit value of
(UCAxBR0 + UCAxBR1 × 256) forms the prescaler value UCBRx.
UCAxMCTL, USCI_Ax Modulation Control Register
7
6
5
4
3
UCBRFx
rw−0
rw−0
2
1
UCBRSx
rw−0
rw−0
rw−0
rw−0
0
UCOS16
rw−0
rw−0
UCBRFx
Bits
7−4
First modulation stage select. These bits determine the modulation pattern
for BITCLK16 when UCOS16 = 1. Ignored with UCOS16 = 0. Table 19−3
shows the modulation pattern.
UCBRSx
Bits
3−1
Second modulation stage select. These bits determine the modulation
pattern for BITCLK. Table 19−2 shows the modulation pattern.
UCOS16
Bit 0
Oversampling mode enabled
0
Disabled
1
Enabled
19-30
Universal Serial Communication Interface, UART Mode
USCI Registers: UART Mode
UCAxSTAT, USCI_Ax Status Register
7
6
5
4
3
2
1
0
UCLISTEN
UCFE
UCOE
UCPE
UCBRK
UCRXERR
UCADDR
UCIDLE
UCBUSY
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
r−0
UCLISTEN
Bit 7
Listen enable. The UCLISTEN bit selects loopback mode.
0
Disabled
1
Enabled. UCAxTXD is internally fed back to the receiver.
UCFE
Bit 6
Framing error flag
0
No error
1
Character received with low stop bit
UCOE
Bit 5
Overrun error flag. This bit is set when a character is transferred into
UCAxRXBUF before the previous character was read. UCOE is cleared
automatically when UCxRXBUF is read, and must not be cleared by
software. Otherwise, it will not function correctly.
0
No error
1
Overrun error occurred
UCPE
Bit 4
Parity error flag. When UCPEN = 0, UCPE is read as 0.
0
No error
1
Character received with parity error
UCBRK
Bit 3
Break detect flag
0
No break condition
1
Break condition occurred
UCRXERR
Bit 2
Receive error flag. This bit indicates a character was received with error(s).
When UCRXERR = 1, on or more error flags (UCFE, UCPE, UCOE) is also
set. UCRXERR is cleared when UCAxRXBUF is read.
0
No receive errors detected
1
Receive error detected
UCADDR
Bit 1
Address received in address-bit multiprocessor mode.
0
Received character is data
1
Received character is an address
UCIDLE
UCBUSY
Idle line detected in idle-line multiprocessor mode.
0
No idle line detected
1
Idle line detected
Bit 0
USCI busy. This bit indicates if a transmit or receive operation is in
progress.
0
USCI inactive
1
USCI transmitting or receiving
Universal Serial Communication Interface, UART Mode
19-31
USCI Registers: UART Mode
UCAxRXBUF, USCI_Ax Receive Buffer Register
7
6
5
4
3
2
1
0
r
r
r
r
UCRXBUFx
r
r
UCRXBUFx
Bits
7−0
r
r
The receive-data buffer is user accessible and contains the last received
character from the receive shift register. Reading UCAxRXBUF resets the
receive-error bits, the UCADDR or UCIDLE bit, and UCAxRXIFG. In 7-bit
data mode, UCAxRXBUF is LSB justified and the MSB is always reset.
UCAxTXBUF, USCI_Ax Transmit Buffer Register
7
6
5
4
3
2
1
0
rw
rw
rw
rw
UCTXBUFx
rw
rw
UCTXBUFx
19-32
Bits
7−0
rw
rw
The transmit data buffer is user accessible and holds the data waiting to
be moved into the transmit shift register and transmitted on UCAxTXD.
Writing to the transmit data buffer clears UCAxTXIFG. The MSB of
UCAxTXBUF is not used for 7-bit data and is reset.
Universal Serial Communication Interface, UART Mode
USCI Registers: UART Mode
UCAxIRTCTL, USCI_Ax IrDA Transmit Control Register
7
6
5
4
3
2
UCIRTXPLx
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
1
0
UCIR
TXCLK
UCIREN
rw−0
rw−0
UCIRTXPLx
Bits
7−2
Transmit pulse length
Pulse Length tPULSE = (UCIRTXPLx + 1) / (2 × fIRTXCLK)
UCIRTXCLK
Bit 1
IrDA transmit pulse clock select
0
BRCLK
1
BITCLK16 when UCOS16 = 1. Otherwise, BRCLK
UCIREN
Bit 0
IrDA encoder/decoder enable.
0
IrDA encoder/decoder disabled
1
IrDA encoder/decoder enabled
UCAxIRRCTL, USCI_Ax IrDA Receive Control Register
7
6
5
4
3
2
UCIRRXFLx
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
1
0
UCIRRXPL
UCIRRXFE
rw−0
rw−0
UCIRRXFLx
Bits
7−2
Receive filter length. The minimum pulse length for receive is given by:
tMIN = (UCIRRXFLx + 4) / (2 × fBRCLK)
UCIRRXPL
Bit 1
IrDA receive input UCAxRXD polarity
0
IrDA transceiver delivers a high pulse when a light pulse is seen
1
IrDA transceiver delivers a low pulse when a light pulse is seen
UCIRRXFE
Bit 0
IrDA receive filter enabled
0
Receive filter disabled
1
Receive filter enabled
Universal Serial Communication Interface, UART Mode
19-33
USCI Registers: UART Mode
UCAxABCTL, USCI_Ax Auto Baud Rate Control Register
7
6
Reserved
r−0
5
4
UCDELIMx
r−0
rw−0
rw−0
3
2
1
0
UCSTOE
UCBTOE
Reserved
UCABDEN
rw−0
rw−0
r−0
rw−0
Reserved
Bits
7-6
Reserved
UCDELIMx
Bits
5−4
Break/synch delimiter length
00 1 bit time
01 2 bit times
10 3 bit times
11 4 bit times
UCSTOE
Bit 3
Synch field time out error
0
No error
1
Length of synch field exceeded measurable time.
UCBTOE
Bit 2
Break time out error
0
No error
1
Length of break field exceeded 22 bit times.
Reserved
Bit 1
Reserved
UCABDEN
Bit 0
Automatic baud rate detect enable
0
Baud rate detection disabled. Length of break and synch field is not
measured.
1
Baud rate detection enabled. Length of break and synch field is
measured and baud rate settings are changed accordingly.
19-34
Universal Serial Communication Interface, UART Mode
USCI Registers: UART Mode
IE2, Interrupt Enable Register 2
7
6
5
4
3
2
1
0
UCA0TXIE
UCA0RXIE
rw−0
rw−0
Bits
7-2
These bits may be used by other modules. See device-specific data sheet.
UCA0TXIE
Bit 1
USCI_A0 transmit interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCA0RXIE
Bit 0
USCI_A0 receive interrupt enable
0
Interrupt disabled
1
Interrupt enabled
IFG2, Interrupt Flag Register 2
7
6
5
4
3
2
1
0
UCA0
TXIFG
UCA0
RXIFG
rw−1
rw−0
Bits
7-2
These bits may be used by other modules (see the device-specific data
sheet).
UCA0
TXIFG
Bit 1
USCI_A0 transmit interrupt flag. UCA0TXIFG is set when UCA0TXBUF is
empty.
0
No interrupt pending
1
Interrupt pending
UCA0
RXIFG
Bit 0
USCI_A0 receive interrupt flag. UCA0RXIFG is set when UCA0RXBUF has
received a complete character.
0
No interrupt pending
1
Interrupt pending
Universal Serial Communication Interface, UART Mode
19-35
USCI Registers: UART Mode
UC1IE, USCI_A1 Interrupt Enable Register
7
6
5
4
Unused
Unused
Unused
rw−0
rw−0
rw−0
3
2
1
0
Unused
UCA1TXIE
UCA1RXIE
rw−0
rw−0
rw−0
Bits
7-4
Unused
Bits
3-2
These bits may be used by other USCI modules (see the device-specific data
sheet).
UCA1TXIE
Bit 1
USCI_A1 transmit interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCA1RXIE
Bit 0
USCI_A1 receive interrupt enable
0
Interrupt disabled
1
Interrupt enabled
Unused
UC1IFG, USCI_A1 Interrupt Flag Register
7
6
5
4
Unused
Unused
Unused
rw−0
rw−0
rw−0
3
2
1
0
Unused
UCA1
TXIFG
UCA1
RXIFG
rw−0
rw−1
rw−0
Bits
7-4
Unused
Bits
3-2
These bits may be used by other USCI modules (see the device-specific data
sheet).
UCA1
TXIFG
Bit 1
USCI_A1 transmit interrupt flag. UCA1TXIFG is set when UCA1TXBUF is
empty.
0
No interrupt pending
1
Interrupt pending
UCA1
RXIFG
Bit 0
USCI_A1 receive interrupt flag. UCA1RXIFG is set when UCA1RXBUF has
received a complete character.
0
No interrupt pending
1
Interrupt pending
Unused
19-36
Universal Serial Communication Interface, UART Mode
Chapter 20
Universal Serial Communication Interface,
SPI Mode
The universal serial communication interface (USCI) supports multiple serial
communication modes with one hardware module. This chapter discusses the
operation of the synchronous peripheral interface or SPI mode.
Topic
Page
20.1 USCI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-2
20.2 USCI Introduction: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-3
20.3 USCI Operation: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-5
20.4 USCI Registers: SPI Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-14
Universal Serial Communication Interface, SPI Mode
20-1
USCI Overview
20.1 USCI Overview
The universal serial communication interface (USCI) modules support
multiple serial communication modes. Different USCI modules support
different modes. Each different USCI module is named with a different letter.
For example, USCI_A is different from USCI_B, etc. If more than one identical
USCI module is implemented on one device, those modules are named with
incrementing numbers. For example, if one device has two USCI_A modules,
they are named USCI_A0 and USCI_A1. See the device-specific data sheet
to determine which USCI modules, if any, are implemented on which devices.
The USCI_Ax modules support:
-
UART mode
Pulse shaping for IrDA communications
Automatic baud rate detection for LIN communications
SPI mode
The USCI_Bx modules support:
- I2C mode
- SPI mode
20-2
Universal Serial Communication Interface, SPI Mode
USCI Introduction: SPI Mode
20.2 USCI Introduction: SPI Mode
In synchronous mode, the USCI connects the MSP430 to an external system
via three or four pins: UCxSIMO, UCxSOMI, UCxCLK, and UCxSTE. SPI
mode is selected when the UCSYNC bit is set and SPI mode (3-pin or 4-pin)
is selected with the UCMODEx bits.
SPI mode features include:
- 7- or 8-bit data length
- LSB-first or MSB-first data transmit and receive
- 3-pin and 4-pin SPI operation
- Master or slave modes
- Independent transmit and receive shift registers
- Separate transmit and receive buffer registers
- Continuous transmit and receive operation
- Selectable clock polarity and phase control
- Programmable clock frequency in master mode
- Independent interrupt capability for receive and transmit
- Slave operation in LPM4
Figure 20−1 shows the USCI when configured for SPI mode.
Universal Serial Communication Interface, SPI Mode
20-3
USCI Introduction: SPI Mode
Figure 20−1. USCI Block Diagram: SPI Mode
Receive State Machine
Set UCOE
Set UCxRXIFG
UCLISTEN
UCMST
Receive Buffer UCxRXBUF
UCxSOMI
0
Receive Shift Register
1
1
0
UCMSB UC7BIT
UCSSELx
Bit Clock Generator
UCCKPH UCCKPL
UCxBRx
N/A
00
ACLK
01
SMCLK
10
SMCLK
11
16
BRCLK
Prescaler/Divider
Clock Direction,
Phase and Polarity
UCxCLK
UCMSB UC7BIT
UCxSIMO
Transmit Shift Register
UCMODEx
2
Transmit Buffer UCxTXBUF
Transmit Enable
Control
UCxSTE
Set UCFE
Transmit State Machine
Set UCxTXIFG
20-4
Universal Serial Communication Interface, SPI Mode
USCI Operation: SPI Mode
20.3 USCI Operation: SPI Mode
In SPI mode, serial data is transmitted and received by multiple devices using
a shared clock provided by the master. An additional pin, UCxSTE, is provided
to enable a device to receive and transmit data and is controlled by the master.
Three or four signals are used for SPI data exchange:
- UCxSIMO
Slave in, master out
Master mode: UCxSIMO is the data output line.
Slave mode: UCxSIMO is the data input line.
- UCxSOMI
Slave out, master in
Master mode: UCxSOMI is the data input line.
Slave mode: UCxSOMI is the data output line.
- UCxCLK
USCI SPI clock
Master mode: UCxCLK is an output.
Slave mode: UCxCLK is an input.
- UCxSTE
Slave transmit enable. Used in 4-pin mode to allow multiple
masters on a single bus. Not used in 3-pin mode. Table 20−1
describes the UCxSTE operation.
Table 20−1.UCxSTE Operation
UCMODEx
UCxSTE Active State
01
high
10
low
UCxSTE
Slave
Master
0
inactive
active
1
active
inactive
0
active
inactive
1
inactive
active
Universal Serial Communication Interface, SPI Mode
20-5
USCI Operation: SPI Mode
20.3.1 USCI Initialization and Reset
The USCI is reset by a PUC or by the UCSWRST bit. After a PUC, the
UCSWRST bit is automatically set, keeping the USCI in a reset condition.
When set, the UCSWRST bit resets the UCxRXIE, UCxTXIE, UCxRXIFG,
UCOE, and UCFE bits and sets the UCxTXIFG flag. Clearing UCSWRST
releases the USCI for operation.
Note: Initializing or Re-Configuring the USCI Module
The recommended USCI initialization/re-configuration process is:
1) Set UCSWRST (BIS.B #UCSWRST,&UCxCTL1)
2) Initialize all USCI registers with UCSWRST=1 (including UCxCTL1)
3) Configure ports.
4) Clear UCSWRST via software (BIC.B
#UCSWRST,&UCxCTL1)
5) Enable interrupts (optional) via UCxRXIE and/or UCxTXIE
20.3.2 Character Format
The USCI module in SPI mode supports 7- and 8-bit character lengths
selected by the UC7BIT bit. In 7-bit data mode, UCxRXBUF is LSB justified
and the MSB is always reset. The UCMSB bit controls the direction of the
transfer and selects LSB or MSB first.
Note: Default Character Format
The default SPI character transmission is LSB first. For communication with
other SPI interfaces it MSB-first mode may be required.
Note: Character Format for Figures
Figures throughout this chapter use MSB first format.
20-6
Universal Serial Communication Interface, SPI Mode
USCI Operation: SPI Mode
20.3.3 Master Mode
Figure 20−2. USCI Master and External Slave
MASTER
Receive Buffer
UCxRXBUF
UCxSIMO
SLAVE
SIMO
Transmit Buffer
UCxTXBUF
SPI Receive Buffer
Px.x
UCxSTE
Receive Shift Register
Transmit Shift Register
UCx
SOMI
UCxCLK
MSP430 USCI
STE
SS
Port.x
SOMI
Data Shift Register (DSR)
SCLK
COMMON SPI
Figure 20−2 shows the USCI as a master in both 3-pin and 4-pin
configurations. The USCI initiates data transfer when data is moved to the
transmit data buffer UCxTXBUF. The UCxTXBUF data is moved to the TX shift
register when the TX shift register is empty, initiating data transfer on
UCxSIMO starting with either the most-significant or least-significant bit
depending on the UCMSB setting. Data on UCxSOMI is shifted into the receive
shift register on the opposite clock edge. When the character is received, the
receive data is moved from the RX shift register to the received data buffer
UCxRXBUF and the receive interrupt flag, UCxRXIFG, is set, indicating the
RX/TX operation is complete.
A set transmit interrupt flag, UCxTXIFG, indicates that data has moved from
UCxTXBUF to the TX shift register and UCxTXBUF is ready for new data. It
does not indicate RX/TX completion.
To receive data into the USCI in master mode, data must be written to
UCxTXBUF because receive and transmit operations operate concurrently.
Universal Serial Communication Interface, SPI Mode
20-7
USCI Operation: SPI Mode
Four-Pin SPI Master Mode
In 4-pin master mode, UCxSTE is used to prevent conflicts with another
master and controls the master as described in Table 20−1. When UCxSTE
is in the master-inactive state:
- UCxSIMO and UCxCLK are set to inputs and no longer drive the bus
- The error bit UCFE is set indicating a communication integrity violation to
be handled by the user.
- The internal state machines are reset and the shift operation is aborted.
If data is written into UCxTXBUF while the master is held inactive by UCxSTE,
it will be transmit as soon as UCxSTE transitions to the master-active state.
If an active transfer is aborted by UCxSTE transitioning to the master-inactive
state, the data must be re-written into UCxTXBUF to be transferred when
UCxSTE transitions back to the master-active state. The UCxSTE input signal
is not used in 3-pin master mode.
20-8
Universal Serial Communication Interface, SPI Mode
USCI Operation: SPI Mode
20.3.4 Slave Mode
Figure 20−3. USCI Slave and External Master
MASTER
SIMO
SLAVE
UCxSIMO
Transmit Buffer
UCxTXBUF
Receive Buffer
UCxRXBUF
Transmit Shift Register
Receive Shift Register
SPI Receive Buffer
Data Shift Register DSR
Px.x
UCxSTE
STE
SS
Port.x
SOMI
SCLK
UCx
SOMI
UCxCLK
COMMON SPI
MSP430 USCI
Figure 20−3 shows the USCI as a slave in both 3-pin and 4-pin configurations.
UCxCLK is used as the input for the SPI clock and must be supplied by the
external master. The data-transfer rate is determined by this clock and not by
the internal bit clock generator. Data written to UCxTXBUF and moved to the
TX shift register before the start of UCxCLK is transmitted on UCxSOMI. Data
on UCxSIMO is shifted into the receive shift register on the opposite edge of
UCxCLK and moved to UCxRXBUF when the set number of bits are received.
When data is moved from the RX shift register to UCxRXBUF, the UCxRXIFG
interrupt flag is set, indicating that data has been received. The overrun error
bit, UCOE, is set when the previously received data is not read from
UCxRXBUF before new data is moved to UCxRXBUF.
Four-Pin SPI Slave Mode
In 4-pin slave mode, UCxSTE is used by the slave to enable the transmit and
receive operations and is provided by the SPI master. When UCxSTE is in the
slave-active state, the slave operates normally. When UCxSTE is in the
slave-inactive state:
- Any receive operation in progress on UCxSIMO is halted
- UCxSOMI is set to the input direction
- The shift operation is halted until the UCxSTE line transitions into the slave
transmit active state.
The UCxSTE input signal is not used in 3-pin slave mode.
Universal Serial Communication Interface, SPI Mode
20-9
USCI Operation: SPI Mode
20.3.5 SPI Enable
When the USCI module is enabled by clearing the UCSWRST bit it is ready
to receive and transmit. In master mode the bit clock generator is ready, but
is not clocked nor producing any clocks. In slave mode the bit clock generator
is disabled and the clock is provided by the master.
A transmit or receive operation is indicated by UCBUSY = 1. The UCBUSY
flag is set by writing UCxTXBUF in master mode and in slave mode with
UCCKPH=1. In slave mode with UCCKPH=0 UCBUSY is set with the first
UCLK edge. UCBUSY is reset by the following conditions:
- In master mode when transfer completed and UCxTXBUF empty.
- In slave mode with UCCKPH=0 when transfer completed.
- In slave mode with UCCKPH=1 when transfer completed and UCxTXBUF
empty.
A PUC or set UCSWRST bit disables the USCI immediately and any active
transfer is terminated.
Transmit Enable
In master mode, writing to UCxTXBUF activates the bit clock generator and
the data will begin to transmit.
In slave mode, transmission begins when a master provides a clock and, in
4-pin mode, when the UCxSTE is in the slave-active state.
Receive Enable
The SPI receives data when a transmission is active. Receive and transmit
operations operate concurrently.
20-10
Universal Serial Communication Interface, SPI Mode
USCI Operation: SPI Mode
20.3.6 Serial Clock Control
UCxCLK is provided by the master on the SPI bus. When UCMST = 1, the bit
clock is provided by the USCI bit clock generator on the UCxCLK pin. The clock
used to generate the bit clock is selected with the UCSSELx bits. When
UCMST = 0, the USCI clock is provided on the UCxCLK pin by the master, the
bit clock generator is not used, and the UCSSELx bits are don’t care. The SPI
receiver and transmitter operate in parallel and use the same clock source for
data transfer.
The 16-bit value of UCBRx in the bit rate control registers UCxxBR1 and
UCxxBR0 is the division factor of the USCI clock source, BRCLK. The
maximum bit clock that can be generated in master mode is BRCLK.
Modulation is not used in SPI mode and UCAxMCTL should be cleared when
using SPI mode for USCI_A. The UCAxCLK/UCBxCLK frequency is given by:
f
f BitClock + BRCLK
UCBRx
Serial Clock Polarity and Phase
The polarity and phase of UCxCLK are independently configured via the
UCCKPL and UCCKPH control bits of the USCI. Timing for each case is shown
in Figure 20−4.
Figure 20−4. USCI SPI Timing with UCMSB = 1
UC
UC
CKPH CKPL
Cycle#
0
0
UCxCLK
0
1
UCxCLK
1
0
UCxCLK
1
1
UCxCLK
1
2
3
4
5
6
7
8
UCxSTE
0
X
UCxSIMO/
UCxSOMI
MSB
LSB
1
X
UCxSIMO
UCxSOMI
MSB
LSB
Move to UCxTXBUF
TX Data Shifted Out
RX Sample Points
Universal Serial Communication Interface, SPI Mode
20-11
USCI Operation: SPI Mode
20.3.7 Using the SPI Mode with Low Power Modes
The USCI module provides automatic clock activation for SMCLK for use with
low-power modes. When SMCLK is the USCI clock source, and is inactive
because the device is in a low-power mode, the USCI module automatically
activates it when needed, regardless of the control-bit settings for the clock
source. The clock remains active until the USCI module returns to its idle
condition. After the USCI module returns to the idle condition, control of the
clock source reverts to the settings of its control bits. Automatic clock activation
is not provided for ACLK.
When the USCI module activates an inactive clock source, the clock source
becomes active for the whole device and any peripheral configured to use the
clock source may be affected. For example, a timer using SMCLK will
increment while the USCI module forces SMCLK active.
In SPI slave mode no internal clock source is required because the clock is
provided by the external master. It is possible to operate the USCI in SPI slave
mode while the device is in LPM4 and all clock sources are disabled. The
receive or transmit interrupt can wake up the CPU from any low power mode.
20.3.8 SPI Interrupts
The USCI has one interrupt vector for transmission and one interrupt vector
for reception.
SPI Transmit Interrupt Operation
The UCxTXIFG interrupt flag is set by the transmitter to indicate that
UCxTXBUF is ready to accept another character. An interrupt request is
generated if UCxTXIE and GIE are also set. UCxTXIFG is automatically reset
if a character is written to UCxTXBUF. UCxTXIFG is set after a PUC or when
UCSWRST = 1. UCxTXIE is reset after a PUC or when UCSWRST = 1.
Note: Writing to UCxTXBUF in SPI Mode
Data written to UCxTXBUF when UCxTXIFG = 0 may result in erroneous
data transmission.
SPI Receive Interrupt Operation
The UCxRXIFG interrupt flag is set each time a character is received and
loaded into UCxRXBUF. An interrupt request is generated if UCxRXIE and GIE
are also set. UCxRXIFG and UCxRXIE are reset by a system reset PUC signal
or when UCSWRST = 1. UCxRXIFG is automatically reset when UCxRXBUF
is read.
20-12
Universal Serial Communication Interface, SPI Mode
USCI Operation: SPI Mode
USCI Interrupt Usage
USCI_Ax and USCI_Bx share the same interrupt vectors. The receive
interrupt flags UCAxRXIFG and UCBxRXIFG are routed to one interrupt
vector, the transmit interrupt flags UCAxTXIFG and UCBxTXIFG share
another interrupt vector.
Shared Interrupt Vectors Software Example
The following software example shows an extract of an interrupt service
routine to handle data receive interrupts from USCI_A0 in either UART or SPI
mode and USCI_B0 in SPI mode.
USCIA0_RX_USCIB0_RX_ISR
BIT.B #UCA0RXIFG, &IFG2 ; USCI_A0 Receive Interrupt?
JNZ
USCIA0_RX_ISR
USCIB0_RX_ISR?
; Read UCB0RXBUF (clears UCB0RXIFG)
...
RETI
USCIA0_RX_ISR
; Read UCA0RXBUF (clears UCA0RXIFG)
...
RETI
The following software example shows an extract of an interrupt service
routine to handle data transmit interrupts from USCI_A0 in either UART or SPI
mode and USCI_B0 in SPI mode.
USCIA0_TX_USCIB0_TX_ISR
BIT.B #UCA0TXIFG, &IFG2 ; USCI_A0 Transmit Interrupt?
JNZ
USCIA0_TX_ISR
USCIB0_TX_ISR
; Write UCB0TXBUF (clears UCB0TXIFG)
...
RETI
USCIA0_TX_ISR
; Write UCA0TXBUF (clears UCA0TXIFG)
...
RETI
Universal Serial Communication Interface, SPI Mode
20-13
USCI Registers: SPI Mode
20.4 USCI Registers: SPI Mode
The USCI registers applicable in SPI mode for USCI_A0 and USCI_B0 are
listed in Table 20−2. Registers applicable in SPI mode for USCI_A1 and
USCI_B1 are listed in Table 20−3.
Table 20−2.USCI_A0 and USCI_B0 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USCI_A0 control register 0
UCA0CTL0
Read/write
060h
Reset with PUC
USCI_A0 control register 1
UCA0CTL1
Read/write
061h
001h with PUC
USCI_A0 Baud rate control register 0
UCA0BR0
Read/write
062h
Reset with PUC
USCI_A0 Baud rate control register 1
UCA0BR1
Read/write
063h
Reset with PUC
USCI_A0 modulation control register
UCA0MCTL
Read/write
064h
Reset with PUC
USCI_A0 status register
UCA0STAT
Read/write
065h
Reset with PUC
USCI_A0 Receive buffer register
UCA0RXBUF
Read
066h
Reset with PUC
USCI_A0 Transmit buffer register
UCA0TXBUF
Read/write
067h
Reset with PUC
USCI_B0 control register 0
UCB0CTL0
Read/write
068h
001h with PUC
USCI_B0 control register 1
UCB0CTL1
Read/write
069h
001h with PUC
USCI_B0 Bit rate control register 0
UCB0BR0
Read/write
06Ah
Reset with PUC
USCI_B0 Bit rate control register 1
UCB0BR1
Read/write
06Bh
Reset with PUC
USCI_B0 status register
UCB0STAT
Read/write
06Dh
Reset with PUC
USCI_B0 Receive buffer register
UCB0RXBUF
Read
06Eh
Reset with PUC
USCI_B0 Transmit buffer register
UCB0TXBUF
Read/write
06Fh
Reset with PUC
SFR interrupt enable register 2
IE2
Read/write
001h
Reset with PUC
SFR interrupt flag register 2
IFG2
Read/write
003h
00Ah with PUC
Note: Modifying SFR bits
To avoid modifying control bits of other modules, it is recommended to set
or clear the IEx and IFGx bits using BIS.B or BIC.B instructions, rather than
MOV.B or CLR.B instructions.
20-14
Universal Serial Communication Interface, SPI Mode
USCI Registers: SPI Mode
Table 20−3.USCI_A1 and USCI_B1 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USCI_A1 control register 0
UCA1CTL0
Read/write
0D0h
Reset with PUC
USCI_A1 control register 1
UCA1CTL1
Read/write
0D1h
001h with PUC
USCI_A1 Baud rate control register 0
UCA1BR0
Read/write
0D2h
Reset with PUC
USCI_A1 Baud rate control register 1
UCA1BR1
Read/write
0D3h
Reset with PUC
USCI_A1 modulation control register
UCA1MCTL
Read/write
0D4h
Reset with PUC
USCI_A1 status register
UCA1STAT
Read/write
0D5h
Reset with PUC
USCI_A1 Receive buffer register
UCA1RXBUF
Read
0D6h
Reset with PUC
USCI_A1 Transmit buffer register
UCA1TXBUF
Read/write
0D7h
Reset with PUC
USCI_B1 control register 0
UCB1CTL0
Read/write
0D8h
001h with PUC
USCI_B1 control register 1
UCB1CTL1
Read/write
0D9h
001h with PUC
USCI_B1 Bit rate control register 0
UCB1BR0
Read/write
0DAh
Reset with PUC
USCI_B1 Bit rate control register 1
UCB1BR1
Read/write
0DBh
Reset with PUC
USCI_B1 status register
UCB1STAT
Read/write
0DDh
Reset with PUC
USCI_B1 Receive buffer register
UCB1RXBUF
Read
0DEh
Reset with PUC
USCI_B1 Transmit buffer register
UCB1TXBUF
Read/write
0DFh
Reset with PUC
USCI_A1/B1 interrupt enable register
UC1IE
Read/write
006h
Reset with PUC
USCI_A1/B1 interrupt flag register
UC1IFG
Read/write
007h
00Ah with PUC
Universal Serial Communication Interface, SPI Mode
20-15
USCI Registers: SPI Mode
UCAxCTL0, USCI_Ax Control Register 0
UCBxCTL0, USCI_Bx Control Register 0
7
6
5
4
3
UCCKPH
UCCKPL
UCMSB
UC7BIT
UCMST
rw-0
rw-0
rw-0
rw-0
rw-0
2
1
UCMODEx
rw-0
0
UCSYNC=1
rw-0
rw-0
UCCKPH
Bit 7
Clock phase select.
0
Data is changed on the first UCLK edge and captured on the
following edge.
1
Data is captured on the first UCLK edge and changed on the
following edge.
UCCKPL
Bit 6
Clock polarity select.
0
The inactive state is low.
1
The inactive state is high.
UCMSB
Bit 5
MSB first select. Controls the direction of the receive and transmit shift
register.
0
LSB first
1
MSB first
UC7BIT
Bit 4
Character length. Selects 7-bit or 8-bit character length.
0
8-bit data
1
7-bit data
UCMST
Bit 3
Master mode select
0
Slave mode
1
Master mode
UCMODEx
Bits
2-1
USCI Mode. The UCMODEx bits select the synchronous mode when
UCSYNC = 1.
00 3-Pin SPI
01 4-Pin SPI with UCxSTE active high: slave enabled when UCxSTE = 1
10 4-Pin SPI with UCxSTE active low: slave enabled when UCxSTE = 0
11 I2C Mode
UCSYNC
Bit 0
Synchronous mode enable
0
Asynchronous mode
1
Synchronous Mode
20-16
Universal Serial Communication Interface, SPI Mode
USCI Registers: SPI Mode
UCAxCTL1, USCI_Ax Control Register 1
UCBxCTL1, USCI_Bx Control Register 1
7
6
5
4
UCSSELx
rw-0
†
‡
3
2
1
Unused
rw-0
rw-0†
r0‡
rw-0
rw-0
0
UCSWRST
rw-0
rw-0
rw-1
UCAxCTL1 (USCI_Ax)
UCBxCTL1 (USCI_Bx)
UCSSELx
Bits
7-6
USCI clock source select. These bits select the BRCLK source clock in
master mode. UCxCLK is always used in slave mode.
00 NA
01 ACLK
10 SMCLK
11 SMCLK
Unused
Bits
5-1
Unused in synchronous mode (UCSYNC=1).
UCSWRST
Bit 0
Software reset enable
0
Disabled. USCI reset released for operation.
1
Enabled. USCI logic held in reset state.
Universal Serial Communication Interface, SPI Mode
20-17
USCI Registers: SPI Mode
UCAxBR0, USCI_Ax Bit Rate Control Register 0
UCBxBR0, USCI_Bx Bit Rate Control Register 0
7
6
5
4
3
2
1
0
rw
rw
rw
2
1
0
rw
rw
rw
UCBRx − low byte
rw
rw
rw
rw
rw
UCAxBR1, USCI_Ax Bit Rate Control Register 1
UCBxBR1, USCI_Bx Bit Rate Control Register 1
7
6
5
4
3
UCBRx − high byte
rw
UCBRx
20-18
rw
rw
rw
rw
Bit clock prescaler setting.
The 16-bit value of (UCxxBR0+UCxxBR1×256) form the prescaler value
UCBRx.
Universal Serial Communication Interface, SPI Mode
USCI Registers: SPI Mode
UCAxSTAT, USCI_Ax Status Register
UCBxSTAT, USCI_Bx Status Register
†
‡
7
6
5
4
3
2
1
0
UCLISTEN
UCFE
UCOE
Unused
Unused
Unused
Unused
UCBUSY
rw-0
rw-0
rw-0
rw-0†
r0‡
rw-0
rw-0
rw-0
r-0
UCAxSTAT (USCI_Ax)
UCBxSTAT (USCI_Bx)
UCLISTEN
Bit 7
Listen enable. The UCLISTEN bit selects loopback mode.
0
Disabled
1
Enabled. The transmitter output is internally fed back to the receiver.
UCFE
Bit 6
Framing error flag. This bit indicates a bus conflict in 4-wire master mode.
UCFE is not used in 3-wire master or any slave mode.
0
No error
1
Bus conflict occurred
UCOE
Bit 5
Overrun error flag. This bit is set when a character is transferred into
UCxRXBUF before the previous character was read. UCOE is cleared
automatically when UCxRXBUF is read, and must not be cleared by
software. Otherwise, it will not function correctly.
0
No error
1
Overrun error occurred
Unused
Bits
4−1
Unused in synchronous mode (UCSYNC=1).
UCBUSY
Bit 0
USCI busy. This bit indicates if a transmit or receive operation is in
progress.
0
USCI inactive
1
USCI transmitting or receiving
Universal Serial Communication Interface, SPI Mode
20-19
USCI Registers: SPI Mode
UCAxRXBUF, USCI_Ax Receive Buffer Register
UCBxRXBUF, USCI_Bx Receive Buffer Register
7
6
5
4
3
2
1
0
r
r
r
r
UCRXBUFx
r
r
UCRXBUFx
Bits
7-0
r
r
The receive-data buffer is user accessible and contains the last received
character from the receive shift register. Reading UCxRXBUF resets the
receive-error bits, and UCxRXIFG. In 7-bit data mode, UCxRXBUF is LSB
justified and the MSB is always reset.
UCAxTXBUF, USCI_Ax Transmit Buffer Register
UCBxTXBUF, USCI_Bx Transmit Buffer Register
7
6
5
4
3
2
1
0
rw
rw
rw
rw
UCTXBUFx
rw
rw
UCTXBUFx
20-20
Bits
7-0
rw
rw
The transmit data buffer is user accessible and holds the data waiting to
be moved into the transmit shift register and transmitted. Writing to the
transmit data buffer clears UCxTXIFG. The MSB of UCxTXBUF is not
used for 7-bit data and is reset.
Universal Serial Communication Interface, SPI Mode
USCI Registers: SPI Mode
IE2, Interrupt Enable Register 2
7
6
5
4
3
2
1
0
UCB0TXIE
UCB0RXIE
UCA0TXIE
UCA0RXIE
rw-0
rw-0
rw-0
rw-0
Bits
7-4
These bits may be used by other modules. See device-specific data sheet.
UCB0TXIE
Bit 3
USCI_B0 transmit interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCB0RXIE
Bit 2
USCI_B0 receive interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCA0TXIE
Bit 1
USCI_A0 transmit interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCA0RXIE
Bit 0
USCI_A0 receive interrupt enable
0
Interrupt disabled
1
Interrupt enabled
Universal Serial Communication Interface, SPI Mode
20-21
USCI Registers: SPI Mode
IFG2, Interrupt Flag Register 2
7
6
5
4
3
2
1
0
UCB0
TXIFG
UCB0
RXIFG
UCA0
TXIFG
UCA0
RXIFG
rw-1
rw-0
rw-1
rw-0
Bits
7-4
These bits may be used by other modules. See device-specific data sheet.
UCB0
TXIFG
Bit 3
USCI_B0 transmit interrupt flag. UCB0TXIFG is set when UCB0TXBUF is
empty.
0
No interrupt pending
1
Interrupt pending
UCB0
RXIFG
Bit 2
USCI_B0 receive interrupt flag. UCB0RXIFG is set when UCB0RXBUF has
received a complete character.
0
No interrupt pending
1
Interrupt pending
UCA0
TXIFG
Bit 1
USCI_A0 transmit interrupt flag. UCA0TXIFG is set when UCA0TXBUF
empty.
0
No interrupt pending
1
Interrupt pending
UCA0
RXIFG
Bit 0
USCI_A0 receive interrupt flag. UCA0RXIFG is set when UCA0RXBUF has
received a complete character.
0
No interrupt pending
1
Interrupt pending
20-22
Universal Serial Communication Interface, SPI Mode
USCI Registers: SPI Mode
UC1IE, USCI_A1/USCI_B1 Interrupt Enable Register
7
6
5
4
3
2
1
0
Unused
Unused
Unused
Unused
UCB1TXIE
UCB1RXIE
UCA1TXIE
UCA1RXIE
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
Unused
Bits
7-4
Unused
UCB1TXIE
Bit 3
USCI_B1 transmit interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCB1RXIE
Bit 2
USCI_B1 receive interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCA1TXIE
Bit 1
USCI_A1 transmit interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCA1RXIE
Bit 0
USCI_A1 receive interrupt enable
0
Interrupt disabled
1
Interrupt enabled
Universal Serial Communication Interface, SPI Mode
20-23
USCI Registers: SPI Mode
UC1IFG, USCI_A1/USCI_B1 Interrupt Flag Register
7
6
5
4
3
2
1
0
Unused
Unused
Unused
Unused
UCB1
TXIFG
UCB1
RXIFG
UCA1
TXIFG
UCA1
RXIFG
rw−0
rw−0
rw−0
rw−0
rw−1
rw−0
rw−1
rw−0
Unused
Bits
7-4
Unused
UCB1
TXIFG
Bit 3
USCI_B1 transmit interrupt flag. UCB1TXIFG is set when UCB1TXBUF is
empty.
0
No interrupt pending
1
Interrupt pending
UCB1
RXIFG
Bit 2
USCI_B1 receive interrupt flag. UCB1RXIFG is set when UCB1RXBUF has
received a complete character.
0
No interrupt pending
1
Interrupt pending
UCA1
TXIFG
Bit 1
USCI_A1 transmit interrupt flag. UCA1TXIFG is set when UCA1TXBUF
empty.
0
No interrupt pending
1
Interrupt pending
UCA1
RXIFG
Bit 0
USCI_A1 receive interrupt flag. UCA1RXIFG is set when UCA1RXBUF has
received a complete character.
0
No interrupt pending
1
Interrupt pending
20-24
Universal Serial Communication Interface, SPI Mode
Chapter 21
Universal Serial Communication Interface,
I 2C Mode
The universal serial communication interface (USCI) supports multiple serial
communication modes with one hardware module. This chapter discusses the
operation of the I2C mode.
Topic
Page
21.1 USCI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-2
21.2 USCI Introduction: I2C Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-3
21.3 USCI Operation: I2C Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-5
21.4 USCI Registers: I2C Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-26
Universal Serial Communication Interface, I2C Mode
21-1
USCI Overview
21.1 USCI Overview
The universal serial communication interface (USCI) modules support
multiple serial communication modes. Different USCI modules support
different modes. Each different USCI module is named with a different letter.
For example, USCI_A is different from USCI_B, etc. If more than one identical
USCI module is implemented on one device, those modules are named with
incrementing numbers. For example, if one device has two USCI_A modules,
they are named USCI_A0 and USCI_A1. See the device-specific data sheet
to determine which USCI modules, if any, are implemented on which devices.
The USCI_Ax modules support:
-
UART mode
Pulse shaping for IrDA communications
Automatic baud rate detection for LIN communications
SPI mode
The USCI_Bx modules support:
- I2C mode
- SPI mode
21-2
Universal Serial Communication Interface, I2C Mode
USCI Introduction: I2C Mode
21.2 USCI Introduction: I2C Mode
In I2C mode, the USCI module provides an interface between the MSP430 and
I2C-compatible devices connected by way of the two-wire I2C serial bus.
External components attached to the I2C bus serially transmit and/or receive
serial data to/from the USCI module through the 2-wire I2C interface.
The I2C mode features include:
- Compliance to the Philips Semiconductor I2C specification v2.1
J 7-bit and 10-bit device addressing modes
J General call
J START/RESTART/STOP
J Multi-master transmitter/receiver mode
J Slave receiver/transmitter mode
J Standard mode up to 100 kbps and fast mode up to 400 kbps support
- Programmable UCxCLK frequency in master mode
- Designed for low power
- Slave receiver START detection for auto-wake up from LPMx modes
- Slave operation in LPM4
Figure 21−1 shows the USCI when configured in I2C mode.
Universal Serial Communication Interface, I2C Mode
21-3
USCI Introduction: I2C Mode
Figure 21−1. USCI Block Diagram: I 2C Mode
UCA10 UCGCEN
Own Address UC1OA
UCxSDA
Receive Shift Register
Receive Buffer UC1RXBUF
I2C State Machine
Transmit Buffer UC1TXBUF
Transmit Shift Register
Slave Address UC1SA
UCSLA10
UCxSCL
UCSSELx
Bit Clock Generator
UCxBRx
UC1CLK
00
ACLK
01
SMCLK
10
SMCLK
11
21-4
16
UCMST
BRCLK
Prescaler/Divider
Universal Serial Communication Interface, I2C Mode
USCI Operation: I2C Mode
21.3 USCI Operation: I2C Mode
The I2C mode supports any slave or master I2C-compatible device.
Figure 21−2 shows an example of an I2C bus. Each I2C device is recognized
by a unique address and can operate as either a transmitter or a receiver. A
device connected to the I2C bus can be considered as the master or the slave
when performing data transfers. A master initiates a data transfer and
generates the clock signal SCL. Any device addressed by a master is
considered a slave.
I2C data is communicated using the serial data pin (SDA) and the serial clock
pin (SCL). Both SDA and SCL are bidirectional, and must be connected to a
positive supply voltage using a pullup resistor.
Figure 21−2. I 2C Bus Connection Diagram
VCC
Device A
MSP430
Serial Data (SDA)
Serial Clock (SCL)
Device B
Device C
Note: SDA and SCL Levels
The MSP430 SDA and SCL pins must not be pulled up above the MSP430
VCC level.
Universal Serial Communication Interface, I2C Mode
21-5
USCI Operation: I2C Mode
21.3.1 USCI Initialization and Reset
The USCI is reset by a PUC or by setting the UCSWRST bit. After a PUC, the
UCSWRST bit is automatically set, keeping the USCI in a reset condition. To
select I2C operation the UCMODEx bits must be set to 11. After module
initialization, it is ready for transmit or receive operation. Clearing UCSWRST
releases the USCI for operation.
Configuring and reconfiguring the USCI module should be done when
UCSWRST is set to avoid unpredictable behavior. Setting UCSWRST in I2C
mode has the following effects:
-
I2C communication stops
SDA and SCL are high impedance
UCBxI2CSTAT, bits 6-0 are cleared
UCBxTXIE and UCBxRXIE are cleared
UCBxTXIFG and UCBxRXIFG are cleared
All other bits and registers remain unchanged.
Note: Initializing or Reconfiguring the USCI Module
The recommended USCI initialization/re-configuration process is:
1) Set UCSWRST (BIS.B #UCSWRST,&UCxCTL1)
2) Initialize all USCI registers with UCSWRST=1 (including UCxCTL1)
3) Configure ports.
4) Clear UCSWRST via software (BIC.B
#UCSWRST,&UCxCTL1)
5) Enable interrupts (optional) via UCxRXIE and/or UCxTXIE
21-6
Universal Serial Communication Interface, I2C Mode
USCI Operation: I2C Mode
21.3.2 I2C Serial Data
One clock pulse is generated by the master device for each data bit
transferred. The I2C mode operates with byte data. Data is transferred most
significant bit first as shown in Figure 21−3.
The first byte after a START condition consists of a 7-bit slave address and the
R/W bit. When R/W = 0, the master transmits data to a slave. When R/W = 1,
the master receives data from a slave. The ACK bit is sent from the receiver
after each byte on the 9th SCL clock.
Figure 21−3. I 2C Module Data Transfer
SDA
MSB
Acknowledgement
Signal From Receiver
Acknowledgement
Signal From Receiver
SCL
1
START
Condition (S)
2
7
8
R/W
9
ACK
1
2
8
9
ACK
STOP
Condition (P)
START and STOP conditions are generated by the master and are shown in
Figure 21−3. A START condition is a high-to-low transition on the SDA line
while SCL is high. A STOP condition is a low-to-high transition on the SDA line
while SCL is high. The bus busy bit, UCBBUSY, is set after a START and
cleared after a STOP.
Data on SDA must be stable during the high period of SCL as shown in
Figure 21−4. The high and low state of SDA can only change when SCL is low,
otherwise START or STOP conditions will be generated.
Figure 21−4. Bit Transfer on the I 2C Bus
Data Line
Stable Data
SDA
SCL
Change of Data Allowed
Universal Serial Communication Interface, I2C Mode
21-7
USCI Operation: I2C Mode
21.3.3 I2C Addressing Modes
The I2C mode supports 7-bit and 10-bit addressing modes.
7-Bit Addressing
In the 7-bit addressing format, shown in Figure 21−5, the first byte is the 7-bit
slave address and the R/W bit. The ACK bit is sent from the receiver after each
byte.
Figure 21−5. I 2C Module 7-Bit Addressing Format
1
1
1
R/W
ACK
7
S
Slave Address
1
8
Data
1
8
ACK
Data
1
ACK P
10-Bit Addressing
In the 10-bit addressing format, shown in Figure 21−6, the first byte is made
up of 11110b plus the two MSBs of the 10-bit slave address and the R/W bit.
The ACK bit is sent from the receiver after each byte. The next byte is the
remaining 8 bits of the 10-bit slave address, followed by the ACK bit and the
8-bit data.
Figure 21−6. I 2C Module 10-Bit Addressing Format
1
1
7
S Slave Address 1st byte
1
1
1
1
0
X
R/W
1
1
8
1
8
ACK Slave Address 2nd byte ACK
Data
1
ACK P
X
Repeated Start Conditions
The direction of data flow on SDA can be changed by the master, without first
stopping a transfer, by issuing a repeated START condition. This is called a
RESTART. After a RESTART is issued, the slave address is again sent out with
the new data direction specified by the R/W bit. The RESTART condition is
shown in Figure 21−7.
Figure 21−7. I 2C Module Addressing Format with Repeated START Condition
1
7
1
S
Slave Address
1
21-8
1
R/W ACK
8
1
1
Data
ACK
S
1
7
Slave Address
Any
Number
Universal Serial Communication Interface, I2C Mode
1
1
R/W ACK
8
1
1
Data
ACK
P
Any Number
USCI Operation: I2C Mode
21.3.4 I2C Module Operating Modes
In I2C mode the USCI module can operate in master transmitter, master
receiver, slave transmitter, or slave receiver mode. The modes are discussed
in the following sections. Time lines are used to illustrate the modes.
Figure 21−8 shows how to interpret the time line figures. Data transmitted by
the master is represented by grey rectangles, data transmitted by the slave by
white rectangles. Data transmitted by the USCI module, either as master or
slave, is shown by rectangles that are taller than the others.
Actions taken by the USCI module are shown in grey rectangles with an arrow
indicating where in the the data stream the action occurs. Actions that must
be handled with software are indicated with white rectangles with an arrow
pointing to where in the data stream the action must take place.
Figure 21−8. I 2C Time line Legend
Other Master
Other Slave
USCI Master
USCI Slave
...
Bits set or reset by software
...
Bits set or reset by hardware
Universal Serial Communication Interface, I2C Mode
21-9
USCI Operation: I2C Mode
Slave Mode
The USCI module is configured as an I2C slave by selecting the I2C mode with
UCMODEx = 11 and UCSYNC = 1 and clearing the UCMST bit.
Initially the USCI module must be configured in receiver mode by clearing the
UCTR bit to receive the I2C address. Afterwards, transmit and receive
operations are controlled automatically depending on the R/W bit received
together with the slave address.
The USCI slave address is programmed with the UCBxI2COA register. When
UCA10 = 0, 7-bit addressing is selected. When UCA10 = 1, 10-bit addressing
is selected. The UCGCEN bit selects if the slave responds to a general call.
When a START condition is detected on the bus, the USCI module will receive
the transmitted address and compare it against its own address stored in
UCBxI2COA. The UCSTTIFG flag is set when address received matches the
USCI slave address.
I 2C Slave Transmitter Mode
Slave transmitter mode is entered when the slave address transmitted by the
master is identical to its own address with a set R/W bit. The slave transmitter
shifts the serial data out on SDA with the clock pulses that are generated by
the master device. The slave device does not generate the clock, but it will hold
SCL low while intervention of the CPU is required after a byte has been
transmitted.
If the master requests data from the slave the USCI module is automatically
configured as a transmitter and UCTR and UCBxTXIFG become set. The SCL
line is held low until the first data to be sent is written into the transmit buffer
UCBxTXBUF. Then the address is acknowledged, the UCSTTIFG flag is
cleared, and the data is transmitted. As soon as the data is transferred into the
shift register the UCBxTXIFG is set again. After the data is acknowledged by
the master the next data byte written into UCBxTXBUF is transmitted or if the
buffer is empty the bus is stalled during the acknowledge cycle by holding SCL
low until new data is written into UCBxTXBUF. If the master sends a NACK
succeeded by a STOP condition the UCSTPIFG flag is set. If the NACK is
succeeded by a repeated START condition the USCI I2C state machine
returns to its address-reception state.
Figure 21−9 illustrates the slave transmitter operation.
21-10
Universal Serial Communication Interface, I2C Mode
USCI Operation: I2C Mode
Figure 21−9. I 2C Slave Transmitter Mode
Reception of own
S
SLA/R
address and
transmission of data
bytes
UCTR= 1(Transmitter)
UCSTTIFG= 1
UCBxTXIFG= 1
UCSTPIFG=?0
UCBxTXBUF discarded
A
DATA
A
DATA
Write data to UCBxTXBUF
UCBxTXIFG= 1
A
DATA
A
P
UCBxTXIFG= 0
UCSTPIFG= 1
UCSTTIFG= 0
Bus stalled (SCL held low)
until data available
Write data to UCBxTXBUF
Repeated start −
continue as
slave transmitter
DATA
A
S
SLA/R
UCBxTXIFG=0
UCTR= 1(Transmitter)
UCSTTIFG= 1
UCBxTXIFG= 1
UCBxTXBUF discarded
Repeated start −
continue as
slave receiver
DATA
A
S
SLA/W
UCBxTXIFG= 0
Arbitration lost as
master and
addressed as slave
UCTR= 0(Receiver)
UCSTTIFG= 1
A
UCALIFG= 1
UCMST= 0
UCTR= 1(Transmitter)
UCSTTIFG= 1
UCBxTXIFG= 1
UCSTPIFG= 0
Universal Serial Communication Interface, I2C Mode
21-11
USCI Operation: I2C Mode
I 2C Slave Receiver Mode
Slave receiver mode is entered when the slave address transmitted by the
master is identical to its own address and a cleared R/W bit is received. In slave
receiver mode, serial data bits received on SDA are shifted in with the clock
pulses that are generated by the master device. The slave device does not
generate the clock, but it can hold SCL low if intervention of the CPU is required
after a byte has been received.
If the slave should receive data from the master the USCI module is
automatically configured as a receiver and UCTR is cleared. After the first data
byte is received the receive interrupt flag UCBxRXIFG is set. The USCI
module automatically acknowledges the received data and can receive the
next data byte.
If the previous data was not read from the receive buffer UCBxRXBUF at the
end of a reception, the bus is stalled by holding SCL low. As soon as
UCBxRXBUF is read the new data is transferred into UCBxRXBUF, an
acknowledge is sent to the master, and the next data can be received.
Setting the UCTXNACK bit causes a NACK to be transmitted to the master
during the next acknowledgment cycle. A NACK is sent even if UCBxRXBUF
is not ready to receive the latest data. If the UCTXNACK bit is set while SCL
is held low the bus will be released, a NACK is transmitted immediately, and
UCBxRXBUF is loaded with the last received data. Since the previous data
was not read that data will be lost. To avoid loss of data the UCBxRXBUF
needs to be read before UCTXNACK is set.
When the master generates a STOP condition the UCSTPIFG flag is set.
If the master generates a repeated START condition the USCI I2C state
machine returns to its address reception state.
Figure 21−10 illustrates the the I2C slave receiver operation.
21-12
Universal Serial Communication Interface, I2C Mode
USCI Operation: I2C Mode
Figure 21−10. I 2C Slave Receiver Mode
Reception of own
address and data
bytes. All are
acknowledged.
S
SLA/W
A
DATA
A
DATA
A
DATA
A
P or S
UCBxRXIFG= 1
UCTR= 0(Receiver)
UCSTTIFG= 1
UCSTPIFG= 0
Bus stalled
(SCL held low)
if UCBxRXBUF not read
Refer to:
Slave Transmitter
Timing Diagram
Read data from UCBxRXBUF
Last byte is not
acknowledged.
DATA
UCTXNACK= 1
A
P or S
UCTXNACK= 0
Bus not stalled even if
UCBxRXBUF not read
Reception of the
general call
address.
Gen Call
A
UCTR= 0(Receiver)
UCSTTIFG= 1
UCGC= 1
Arbitration lost as
master and
addressed as slave
A
UCALIFG= 1
UCMST= 0
UCTR= 0 (Receiver)
UCSTTIFG= 1
(UCGC= 1if general call)
UCBxTXIFG= 0
UCSTPIFG= 0
Universal Serial Communication Interface, I2C Mode
21-13
USCI Operation: I2C Mode
I 2C Slave 10-Bit Addressing Mode
The 10-bit addressing mode is selected when UCA10 = 1 and is as shown in
Figure 21−11. In 10-bit addressing mode, the slave is in receive mode after the
full address is received. The USCI module indicates this by setting the
UCSTTIFG flag while the UCTR bit is cleared. To switch the slave into
transmitter mode the master sends a repeated START condition together with
the first byte of the address but with the R/W bit set. This will set the UCSTTIFG
flag if it was previously cleared by software and the USCI modules switches
to transmitter mode with UCTR = 1.
Figure 21−11.I 2C Slave 10-bit Addressing Mode
Slave Receiver
Reception of own
address and data
bytes. All are
acknowledged.
S
11110 xx/W
A
SLA (2.)
DATA
A
DATA
A
A
P or S
UCBxRXIFG= 1
UCTR= 0( Receiver)
UCSTTIFG= 1
UCSTPIFG= 0
Reception of the
general call
address.
Gen Call
A
DATA
DATA
A
A
P or S
UCBxRXIFG= 1
UCTR= 0(Receiver)
UCSTTIFG= 1
UCGC= 1
Slave Transmitter
Reception of own
address and
transmission of data
bytes
S
11110 xx/W
A
SLA (2.)
A
S
11110 xx/R
DATA
UCSTTIFG= 0
UCTR= 0(Receiver)
UCSTTIFG= 1
UCSTPIFG= 0
UCTR= 1(Transmitter)
UCSTTIFG= 1
UCBxTXIFG= 1
UCSTPIFG= 0
21-14
A
Universal Serial Communication Interface, I2C Mode
A
P or S
USCI Operation: I2C Mode
Master Mode
The USCI module is configured as an I2C master by selecting the I2C mode
with UCMODEx = 11 and UCSYNC = 1 and setting the UCMST bit. When the
master is part of a multi-master system, UCMM must be set and its own
address must be programmed into the UCBxI2COA register. When
UCA10 = 0, 7-bit addressing is selected. When UCA10 = 1, 10-bit addressing
is selected. The UCGCEN bit selects if the USCI module responds to a general
call.
I 2C Master Transmitter Mode
After initialization, master transmitter mode is initiated by writing the desired
slave address to the UCBxI2CSA register, selecting the size of the slave
address with the UCSLA10 bit, setting UCTR for transmitter mode, and setting
UCTXSTT to generate a START condition.
The USCI module checks if the bus is available, generates the START
condition, and transmits the slave address. The UCBxTXIFG bit is set when
the START condition is generated and the first data to be transmitted can be
written into UCBxTXBUF. As soon as the slave acknowledges the address the
UCTXSTT bit is cleared.
Note: Handling of TXIFG in a multi-master system
In a multi−master system (UCMM =1), if the bus is unavailable, the USCI
module waits and checks for bus release. Bus unavailability can occur even
after the UCTXSTT bit has been set. While waiting for the bus to become
available, the USCI may update the TXIFG based on SCL clock line activity.
Checking the UCTXSTT bit to verify if the START condition has been sent
ensures that the TXIFG is being serviced correctly.
The data written into UCBxTXBUF is transmitted if arbitration is not lost during
transmission of the slave address. UCBxTXIFG is set again as soon as the
data is transferred from the buffer into the shift register. If there is no data
loaded to UCBxTXBUF before the acknowledge cycle, the bus is held during
the acknowledge cycle with SCL low until data is written into UCBxTXBUF.
Data is transmitted or the bus is held as long as the UCTXSTP bit or UCTXSTT
bit is not set.
Setting UCTXSTP will generate a STOP condition after the next acknowledge
from the slave. If UCTXSTP is set during the transmission of the slave’s
address or while the USCI module waits for data to be written into
UCBxTXBUF, a STOP condition is generated even if no data was transmitted
to the slave. When transmitting a single byte of data, the UCTXSTP bit must
be set while the byte is being transmitted, or anytime after transmission
begins, without writing new data into UCBxTXBUF. Otherwise, only the
address will be transmitted. When the data is transferred from the buffer to the
shift register, UCBxTXIFG will become set indicating data transmission has
begun and the UCTXSTP bit may be set.
Universal Serial Communication Interface, I2C Mode
21-15
USCI Operation: I2C Mode
Setting UCTXSTT will generate a repeated START condition. In this case,
UCTR may be set or cleared to configure transmitter or receiver, and a different
slave address may be written into UCBxI2CSA if desired.
If the slave does not acknowledge the transmitted data the not-acknowledge
interrupt flag UCNACKIFG is set. The master must react with either a STOP
condition or a repeated START condition. If data was already written into
UCBxTXBUF it will be discarded. If this data should be transmitted after a
repeated START it must be written into UCBxTXBUF again. Any set UCTXSTT
is discarded, too. To trigger a repeated start, UCTXSTT needs to be set again.
Figure 21−12 illustrates the I2C master transmitter operation.
21-16
Universal Serial Communication Interface, I2C Mode
USCI Operation: I2C Mode
Figure 21−12. I 2C Master Transmitter Mode
Successful
transmission to a
slave receiver
S
A
SLA/W
1) UCTR= 1(Transmitter)
2) UCTXSTT= 1
DATA
A
DATA
A
DATA
A
P
UCTXSTT= 0
UCTXSTP= 0
UCBxTXIFG= 1
UCTXSTP= 1
UCBxTXIFG=0
UCBxTXIFG= 1
UCBxTXBUF discarded
Bus stalled (SCL held low)
until data available
Next transfer started
with a repeated start
condition
DATA
Write data to UCBxTXBUF
A
S
SLA/W
1) UCTR= 1(Transmitter)
2) UCTXSTT= 1
UCTXSTT= 0
UCNACKIFG= 1
UCBxTXIFG= 0
UCBxTXBUF discarded
DATA
A
S
SLA/R
1) UCTR= 0(Receiver)
2) UCTXSTT= 1
3) UCBxTXIFG= 0
UCTXSTP= 1
Not acknowledge
received after slave
address
A
P
UCTXSTP= 0
1) UCTR= 1(Transmitter)
2) UCTXSTT= 1
Not acknowledge
received after a data
byte
A
S
SLA/W
S
SLA/R
UCBxTXIFG= 1
UCBxTXBUF discarded
1) UCTR= 0(Receiver)
2) UCTXSTT= 1
UCNACKIFG= 1
UCBxTXIFG= 0
UCBxTXBUF discarded
Arbitration lost in
slave address or
data byte
Other master continues
Other master continues
UCALIFG= 1
UCMST= 0
(UCSTTIFG= 0)
UCALIFG= 1
UCMST= 0
(UCSTTIFG= 0)
Arbitration lost and
addressed as slave
A
Other master continues
UCALIFG= 1
UCMST= 0
UCTR= 0(Receiver)
UCSTTIFG= 1
(UCGC= 1if general call)
UCBxTXIFG= 0
UCSTPIFG= 0
USCI continues as Slave Receiver
Universal Serial Communication Interface, I2C Mode
21-17
USCI Operation: I2C Mode
I 2C Master Receiver Mode
After initialization, master receiver mode is initiated by writing the desired
slave address to the UCBxI2CSA register, selecting the size of the slave
address with the UCSLA10 bit, clearing UCTR for receiver mode, and setting
UCTXSTT to generate a START condition.
The USCI module checks if the bus is available, generates the START
condition, and transmits the slave address. As soon as the slave
acknowledges the address the UCTXSTT bit is cleared.
After the acknowledge of the address from the slave the first data byte from
the slave is received and acknowledged and the UCBxRXIFG flag is set. Data
is received from the slave as long as UCTXSTP or UCTXSTT is not set. If
UCBxRXBUF is not read the master holds the bus during reception of the last
data bit and until the UCBxRXBUF is read.
If the slave does not acknowledge the transmitted address the
not-acknowledge interrupt flag UCNACKIFG is set. The master must react
with either a STOP condition or a repeated START condition.
Setting the UCTXSTP bit will generate a STOP condition. After setting
UCTXSTP, a NACK followed by a STOP condition is generated after reception
of the data from the slave, or immediately if the USCI module is currently
waiting for UCBxRXBUF to be read.
If a master wants to receive a single byte only, the UCTXSTP bit must be set
while the byte is being received. For this case, the UCTXSTT may be polled
to determine when it is cleared:
BIS.B
POLL_STT BIT.B
JC
BIS.B
#UCTXSTT,&UCB0CTL1
#UCTXSTT,&UCB0CTL1
POLL_STT
#UCTXSTP,&UCB0CTL1
;Transmit START cond.
;Poll UCTXSTT bit
;When cleared,
;transmit STOP cond.
Setting UCTXSTT will generate a repeated START condition. In this case,
UCTR may be set or cleared to configure transmitter or receiver, and a different
slave address may be written into UCBxI2CSA if desired.
Figure 21−13 illustrates the I2C master receiver operation.
Note: Consecutive Master Transactions Without Repeated Start
When performing multiple consecutive I2C master transactions without the
repeated start feature, the current transaction must be completed before the
next one is initiated. This can be done by ensuring that the transmit stop
condition flag UCTXSTP is cleared before the next I2C transaction is initiated
with setting UCTXSTT = 1. Otherwise, the current transaction might be
affected.
21-18
Universal Serial Communication Interface, I2C Mode
USCI Operation: I2C Mode
Figure 21−13. I 2C Master Receiver Mode
Successful
reception from a
slave transmitter
S
SLA/R
A
DATA
1) UCTR= 0 (Receiver)
2) UCTXSTT= 1
DATA
A
UCTXSTT= 0
A
UCBxRXIFG= 1
Next transfer started
with a repeated start
condition
DATA
A
P
UCTXSTP= 1
DATA
A
UCTXSTP= 0
S
SLA/W
1) UCTR= 1(Transmitter)
2) UCTXSTT= 1
DATA
UCTXSTP= 1
Not acknowledge
received after slave
address
A
P
A
S
SLA/R
1) UCTR=0 (Receiver)
2) UCTXSTT= 1
UCTXSTP= 0
UCTXSTT= 0
UCNACKIFG= 1
S
SLA/W
1) UCTR=1 (Transmitter)
2) UCTXSTT= 1
UCBxTXIFG= 1
S
Arbitration lost in
slave address or
data byte
SLA/R
1) UCTR=0 (Receiver)
2) UCTXSTT= 1
Other master continues
Other master continues
UCALIFG= 1
UCMST= 0
(UCSTTIFG= 0)
UCALIFG= 1
UCMST= 0
(UCSTTIFG= 0)
Arbitration lost and
addressed as slave
A
Other master continues
UCALIFG= 1
UCMST= 0
UCTR= 1( Transmitter)
UCSTTIFG= 1
UCBxTXIFG= 1
UCSTPIFG= 0
USCI continues as Slave Transmitter
Universal Serial Communication Interface, I2C Mode
21-19
USCI Operation: I2C Mode
I 2C Master 10-Bit Addressing Mode
The 10-bit addressing mode is selected when UCSLA10 = 1 and is shown in
Figure 21−14.
Figure 21−14. I 2C Master 10-bit Addressing Mode
Master Transmitter
Successful
transmission to a
slave receiver
S
11110 xx/W
A
SLA (2.)
A
1) UCTR=1 (Transmitter)
2) UCTXSTT= 1
DATA
A
DATA
A
P
UCTXSTT= 0
UCTXSTP= 0
UCBxTXIFG = 1
UCTXSTP= 1
UCBxTXIFG= 1
Master Receiver
Successful
reception from a
slave transmitter
S
11110 xx/W
A
1) UCTR= 0 (Receiver)
2) UCTXSTT= 1
SLA (2.)
A
S
11110 xx/R
A
UCTXSTT= 0
DATA
A
UCBxRXIFG= 1
UCTXSTP= 1
21-20
Universal Serial Communication Interface, I2C Mode
DATA
A
P
UCTXSTP= 0
USCI Operation: I2C Mode
Arbitration
If two or more master transmitters simultaneously start a transmission on the
bus, an arbitration procedure is invoked. Figure 21−15 illustrates the
arbitration procedure between two devices. The arbitration procedure uses
the data presented on SDA by the competing transmitters. The first master
transmitter that generates a logic high is overruled by the opposing master
generating a logic low. The arbitration procedure gives priority to the device
that transmits the serial data stream with the lowest binary value. The master
transmitter that lost arbitration switches to the slave receiver mode, and sets
the arbitration lost flag UCALIFG. If two or more devices send identical first
bytes, arbitration continues on the subsequent bytes.
Figure 21−15. Arbitration Procedure Between Two Master Transmitters
Bus Line
SCL
Device #1 Lost Arbitration
and Switches Off
n
Data From
Device #1
1
Data From
Device #2
0
0
0
0
1
Bus Line
SDA
1
0
1
1
0
1
1
If the arbitration procedure is in progress when a repeated START condition
or STOP condition is transmitted on SDA, the master transmitters involved in
arbitration must send the repeated START condition or STOP condition at the
same position in the format frame. Arbitration is not allowed between:
- A repeated START condition and a data bit
- A STOP condition and a data bit
- A repeated START condition and a STOP condition
Universal Serial Communication Interface, I2C Mode
21-21
USCI Operation: I2C Mode
21.3.5 I2C Clock Generation and Synchronization
The I2C clock SCL is provided by the master on the I2C bus. When the USCI
is in master mode, BITCLK is provided by the USCI bit clock generator and the
clock source is selected with the UCSSELx bits. In slave mode the bit clock
generator is not used and the UCSSELx bits are don’t care.
The 16-bit value of UCBRx in registers UCBxBR1 and UCBxBR0 is the division
factor of the USCI clock source, BRCLK. The maximum bit clock that can be
used in single master mode is fBRCLK/4. In multi-master mode the maximum
bit clock is fBRCLK/8. The BITCLK frequency is given by:
f
f BitClock + BRCLK
UCBRx
The minimum high and low periods of the generated SCL are
t LOW,MIN + t HIGH,MIN +
UCBRxń2
f BRCLK
t LOW,MIN + t HIGH,MIN +
(UCBRx * 1)ń2
f BRCLK
when UCBRx is even and
when UCBRx is odd.
The USCI clock source frequency and the prescaler setting UCBRx must to
be chosen such that the minimum low and high period times of the I2C
specification are met.
During the arbitration procedure the clocks from the different masters must be
synchronized. A device that first generates a low period on SCL overrules the
other devices forcing them to start their own low periods. SCL is then held low
by the device with the longest low period. The other devices must wait for SCL
to be released before starting their high periods. Figure 21−16 illustrates the
clock synchronization. This allows a slow slave to slow down a fast master.
Figure 21−16. Synchronization of Two I 2C Clock Generators During Arbitration
Wait
State
SCL From
Device #1
SCL From
Device #2
Bus Line
SCL
21-22
Universal Serial Communication Interface, I2C Mode
Start HIGH
Period
USCI Operation: I2C Mode
Clock Stretching
The USCI module supports clock stretching and also makes use of this feature
as described in the operation mode sections.
The UCSCLLOW bit can be used to observe if another device pulls SCL low
while the USCI module already released SCL due to the following conditions:
- USCI is acting as master and a connected slave drives SCL low.
- USCI is acting as master and another master drives SCL low during
arbitration.
The UCSCLLOW bit is also active if the USCI holds SCL low because it is
waiting as transmitter for data being written into UCBxTXBUF or as receiver
for the data being read from UCBxRXBUF.
The UCSCLLOW bit might get set for a short time with each rising SCL edge
because the logic observes the external SCL and compares it to the internally
generated SCL.
21.3.6 Using the USCI Module in I2C Mode With Low-Power Modes
The USCI module provides automatic clock activation for SMCLK for use with
low-power modes. When SMCLK is the USCI clock source, and is inactive
because the device is in a low-power mode, the USCI module automatically
activates it when needed, regardless of the control-bit settings for the clock
source. The clock remains active until the USCI module returns to its idle
condition. After the USCI module returns to the idle condition, control of the
clock source reverts to the settings of its control bits. Automatic clock activation
is not provided for ACLK.
When the USCI module activates an inactive clock source, the clock source
becomes active for the whole device and any peripheral configured to use the
clock source may be affected. For example, a timer using SMCLK will
increment while the USCI module forces SMCLK active.
In I2C slave mode no internal clock source is required because the clock is
provided by the external master. It is possible to operate the USCI in I2C slave
mode while the device is in LPM4 and all internal clock sources are disabled.
The receive or transmit interrupts can wake up the CPU from any low power
mode.
Universal Serial Communication Interface, I2C Mode
21-23
USCI Operation: I2C Mode
21.3.7 USCI Interrupts in I2C Mode
Their are two interrupt vectors for the USCI module in I2C mode. One interrupt
vector is associated with the transmit and receive interrupt flags. The other
interrupt vector is associated with the four state change interrupt flags. Each
interrupt flag has its own interrupt enable bit. When an interrupt is enabled, and
the GIE bit is set, the interrupt flag will generate an interrupt request. DMA
transfers are controlled by the UCBxTXIFG and UCBxRXIFG flags on devices
with a DMA controller.
I2C Transmit Interrupt Operation
The UCBxTXIFG interrupt flag is set by the transmitter to indicate that
UCBxTXBUF is ready to accept another character. An interrupt request is
generated if UCBxTXIE and GIE are also set. UCBxTXIFG is automatically
reset if a character is written to UCBxTXBUF or if a NACK is received.
UCBxTXIFG is set when UCSWRST = 1 and the I2C mode is selected.
UCBxTXIE is reset after a PUC or when UCSWRST = 1.
I2C Receive Interrupt Operation
The UCBxRXIFG interrupt flag is set when a character is received and loaded
into UCBxRXBUF. An interrupt request is generated if UCBxRXIE and GIE are
also set. UCBxRXIFG and UCBxRXIE are reset after a PUC signal or when
UCSWRST = 1. UCxRXIFG is automatically reset when UCxRXBUF is read.
I2C State Change Interrupt Operation.
Table 21−1 Describes the I2C state change interrupt flags.
Table 21−1.I 2C State Change Interrupt Flags
21-24
Interrupt Flag
Interrupt Condition
UCALIFG
Arbitration-lost. Arbitration can be lost when two or more
transmitters start a transmission simultaneously, or when the
USCI operates as master but is addressed as a slave by another
master in the system. The UCALIFG flag is set when arbitration is
lost. When UCALIFG is set the UCMST bit is cleared and the I2C
controller becomes a slave.
UCNACKIFG
Not-acknowledge interrupt. This flag is set when an acknowledge
is expected but is not received. UCNACKIFG is automatically
cleared when a START condition is received.
UCSTTIFG
Start condition detected interrupt. This flag is set when the I2C
module detects a START condition together with its own address
while in slave mode. UCSTTIFG is used in slave mode only and
is automatically cleared when a STOP condition is received.
UCSTPIFG
Stop condition detected interrupt. This flag is set when the I2C
module detects a STOP condition while in slave mode.
UCSTPIFG is used in slave mode only and is automatically
cleared when a START condition is received.
Universal Serial Communication Interface, I2C Mode
USCI Operation: I2C Mode
Interrupt Vector Assignment
USCI_Ax and USCI_Bx share the same interrupt vectors. In I2C mode the
state change interrupt flags UCSTTIFG, UCSTPIFG, UCNACKIFG, UCALIFG
from USCI_Bx and UCAxRXIFG from USCI_Ax are routed to one interrupt
vector. The I2C transmit and receive interrupt flags UCBxTXIFG and
UCBxRXIFG from USCI_Bx and UCAxTXIFG from USCI_Ax share another
interrupt vector.
Shared Interrupt Vectors Software Example
The following software example shows an extract of the interrupt service
routine to handle data receive interrupts from USCI_A0 in either UART or SPI
mode and state change interrupts from USCI_B0 in I2C mode.
USCIA0_RX_USCIB0_I2C_STATE_ISR
BIT.B #UCA0RXIFG, &IFG2 ; USCI_A0 Receive Interrupt?
JNZ
USCIA0_RX_ISR
USCIB0_I2C_STATE_ISR
; Decode I2C state changes ...
; Decode I2C state changes ...
...
RETI
USCIA0_RX_ISR
; Read UCA0RXBUF ... − clears UCA0RXIFG
...
RETI
The following software example shows an extract of the interrupt service
routine that handles data transmit interrupts from USCI_A0 in either UART or
SPI mode and the data transfer interrupts from USCI_B0 in I2C mode.
USCIA0_TX_USCIB0_I2C_DATA_ISR
BIT.B #UCA0TXIFG, &IFG2 ; USCI_A0 Transmit Interrupt?
JNZ
USCIA0_TX_ISR
USCIB0_I2C_DATA_ISR
BIT.B #UCB0RXIFG, &IFG2
JNZ
USCIB0_I2C_RX
USCIB0_I2C_TX
; Write UCB0TXBUF... − clears UCB0TXIFG
...
RETI
USCIB0_I2C_RX
; Read UCB0RXBUF... − clears UCB0RXIFG
...
RETI
USCIA0_TX_ISR
; Write UCA0TXBUF ... − clears UCA0TXIFG
...
RETI
Universal Serial Communication Interface, I2C Mode
21-25
USCI Registers: I2C Mode
21.4 USCI Registers: I2C Mode
The USCI registers applicable in I2C mode for USCI_B0 are listed in
Table 21−2 and for USCI_B1 in Table 21−3.
Table 21−2.USCI_B0 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USCI_B0 control register 0
UCB0CTL0
Read/write
068h
001h with PUC
USCI_B0 control register 1
UCB0CTL1
Read/write
069h
001h with PUC
USCI_B0 bit rate control register 0
UCB0BR0
Read/write
06Ah
Reset with PUC
USCI_B0 bit rate control register 1
UCB0BR1
Read/write
06Bh
Reset with PUC
USCI_B0 I2C interrupt enable register
UCB0I2CIE
Read/write
06Ch
Reset with PUC
USCI_B0 status register
UCB0STAT
Read/write
06Dh
Reset with PUC
USCI_B0 receive buffer register
UCB0RXBUF
Read
06Eh
Reset with PUC
USCI_B0 transmit buffer register
UCB0TXBUF
Read/write
06Fh
Reset with PUC
USCI_B0 I2C own address register
UCB0I2COA
Read/write
0118h
Reset with PUC
USCI_B0 I2C slave address register
UCB0I2CSA
Read/write
011Ah
Reset with PUC
SFR interrupt enable register 2
IE2
Read/write
001h
Reset with PUC
SFR interrupt flag register 2
IFG2
Read/write
003h
00Ah with PUC
Note: Modifying SFR bits
To avoid modifying control bits of other modules, it is recommended to set
or clear the IEx and IFGx bits using BIS.B or BIC.B instructions, rather than
MOV.B or CLR.B instructions.
Table 21−3.USCI_B1 Control and Status Registers
Register
Short Form
Register Type Address
Initial State
USCI_B1 control register 0
UCB1CTL0
Read/write
0D8h
Reset with PUC
USCI_B1 control register 1
UCB1CTL1
Read/write
0D9h
001h with PUC
USCI_B1 baud rate control register 0
UCB1BR0
Read/write
0DAh
Reset with PUC
USCI_B1 baud rate control register 1
UCB1BR1
Read/write
0DBh
Reset with PUC
USCI_B1 I2C Interrupt enable register
UCB1I2CIE
Read/write
0DCh
Reset with PUC
USCI_B1 status register
UCB1STAT
Read/write
0DDh
Reset with PUC
USCI_B1 receive buffer register
UCB1RXBUF
Read
0DEh
Reset with PUC
USCI_B1 transmit buffer register
UCB1TXBUF
Read/write
0DFh
Reset with PUC
USCI_B1 I2C own address register
UCB1I2COA
Read/write
017Ch
Reset with PUC
USCI_B1 I2C slave address register
UCB1I2CSA
Read/write
017Eh
Reset with PUC
USCI_A1/B1 interrupt enable register
UC1IE
Read/write
006h
Reset with PUC
USCI_A1/B1 interrupt flag register
UC1IFG
Read/write
007h
00Ah with PUC
21-26
Universal Serial Communication Interface, I2C Mode
USCI Registers: I2C Mode
UCBxCTL0, USCI_Bx Control Register 0
7
6
5
4
3
UCA10
UCSLA10
UCMM
Unused
UCMST
rw−0
rw−0
rw−0
rw−0
rw−0
2
1
UCMODEx=11
rw−0
0
UCSYNC=1
rw−0
r−1
UCA10
Bit 7
Own addressing mode select
0
Own address is a 7-bit address
1
Own address is a 10-bit address
UCSLA10
Bit 6
Slave addressing mode select
0
Address slave with 7-bit address
1
Address slave with 10-bit address
UCMM
Bit 5
Multi-master environment select
0
Single master environment. There is no other master in the system.
The address compare unit is disabled.
1
Multi master environment
Unused
Bit 4
Unused
UCMST
Bit 3
Master mode select. When a master looses arbitration in a multi-master
environment (UCMM = 1) the UCMST bit is automatically cleared and the
module acts as slave.
0
Slave mode
1
Master mode
UCMODEx
Bits
2−1
USCI Mode. The UCMODEx bits select the synchronous mode when
UCSYNC = 1.
00 3-pin SPI
01 4−Pin SPI (master/slave enabled if STE = 1)
10 4−Pin SPI (master/slave enabled if STE = 0)
11 I2C mode
UCSYNC
Bit 0
Synchronous mode enable
0
Asynchronous mode
1
Synchronous mode
Universal Serial Communication Interface, I2C Mode
21-27
USCI Registers: I2C Mode
UCBxCTL1, USCI_Bx Control Register 1
7
6
UCSSELx
rw−0
rw−0
5
4
3
2
1
0
Unused
UCTR
UCTXNACK
UCTXSTP
UCTXSTT
UCSWRST
r0
rw−0
rw−0
rw−0
rw−0
rw−1
UCSSELx
Bits
7-6
USCI clock source select. These bits select the BRCLK source clock.
00 UCLKI
01 ACLK
10 SMCLK
11 SMCLK
Unused
Bit 5
Unused
UCTR
Bit 4
Transmitter/Receiver
0
Receiver
1
Transmitter
UCTXNACK
Bit 3
Transmit a NACK. UCTXNACK is automatically cleared after a NACK is
transmitted.
0
Acknowledge normally
1
Generate NACK
UCTXSTP
Bit 2
Transmit STOP condition in master mode. Ignored in slave mode. In
master receiver mode the STOP condition is preceded by a NACK.
UCTXSTP is automatically cleared after STOP is generated.
0
No STOP generated
1
Generate STOP
UCTXSTT
Bit 1
Transmit START condition in master mode. Ignored in slave mode. In
master receiver mode a repeated START condition is preceded by a
NACK. UCTXSTT is automatically cleared after START condition and
address information is transmitted.
Ignored in slave mode.
0
Do not generate START condition
1
Generate START condition
UCSWRST
Bit 0
Software reset enable
0
Disabled. USCI reset released for operation.
1
Enabled. USCI logic held in reset state.
21-28
Universal Serial Communication Interface, I2C Mode
USCI Registers: I2C Mode
UCBxBR0, USCI_Bx Baud Rate Control Register 0
7
6
5
4
3
2
1
0
rw
rw
rw
2
1
0
rw
rw
rw
UCBRx − low byte
rw
rw
rw
rw
rw
UCBxBR1, USCI_Bx Baud Rate Control Register 1
7
6
5
4
3
UCBRx − high byte
rw
UCBRx
rw
rw
rw
rw
Bit clock prescaler setting.
The 16-bit value of (UCBxBR0 + UCBxBR1 × 256} forms the prescaler
value.
Universal Serial Communication Interface, I2C Mode
21-29
USCI Registers: I2C Mode
UCBxSTAT, USCI_Bx Status Register
7
6
5
4
3
2
1
0
Unused
UC
SCLLOW
UCGC
UCBBUSY
UCNACK
IFG
UCSTPIFG
UCSTTIFG
UCALIFG
rw−0
r−0
rw−0
r−0
rw−0
rw−0
rw−0
rw−0
Unused
Bit 7
Unused.
UC
SCLLOW
Bit 6
SCL low
0
SCL is not held low
1
SCL is held low
UCGC
Bit 5
General call address received. UCGC is automatically cleared when a
START condition is received.
0
No general call address received
1
General call address received
UCBBUSY
Bit 4
Bus busy
0
Bus inactive
1
Bus busy
UCNACK
IFG
Bit 3
Not-acknowledge received interrupt flag. UCNACKIFG is automatically
cleared when a START condition is received.
0
No interrupt pending
1
Interrupt pending
UCSTPIFG
Bit 2
Stop condition interrupt flag. UCSTPIFG is automatically cleared when a
START condition is received.
0
No interrupt pending
1
Interrupt pending
UCSTTIFG
Bit 1
Start condition interrupt flag. UCSTTIFG is automatically cleared if a STOP
condition is received.
0
No interrupt pending
1
Interrupt pending
UCALIFG
Bit 0
Arbitration lost interrupt flag
0
No interrupt pending
1
Interrupt pending
21-30
Universal Serial Communication Interface, I2C Mode
USCI Registers: I2C Mode
UCBxRXBUF, USCI_Bx Receive Buffer Register
7
6
5
4
3
2
1
0
r
r
r
r
UCRXBUFx
r
UCRXBUFx
r
Bits
7−0
r
r
The receive-data buffer is user accessible and contains the last received
character from the receive shift register. Reading UCBxRXBUF resets
UCBxRXIFG.
UCBxTXBUF, USCI_Bx Transmit Buffer Register
7
6
5
4
3
2
1
0
rw
rw
rw
rw
UCTXBUFx
rw
UCTXBUFx
rw
Bits
7−0
rw
rw
The transmit data buffer is user accessible and holds the data waiting to
be moved into the transmit shift register and transmitted. Writing to the
transmit data buffer clears UCBxTXIFG.
Universal Serial Communication Interface, I2C Mode
21-31
USCI Registers: I2C Mode
UCBxI2COA, USCIBx I2C Own Address Register
15
14
13
12
11
10
9
8
UCGCEN
0
0
0
0
0
rw−0
r0
r0
r0
r0
r0
rw−0
rw−0
7
6
5
4
3
2
1
0
rw−0
rw−0
rw−0
rw−0
I2COAx
I2COAx
rw−0
rw−0
rw−0
rw−0
UCGCEN
Bit 15
General call response enable
0
Do not respond to a general call
1
Respond to a general call
I2COAx
Bits
9-0
I2C own address. The I2COAx bits contain the local address of the USCI_Bx
I2C controller. The address is right-justified. In 7-bit addressing mode Bit 6 is
the MSB, Bits 9-7 are ignored. In 10-bit addressing mode Bit 9 is the MSB.
UCBxI2CSA, USCI_Bx I2C Slave Address Register
15
14
13
12
11
10
9
8
0
0
0
0
0
0
r0
r0
r0
r0
r0
r0
rw−0
rw−0
7
6
5
4
3
2
1
0
rw−0
rw−0
rw−0
rw−0
I2CSAx
I2CSAx
rw−0
I2CSAx
21-32
rw−0
Bits
9-0
rw−0
rw−0
I2C slave address. The I2CSAx bits contain the slave address of the external
device to be addressed by the USCI_Bx module. It is only used in master
mode. The address is right-justified. In 7-bit slave addressing mode Bit 6 is
the MSB, Bits 9-7 are ignored. In 10-bit slave addressing mode Bit 9 is the
MSB.
Universal Serial Communication Interface, I2C Mode
USCI Registers: I2C Mode
UCBxI2CIE, USCI_Bx I2C Interrupt Enable Register
7
6
5
4
Reserved
rw−0
rw−0
rw−0
rw−0
3
2
1
0
UCNACKIE
UCSTPIE
UCSTTIE
UCALIE
rw−0
rw−0
rw−0
rw−0
Reserved
Bits
7−4
Reserved
UCNACKIE
Bit 3
Not-acknowledge interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCSTPIE
Bit 2
Stop condition interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCSTTIE
Bit 1
Start condition interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCALIE
Bit 0
Arbitration lost interrupt enable
0
Interrupt disabled
1
Interrupt enabled
Universal Serial Communication Interface, I2C Mode
21-33
USCI Registers: I2C Mode
IE2, Interrupt Enable Register 2
7
6
5
4
3
2
UCB0TXIE
UCB0RXIE
rw−0
rw−0
1
0
Bits
7-4
These bits may be used by other modules (see the device-specific data
sheet).
UCB0TXIE
Bit 3
USCI_B0 transmit interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCB0RXIE
Bit 2
USCI_B0 receive interrupt enable
0
Interrupt disabled
1
Interrupt enabled
Bits
1-0
These bits may be used by other modules (see the device-specific data
sheet).
IFG2, Interrupt Flag Register 2
7
6
5
4
3
2
UCB0
TXIFG
UCB0
RXIFG
rw−1
rw−0
1
0
Bits
7-4
These bits may be used by other modules (see the device-specific data
sheet).
UCB0
TXIFG
Bit 3
USCI_B0 transmit interrupt flag. UCB0TXIFG is set when UCB0TXBUF is
empty.
0
No interrupt pending
1
Interrupt pending
UCB0
RXIFG
Bit 2
USCI_B0 receive interrupt flag. UCB0RXIFG is set when UCB0RXBUF has
received a complete character.
0
No interrupt pending
1
Interrupt pending
Bits
1-0
These bits may be used by other modules (see the device-specific data
sheet).
21-34
Universal Serial Communication Interface, I2C Mode
USCI Registers: I2C Mode
UC1IE, USCI_B1 Interrupt Enable Register
7
6
5
4
3
2
Unused
Unused
Unused
Unused
UCB1TXIE
UCB1RXIE
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
1
0
Unused
Bits
7-4
Unused
UCB1TXIE
Bit 3
USCI_B1 transmit interrupt enable
0
Interrupt disabled
1
Interrupt enabled
UCB1RXIE
Bit 2
USCI_B1 receive interrupt enable
0
Interrupt disabled
1
Interrupt enabled
Bits
1-0
These bits may be used by other USCI modules (see the device-specific data
sheet).
UC1IFG, USCI_B1 Interrupt Flag Register
7
6
5
4
3
2
Unused
Unused
Unused
Unused
UCB1
TXIFG
UCB1
RXIFG
rw−0
rw−0
rw−0
rw−0
rw−1
rw−0
1
0
Unused
Bits
7-4
Unused.
UCB1
TXIFG
Bit 3
USCI_B1 transmit interrupt flag. UCB1TXIFG is set when UCB1TXBUF is
empty.
0
No interrupt pending
1
Interrupt pending
UCB1
RXIFG
Bit 2
USCI_B1 receive interrupt flag. UCB1RXIFG is set when UCB1RXBUF has
received a complete character.
0
No interrupt pending
1
Interrupt pending
Bits
1-0
These bits may be used by other modules (see the device-specific data
sheet).
Universal Serial Communication Interface, I2C Mode
21-35
21-36
Universal Serial Communication Interface, I2C Mode
Chapter 22
OA
The OA is a general purpose operational amplifier. This chapter describes the
OA. Three OA modules are implemented in the MSP430FG43x and
MSP430xG461x devices. Two OA modules are implemented in the
MSP430FG42x0 and MSP430FG47x devices.
Topic
Page
22.1 OA Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-2
22.2 OA Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-4
22.3 OA Modules in MSP430FG42x0 Devices . . . . . . . . . . . . . . . . . . . . . . 22-11
22.4 OA Modules in MSP430FG47x Devices . . . . . . . . . . . . . . . . . . . . . . . . 22-16
22.5 OA Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-24
22.6 OA Registers in MSP430FG42x0 Devices . . . . . . . . . . . . . . . . . . . . . 22-27
22.7 OA Registers in MSP430FG47x Devices . . . . . . . . . . . . . . . . . . . . . . . 22-31
OA
22-1
OA Introduction
22.1 OA Introduction
The OA op amps support front-end analog signal conditioning prior to
analog-to-digital conversion.
Features of the OA include:
- Single supply, low-current operation
- Rail-to-rail output
- Software selectable rail-to-rail input
- Programmable settling time vs power consumption
- Software selectable configurations
- Software selectable feedback resistor ladder for PGA implementations
Note: Multiple OA Modules
Some devices may integrate more than one OA module. If more than one OA
module is present on a device, the multiple OA modules operate identically.
Throughout this chapter, nomenclature appears such as OAxCTL0 to
describe register names. When this occurs, the x is used to indicate which
OA module is being discussed. In cases where operation is identical, the
register is simply referred to as OAxCTL0.
The block diagram of the OA module is shown in Figure 22−1.
22-2
OA
OA Introduction
Figure 22−1. OA Block Diagram
OAPx=3
OAFCx=6
OANx=3
OAADC0
A12 ext. (OA0)
A13 ext. (OA1)
A14 ext. (OA2)
1
OAPx
OAxI0
OA0I1 (FG43x)
OAxI1 (FG461x)
Int. DAC12_0OUT
00
Int. DAC12_1OUT
11
OAADC1
OAFCx=0
OAPMx
01
0
10
+
1
−
0
1
1
00
OAxI1
01
Int. DAC12_0OUT
10
Int. DAC12_1OUT
11
A1 int./ext., OA0O (OA0)
A3 int./ext., OA1O (OA1)
A5 int./ext., OA2O (OA2)
1
OAxOUT
OAx
OA1TAP (OA0)
OA2TAP (OA1)
OANx OA0TAP (OA2)
OAxI0
A12 int. (OA0)
A13 int. (OA1)
A14 int. (OA2)
0
OAFCx={2,4,5,6}
OAADC1
OANx = 0
OAFCx = 7
00
RBOTTOM
OA1RBOTTOM (OA0)
OA2RBOTTOM (OA1)
OA0RBOTTOM (OA2)
1
01
10
NA
11
OAFCx = {0,1,3}
1
OAFCx=1
OAFCx={2 − 7}
OAFBRx
3
RTOP
000
4R
001
4R
010
2R
OAFCx
011
OAxTAP
2R
3
R
000
unused
R
001
OAxOUT
R
010
reserved
R
011
AV CC
100
101
110
111
RBOTTOM
OAFBRx > 0
100
101
reserved 00
OAxI0
01
OAxI1
110
111
unused
10
11
OA2OUT (OA0)
OA0OUT (OA1)
OA1OUT (OA2)
OANx
OA
22-3
OA Operation
22.2 OA Operation
The OA module is configured with user software. The setup and operation of
the OA is discussed in the following sections.
22.2.1 OA Amplifier
The OA is a configurable low-current rail-to-rail operational amplifier. It can be
configured as an inverting amplifier or a non-inverting amplifier, or it can be
combined with other OA modules to form differential amplifiers. The output
slew rate of the OA can be configured for optimized settling time vs power
consumption with the OAPMx bits. When OAPMx = 00, the OA is off, and the
output is high-impedance. When OAPMx > 0, the OA is on. See the
device-specific data sheet for parameters.
22.2.2 OA Input
The OA has configurable input selection. The signals for the + and − inputs are
individually selected with the OANx and OAPx bits and can be selected as
external signals or internal signals from one of the DAC12 modules. One of the
non-inverting inputs is tied together internally for all OA modules.
The OA input signal swing is software selectable with the OARRIP bit. When
OARRIP = 0, rail-to-rail input mode is selected, and the OA uses higher
quiescent current. See the device data sheet for parameters.
22.2.3 OA Output
The OA has configurable output selection. The OA output signals can be
routed to ADC12 inputs A12 (OA0), A13 (OA1), or A14 (OA2) with the
OAADC0 bit. When OAADC0 = 1 and OAPMx > 0, the OA output is connected
internally to the corresponding ADC input, and the external ADC input is not
connected. The OA output signals can also be routed to ADC12 inputs A1
(OA0), A3 (OA1), or A5 (OA2) when OAFCx = 0 or when OAADC1 = 1. In this
case, the OA output is connected to both the ADC12 input internally and the
corresponding pin on the device. The OA output is also connected to an
internal R-ladder with the OAFCx bits. The R-ladder tap is selected with the
OAFBRx bits to provide programmable gain amplifier functionality.
22-4
OA
OA Operation
22.2.4 OA Configurations
The OA can be configured for different amplifier functions with the OAFCx bits.
as listed in Table 22−1.
Table 22−1.OA Mode Select
OAFCx
OA Mode
000
General-purpose op amp
001
Unity gain buffer
010
Reserved
011
Comparator
100
Non-inverting PGA amplifier
101
Reserved
110
Inverting PGA amplifier
111
Differential amplifier
General-Purpose Opamp Mode
In this mode, the feedback resistor ladder is isolated from the OAx, and the
OAxCTL0 bits define the signal routing. The OAx inputs are selected with the
OAPx and OANx bits. The OAx output is connected internally to the ADC12
input channel as selected by the OAxCTL0 bits.
Unity Gain Mode
In this mode, the output of the OAx is connected to RBOTTOM, and the inverting
input of the OAx providing a unity-gain buffer. The non-inverting input is
selected by the OAPx bits. The external connection for the inverting input is
disabled, and the OANx bits are don’t care. The OAx output is connected
internally to the ADC12 input channel as selected by the OAxCTL0 bits.
Comparator Mode
In this mode, the output of the OAx is isolated from the resistor ladder. RTOP
is connected to AVSS, and RBOTTOM is connected to AVCC. The OAxTAP signal
is connected to the inverting input of the OAx, providing a comparator with a
programmable threshold voltage selected by the OAFBRx bits. The
non-inverting input is selected by the OAPx bits. Hysteresis can be added by
an external positive feedback resistor. The external connection for the
inverting input is disabled, and the OANx bits are don’t care. The OAx output
is connected internally to the ADC12 input channel as selected by the
OAxCTL0 bits.
OA
22-5
OA Operation
Non-Inverting PGA Mode
In this mode, the output of the OAx is connected to RTOP, and RBOTTOM is
connected to AVSS. The OAxTAP signal is connected to the inverting input of
the OAx, providing a non-inverting amplifier configuration with a
programmable gain of [1+ OAxTAP ratio]. The OAxTAP ratio is selected by the
OAFBRx bits. If the OAFBRx bits = 0, the gain is unity. The non-inverting input
is selected by the OAPx bits. The external connection for the inverting input
is disabled, and the OANx bits are don’t care. The OAx output is connected
internally to the ADC12 input channel as selected by the OAxCTL0 bits.
Inverting PGA Mode
In this mode, the output of the OAx is connected to RTOP, and RBOTTOM is
connected to an analog multiplexer that multiplexes the OAxI0, OAxI1, or the
output of one of the remaining OAs, selected with the OANx bits. The OAxTAP
signal is connected to the inverting input of the OAx, providing an inverting
amplifier with a gain of −OAxTAP ratio. The OAxTAP ratio is selected by the
OAFBRx bits. The non-inverting input is selected by the OAPx bits. The OAx
output is connected internally to the ADC12 input channel as selected by the
OAxCTL0 bits.
Differential Amplifier Mode
This mode allows internal routing of the OA signals for a two-opamp or
three-opamp instrumentation amplifier. Figure 22−2 shows a two-opamp
configuration with OA0 and OA1. In this mode, the output of the OAx is
connected to RTOP by routing through another OAx in the Inverting PGA mode.
RBOTTOM is unconnected, providing a unity-gain buffer. This buffer is
combined with one or two remaining OAx modules to form the differential
amplifier. The OAx output is connected internally to the ADC12 input channel
as selected by the OAxCTL0 bits.
22-6
OA
OA Operation
Figure 22−2 shows an example of a two-opamp differential amplifier using
OA0 and OA1. The control register settings and are shown in Table 22−2. The
gain for the amplifier is selected by the OAFBRx bits for OA1 and is shown in
Table 22−3. The OAx interconnections are shown in Figure 22−3.
Table 22−2.Two-Opamp Differential Amplifier Control Register Settings
Register
Settings (Binary)
OA0CTL0
00 xx xx 0 0
OA0CTL1
000 111 0 x
OA1CTL0
10 xx xx x x
OA1CTL1
xxx 110 0 x
Table 22−3.Two-Opamp Differential Amplifier Gain Settings
OA1 OAFBRx
Gain
000
0
001
1/3
010
1
011
1 2/3
100
3
101
4 1/3
110
7
111
15
Figure 22−2. Two Opamp Differential Amplifier
V2
+
OA1
−
V1
Vdiff =
+
(V 2 − V 1) xR 2
R1
OA0
−
R1
R2
OA
22-7
OA Operation
Figure 22−3. Two Opamp Differential Amplifier OAx Interconnections
OAADC0
A13 ext.
1
OAPMx
00
01
A13 int.
0
OAPx
OAADC1
V2
0
10
+
1
11
1
A3 int./ext., OA1O
OA1
−
0
1
00
OAADC1
01
10
11
OAFBRx
3
000
4R
001
4R
010
2R
011
2R
OAPx
100
01
10
11
V1
0
1
R
000
R
001
R
010
R
011
101
OAPMx
00
110
+
111
OA0
−
OA1RBOTTOM
100
00
101
01
01
10
11
111
001
011
100
101
110
111
OA
110
000
010
22-8
00
OA0OUT
10
11
OA Operation
Figure 22−4 shows an example of a three-opamp differential amplifier using
OA0, OA1, and OA2. The control register settings are shown in Table 22−4.
The gain for the amplifier is selected by the OAFBRx bits of OA0 and OA2. The
OAFBRx settings for both OA0 and OA2 must be equal. The gain settings are
shown in Table 22−5. The OAx interconnections are shown in Figure 22−5.
Table 22−4.Three-Opamp Differential Amplifier Control Register Settings
Register
Settings (Binary)
OA0CTL0
00 xx xx 0 0
OA0CTL1
xxx 001 0 x
OA1CTL0
00 xx xx 0 0
OA1CTL1
000 111 0 x
OA2CTL0
11 11 xx x x
OA2CTL1
xxx 110 0 x
Table 22−5.Three-Opamp Differential Amplifier Gain Settings
OA0/OA2 OAFBRx
Gain
000
0
001
1/3
010
1
011
1 2/3
100
3
101
4 1/3
110
7
111
15
Figure 22−4. Three-Opamp Differential Amplifier
V2
+
R1
R2
OA0
−
+
OA2
−
V1
+
Vdiff
=
(V 2 − V 1) xR 2
R1
OA1
−
R1
R2
OA
22-9
OA Operation
Figure 22−5. Three-Opamp Differential Amplifier OAx Interconnections
OAPx
OAADC0
OAPMx
00
01
A14 ext.
0
10
1
11
1
+
OA0OUT
OA0
OAPMx
−
OAADC1
0
11
1
4R
001
00
2R
10
2R
11
011
100
OAFBRx
R
000
3
R
001
000
R
010
001
R
011
010
100
011
101
100
110
101
101
110
111
OA0RBOTTOM
OAADC1
01
010
4R
4R
2R
2R
OAPx
OAPMx
00
11
0
000
OA0TAP
10
A5 int./ext., OA2O
−
OA0TAP
4R
01
1
OA2
3
01
10
+
1
OAFBRx
00
A14 int.
0
V2
V1
111
0
1
R
000
R
001
R
010
R
011
110
+
111
OA1
−
OA2RBOTTOM
100
00
101
01
01
10
11
111
001
011
100
101
110
111
OA
110
000
010
22-10
00
OA1OUT
10
11
OA Modules in MSP430FG42x0 Devices
22.3 OA Modules in MSP430FG42x0 Devices
In MSP430FG42x0 devices, two operational amplifiers, a DAC, and a
sigma-delta converter are combined into a measurement front end. The
DAC12 module and the SD16A_1 module are described in separate chapters.
The block diagram of the operational amplifier is shown in Figure 22−6.
Figure 22−6. FG42x0 Operational Amplifiers Block Diagram
OACAL
1
0
OAPx
Int. SD16_A.A0−(OA0)
Int. SD16_A.A1−(OA1)
OAPMx
OAxI0
00
OA0I0
01
Int. DAC12
10
OAxP
+
OA0OUT/A0+ (OA0)
OA1OUT/A1+ (OA1)
OAx
11
−
OANx
OAxI1
00
OAxI2
01
Int. DAC12
10
0
1
11
OAFCx=001
1
SWCTL3 (OA0)
OAFCx SWCTL7 (OA1)
3
unused
OAN0
000
unused
001
reserved
...
reserved
OA0FB/A0−(OA0)
OA1FB/A1−(OA1)
101
0
110
1
unused
111
2
SWCTL2 (OA0)
SWCTL6 (OA1)
SWxC
SWCTL0/1 (OA0)
SWCTL6/7 (OA1)
1
OA
22-11
OA Modules in MSP430FG42x0 Devices
22.3.1 OA Amplifier
Each OA is a configurable low-current operational amplifier that can be
configured as an inverting amplifier or a non-inverting amplifier.
22.3.2 OA Inputs
The OA has configurable input selection. The signals for the + and − inputs are
individually selected with the OANx and OAPx bits and can be selected as
external signals or internal signals from the DAC12 modules or VSS. One of
the non-inverting inputs (OA0I0) is tied together internally for all OA modules.
The SWCTL0, SWCTL1, SWCTL4, and SWCTL5 bits force settings of the
OANx and OAPx bits. See section Switch Control for more details.
22.3.3 OA Outputs
The OA outputs are routed to the respective output pin OAxOUT and the
positive SD16_A inputs A0+ (OA0), or A1+ (OA1).
22.3.4 OA Configurations
The OA can be configured for different amplifier functions with the OAFCx bits
as listed in Table 22−6. The SWCTL0, SWCTL1, SWCTL4, and SWCTL5 bits
force settings of the OAFCx bits. See section Switch Control for more details.
Table 22−6.FG42x0 OA Mode Select
OAFCx
OA Mode
000
General-purpose opamp
001
Unity gain buffer
010
Reserved
011
Reserved
100
Reserved
101
Reserved
110
Inverting amplifier
111
Reserved
General-Purpose Opamp Mode
In this mode, the OAx inputs are selected with the OAPx and OANx bits. The
OAx output is connected to the output pin and to the SD16_A input. Any
feedback needs to be done externally from the output pins OAxOUT to one of
the input pins OAxI0 to OAxI2.
22-12
OA
OA Modules in MSP430FG42x0 Devices
Unity-Gain Mode
In this mode, the output of the OAx is connected directly to the inverting input
of the OAx providing a unity-gain buffer. The non-inverting input is selected by
the OAPx bits. The external connection for the inverting input is disabled, and
the OANx bits are don’t care.
Inverting Amplifier Mode
In this mode, an additional feedback connection is provided as shown in
Figure 22−7. The OANx bits select the inverting input signal, which is also
connected to the feedback input and to the negative SD16_A input. The
circuitry shown in Figure 22−7 mimics a low resistive multiplexer between the
inputs OAxI1 and OAxI2. Because the current into the negative terminal of
operational amplifier is very low, the voltage drop over the negative input
multiplexer can be neglected. The multiplexer connecting the input OAxI1 or
OAxI2 to the feedback path is included in the feedback loop, thus
compensating for the voltage drop across this multiplexer. This mode is
especially useful for transimpedance amplifiers as shown in Figure 22−12.
The non-inverting input is selected by the OAPx bits. The OAx output is
connected to the output pin and to the positive SD16_A input.
Figure 22−7. Inverting Amplifier Configuration
OAPx
OAPMx
+
OAx
OANx
OAxI1
00
OAxI2
01
−
OA0OUT/A0+ (OA0)
OA1OUT/A1+ (OA1)
10
11
0
1
OA0FB/A0−(OA0)
OA1FB/A1−(OA1)
OA
22-13
OA Modules in MSP430FG42x0 Devices
Figure 22−8. Transimpedance Amplifier With Two Current Inputs
OAPx
to SD16_A
00
01
10
DAC12
OA0OUT/A0+ (OA0)
OA1OUT/A1+ (OA1)
+
11
OAx
−
OANx
I1
OAxI1
I2
OAxI2
RFB
OA0FB/A0−(OA0)
OA1FB/A1−(OA1)
00
01
10
11
22.3.5 Switch Control
The switch control register SWCTL controls the low resistive switches to
ground SW0C and SW1C as well as simplifies the operation of the operational
amplifier as transimpedance amplifier.
SWCTL2 closes the switch SW0C to ground, and SWCTL6 closes the switch
SW1C. SWCTL3 shorts the external feedback resistor for OA0, and SWCTL7
shorts the external feedback resistor for OA1. SWCTL0 and SWCTL1 select
the negative analog input to the transimpedance amplifier OA0, and SWCTL4
and SWCTL5 select them for OA1 as shown in Table 22−9.
Table 22−7.Input Control of Transimpedance Amplifier
22-14
OA
SWCTL0 (OA0)
SWCTL4 (OA1)
SWCTL1 (OA0)
SWCTL5 (OA1)
1
0
OANx = 00
OAFCx = 110
0
1
OANx = 01
OAFCx = 110
0
0
No forced settings
1
1
No forced settings
Forced Settings
OA Modules in MSP430FG42x0 Devices
22.3.6 Offset Calibration
Figure 22−9 shows the configuration for the offset measurement. To measure
the offset of the operational amplifier OAx, the unity-gain buffer mode needs
to be selected with OAFCx = 001, and the positive input of the amplifier needs
to be connected to the negative input of the sigma-delta ADC by setting the
calibration bit OACAL. The voltage that can be measured between the
negative and the positive SD16_A input represents the offset voltage of the
operational amplifier. The measurement result can be incorporated into the
later measurement results to compensate for the offset of the amplifier.
Figure 22−9. Offset Calibration
OACAL
1
0
OAPx
OAxI0
00
OA0I0
01
Int. DAC12
10
11
A0−(OA0)
A1−(OA1)
VOffset
+
OAx
−
to SD16_A
A0+ (OA0)
A1+ (OA1)
OA
22-15
OA Modules in MSP430FG47x Devices
22.4 OA Modules in MSP430FG47x Devices
In the MSP430FG47x devices, two operational amplifiers, two DAC modules,
and a sigma-delta converter are combined into a measurement front end. The
DAC12 modules and the SD16_A module are described in separate chapters.
The block diagram of the operational amplifier is shown in Figure 22−10.
22-16
OA
OA Modules in MSP430FG47x Devices
Figure 22-- 10. MSP430FG47x Operational Amplifiers 0/1 (OA0/1) Block Diagram
OAPx
SWCTLx
2
3
OACALx
Control
logic
DAC12OPSx
1
OA0I0
DAC12_x
1
OAxI0
to
Ax-
0
00
01
0
See Note 1
10
Vss
11
OANx
OAPMx
+
-
SWCTLx
2
3
OAx
OAxO/Ax+
Control
logic
OAFCx = 001
OAxI1
00
OAxI2
01
OAxI3
10
int. DAC12_x
11
0
1
1
00
01
10
0
OAFCx = 110
SWCTL3 (OA0)
SWCTL7 (OA1)
1
OAxFB
0
OAFCx = 110 & SWCTL9 (OA0)
OAFCx = 110 & SWCTL13 (OA1)
00
01
10
OAxRFB
1
0
Note 1: DAC12_0 is routed to OA1. DAC12_1 is routed to OA0 only if DAC12OPS1 = 0.
OA
22-17
OA Modules in MSP430FG47x Devices
22.4.1 OA Amplifier
Each OA is a configurable low-current operational amplifier that can be
configured as an inverting amplifier or a non-inverting amplifier.
22.4.2 OA Inputs
The OA has configurable input selection. The signals for the + and − inputs are
individually selected with the OANx and OAPx bits and can be selected as
external signals or internal signals from the DAC12 module. One of the
non-inverting inputs (OA0I0) is tied together internally for both OA modules.
The SWCTL0, SWCTL1, SWCTL4, SWCTL5, SWCTL8, and SWCTL12 bits
overwrite settings given by the OANx and OAPx bits. See section Switch
Control for more details. Also the untiy gain buffer mode sets the input for the
−input of the OAx module to the OAx output.
22.4.3 OA Outputs
The OA outputs are routed to the respective output pin OAxOUT and the
positive SD16_A inputs A0+ (OA0), or A1+ (OA1).
22.4.4 OA Configurations
The OA can be configured for different amplifier functions with the OAFCx bits
as listed in Table 22−8. The SWCTL0, SWCTL1, SWCTL4, SWCTL5,
SWCTL8, and SWCTL12 bits force settings of the OAFCx bits. See section
Switch Control for more details.
Table 22−8.MSP430FG47x OAx Mode Select
OAFCx
OAx Mode
000
General-purpose op amp
001
Unity-gain buffer
010
Reserved
011
Reserved
100
Reserved
101
Reserved
110
Inverting amplifier
111
Reserved
General-Purpose Opamp Mode
In this mode the OAx inputs are selected with the OAPx and OANx bits. The
OAx output is connected to the output pin and to the SD16_A inputs. Any
feedback needs to be done externally from the output pins OAxOUT to one of
the input pins OAxI0 to OAxI3.
22-18
OA
OA Modules in MSP430FG47x Devices
Unity Gain Mode
In this mode the output of the OAx is connected directly to the inverting input
of the OAx providing a unity gain buffer. The non-inverting input is selected by
the OAPx bits. The external connection for the inverting input is disabled and
the OANx bits are don’t care.
Inverting Amplifier Mode
In this mode an additional feedback connection is provided as shown in
Figure 22−11. The OANx bits select the inverting input signal, which is also
connected to the feedback input and to the negative SD16_A input. The
circuitry shown in Figure 22−11 mimics a low resistive multiplexer between the
inputs OAxI1 and OAxI2. Because the current into the negative terminal of
operational amplifier is very low, the voltage drop over the negative input
multiplexer can be neglected. The multiplexer connecting the input OAxI1 or
OAxI2 to the feedback path is included in the feedback loop, thus
compensating for the voltage drop across this multiplexer. This mode is
especially useful for transimpedance amplifiers as shown in Figure 22−12.
The non-inverting input is selected by the OAPx bits. The OAx output is
connected to the output pin and to the positive SD16_A input.
OA
22-19
OA Modules in MSP430FG47x Devices
Figure 22-- 11.Inverting Amplifier Configuration
OAPMx
OANx
+
SWCTLx
2
-
3
OAx
OAxO/Ax+
Control
logic
OAxI1
00
OAxI2
01
OAxI3
10
int. DAC12_x
11
00
OAxFB
01
10
SWCTL9 (OA0)
SWCTL13 (OA1)
00
01
10
22-20
OA
1
0
OAxRFB
OA Modules in MSP430FG47x Devices
Figure 22-- 12. Transimpedance Amplifier With Three Current Inputs
OAPx
SW C TLx
2
C o n tro l
lo g ic
D AC12O PSx
00
1
D AC 12_x
0
3
01
S e e N o te 1
10
V ss
11
OANx
SW C TLx
2
to S D 1 6 _
OAPMx
3
+
O A x O /A x +
OAx
-
C o n tro l
lo g ic
O A x I1
00
O A x I2
01
O A x I3
10
O A x F B /A x -
11
N o te 1 : D A C 1 2 _ 0 is ro u te d to O A 1 . D A C 1 2 _ 1 is ro u te d to O A 0 o n ly if D A C 1 2 O P S 1 = 0 .
OA
22-21
OA Modules in MSP430FG47x Devices
22.4.5 Switch Control of the FG47x devices
The switch control register OASWCTL0 simplifies the operation of the
operational amplifier.
SWCTL3 shorts the external feedback resistor for OA0 and SWCTL7 shorts
the external feedback resistor for OA1. SWCTL0 and SWCTL1 select the
negative analog input to the transimpedance amplifier OA0, SWCTL4 and
SWCTL5 select them for OA1 as shown in Table 22−9.
Table 22−9.Input Control of Transimpedance Amplifier
OASWCTL0
22-22
OA
Forced Settings
Description
p
SWCTLx
BIT
OAFCx
OANx
0
8
110
00
Selects channel 0 at the − terminal of OA0.
1
9
110
01
Selects channel 1 at the − terminal of OA0.
2
10
−
−
Reserved.
3
11
−
−
OA0OUT and OA0FB are shorted.
4
12
110
00
Selects channel 0 at the − terminal of OA1.
5
13
110
01
Selects channel 1 at the − terminal of OA1.
6
14
−
−
Reserved.
7
15
−
−
OA1OUT and OA1FB are shorted.
8
0
110
10
Selects channel 2 at the − terminal of OA0.
9
1
−
−
Range switch control of OA0 (OA0RFB).
10
2
−
−
Reserved.
11
3
−
−
Reserved
12
4
110
10
Selects channel 2 at the − terminal of OA1.
13
5
−
−
Range switch control of OA1 (OA1RFB).
14
6
−
−
Reserved.
15
7
−
−
Reserved
OA Modules in MSP430FG47x Devices
22.4.6 Offset Calibration
Figure 22−9 shows the configuration for the offset measurement. To measure
the offset of the operational amplifier OAx the OAxCAL bit must be set. The
voltage that can be measured between the negative and the positive SD16_A
input represents the offset voltage of the operational amplifier. The
measurement result can be incorporated into the later measurement results
to compensate for the offset of the amplifier. For both OA modules the
DAC12OPS bit of DAC12_0 module selects if the internal or the external
DAC12_x is used.
Figure 22−13. Offset Calibration
OACALx
1
0
OAPx
A0−(OA0)
A1−(OA1)
VOffset
00
to SD16_A
01
DAC 12_x
10
11
+
OAx
−
A0+ (OA0)
A1+ (OA1)
OA
22-23
OA Registers
22.5 OA Registers
The OA registers are listed in Table 22−10.
Table 22−10. OA Registers
Register
Short Form
Register Type Address
Initial State
OA0 control register 0
OA0CTL0
Read/write
0C0h
Reset with PUC
OA0 control register 1
OA0CTL1
Read/write
0C1h
Reset with PUC
OA1 control register 0
OA1CTL0
Read/write
0C2h
Reset with PUC
OA1 control register 1
OA1CTL1
Read/write
0C3h
Reset with PUC
OA2 control register 0
OA2CTL0
Read/write
0C4h
Reset with PUC
OA2 control register 1
OA2CTL1
Read/write
0C5h
Reset with PUC
22-24
OA
OA Registers
OAxCTL0, Opamp Control Register 0
7
6
5
OANx
rw−0
4
3
OAPx
rw−0
rw−0
2
OAPMx
rw−0
rw−0
rw−0
1
0
OAADC1
OAADC0
rw−0
rw−0
OANx
Bits
7-6
Inverting input select. These bits select the input signal for the OA inverting
input.
00 OAxI0
01 OAxI1
10 DAC0 internal
11 DAC1 internal
OAPx
Bits
5-4
Non-inverting input select. These bits select the input signal for the OA
non-inverting input.
00 OAxI0
01 OA0I1
10 DAC0 internal
11 DAC1 internal
OAPMx
Bits
3-2
Slew rate select These bits select the slew rate vs. current consumption for
the OA.
00 Off, output high Z
01 Slow
10 Medium
11 Fast
OAADC1
Bit 1
OA output select. This bit connects the OAx output to ADC12 input Ax and
output pin OAxO when OAFCx > 0.
0
OAx output not connected to internal/external A1 (OA0), A3 (OA1), or
A5 (OA2) signals
1
OAx output connected to internal/external A1 (OA0), A3 (OA1), or A5
(OA2) signals
OAADC0
Bit 0
OA output select. This bit connects the OAx output to ADC12 input Ax
when OAPMx > 0.
0
OAx output not connected to internal A12 (OA0), A13 (OA1), or A14
(OA2) signals
1
OAx output connected to internal A12 (OA0), A13 (OA1), or A14
(OA2) signals
OA
22-25
OA Registers
OAxCTL1, Opamp Control Register 1
7
6
5
4
OAFBRx
rw−0
rw−0
3
2
OAFCx
rw−0
rw−0
rw−0
rw−0
1
0
Reserved
OARRIP
rw−0
rw−0
OAFBRx
Bits
7-5
OAx feedback resistor select
000 Tap 0
001 Tap 1
010 Tap 2
011 Tap 3
100 Tap 4
101 Tap 5
110 Tap 6
111 Tap 7
OAFCx
Bits
4-2
OAx function control. This bit selects the function of OAx
000 General purpose
001 Unity gain buffer
010 Reserved
011 Comparing amplifier
100 Non-inverting PGA
101 Reserved
110 Inverting PGA
111 Differential amplifier
Reserved
Bit 1
Reserved
OARRIP
Bit 0
OA rail-to-rail input off.
0
OAx input signal range is rail-to-rail
1
OAx input signal range is limited. See the device-specific data sheet
for parameters.
22-26
OA
OA Registers in MSP430FG42x0 Devices
22.6 OA Registers in MSP430FG42x0 Devices
The OA registers are listed in Table 22−10.
Table 22−11. OA Registers
Register
Short Form
Register Type Address
Initial State
OA0 control register 0
OA0CTL0
Read/write
0C0h
Reset with PUC
OA0 control register 1
OA0CTL1
Read/write
0C1h
Reset with PUC
OA1 control register 0
OA1CTL0
Read/write
0C2h
Reset with PUC
OA1 control register 1
OA1CTL1
Read/write
0C3h
Reset with PUC
Switch control register
SWCTL
Read/write
0CFh
Reset with PUC
OA
22-27
OA Registers in MSP430FG42x0 Devices
OAxCTL0, Opamp Control Register 0
7
6
5
OANx
rw−0
4
3
OAPx
rw−0
rw−0
2
OAPMx
rw−0
rw−0
rw−0
1
0
Reserved
Reserved
rw−0
rw−0
OANx
Bits
7−6
Inverting input select
These bits select the input signal for the OAx inverting input.
00 OAxI1
01 OAxI2
10 DAC internal
11 VSS
OAPx
Bits
5−4
Non-inverting input select
These bits select the input signal for the OAx non-inverting input.
00 OAxI0
01 OA0I0
10 DAC internal
11 VSS
OAPMx
Bits
3−2
Slew rate select
These bits select the slew rate vs. current consumption of the OAx.
00 Off, output high Z
01 Slow
10 Medium
11 Fast
Reserved
Bits
1−0
Reserved
22-28
OA
OA Registers in MSP430FG42x0 Devices
OAxCTL1, Opamp Control Register 1
7
6
5
4
Reserved
rw−0
rw−0
3
2
OAFCx
rw−0
rw−0
rw−0
Reserved
Bits
7−5
Reserved
OAFCx
Bit 4−2
OAx function control
These bits select the function of OAx
000 General purpose
001 Unity gain buffer
010 Reserved
011 Reserved
100 Reserved
101 Reserved
110 Inverting amplifier
111 Reserved
OACAL
Bit 1
Offset calibration
This bit enables the offset calibration.
0
Offset calibration disabled
1
Offset calibration enabled
Reserved
Bit 0
Reserved
rw−0
1
0
OACAL
Reserved
rw−0
rw−0
OA
22-29
OA Registers in MSP430FG42x0 Devices
SWCTL, Switch Control Register
7
6
5
4
3
2
1
0
SWCTL7
SWCTL6
SWCTL5
SWCTL4
SWCTL3
SWCTL2
SWCTL1
SWCTL0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
SWCTL7
Bit 7
Shunt switch for OA1
0
Switch open
1
OA1OUT and OA1FB shorted together
SWCTL6
Bit 6
SW1C control
0
Switch open
1
SW1C shorted to VSS
SWCTL5,
SWCTL4
Bits
5−4
OANx and OAFCx forced settings for OA1
00 No forced settings
01 OANx forced to 00; OAFCx forced to 110.
10 OANx forced to 01; OAFCx forced to 110.
11 No forced settings
SWCTL3
Bit 3
Shunt switch for OA0
0
Switch open
1
OA0OUT and OA0FB shorted together
SWCTL2
Bit 2
SW0C control
0
Switch open
1
SW0C shorted to VSS
SWCTL1,
SWCTL0
Bits
1−0
OANx and OAFCx forced settings for OA0
00 No forced settings
01 OANx forced to 00; OAFCx forced to 110.
10 OANx forced to 01; OAFCx forced to 110.
11 No forced settings
22-30
OA
OA Registers in MSP430FG47x Devices
22.7 OA Registers in MSP430FG47x Devices
The OA registers are listed in Table 22−12.
Table 22−12. OA Registers
Register
Short Form
Register Type Address
Initial State
OA0 control register 0
OA0CTL0
Read/write
0C0h
Reset with PUC
OA0 control register 1
OA0CTL1
Read/write
0C1h
Reset with PUC
OA1 control register 0
OA1CTL0
Read/write
0C2h
Reset with PUC
OA1 control register 1
OA1CTL1
Read/write
0C3h
Reset with PUC
OA Switch control register high byte
OASWCTL_H
Read/write
0CEh
Reset with PUC
OA Switch control register low byte
OASWCTL_L
Read/write
0CFh
Reset with PUC
OA switch control register word
OASWCTL0
Read/write
0CEh
Reset with PUC
OA
22-31
OA Registers in MSP430FG47x Devices
OAxCTL0, Opamp Control Register 0
7
6
5
OANx
rw−0
4
3
OAPx
rw−0
rw−0
2
OAPMx
rw−0
rw−0
rw−0
1
0
Reserved
Reserved
r−0
r−0
OANx
Bits
7−6
Inverting input select
These bits select the input signal for the OAx inverting input.
00 OAxI1
01 OAxI2
10 OAxI3
11 DAC12_0 (OA0), DAC12_1 (OA1) if the DAC12OPS bits are cleared.
OAPx
Bits
5−4
Non-inverting input select
These bits select the input signal for the OAx non-inverting input.
00 OAxI0
01 OA0I0 if DAC12OPS is set. If DAC12OPS is 0 then DAC12_0 (OA0)/
DAC12_1 (OA1) is used.
10 DAC12_1 (OA0)/ DAC12_0 (OA1)
11 VSS
OAPMx
Bits
3−2
Slew rate select
These bits select the slew rate vs. current consumption of the OAx.
00 Off, output high Z
01 Slow
10 Medium
11 Fast
Reserved
Bits
1−0
Reserved
22-32
OA
OA Registers in MSP430FG47x Devices
OAxCTL1, Opamp Control Register 1
7
6
5
4
Reserved
r−0
r−0
3
2
OAFCx
r−0
rw−0
rw−0
Reserved
Bits
7−5
Reserved
OAFCx
Bit 4−2
OAx function control
These bits select the function of OAx
000 General purpose
001 Unity gain buffer
010 Reserved
011 Reserved
100 Reserved
101 Reserved
110 Inverting amplifier
111 Reserved
OACAL
Bit 1
Offset calibration
This bit enables the offset calibration.
0
Offset calibration disabled
1
Offset calibration enabled
Reserved
Bit 0
Reserved
rw−0
1
0
OACAL
Reserved
rw−0
r−0
OA
22-33
OA Registers in MSP430FG47x Devices
OASWCTL0, Switch Control Register 0
15
14
13
12
11
10
9
8
SWCTL7
Reserved
SWCTL5
SWCTL4
SWCTL3
Reserved
SWCTL1
SWCTL0
rw−0
r−0
rw−0
rw−0
rw−0
r−0
rw−0
rw−0
7
6
5
4
3
2
1
0
Reserved
Reserved
SWCTL13
SWCTL12
Reserved
Reserved
SWCTL9
SWCTL8
r−0
r−0
rw−0
rw−0
r−0
r−0
rw−0
rw−0
SWCTL7
Bit 15
Shunt switch for OA1
0
Switch open
1
OA1OUT and OA1FB shorted together
Reserved
Bit 14
Reserved
SWCTL5
Bit 13
OANx and OAFCx forced settings for OA1
0
No forced settings
1
OA1I2 enabled; OAFCx forced to 110.
SWCTL4
Bit 12
OANx and OAFCx forced settings for OA1
0
No forced settings
1
OA1I1 enabled; OAFCx forced to 110.
SWCTL3
Bit 11
Shunt switch for OA0
0
Switch open
1
OA0OUT and OA0FB shorted together
Reserved
Bit 10
Reserved
SWCTL1
Bit 9
OANx and OAFCx forced settings for OA0
0
No forced settings
1
OA0I2 enabled; OAFCx forced to 110.
SWCTL0
Bit 8
OANx and OAFCx forced settings for OA0
0
No forced settings
1
OA0I1 enabled; OAFCx forced to 110.
Reserved
Bits
7−6
Reserved
SWCTL13
Bit 5
Range switch control for OA1
0
Switch open
1
Switch closed.
SWCTL12
Bit 4
OANx and OAFCx forced settings for OA1
0
No forced settings
1
OA1I3 enabled; OAFCx forced to 110.
Reserved
Bits
3−2
Reserved
22-34
OA
OA Registers in MSP430FG47x Devices
SWCTL9
Bit 1
Range feedback switch control for OA0
0
Switch open
1
Switch closed.
SWCTL8
Bit 0
OANx and OAFCx forced settings for OA0
0
No forced settings
1
OA0I3 enabled; OAFCx forced to 110.
OA
22-35
22-36
OA
Chapter 23
Comparator_A
Comparator_A is an analog voltage comparator. This chapter describes
Comparator_A. Comparator_A is implemented in all MSP430x4xx devices.
Topic
Page
23.1 Comparator_A Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-2
23.2 Comparator_A Operation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-4
23.3 Comparator_A Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-9
Comparator_A
23-1
Comparator_A Introduction
23.1 Comparator_A Introduction
The comparator_A module supports precision slope analog-to-digital
conversions, supply voltage supervision, and monitoring of external analog
signals.
Features of Comparator_A include:
- Inverting and non-inverting terminal input multiplexer
- Software selectable RC-filter for the comparator output
- Output provided to Timer_A capture input
- Software control of the port input buffer
- Interrupt capability
- Selectable reference voltage generator
- Comparator and reference generator can be powered down
The Comparator_A block diagram is shown in Figure 23−1.
23-2
Comparator_A
Comparator_A Introduction
Figure 23−1. Comparator_A Block Diagram
VCC 0V
P2CA0
CAEX
1
0
CAON
0
CA0
1
1
0
CA1
CAF
0
CCI1B
++
0
0
−−
1
1
CAOUT
0
1
1
Set_CAIFG
Tau ~ 2.0s
P2CA1
0V
1
0
CAREFx
CARSEL
0.5x VCC
00
0
1
VCAREF
01
0.25x VCC
10
11
G
D
S
Comparator_A
23-3
Comparator_A Operation
23.2 Comparator_A Operation
The comparator_A module is configured with user software. The setup and
operation of comparator_A is discussed in the following sections.
23.2.1 Comparator
The comparator compares the analog voltages at the + and – input terminals.
If the + terminal is more positive than the – terminal, the comparator output
CAOUT is high. The comparator can be switched on or off using control bit
CAON. The comparator should be switched off when not in use to reduce
current consumption. When the comparator is switched off, the CAOUT is
always low.
23.2.2 Input Analog Switches
The analog input switches connect or disconnect the two comparator input
terminals to associated port pins using the P2CAx bits. Both comparator
terminal inputs can be controlled individually. The P2CAx bits allow:
- Application of an external signal to the + and – terminals of the comparator
- Routing of an internal reference voltage to an associated output port pin
Internally, the input switch is constructed as a T-switch to suppress distortion
in the signal path.
Note: Comparator Input Connection
When the comparator is on, the input terminals should be connected to a
signal, power, or ground. Otherwise, floating levels may cause unexpected
interrupts and increased current consumption.
The CAEX bit controls the input multiplexer, exchanging which input signals
are connected to the comparator’s + and – terminals. Additionally, when the
comparator terminals are exchanged, the output signal from the comparator
is inverted. This allows the user to determine or compensate for the
comparator input offset voltage.
23-4
Comparator_A
Comparator_A Operation
23.2.3 Output Filter
The output of the comparator can be used with or without internal filtering.
When control bit CAF is set, the output is filtered with an on-chip RC-filter.
Any comparator output oscillates if the voltage difference across the input
terminals is small. Internal and external parasitic effects and cross coupling on
and between signal lines, power supply lines, and other parts of the system
are responsible for this behavior as shown in Figure 23−2. The comparator
output oscillation reduces accuracy and resolution of the comparison result.
Selecting the output filter can reduce errors associated with comparator
oscillation.
Figure 23−2. RC-Filter Response at the Output of the Comparator
+ Terminal
− Terminal
Comparator Inputs
Comparator Output
Unfiltered at CAOUT
Comparator Output
Filtered at CAOUT
23.2.4 Voltage Reference Generator
The voltage reference generator is used to generate VCAREF, which can be
applied to either comparator input terminal. The CAREFx bits control the
output of the voltage generator. The CARSEL bit selects the comparator
terminal to which VCAREF is applied. If external signals are applied to both
comparator input terminals, the internal reference generator should be turned
off to reduce current consumption. The voltage reference generator can
generate a fraction of the device’s VCC or a fixed transistor threshold voltage
of ~ 0.55 V.
Comparator_A
23-5
Comparator_A Operation
23.2.5 Comparator_A, Port Disable Register CAPD
The comparator input and output functions are multiplexed with the associated
I/O port pins, which are digital CMOS gates. When analog signals are applied
to digital CMOS gates, parasitic current can flow from VCC to GND. This
parasitic current occurs if the input voltage is near the transition level of the
gate. Disabling the port pin buffer eliminates the parasitic current flow and
therefore reduces overall current consumption.
The CAPDx bits, when set, disable the corresponding P1 input buffer as shown
in Figure 23−3. When current consumption is critical, any P1 pin connected to
analog signals should be disabled with their associated CAPDx bit.
Figure 23−3. Transfer Characteristic and Power Dissipation in a CMOS Inverter/Buffer
VCC
VI
VO
ICC
ICC
VI
VCC
0
CAPD.x = 1
VCC
VSS
23.2.6 Comparator_A Interrupts
One interrupt flag and one interrupt vector are associated with the
Comparator_A as shown in Figure 23−4. The interrupt flag CAIFG is set on
either the rising or falling edge of the comparator output, selected by the
CAIES bit. If both the CAIE and the GIE bits are set, then the CAIFG flag
generates an interrupt request. The CAIFG flag is automatically reset when
the interrupt request is serviced or may be reset with software.
Figure 23−4. Comparator_A Interrupt System
CAIE
VCC
CAIES
SET_CAIFG
0
1
D
IRQ, Interrupt Service Requested
Q
Reset
IRACC, Interrupt Request Accepted
POR
23-6
Comparator_A
Comparator_A Operation
23.2.7 Comparator_A Used to Measure Resistive Elements
The Comparator_A can be optimized to precisely measure resistive elements
using single slope analog-to-digital conversion. For example, temperature can
be converted into digital data using a thermistor, by comparing the thermistor’s
capacitor discharge time to that of a reference resistor as shown in
Figure 23−5. A reference resister Rref is compared to Rmeas.
Figure 23−5. Temperature Measurement System
Rref
Px.x
Rmeas
Px.y
CA0
++
−−
CCI1B
Capture
Input
Of Timer_A
0.25xVCC
The MSP430 resources used to calculate the temperature sensed by Rmeas
are:
- Two digital I/O pins to charge and discharge the capacitor.
- I/O set to output high (VCC) to charge capacitor, reset to discharge.
- I/O switched to high-impedance input with CAPDx set when not in use.
- One output charges and discharges the capacitor via Rref.
- One output discharges capacitor via Rmeas.
- The + terminal is connected to the positive terminal of the capacitor.
- The – terminal is connected to a reference level, for example 0.25 x VCC.
- The output filter should be used to minimize switching noise.
- CAOUT used to gate Timer_A CCI1B, capturing capacitor discharge time.
More than one resistive element can be measured. Additional elements are
connected to CA0 with available I/O pins and switched to high impedance
when not being measured.
Comparator_A
23-7
Comparator_A Operation
The thermistor measurement is based on a ratiometric conversion principle.
The ratio of two capacitor discharge times is calculated as shown in
Figure 23−6.
Figure 23−6. Timing for Temperature Measurement Systems
VC
VCC
Rmeas
Rref
0.25 × VCC
Phase I:
Charge
Phase III:
Charge
Phase II:
Discharge
tref
Phase IV:
Discharge
t
tmeas
The VCC voltage and the capacitor value should remain constant during the
conversion, but are not critical since they cancel in the ratio:
N meas
+
N ref
–R meas
–R ref
C
C
N meas
R
+ meas
N ref
R ref
R meas + R ref
23-8
Comparator_A
N meas
N ref
ln
ln
V ref
V CC
V ref
V CC
Comparator_A Registers
23.3 Comparator_A Registers
The Comparator_A registers are listed in Table 23−1.
Table 23−1.Comparator_A Registers
Register
Short Form
Register Type Address
Initial State
Comparator_A control register 1
CACTL1
Read/write
Reset with POR
059h
Comparator_A control register 2
CACTL2
Read/write
05Ah
Reset with POR
Comparator_A port disable
CAPD
Read/write
05Bh
Reset with POR
Comparator_A
23-9
Comparator_A Registers
CACTL1, Comparator_A Control Register 1
7
6
CAEX
CARSEL
rw−(0)
rw−(0)
5
4
CAREFx
rw−(0)
rw−(0)
3
2
1
0
CAON
CAIES
CAIE
CAIFG
rw−(0)
rw−(0)
rw−(0)
rw−(0)
CAEX
Bit 7
Comparator_A exchange. This bit exchanges the comparator inputs and
inverts the comparator output.
CARSEL
Bit 6
Comparator_A reference select. This bit selects which terminal the VCAREF
is applied to.
When CAEX = 0:
0
VCAREF is applied to the + terminal
1
VCAREF is applied to the – terminal
When CAEX = 1:
0
VCAREF is applied to the – terminal
1
VCAREF is applied to the + terminal
CAREF
Bits
5-4
Comparator_A reference. These bits select the reference voltage VCAREF.
00 Internal reference off. An external reference can be applied.
01 0.25*VCC
10 0.50*VCC
11 Diode reference is selected
CAON
Bit 3
Comparator_A on. This bit turns on the comparator. When the comparator
is off it consumes no current. The reference circuitry is enabled or disabled
independently.
0
Off
1
On
CAIES
Bit 2
Comparator_A interrupt edge select
0
Rising edge
1
Falling edge
CAIE
Bit 1
Comparator_A interrupt enable
0
Disabled
1
Enabled
CAIFG
Bit 0
The Comparator_A interrupt flag
0
No interrupt pending
1
Interrupt pending
23-10
Comparator_A
Comparator_A Registers
CACTL2, Comparator_A Control Register 2
7
6
5
4
Unused
rw−(0)
rw−(0)
rw−(0)
rw−(0)
3
2
1
0
P2CA1
P2CA0
CAF
CAOUT
rw−(0)
rw−(0)
rw−(0)
r−(0)
Unused
Bits
7-4
Unused.
P2CA1
Bit 3
Pin to CA1. This bit selects the CA1 pin function.
0
The pin is not connected to CA1
1
The pin is connected to CA1
P2CA0
Bit 2
Pin to CA0. This bit selects the CA0 pin function.
0
The pin is not connected to CA0
1
The pin is connected to CA0
CAF
Bit 1
Comparator_A output filter
0
Comparator_A output is not filtered
1
Comparator_A output is filtered
CAOUT
Bit 0
Comparator_A output. This bit reflects the value of the comparator output.
Writing this bit has no effect.
CAPD, Comparator_A Port Disable Register
7
6
5
4
3
2
1
0
CAPD7
CAPD6
CAPD5
CAPD4
CAPD3
CAPD2
CAPD1
CAPD0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
CAPDx
Bits
7-0
Comparator_A port disable. These bits individually disable the input buffer
for the pins of the port associated with Comparator_A. For example, the
CAPDx bits can be used to individually enable or disable each P1.x pin
buffer. CAPD0 disables P1.0, CAPD1 disables P1.1, etc.
0
The input buffer is enabled.
1
The input buffer is disabled.
Comparator_A
23-11
23-12
Comparator_A
Chapter 24
Comparator_A+
Comparator_A+ is an analog voltage comparator. This chapter describes the
operation of the Comparator_A+ of the 4xx family. It is available on the
MSP430F41x2 devices.
Topic
Page
24.1 Comparator_A+ Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-2
24.2 Comparator_A+ Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-4
24.3 Comparator_A+ Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-10
Comparator_A+
24-1
Comparator_A+ Introduction
24.1 Comparator_A+ Introduction
The Comparator_A+ module supports precision slope analog-to-digital
conversions, supply voltage supervision, and monitoring of external analog
signals.
Features of Comparator_A+ include:
- Inverting and non-inverting terminal input multiplexer
- Software selectable RC-filter for the comparator output
- Output provided to Timer_A capture input
- Software control of the port input buffer
- Interrupt capability
- Selectable reference voltage generator
- Comparator and reference generator can be powered down
- Input Multiplexer
The Comparator_A+ block diagram is shown in Figure 24−1.
24-2
Comparator_A+
Comparator_A+ Introduction
Figure 24−1. Comparator_A+ Block Diagram
P2CA4
P2CA0
00
CA0
01
CA1
10
CA2
11
VCC 0V
CAEX
1
0
CAON
CAF
0
1
CASHORT
000
0
CA1
001
1
CA2
010
CA3
011
CA4
100
CA5
101
CA6
110
CA7
111
CCI1B
++
0
0
−−
1
1
CAOUT
Set_CAIFG
Tau ~ 2.0ns
0V
1
0
CAREFx
P2CA3
P2CA2
P2CA1
CARSEL
0.5xVCC
00
0
1
V CAREF
01
0.25xVCC
10
11
G
D
S
Comparator_A+
24-3
Comparator_A+ Operation
24.2 Comparator_A+ Operation
The Comparator_A+ module is configured with user software. The setup and
operation of Comparator_A+ is discussed in the following sections.
24.2.1 Comparator
The comparator compares the analog voltages at the + and – input terminals.
If the + terminal is more positive than the – terminal, the comparator output
CAOUT is high. The comparator can be switched on or off using control bit
CAON. The comparator should be switched off when not in use to reduce
current consumption. When the comparator is switched off, the CAOUT is
always low.
24.2.2 Input Analog Switches
The analog input switches connect or disconnect the two comparator input
terminals to associated port pins using the P2CAx bits. Both comparator
terminal inputs can be controlled individually. The P2CAx bits allow:
- Application of an external signal to the + and – terminals of the comparator
- Routing of an internal reference voltage to an associated output port pin
Internally, the input switch is constructed as a T-switch to suppress distortion
in the signal path.
Note: Comparator Input Connection
When the comparator is on, the input terminals should be connected to a
signal, power, or ground. Otherwise, floating levels may cause unexpected
interrupts and increased current consumption.
The CAEX bit controls the input multiplexer, exchanging which input signals
are connected to the comparator’s + and – terminals. Additionally, when the
comparator terminals are exchanged, the output signal from the comparator
is inverted. This allows the user to determine or compensate for the
comparator input offset voltage.
24-4
Comparator_A+
Comparator_A+ Operation
24.2.3 Input Short Switch
The CASHORT bit shorts the comparator_A+ inputs. This can be used to build
a simple sample-and-hold for the comparator as shown in Figure 24−2.
Figure 24−2. Comparator_A+ Sample−And−Hold
Sampling Capacitor, C s
CASHORT
Analog Inputs
The required sampling time is proportional to the size of the sampling capacitor
(CS), the resistance of the input switches in series with the short switch (Ri),
and the resistance of the external source (RS). The total internal resistance
(RI) is typically in the range of 2 − 10 kΩ. The sampling capacitor CS should
be greater than 100pF. The time constant, Tau, to charge the sampling
capacitor CS can be calculated with the following equation:
Tau = (RI + RS) x CS
Depending on the required accuracy 3 to 10 Tau should be used as a sampling
time. With 3 Tau the sampling capacitor is charged to approximately 95% of
the input signals voltage level, with 5 Tau it is charge to more than 99% and
with 10 Tau the sampled voltage is sufficient for 12−bit accuracy.
Comparator_A+
24-5
Comparator_A+ Operation
24.2.4 Output Filter
The output of the comparator can be used with or without internal filtering.
When control bit CAF is set, the output is filtered with an on-chip RC-filter.
Any comparator output oscillates if the voltage difference across the input
terminals is small. Internal and external parasitic effects and cross coupling on
and between signal lines, power supply lines, and other parts of the system
are responsible for this behavior as shown in Figure 24−3. The comparator
output oscillation reduces accuracy and resolution of the comparison result.
Selecting the output filter can reduce errors associated with comparator
oscillation.
Figure 24−3. RC-Filter Response at the Output of the Comparator
+ Terminal
− Terminal
Comparator Inputs
Comparator Output
Unfiltered at CAOUT
Comparator Output
Filtered at CAOUT
24.2.5 Voltage Reference Generator
The voltage reference generator is used to generate VCAREF, which can be
applied to either comparator input terminal. The CAREFx bits control the
output of the voltage generator. The CARSEL bit selects the comparator
terminal to which VCAREF is applied. If external signals are applied to both
comparator input terminals, the internal reference generator should be turned
off to reduce current consumption. The voltage reference generator can
generate a fraction of the device’s VCC or a fixed transistor threshold voltage
of ~ 0.55 V.
24-6
Comparator_A+
Comparator_A+ Operation
24.2.6 Comparator_A+, Port Disable Register CAPD
The comparator input and output functions are multiplexed with the associated
I/O port pins, which are digital CMOS gates. When analog signals are applied
to digital CMOS gates, parasitic current can flow from VCC to GND. This
parasitic current occurs if the input voltage is near the transition level of the
gate. Disabling the port pin buffer eliminates the parasitic current flow and
therefore reduces overall current consumption.
The CAPDx bits, when set, disable the corresponding Px input and output
buffers as shown in Figure 24−4. When current consumption is critical, any
port pin connected to analog signals should be disabled with its CAPDx bit.
Selecting an input pin to the comparator multiplexer with the P2CAx bits
automatically disables the input and output buffers for that pin, regardless of
the state of the associated CAPDx bit.
Figure 24−4. Transfer Characteristic and Power Dissipation in a CMOS Inverter/Buffer
VCC
VI
VO
ICC
ICC
VI
VCC
0
CAPD.x = 1
VCC
VSS
24.2.7 Comparator_A+ Interrupts
One interrupt flag and one interrupt vector are associated with the
Comparator_A+ as shown in Figure 24−5. The interrupt flag CAIFG is set on
either the rising or falling edge of the comparator output, selected by the
CAIES bit. If both the CAIE and the GIE bits are set, then the CAIFG flag
generates an interrupt request. The CAIFG flag is automatically reset when
the interrupt request is serviced or may be reset with software.
Figure 24−5. Comparator_A+ Interrupt System
CAIE
VCC
CAIES
SET_CAIFG
0
1
D
IRQ, Interrupt Service Requested
Q
Reset
IRACC, Interrupt Request Accepted
POR
Comparator_A+
24-7
Comparator_A+ Operation
24.2.8 Comparator_A+ Used to Measure Resistive Elements
The Comparator_A+ can be optimized to precisely measure resistive
elements using single slope analog-to-digital conversion. For example,
temperature can be converted into digital data using a thermistor, by
comparing the thermistor’s capacitor discharge time to that of a reference
resistor as shown in Figure 24−6. A reference resister Rref is compared to
Rmeas.
Figure 24−6. Temperature Measurement System
Rref
Px.x
Rmeas
Px.y
CA0
++
−−
CCI1B
Capture
Input
Of Timer_A
0.25xVCC
The MSP430 resources used to calculate the temperature sensed by Rmeas
are:
- Two digital I/O pins to charge and discharge the capacitor.
- I/O set to output high (VCC) to charge capacitor, reset to discharge.
- I/O switched to high-impedance input with CAPDx set when not in use.
- One output charges and discharges the capacitor via Rref.
- One output discharges capacitor via Rmeas.
- The + terminal is connected to the positive terminal of the capacitor.
- The – terminal is connected to a reference level, for example 0.25 x VCC.
- The output filter should be used to minimize switching noise.
- CAOUT used to gate Timer_A CCI1B, capturing capacitor discharge time.
More than one resistive element can be measured. Additional elements are
connected to CA0 with available I/O pins and switched to high impedance
when not being measured.
24-8
Comparator_A+
Comparator_A+ Operation
The thermistor measurement is based on a ratiometric conversion principle.
The ratio of two capacitor discharge times is calculated as shown in
Figure 24−7.
Figure 24−7. Timing for Temperature Measurement Systems
VC
VCC
Rmeas
Rref
0.25 × VCC
Phase I:
Charge
Phase III:
Charge
Phase II:
Discharge
tref
Phase IV:
Discharge
t
tmeas
The VCC voltage and the capacitor value should remain constant during the
conversion, but are not critical since they cancel in the ratio:
N meas
+
N ref
–R meas
–R ref
C
C
ln
ln
V ref
V CC
V ref
V CC
N meas
R
+ meas
N ref
R ref
R meas + R ref
N meas
N ref
Comparator_A+
24-9
Comparator_A+ Registers
24.3 Comparator_A+ Registers
The Comparator_A+ registers are listed in Table 24−1:
Table 24−1.Comparator_A+ Registers
Register
Short Form
Register Type Address
Initial State
Comparator_A+ control register 1
CACTL1
Read/write
Reset with POR
059h
Comparator_A+ control register 2
CACTL2
Read/write
05Ah
Reset with POR
Comparator_A+ port disable
CAPD
Read/write
05Bh
Reset with POR
24-10
Comparator_A+
Comparator_A+ Registers
CACTL1, Comparator_A+ Control Register 1
7
6
CAEX
CARSEL
rw−(0)
rw−(0)
5
4
CAREFx
rw−(0)
rw−(0)
3
2
1
0
CAON
CAIES
CAIE
CAIFG
rw−(0)
rw−(0)
rw−(0)
rw−(0)
CAEX
Bit 7
Comparator_A+ exchange. This bit exchanges the comparator inputs and
inverts the comparator output.
CARSEL
Bit 6
Comparator_A+ reference select. This bit selects which terminal the
VCAREF is applied to.
When CAEX = 0:
0
VCAREF is applied to the + terminal
1
VCAREF is applied to the – terminal
When CAEX = 1:
0
VCAREF is applied to the – terminal
1
VCAREF is applied to the + terminal
CAREF
Bits
5-4
Comparator_A+ reference. These bits select the reference voltage VCAREF.
00 Internal reference off. An external reference can be applied.
01 0.25*VCC
10 0.50*VCC
11 Diode reference is selected
CAON
Bit 3
Comparator_A+ on. This bit turns on the comparator. When the
comparator is off it consumes no current. The reference circuitry is enabled
or disabled independently.
0
Off
1
On
CAIES
Bit 2
Comparator_A+ interrupt edge select
0
Rising edge
1
Falling edge
CAIE
Bit 1
Comparator_A+ interrupt enable
0
Disabled
1
Enabled
CAIFG
Bit 0
The Comparator_A+ interrupt flag
0
No interrupt pending
1
Interrupt pending
Comparator_A+
24-11
Comparator_A+ Registers
CACTL2, Comparator_A+, Control Register
7
6
5
4
3
2
1
0
CASHORT
P2CA4
P2CA3
P2CA2
P2CA1
P2CA0
CAF
CAOUT
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
r−(0)
CASHORT
Bit 7
Input short. This bit shorts the + and − input terminals.
0
Inputs not shorted.
1
Inputs shorted.
P2CA4
Bit 6
Input select. This bit together with P2CA0 selects the + terminal input when
CAEX = 0 and the − terminal input when CAEX = 1.
P2CA3
P2CA2
P2CA1
Bits
5-3
Input select. These bits select the − terminal input when CAEX = 0 and the
+ terminal input when CAEX = 1.
000 No connection
001 CA1
010 CA2
011 CA3
100 CA4
101 CA5
110 CA6
111 CA7
P2CA0
Bit 2
Input select. This bit, together with P2CA4, selects the + terminal input
when CAEX = 0 and the − terminal input when CAEX = 1.
00 No connection
01 CA0
10 CA1
11 CA2
CAF
Bit 1
Comparator_A+ output filter
0
Comparator_A+ output is not filtered
1
Comparator_A+ output is filtered
CAOUT
Bit 0
Comparator_A+ output. This bit reflects the value of the comparator output.
Writing this bit has no effect.
24-12
Comparator_A+
Comparator_A+ Registers
CAPD, Comparator_A+, Port Disable Register
7
6
5
4
3
2
1
0
CAPD7
CAPD6
CAPD5
CAPD4
CAPD3
CAPD2
CAPD1
CAPD0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
CAPDx
Bits
7-0
Comparator_A+ port disable. These bits individually disable the input
buffer for the pins of the port associated with Comparator_A+. For
example, if CA0 is on pin P2.3, the CAPDx bits can be used to individually
enable or disable each port pin buffer. CAPD0 disables the pin associated
with CA0, CAPD1 disables the pin connected associated with CA1, etc.
0
The input buffer is enabled.
1
The input buffer is disabled.
Comparator_A+
24-13
24-14
Comparator_A+
Chapter 25
LCD Controller
The LCD controller drives static, 2-mux, 3-mux, or 4-mux LCDs. This chapter
describes LCD controller. The LCD controller is implemented on all
MSP430x4xx devices, except the MSP430F41x2, MSP430x42x0,
MSP430FG461x, MSP430F47x, MSP430FG47x, MSP430F47x3/4, and
MSP430F471xx devices.
Topic
Page
25.1 LCD Controller Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-2
25.2 LCD Controller Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-4
25.3 LCD Controller Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-18
LCD Controller
25-1
LCD Controller Introduction
25.1 LCD Controller Introduction
The LCD controller directly drives LCD displays by creating the ac segment
and common voltage signals automatically. The MSP430 LCD controller can
support static, 2-mux, 3-mux, and 4-mux LCDs.
The LCD controller features are:
- Display memory
- Automatic signal generation
- Configurable frame frequency
- Blinking capability
- Support for 4 types of LCDs:
J
Static
J
2-mux, 1/2 bias
J
3-mux, 1/3 bias
J
4-mux, 1/3 bias
The LCD controller block diagram is shown in Figure 25−1.
Note: Max LCD Segment Control
The maximum number of segment lines available differs with device. See the
device-specific datasheet for details.
25-2
LCD Controller
LCD Controller Introduction
Figure 25−1. LCD Controller Block Diagram
SEG39
0A4h
S39
Mux
SEG38
Mux
S38
Segment
Output
Control
Display
Memory
20x
8-bits
SEG1
Mux
S1
SEG0
091h
Mux
S0
LCDP2
COM3
LCDP1
Common
Output
Control
LCDP0
LCDMX1
COM2
COM1
COM0
LCDMX0
LCDSON
VA VB VC VD
V1
LCDON
R33
R
f LCD
Timing Generator
(from Basic Timer)
OSCOFF
(from SR)
V2
Analog
Voltage
V3
Multiplexer
V4
V5
R23
R13
R
R
R
R
Rx
Rx
R03
Rx
Static 2Mux 3Mux
4Mux
External Resistors
Rx = Optional Contrast Control
LCD Controller
25-3
LCD Controller Operation
25.2 LCD Controller Operation
The LCD controller is configured with user software. The setup and operation
of LCD controller is discussed in the following sections.
25.2.1 LCD Memory
The LCD memory map is shown in Figure 25−2. Each memory bit corresponds
to one LCD segment, or is not used, depending on the mode. To turn on an
LCD segment, its corresponding memory bit is set.
Figure 25−2. LCD Memory
Associated
Common Pins
Address
0A4h
0A3h
0A2h
0A1h
0A0h
09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
3
2
1
0
3
2
1
0
7
---
---
---
---
---
---
---
0
---
-------------
-------------
-------------
-------------
-------------
-------------
-------------
-------------
------
------
------
------
------
------
------
------
--
--
--
--
--
--
--
--
Sn+1
Associated
Segment Pins
n
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
39, 38
37, 36
35, 34
33, 32
31, 30
29, 28
27, 26
25, 24
23, 22
21, 20
19, 18
17, 16
15, 14
13, 12
11, 10
9, 8
7, 6
5, 4
3, 2
1, 0
Sn
25.2.2 Blinking the LCD
The LCD controller supports blinking. The LCDSON bit is ANDed with each
segment’s memory bit. When LCDSON = 1, each segment is on or off
according to its bit value. When LCDSON = 0, each LCD segment is off.
25.2.3 LCD Timing Generation
The LCD controller uses the fLCD signal from the Basic Timer1 to generate the
timing for common and segment lines. The proper frequency fLCD depends on
the LCD’s requirement for framing frequency and LCD multiplex rate. See the
Basic Timer1 chapter for more information on configuring the fLCD frequency.
25-4
LCD Controller
LCD Controller Operation
25.2.4 LCD Voltage Generation
The voltages required for the LCD signals are supplied externally to pins R33,
R23, R13, and R03. Using an equally weighted resistor divider ladder between
these pins establishes the analog voltages as shown in Table 25−1. The
resistor value R is typically 680 k Values of R from 100k to 1M can be
used depending on LCD requirements.
R33 is a switched-VCC output. This allows the power to the resistor ladder to
be turned off eliminating current consumption when the LCD is not used.
Table 25−1.External LCD Module Analog Voltage
OSCOFF
LCDMXx
LCDON
VA
VB
VC
VD
R33
x
xx
0
0
0
0
0
Off
1
xx
x
0
0
0
0
Off
0
00
1
V5/V1
V1/V5
V5/V1
V1/V5
On
0
01
1
V5/V1
V1/V5
V3/V3
V1/V5
On
0
1x
1
V5/V1
V2/V4
V4/V2
V1/V5
On
LCD Contrast Control
LCD contrast can be controlled by the R03 voltage level with external circuitry,
typically an additional resistor Rx to GND. Increasing the voltage at R03
reduces the total applied segment voltage decreasing the LCD contrast.
25.2.5 LCD Outputs
Some LCD segment, common, and Rxx functions are multiplexed with digital
I/O functions. These pins can function either as digital I/O or as LCD functions.
The pin functions for COMx and Rxx, when multiplexed with digital I/O, are
selected using the applicable PxSELx bits as described in the Digital I/O
chapter. The LCD segment functions, when multiplexed with digital I/O, are
selected using the LCDPx bits.
The LCDPx bits selects the LCD function for groups of pins. When LCDPx = 0,
no multiplexed pin is set to LCD function. When LCDPx = 1, segments S0 to
S15 are selected as LCD function. When LCDPx > 1, LCD segment functions
are selected in groups of four. For example, when LCDPx = 2, segments S0
to S19 are selected as LCD function.
Note: LCDPx Bits Do Not Affect Dedicated LCD Segment Pins
The LCDPx bits only affect pins with multiplexed LCD segment functions and
digital I/O functions. Dedicated LCD segment pins are not affected by the
LCDPx bits.
LCD Controller
25-5
LCD Controller Operation
25.2.6 Static Mode
In static mode, each MSP430 segment pin drives one LCD segment, and one
common line, COM0, is used. Figure 25−3 shows some example static
waveforms.
Figure 25−3. Example Static Waveforms
V1
COM0
V5
fframe
V1
SP1
COM0
V1
SP2
SP1
SP6
V5
a
V5
V1
SP2
b
SP7
SP3
Resulting Voltage for
Segment a (COM0−SP1)
Segment Is On.
0V
V1
SP5
SP8
SP4
SP = Segment Pin
25-6
LCD Controller
Resulting Voltage for
Segment b (COM0−SP2)
Segment Is Off.
0V
LCD Controller Operation
Figure 25−4 shows an example static LCD, pinout, LCD-to-MSP430
connections, and the resulting segment mapping. This is only an example.
Segment mapping in a user’s application depends on the LCD pinout and on
the MSP430-to-LCD connections.
Figure 25−4. Static LCD Example
LCD
a
f
a
f
b
g
c
e
d
h
c
d
Connections
c
d
c
e
d
h
b
g
h
Display Memory
COM
3
2
1
0
3
2
1
0
MAB 0A0h
--
--
--
h
--
--
--
g
09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
---
---
---
f
d
---
---
---
e
c
--------------
--------------
--------------
b
h
f
d
b
h
f
d
b
h
f
d
b
--------------
--------------
--------------
a
g
e
c
a
g
e
c
a
g
e
c
a
3
2
1
0
3
2
1
0
LCD Pinout
PIN
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
S30
S31
COM0
COM1
COM2
COM3
f
b
g
e
h
Pinout and Connections
’430 Pins
f
b
g
e
a
a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
COM0
1a
1b
1c
1d
1e
1f
1g
1h
2a
2b
2c
2d
2e
2f
2g
2h
3a
3b
3c
3d
3e
3f
3g
3h
4a
4b
4c
4d
4e
4f
4g
4h
COM0
A
G0
B
3
Sn+1
n = 30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
A
0
G
3
B
Digit 4
Digit 3
Digit 2
Digit 1
Parallel-Serial
Conversion
Sn
NC
NC
NC
LCD Controller
25-7
LCD Controller Operation
Static Mode Software Example
;
;
;
a
b
c
d
e
f
g
h
;
:
;
All eight segments of a digit are often located in four
display memory bytes with the static display method.
EQU
001h
EQU
010h
EQU
002h
EQU
020h
EQU
004h
EQU
040h
EQU
008h
EQU
080h
The register content of Rx should be displayed.
The Table represents the ’on’−segments according to the
content of Rx.
MOV.B Table (Rx),RY
; Load segment information
; into temporary memory.
; (Ry) = 0000 0000 hfdb geca
MOV.B Ry,&LCDn
; Note:
; All bits of an LCD memory
’ byte are written
RRA
Ry
; (Ry) = 0000 0000 0hfd bgec
MOV.B Ry,&LCDn+1
; Note:
; All bits of an LCD memory
; byte are written
RRA
Ry
; (Ry) = 0000 0000 00hf dbge
MOV.B Ry,&LCDn+2
; Note:
; All bits of an LCD memory
’ byte are written
RRA
Ry
; (Ry) = 0000 0000 000h fdbg
MOV.B Ry,&LCDn+3
; Note:
; All bits of an LCD memory
’ byte are written
...........
...........
;
Table DB
a+b+c+d+e+f
DB
b+c;
...........
...........
DB
...........
25-8
LCD Controller
; displays ”0”
; displays ”1”
LCD Controller Operation
25.2.7 2-Mux Mode
In 2-mux mode, each MSP430 segment pin drives two LCD segments, and two
common lines, COM0 and COM1, are used. Figure 25−5 shows some
example 2-mux waveforms.
Figure 25−5. Example 2-Mux Waveforms
COM1
COM0
fframe
COM1
COM0
V1
V3
V5
V1
V3
V5
V1
SP1
V5
SP2
V1
b
V5
h
V1
V3
0V
−V3
−V1
SP1
SP4
SP2
Resulting Voltage for
Segment h (COM0−SP2)
Segment Is On.
SP3
SP = Segment Pin
Resulting Voltage for
Segment b (COM1−SP2)
Segment Is Off.
V1
V3
0V
−V3
−V5
LCD Controller
25-9
LCD Controller Operation
Figure 25−6 shows an example 2-mux LCD, pinout, LCD-to-MSP430
connections, and the resulting segment mapping. This is only an example.
Segment mapping in a user’s application completely depends on the LCD
pinout and on the MSP430-to-LCD connections.
Figure 25−6. 2−Mux LCD Example
LCD
a
a
f
f
b
g
c
e
d
d
h
LCD Pinout
PIN
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
S30
S31
COM0
COM1
COM2
COM3
25-10
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
COM0 COM1
1f
1a
1h
1b
1d
1c
1e
1g
2f
2a
2h
2b
2d
2c
2e
2g
3f
3a
3h
3b
3d
3c
3e
3g
4f
4a
4h
4b
4d
4c
4e
4g
5f
5a
5h
5b
5d
5c
5e
5g
6f
6a
6h
6b
6d
6c
6e
6g
7f
7a
7h
7b
7d
7c
7e
7g
8f
8a
8h
8b
8d
8c
8e
8g
COM0
COM1
NC
NC
LCD Controller
h
DIGIT1
Pinout and Connections
’430 Pins
c
e
DIGIT8
Connections
b
g
Display Memory
COM
3
2
1
0
3
2
1
0
MAB 0A0h
--------
--------
g
b
g
b
g
b
g
e
h
e
h
e
h
e
--------
--------
c
a
c
a
c
a
c
d
f
d
----------
----------
b
g
b
g
b
g
b
g
b
h
e
h
e
h
e
h
e
h
----------
----------
a
c
a
c
a
c
a
c
a
f
d
f
d
f
d
f
d
f
3
2
1
0
3
2
1
0
09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
A
G0
B
3
Sn+1
Sn
f
d
f
d
n = 30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
A
0
G
3
B
1/2 Digit 8
Digit 7
Digit 6
Digit 5
Digit 4
Digit 3
Digit 2
Digit 1
ParallelSerial
Conversion
LCD Controller Operation
2-Mux Mode Software Example
;
;
;
a
b
c
d
e
f
g
h
;
;
;
;
All eight segments of a digit are often located in two
display memory bytes with the 2mux display rate
EQU
002h
EQU
020h
EQU
008h
EQU
004h
EQU
040h
EQU
001h
EQU
080h
EQU
010h
The register content of Rx should be displayed.
The Table represents the ’on’−segments according to the
content of Rx.
...........
...........
MOV.B Table(Rx),Ry ;
;
MOV.B Ry,&LCDn
;
;
;
;
RRA
Ry
;
RRA
Ry
;
MOV.B Ry,&LCDn+1
;
;
...........
...........
...........
Table DB
a+b+c+d+e+f
...........
DB
a+b+c+d+e+f+g+
...........
...........
DB
...........
;
Load segment information into
temporary memory.
(Ry) = 0000 0000 gebh cdaf
Note:
All bits of an LCD memory byte
are written
(Ry) = 0000 0000 0geb hcda
(Ry) = 0000 0000 00ge bhcd
; Note:
All bits of an LCD memory byte
are written
; displays ”0”
; displays ”8”
LCD Controller
25-11
LCD Controller Operation
25.2.8 3-Mux Mode
In 3-mux mode, each MSP430 segment pin drives three LCD segments, and
three common lines, COM0, COM1 and COM2 are used. Figure 25−7 shows
some example 3-mux waveforms.
Figure 25−7. Example 3-Mux Waveforms
COM2
COM0
fframe
COM1
COM1
COM0
COM2
SP1
e
V1
V2
V4
V5
V1
V2
V4
V5
V1
V2
V4
V5
V1
d
SP1
V1
V2
V4
V5
SP2
SP3
SP2
SP = Segment Pin
SP3
Resulting Voltage for
Segment e (COM0−SP1)
Segment Is Off.
V5
V1
V2
V4
V5
V1
0V
−V1
V1
Resulting Voltage for
Segment d (COM0−SP2)
Segment Is On.
25-12
LCD Controller
0V
−V1
LCD Controller Operation
Figure 25−8 shows an example 3-mux LCD, pinout, LCD-to-MSP430
connections, and the resulting segment mapping. This is only an example.
Segment mapping in a user’s application depends on the LCD pinout and on
the MSP430-to-LCD connections.
Figure 25−8. 3-Mux LCD Example
LCD
y
a
f
y
f
b
g
c
e
d
c
e
d
h
h
DIGIT1
Pinout and Connections
PIN
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
COM0
COM1
COM2
COM3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
LCD Pinout
COM0 COM1 COM2
1y
1e
1f
1a
1d
1g
1b
1h
1c
2y
2e
2f
2a
2d
2g
2b
2h
2c
3y
3e
3f
3a
3d
3g
3b
3h
3c
4y
4e
4f
4a
4d
4g
4b
4h
4c
5y
5e
5f
5a
5d
5g
5b
5h
5c
6y
6e
6f
6a
6d
6g
6b
6h
6c
7y
7e
7f
7a
7d
7g
7b
7h
7c
8y
8e
8f
8a
8d
8g
8b
8h
8c
9y
9e
9f
9a
9d
9g
9b
9h
9c
10y
10e
10f
10a
10d
10g
10b
10h
10c
COM0
COM1
COM2
b
g
DIGIT10
Connections
’430 Pins
a
Display Memory
3
2
1
0
3
2
1
0
MAB 09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
----
a
b
y
g
c
f
d
h
e
----
y
a
b
f
g
c
e
d
h
---
a
b
g
c
d
h
---
y
a
f
g
e
d
---
y
a
f
g
e
d
---
b
y
c
f
h
e
---
b
y
c
f
h
e
---
a
b
g
c
d
h
---
a
b
g
c
d
h
---
y
a
f
g
e
d
h
A
COM
B
G
0
3
--
y
f
e
--
b
c
--
a
g
d
--
y
f
e
---
b
y
c
f
h
e
---
a
b
g
c
d
h
--
a
g
d
--
y
f
e
3
2
1
0
3
2
1
0
Sn+1
n = 30
28
Digit 10
26
Digit 9
24
22
Digit 8
20
Digit 7
18
16
Digit 6
14
Digit 5
12
10
Digit 4
8
Digit 3
6
4
Digit 2
2
Digit 1
0
A Parallel0
Serial
G
3
B Conversion
Sn
NC
LCD Controller
25-13
LCD Controller Operation
3-Mux Mode Software Example
; The 3mux rate can support nine segments for each
; digit. The nine segments of a digit are located in
; 1 1/2 display memory bytes.
;
a
EQU
0040h
b
EQU
0400h
c
EQU
0200h
d
EQU
0010h
e
EQU
0001h
f
EQU
0002h
g
EQU
0020h
h
EQU
0100h
Y
EQU
0004h
; The LSDigit of register Rx should be displayed.
; The Table represents the ’on’−segments according to the
; LSDigit of register of Rx.
; The register Ry is used for temporary memory
;
ODDDIG RLA
Rx
; LCD in 3mux has 9 segments per
; digit; word table required for
; displayed characters.
MOV
Table(Rx),Ry ; Load segment information to
; temporary mem.
; (Ry) = 0000 0bch 0agd 0yfe
MOV.B Ry,&LCDn
; write ’a, g, d, y, f, e’ of
; Digit n (LowByte)
SWPB Ry
; (Ry) = 0agd 0yfe 0000 0bch
BIC.B #07h,&LCDn+1 ; write ’b, c, h’ of Digit n
; (HighByte)
BIS.B Ry,&LCDn+1
.....
EVNDIG RLA
Rx
; LCD in 3mux has 9 segments per
; digit; word table required for
; displayed characters.
MOV
Table(Rx),Ry ; Load segment information to
; temporary mem.
; (Ry) = 0000 0bch 0agd 0yfe
RLA
Ry
; (Ry) = 0000 bch0 agd0 yfe0
RLA
Ry
; (Ry) = 000b ch0a gd0y fe00
RLA
Ry
; (Ry) = 00bc h0ag d0yf e000
RLA
Ry
; (Ry) = 0bch 0agd 0yfe 0000
BIC.B #070h,&LCDn+1
BIS.B Ry,&LCDn+1
; write ’y, f, e’ of Digit n+1
; (LowByte)
SWPB Ry
; (Ry) = 0yfe 0000 0bch 0agd
MOV.B Ry,&LCDn+2
; write ’b, c, h, a, g, d’ of
; Digit n+1 (HighByte)
...........
Table DW
a+b+c+d+e+f ; displays ”0”
DW
b+c
; displays ”1”
...........
...........
DW
a+e+f+g
; displays ”F”
25-14
LCD Controller
LCD Controller Operation
25.2.9 4-Mux Mode
In 4-mux mode, each MSP430 segment pin drives four LCD segments, and
all four common lines, COM0, COM1, COM2, and COM3 are used.
Figure 25−9 shows some example 4-mux waveforms.
Figure 25−9. Example 4-Mux Waveforms
COM3
COM0
COM2
COM1
fframe
COM1
V1
V2
V4
V5
COM2
V1
V2
V4
V5
COM0
COM3
e
V1
V2
V4
V5
V1
V2
V4
V5
SP1
V1
V2
V4
V5
SP2
V1
V2
V4
V5
c
SP2
SP1
SP = Segment Pin
V1
Resulting Voltage for
Segment e (COM1−SP1)
Segment Is Off.
0V
−V1
V1
Resulting Voltage for
Segment c (COM1−SP2)
Segment Is On.
0V
−V1
LCD Controller
25-15
LCD Controller Operation
Figure 25−10 shows an example 4-mux LCD, pinout, LCD-to-MSP430
connections, and the resulting segment mapping. This is only an example.
Segment mapping in a user’s application depends on the LCD pinout and on
the MSP430-to-LCD connections.
Figure 25−10. 4-Mux LCD Example
LCD
a
f
a
f
b
g
c
e
d
c
e
d
h
DIGIT15
Display Memory
Connections
COM
3
2
1
0
3
2
1
0
MAB 09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
a
a
a
b
b
b
c
c
c
h
h
h
f
f
f
g
g
g
e
e
e
d
d
d
n = 30 Digit 16
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
24 Digit 13
22 Digit 12
20 Digit 11
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
b
c
h
f
g
e
d
3
2
1
0
3
1
0
LCD Pinout
’430 Pins
PIN
25-16
h
DIGIT1
Pinout and Connections
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
COM0
COM1
COM2
COM3
b
g
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
COM0 COM1 COM2 COM3
1d
1h
2d
2h
3d
3h
4d
4h
5d
5h
6d
6h
7d
7h
8d
8h
9d
9h
10d
10h
11d
11h
12d
12h
13d
13h
14d
14h
15d
15h
COM0
1e
1c
2e
2c
3e
3c
4e
4c
5e
5c
6e
6c
7e
7c
8e
8c
9e
9c
10e
10c
11e
11c
12e
12c
13e
13c
14e
14c
15e
15c
1g
1b
2g
2b
3g
3b
4g
4b
5g
5b
6g
6b
7g
7b
8g
8b
9g
9b
10g
10b
11g
11b
12g
12b
13g
13b
14g
14b
15g
15b
1f
1a
2f
2a
3f
3a
4f
4a
5f
5a
6f
6a
7f
7a
8f
8a
9f
9a
10f
10a
11f
11a
12f
12a
13f
13a
14f
14a
15f
15a
COM1
LCD Controller
COM2
COM3
A
B
G
2
0
3
Sn+1
Sn
28 Digit 15
26 Digit 14
18 Digit 10
16 Digit 9
14 Digit 8
12 Digit 7
10 Digit 6
8
6
4
Digit 5
Digit 4
Digit 3
2
Digit 2
0
Digit 1
A Parallel0
Serial
G
3
B Conversion
LCD Controller Operation
4-Mux Mode Software Example
;
;
;
a
b
c
d
e
f
g
h
;
;
;
;
;
The 4mux rate supports eight segments for each digit.
All eight segments of a digit can often be located in
one display memory byte
EQU
080h
EQU
040h
EQU
020h
EQU
001h
EQU
002h
EQU
008h
EQU
004h
EQU
010h
The LSDigit of register Rx should be displayed.
The Table represents the ’on’−segments according to the
content of Rx.
MOV.B Table(Rx),&LCDn ;
;
;
;
...........
...........
Table DB
a+b+c+d+e+f
DB
b+c
...........
...........
DB
b+c+d+e+g
DB
a+d+e+f+g
DB
a+e+f+g
n = 1 ..... 15
all eight segments are
written to the display
memory
; displays ”0”
; displays ”1”
; displays ”d”
; displays ”E”
; displays ”F”
LCD Controller
25-17
LCD Controller Operation
25.3 LCD Controller Registers
The LCD controller registers are listed in Table 25−2.
Table 25−2.LCD Controller Registers
Register
Short Form
Register Type Address
Initial State
LCD control register
LCDCTL
Read/write
090h
Reset with PUC
LCD memory 1
LCDM1
Read/write
091h
Unchanged
LCD memory 2
LCDM2
Read/write
092h
Unchanged
LCD memory 3
LCDM3
Read/write
093h
Unchanged
LCD memory 4
LCDM4
Read/write
094h
Unchanged
LCD memory 5
LCDM5
Read/write
095h
Unchanged
LCD memory 6
LCDM6
Read/write
096h
Unchanged
LCD memory 7
LCDM7
Read/write
097h
Unchanged
LCD memory 8
LCDM8
Read/write
098h
Unchanged
LCD memory 9
LCDM9
Read/write
099h
Unchanged
LCD memory 10
LCDM10
Read/write
09Ah
Unchanged
LCD memory 11
LCDM11
Read/write
09Bh
Unchanged
LCD memory 12
LCDM12
Read/write
09Ch
Unchanged
LCD memory 13
LCDM13
Read/write
09Dh
Unchanged
LCD memory 14
LCDM14
Read/write
09Eh
Unchanged
LCD memory 15
LCDM15
Read/write
09Fh
Unchanged
LCD memory 16
LCDM16
Read/write
0A0h
Unchanged
LCD memory 17
LCDM17
Read/write
0A1h
Unchanged
LCD memory 18
LCDM18
Read/write
0A2h
Unchanged
LCD memory 19
LCDM19
Read/write
0A3h
Unchanged
LCD memory 20
LCDM20
Read/write
0A4h
Unchanged
25-18
LCD Controller
LCD Controller Operation
LCDCTL, LCD Control Register
7
6
5
4
LCDPx
rw−0
rw−0
3
LCDMXx
rw−0
rw−0
rw−0
2
1
0
LCDSON
Unused
LCDON
rw−0
rw−0
rw−0
LCDPx
Bits
7-5
LCD port select. These bits select the pin function to be port I/O or LCD
function for groups of segments pins. These bits ONLY affect pins with
multiplexed functions. Dedicated LCD pins are always LCD function.
000 No multiplexed pins are LCD function
001 S0-S15 are LCD function
010 S0-S19 are LCD function
011 S0-S23 are LCD function
100 S0-S27 are LCD function
101 S0-S31 are LCD function
110 S0-S35 are LCD function
111 S0-S39 are LCD function
LCDMXx
Bits
4-3
LCD mux rate. These bits select the LCD mode.
00 Static
01 2-mux
10 3-mux
11 4-mux
LCDSON
Bit 2
LCD segments on. This bit supports flashing LCD applications by turning
off all segment lines, while leaving the LCD timing generator and R33
enabled.
0
All LCD segments are off
1
All LCD segments are enabled and on or off according to their
corresponding memory location.
Unused
Bit 1
Unused
LCDON
Bit 0
LCD On. This bit turns on the LCD timing generator and R33.
0
LCD timing generator and Ron are off
1
LCD timing generator and Ron are on
LCD Controller
25-19
25-20
LCD Controller
Chapter 26
LCD_A Controller
The LCD_A controller drives static, 2-mux, 3-mux, or 4-mux LCDs. This
chapter describes the LCD_A controller. LCD_A controller is implemented on
MSP430F41x2,
MSP430x42x0,
MSP430FG461x,
MSP430F47x,
MSP430FG47x, MSP430F47x3/4, and MSP430F471xx devices.
Topic
Page
26.1 LCD_A Controller Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-2
26.2 LCD_A Controller Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-4
26.3 LCD_A Controller Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-21
LCD_A Controller
26-1
LCD_A Controller Introduction
26.1 LCD_A Controller Introduction
The LCD_A controller directly drives LCD displays by creating the ac segment
and common voltage signals automatically. The MSP430 LCD controller can
support static, 2-mux, 3-mux, and 4-mux LCDs.
The LCD controller features are:
- Display memory
- Automatic signal generation
- Configurable frame frequency
- Blinking capability
- Regulated charge pump
- Contrast control by software
- Support for 4 types of LCDs:
J
Static
J
2-mux, 1/2 bias or 1/3 bias
J
3-mux, 1/2 bias or 1/3 bias
J
4-mux, 1/2 bias or 1/3 bias
The LCD controller block diagram is shown in Figure 26−1.
Note: Maximum LCD Segment Control
The maximum number of segment lines available differs with device. See the
device-specific data sheet for available segment pins.
26-2
LCD_A Controller
LCD_A Controller Introduction
Figure 26−1. LCD_A Controller Block Diagram
SEG39
0A4h
Mux
S39
SEG38
Mux
S38
Segment
Output
Control
Display
Memory
20x
8−bits
SEG1
S1
Mux
SEG0
091h
S0
Mux
10
COM3
LCDSx
LCDSON
Common
Output
Control
COM2
COM1
COM0
Divider
/32 .. /512
ACLK
32768 Hz
VA VB VC VD
V1
LCDON
LCDFREQx
fLCD
VLCD
V2
Analog
Voltage
V3
Multiplexer
V4
Timing
Generator
V5
LCDMXx
OSCOFF
(from SR)
LCDMXx REXT
R03EXT
VLCDREFx VLCDx
V1
4
Regulated Charge
Pump/
Contrast Control
V2
VLCD
LCD Bias Generator
V3
V4
V5
LCDCPEN
LCDCAP/R33
LCDREF/R23
LCDREF/R13
R03
LCD2B
LCD_A Controller
26-3
LCD_A Controller Operation
26.2 LCD_A Controller Operation
The LCD_A controller is configured with user software. The setup and
operation of the LCD_A controller is discussed in the following sections.
26.2.1 LCD Memory
The LCD memory map is shown in Figure 26−2. Each memory bit corresponds
to one LCD segment, or is not used, depending on the mode. To turn on an
LCD segment, its corresponding memory bit is set.
Figure 26−2. LCD memory
Associated
Common Pins
Address
0A4h
0A3h
0A2h
0A1h
0A0h
09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
3
2
1
0
3
2
1
0
7
---
---
---
---
---
---
---
0
---
-------------
-------------
-------------
-------------
-------------
-------------
-------------
-------------
------
------
------
------
------
------
------
------
--
--
--
--
--
--
--
--
Sn+1
Associated
Segment Pins
n
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
39, 38
37, 36
35, 34
33, 32
31, 30
29, 28
27, 26
25, 24
23, 22
21, 20
19, 18
17, 16
15, 14
13, 12
11, 10
9, 8
7, 6
5, 4
3, 2
1, 0
Sn
26.2.2 Blinking the LCD
The LCD controller supports blinking. The LCDSON bit is ANDed with each
segment’s memory bit. When LCDSON = 1, each segment is on or off
according to its bit value. When LCDSON = 0, each LCD segment is off.
26-4
LCD_A Controller
LCD_A Controller Operation
26.2.3 LCD_A Voltage And Bias Generation
The LCD_A module allows selectable sources for the peak output waveform
voltage, V1, as well as the fractional LCD biasing voltages V2 − V5. VLCD may
be sourced from AVCC, an internal charge pump, or externally.
All internal voltage generation is disabled if the oscillator sourcing ACLK is
turned off (OSCOFF = 1) or the LCD_A module is disabled (LCDON = 0).
LCD Voltage Selection
VLCD is sourced from AVCC when VLCDEXT = 0, VLCDx = 0, and VREFx = 0.
VLCD is sourced from the internal charge pump when VLCDEXT = 0,
VLCDPEN = 1, and VLCDx > 0. The charge pump is always sourced from
DVCC. The VLCDx bits provide a software selectable LCD voltage from 2.6 V
to 3.44 V (typical) independent of DVCC. See the device-specific data sheet
for specifications.
When the internal charge pump is used, a 4.7 μF or larger capacitor must be
connected between pin LCDCAP and ground. Otherwise, irreversible damage
can occur. When the charge pump is enabled, peak currents of 2 mA typical
occur on DVCC. However, the charge pump duty cycle is approximately
1/1000, resulting in a 2 μA average current. The charge pump may be
temporarily disabled by setting LCDCPEN = 0 with VLCDx > 0 to reduce
system noise. In this case, the voltage present at the external capacitor is used
for the LCD voltages until the charge pump is re-enabled.
Note: Capacitor Required For Internal Charge Pump
A 4.7 μF or larger capacitor must be connected from pin LCDCAP to ground
when the internal charge pump is enabled. Otherwise, damage can occur.
The internal charge pump may use an external reference voltage when
VLCDREFx = 01. In this case, the charge pump voltage will be 3x the voltage
applied externally to the LCDREF pin and the VLCDx bits are ignored.
When VLCDEXT = 1, VLCD is sourced externally from the LCDCAP pin and
the internal charge pump is disabled. The charge pump and internal bias
generation require an input clock source of 32768 Hz +/− 10%. If neither is
used, the input clock frequency may be different per the application needs.
LCD Bias Generation
The fractional LCD biasing voltages, V2 − V5 can be generated internally or
externally, independent of the source for VLCD. The LCD bias generation block
diagram is shown in Figure 26−3.
LCD_A Controller
26-5
LCD_A Controller Operation
To source the bias voltages V2 − V4 externally, REXT is set. This also disables
the internal bias generation. Typically an equally weighted resistor divider is
used with resistors ranging from 100 k to 1 M When using an external
resistor divider, the VLCD voltage may be sourced from the internal charge
pump when VLCDEXT = 0. V5 can also be sourced externally when R03EXT
is set.
When using an external resistor divider R33 may serve as a switched-VLCD
output when VLCDEXT = 0. This allows the power to the resistor ladder to be
turned off eliminating current consumption when the LCD is not used. When
VLCDEXT = 1, R33 serves as a VLCD input.
Figure 26−3. Bias Generation
DVCC
Charge
Pump
VLCDx > 0
VLCDREFx > 0
AV CC
VLCD
0
Internal V LCD
1
LCD Off
0
LCDCAP/R33
VLCDEXT
V1 (VLCD)
0
REXT
0
R
LCD2B
V2 int.
0
1
R23
R
R
V2 (2/3 VLCD)
V3 int.
0
1
LCDREF/R13
V3 (1/2 VLCD)
V4 int.
0
R
R
1
V4 (1/3 VLCD)
0
R03
Rx
Rx
Rx
Optional External Resistors
Rx = Optional Contrast Control
Static 1/2 Bias 1/3 Bias
26-6
LCD_A Controller
1
R03EXT
V5
LCD_A Controller Operation
The internal bias generator supports 1/2 bias LCDs when LCD2B = 1, and
1/3 bias LCDs when LCD2B = 0 in 2-mux, 3-mux, and 4-mux modes. In static
mode, the internal divider is disabled.
Some devices share the LCDCAP, R33, and R23 functions. In this case, the
charge pump cannot be used together with an external resistor divider with
1/3 biasing. When R03 is not available externally, V5 is always AVSS.
LCD Contrast Control
The peak voltage of the output waveforms together with the selected mode
and biasing determine the contrast and the contrast ratio of the LCD. The LCD
contrast can be controlled in software by adjusting the LCD voltage generated
by the integrated charge pump using the VLCDx settings.
The contrast ratio depends on the used LCD display and the selected biasing
scheme. Table 26−1 shows the biasing configurations that apply to the
different modes together with the RMS voltages for the segments turned on
(VRMS,ON) and turned off (VRMS,OFF) as functions of VLCD. It also shows the
resulting contrast ratios between the on and off states.
Table 26−1.LCD Voltage and Biasing Characteristics
Mode
Bias
Config
LCDMx
LCD2B
COM
Lines
Voltage
Levels
VRMS,OFF/
VLCD
VRMS,ON/
VLCD
Contrast
Ratio
VRMS,ON/
VRMS,OFF
Static
Static
00
X
1
V1, V5
0
1
1/0
2−mux
1/2
01
1
2
V1, V3, V5
0.354
0.791
2.236
2−mux
1/3
01
0
2
V1, V2, V4, V5
0.333
0.745
2.236
3−mux
1/2
10
1
3
V1, V3, V5
0.408
0.707
1.732
3−mux
1/3
10
0
3
V1, V2, V4, V5
0.333
0.638
1.915
4−mux
1/2
11
1
4
V1, V3, V5
0.433
0.661
1.528
4−mux
1/3
11
0
4
V1, V2, V4, V5
0.333
0.577
1.732
A typical approach to determine the required VLCD is by equating VRMS,OFF
with a defined LCD threshold voltage, typically when the LCD exhibits
approximately 10% contrast (Vth,10%): VRMS,OFF = Vth,10%. Using the values
provided
in
the
table
results
in
for
VRMS,OFF/VLCD
VLCD = Vth,10%/(VRMS,OFF/VLCD). In the static mode, a suitable choice is VLCD
greater or equal than 3 times Vth,10%.
In 3-mux and 4-mux mode typically a 1/3 biasing is used but a 1/2 biasing
scheme is also possible. The 1/2 bias reduces the contrast ratio but the
advantage is a reduction of the required full-scale LCD voltage VLCD.
LCD_A Controller
26-7
LCD_A Controller Operation
26.2.4 LCD Timing Generation
The LCD_A controller uses the fLCD signal from the integrated ACLK prescaler
to generate the timing for common and segment lines. ACLK is assumed to
be 32768 Hz for generating fLCD. The fLCD frequency is selected with the
LCDFREQx bits. The proper fLCD frequency depends on the LCD’s
requirement for framing frequency and the LCD multiplex rate and is
calculated by:
fLCD = 2 × mux × fFrame
For example, to calculate fLCD for a 3-mux LCD, with a frame frequency of
30 Hz to 100 Hz:
fFrame (from LCD data sheet) = 30 Hz to 100 Hz
fLCD = 2 × 3 × fFrame
fLCD(min) = 180 Hz
fLCD(max) = 600 Hz
select fLCD = 32768/128 = 256 Hz or 2768/96 = 341 Hz or 32768/64 = 512 Hz.
The lowest frequency has the lowest current consumption. The highest
frequency has the least flicker.
26.2.5 LCD Outputs
Some LCD segment, common, and Rxx functions are multiplexed with digital
I/O functions. These pins can function either as digital I/O or as LCD functions.
The pin functions for COMx and Rxx, when multiplexed with digital I/O, are
selected using the applicable PxSELx bits as described in the Digital I/O
chapter. The LCD segment functions, when multiplexed with digital I/O, are
selected using the LCDSx bits in the LCDAPCTLx registers.
Note: Using shared pins as digital I/Os
If pins that share digital I/O and LCD functions are used as digital I/Os they
should not be toggled at frequencies >10kHz while the LCD is enabled
(LCDON=1); otherwise, increased current consumption could be observed.
The LCDSx bits selects the LCD function in groups of four pins. When
LCDSx = 0, no multiplexed pin is set to LCD function. When LCDSx = 1, the
complete group of four is selected as LCD function.
Note: LCDSx Bits Do Not Affect Dedicated LCD Segment Pins
The LCDSx bits only affect pins with multiplexed LCD segment functions and
digital I/O functions. Dedicated LCD segment pins are not affected by the
LCDSx bits.
26-8
LCD_A Controller
LCD_A Controller Operation
26.2.6 Static Mode
In static mode, each MSP430 segment pin drives one LCD segment and one
common line, COM0, is used. Figure 26−4 shows some example static
waveforms.
Figure 26−4. Example Static Waveforms
V1
COM0
V5
fframe
V1
SP1
V5
COM0
SP6
V1
V5
SP2
SP1
a
V1
SP2
b
SP7
SP3
Resulting Voltage for
Segment a (COM0−SP1)
Segment Is On.
0V
V1
SP5
SP8
SP4
SP = Segment Pin
Resulting Voltage for
Segment b (COM0−SP2)
Segment Is Off.
0V
LCD_A Controller
26-9
LCD_A Controller Operation
Figure 26−5 shows an example static LCD, pinout, LCD-to-MSP430
connections, and the resulting segment mapping. This is only an example.
Segment mapping in a user’s application depends on the LCD pinout and on
the MSP430-to-LCD connections.
Figure 26−5. Static LCD Example
LCD
a
f
a
f
b
g
c
e
d
c
d
h
f
b
g
e
a
a
c
e
d
h
f
b
g
d
h
Display Memory
26-10
COM
3
2
1
0
3
2
1
0
MAB 0A0h
--
--
--
h
--
--
--
g
09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
---
---
---
f
d
---
---
---
e
c
--------------
--------------
--------------
b
h
f
d
b
h
f
d
b
h
f
d
b
--------------
--------------
--------------
a
g
e
c
a
g
e
c
a
g
e
c
a
3
2
1
0
3
2
1
0
LCD Pinout
PIN
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
S30
S31
COM0
COM1
COM2
COM3
h
DIGIT1
Pinout and Connections
Connections
c
e
DIGIT4
’430 Pins
b
g
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
COM0
1a
1b
1c
1d
1e
1f
1g
1h
2a
2b
2c
2d
2e
2f
2g
2h
3a
3b
3c
3d
3e
3f
3g
3h
4a
4b
4c
4d
4e
4f
4g
4h
COM0
NC
NC
NC
LCD_A Controller
A
G0
B
3
Sn+1
Sn
n = 30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
A
0
G
3
B
Digit 4
Digit 3
Digit 2
Digit 1
Parallel-Serial
Conversion
LCD_A Controller Operation
Static Mode Software Example
;
;
;
a
b
c
d
e
f
g
h
;
:
;
All eight segments of a digit are often located in four
display memory bytes with the static display method.
EQU
001h
EQU
010h
EQU
002h
EQU
020h
EQU
004h
EQU
040h
EQU
008h
EQU
080h
The register content of Rx should be displayed.
The Table represents the ’on’−segments according to the
content of Rx.
MOV.B Table (Rx),RY
; Load segment information
; into temporary memory.
; (Ry) = 0000 0000 hfdb geca
MOV.B Ry,&LCDn
; Note:
; All bits of an LCD memory
’ byte are written
RRA
Ry
; (Ry) = 0000 0000 0hfd bgec
MOV.B Ry,&LCDn+1
; Note:
; All bits of an LCD memory
; byte are written
RRA
Ry
; (Ry) = 0000 0000 00hf dbge
MOV.B Ry,&LCDn+2
; Note:
; All bits of an LCD memory
’ byte are written
RRA
Ry
; (Ry) = 0000 0000 000h fdbg
MOV.B Ry,&LCDn+3
; Note:
; All bits of an LCD memory
’ byte are written
...........
...........
;
Table DB
a+b+c+d+e+f
DB
b+c;
...........
...........
DB
...........
; displays ”0”
; displays ”1”
LCD_A Controller
26-11
LCD_A Controller Operation
26.2.7 2-Mux Mode
In 2-mux mode, each MSP430 segment pin drives two LCD segments and two
common lines, COM0 and COM1, are used. Figure 26−6 shows some
example 2-mux, 1/2 bias waveforms.
Figure 26−6. Example 2-Mux Waveforms
COM1
COM0
fframe
COM1
COM0
V1
V3
V5
V1
V3
V5
V1
SP1
V5
SP2
V1
b
V5
h
V1
V3
0V
−V3
−V1
SP1
SP4
SP2
Resulting Voltage for
Segment h (COM0−SP2)
Segment Is On.
SP3
SP = Segment Pin
Resulting Voltage for
Segment b (COM1−SP2)
Segment Is Off.
26-12
LCD_A Controller
V1
V3
0V
−V3
−V5
LCD_A Controller Operation
Figure 26−7 shows an example 2-mux LCD, pinout, LCD-to-MSP430
connections, and the resulting segment mapping. This is only an example.
Segment mapping in a user’s application completely depends on the LCD
pinout and on the MSP430-to-LCD connections.
Figure 26−7. 2−Mux LCD Example
LCD
a
a
f
f
b
g
c
e
d
d
h
LCD Pinout
PIN
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
S30
S31
COM0
COM1
COM2
COM3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
COM0 COM1
1f
1a
1h
1b
1d
1c
1e
1g
2f
2a
2h
2b
2d
2c
2e
2g
3f
3a
3h
3b
3d
3c
3e
3g
4f
4a
4h
4b
4d
4c
4e
4g
5f
5a
5h
5b
5d
5c
5e
5g
6f
6a
6h
6b
6d
6c
6e
6g
7f
7a
7h
7b
7d
7c
7e
7g
8f
8a
8h
8b
8d
8c
8e
8g
COM0
COM1
h
DIGIT1
Pinout and Connections
’430 Pins
c
e
DIGIT8
Connections
b
g
Display Memory
COM
3
2
1
0
3
2
1
0
MAB 0A0h
--------
--------
g
b
g
b
g
b
g
e
h
e
h
e
h
e
--------
--------
c
a
c
a
c
a
c
d
f
d
----------
----------
b
g
b
g
b
g
b
g
b
h
e
h
e
h
e
h
e
h
----------
----------
a
c
a
c
a
c
a
c
a
f
d
f
d
f
d
f
d
f
3
2
1
0
3
2
1
0
09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
A
G0
B
3
Sn+1
f
d
f
d
n = 30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
A
0
G
3
B
1/2 Digit 8
Digit 7
Digit 6
Digit 5
Digit 4
Digit 3
Digit 2
Digit 1
ParallelSerial
Conversion
Sn
NC
NC
LCD_A Controller
26-13
LCD_A Controller Operation
2-Mux Mode Software Example
;
;
;
a
b
c
d
e
f
g
h
;
;
;
;
All eight segments of a digit are often located in two
display memory bytes with the 2mux display rate
EQU
002h
EQU
020h
EQU
008h
EQU
004h
EQU
040h
EQU
001h
EQU
080h
EQU
010h
The register content of Rx should be displayed.
The Table represents the ’on’−segments according to the
content of Rx.
...........
...........
MOV.B Table(Rx),Ry ;
;
MOV.B Ry,&LCDn
;
;
;
;
RRA
Ry
;
RRA
Ry
;
MOV.B Ry,&LCDn+1
;
;
...........
...........
...........
Table DB
a+b+c+d+e+f
...........
DB
a+b+c+d+e+f+g
...........
...........
DB
...........
;
26-14
LCD_A Controller
Load segment information into
temporary memory.
(Ry) = 0000 0000 gebh cdaf
Note:
All bits of an LCD memory byte
are written
(Ry) = 0000 0000 0geb hcda
(Ry) = 0000 0000 00ge bhcd
; Note:
All bits of an LCD memory byte
are written
; displays ”0”
; displays ”8”
LCD_A Controller Operation
26.2.8 3-Mux Mode
In 3-mux mode, each MSP430 segment pin drives three LCD segments and
three common lines (COM0, COM1, and COM2) are used. Figure 26−8 shows
some example 3-mux, 1/3 bias waveforms.
Figure 26−8. Example 3-Mux Waveforms
COM2
COM0
fframe
COM1
COM1
COM0
COM2
SP1
e
V1
V2
V4
V5
V1
V2
V4
V5
V1
V2
V4
V5
V1
d
SP1
V1
V2
V4
V5
SP2
V5
SP3
SP2
SP = Segment Pin
V1
SP3
V5
V1
Resulting Voltage for
Segment e (COM0−SP1)
Segment Is Off.
0V
−V1
V1
Resulting Voltage for
Segment d (COM0−SP2)
Segment Is On.
0V
−V1
LCD_A Controller
26-15
LCD_A Controller Operation
Figure 26−9 shows an example 3-mux LCD, pinout, LCD-to-MSP430
connections, and the resulting segment mapping. This is only an example.
Segment mapping in a user’s application depends on the LCD pinout and on
the MSP430-to-LCD connections.
Figure 26−9. 3-Mux LCD Example
LCD
y
a
f
y
f
b
g
c
e
d
c
e
d
h
h
DIGIT1
Pinout and Connections
PIN
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
COM0
COM1
COM2
COM3
26-16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
LCD Pinout
COM0 COM1 COM2
1y
1e
1f
1a
1d
1g
1b
1h
1c
2y
2e
2f
2a
2d
2g
2b
2h
2c
3y
3e
3f
3a
3d
3g
3b
3h
3c
4y
4e
4f
4a
4d
4g
4b
4h
4c
5y
5e
5f
5a
5d
5g
5b
5h
5c
6y
6e
6f
6a
6d
6g
6b
6h
6c
7y
7e
7f
7a
7d
7g
7b
7h
7c
8y
8e
8f
8a
8d
8g
8b
8h
8c
9y
9e
9f
9a
9d
9g
9b
9h
9c
10y
10e
10f
10a
10d
10g
10b
10h
10c
COM0
COM1
COM2
NC
LCD_A Controller
b
g
DIGIT10
Connections
’430 Pins
a
Display Memory
3
2
1
0
3
2
1
0
MAB 09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
----
a
b
y
g
c
f
d
h
e
----
y
a
b
f
g
c
e
d
h
---
a
b
g
c
d
h
---
y
a
f
g
e
d
---
y
a
f
g
e
d
---
b
y
c
f
h
e
---
b
y
c
f
h
e
---
a
b
g
c
d
h
---
a
b
g
c
d
h
---
y
a
f
g
e
d
h
A
COM
B
G
0
3
--
y
f
e
--
b
c
--
a
g
d
--
y
f
e
---
b
y
c
f
h
e
---
a
b
g
c
d
h
--
a
g
d
--
y
f
e
3
2
1
0
3
2
1
0
Sn+1
Sn
n = 30
28
Digit 10
26
Digit 9
24
22
Digit 8
20
Digit 7
18
16
Digit 6
14
Digit 5
12
10
Digit 4
8
Digit 3
6
4
Digit 2
2
Digit 1
0
A Parallel0
Serial
G
3
B Conversion
LCD_A Controller Operation
3-Mux Mode Software Example
; The 3mux rate can support nine segments for each
; digit. The nine segments of a digit are located in
; 1 1/2 display memory bytes.
;
a
EQU
0040h
b
EQU
0400h
c
EQU
0200h
d
EQU
0010h
e
EQU
0001h
f
EQU
0002h
g
EQU
0020h
h
EQU
0100h
Y
EQU
0004h
; The LSDigit of register Rx should be displayed.
; The Table represents the ’on’−segments according to the
; LSDigit of register of Rx.
; The register Ry is used for temporary memory
;
ODDDIG RLA
Rx
; LCD in 3mux has 9 segments per
; digit; word table required for
; displayed characters.
MOV
Table(Rx),Ry ; Load segment information to
; temporary mem.
; (Ry) = 0000 0bch 0agd 0yfe
MOV.B Ry,&LCDn
; write ’a, g, d, y, f, e’ of
; Digit n (LowByte)
SWPB Ry
; (Ry) = 0agd 0yfe 0000 0bch
BIC.B #07h,&LCDn+1 ; write ’b, c, h’ of Digit n
; (HighByte)
BIS.B Ry,&LCDn+1
.....
EVNDIG RLA
Rx
; LCD in 3mux has 9 segments per
; digit; word table required for
; displayed characters.
MOV
Table(Rx),Ry ; Load segment information to
; temporary mem.
; (Ry) = 0000 0bch 0agd 0yfe
RLA
Ry
; (Ry) = 0000 bch0 agd0 yfe0
RLA
Ry
; (Ry) = 000b ch0a gd0y fe00
RLA
Ry
; (Ry) = 00bc h0ag d0yf e000
RLA
Ry
; (Ry) = 0bch 0agd 0yfe 0000
BIC.B #070h,&LCDn+1
BIS.B Ry,&LCDn+1
; write ’y, f, e’ of Digit n+1
; (LowByte)
SWPB Ry
; (Ry) = 0yfe 0000 0bch 0agd
MOV.B Ry,&LCDn+2
; write ’b, c, h, a, g, d’ of
; Digit n+1 (HighByte)
...........
Table DW
a+b+c+d+e+f ; displays ”0”
DW
b+c
; displays ”1”
...........
...........
DW
a+e+f+g
; displays ”F”
LCD_A Controller
26-17
LCD_A Controller Operation
26.2.9 4-Mux Mode
In 4-mux mode, each MSP430 segment pin drives four LCD segments and all
four common lines (COM0, COM1, COM2, and COM3) are used.
Figure 26−10 shows some example 4-mux, 1/3 bias waveforms.
Figure 26−10. Example 4-Mux Waveforms
COM3
COM0
COM2
COM1
fframe
COM1
V1
V2
V4
V5
COM2
V1
V2
V4
V5
COM0
COM3
e
V1
V2
V4
V5
V1
V2
V4
V5
SP1
V1
V2
V4
V5
SP2
V1
V2
V4
V5
c
SP2
SP1
SP = Segment Pin
V1
Resulting Voltage for
Segment e (COM1−SP1)
Segment Is Off.
0V
−V1
V1
Resulting Voltage for
Segment c (COM1−SP2)
Segment Is On.
26-18
LCD_A Controller
0V
−V1
LCD_A Controller Operation
Figure 26−11 shows an example 4-mux LCD, pinout, LCD-to-MSP430
connections, and the resulting segment mapping. This is only an example.
Segment mapping in a user’s application depends on the LCD pinout and on
the MSP430-to-LCD connections.
Figure 26−11.4-Mux LCD Example
LCD
a
f
a
f
b
g
c
e
d
c
e
d
h
DIGIT15
h
DIGIT1
Display Memory
Pinout and Connections
Connections
COM
3
2
1
0
3
2
1
0
MAB 09Fh
09Eh
09Dh
09Ch
09Bh
09Ah
099h
098h
097h
096h
095h
094h
093h
092h
091h
a
a
a
b
b
b
c
c
c
h
h
h
f
f
f
g
g
g
e
e
e
d
d
d
n = 30 Digit 16
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
24 Digit 13
22 Digit 12
20 Digit 11
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
a
b
b
c
c
h
h
f
f
g
g
e
e
d
d
a
b
c
h
f
g
e
d
3
2
1
0
3
1
0
LCD Pinout
’430 Pins
PIN
S0
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
COM0
COM1
COM2
COM3
b
g
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
COM0 COM1 COM2 COM3
1d
1h
2d
2h
3d
3h
4d
4h
5d
5h
6d
6h
7d
7h
8d
8h
9d
9h
10d
10h
11d
11h
12d
12h
13d
13h
14d
14h
15d
15h
COM0
1e
1c
2e
2c
3e
3c
4e
4c
5e
5c
6e
6c
7e
7c
8e
8c
9e
9c
10e
10c
11e
11c
12e
12c
13e
13c
14e
14c
15e
15c
1g
1b
2g
2b
3g
3b
4g
4b
5g
5b
6g
6b
7g
7b
8g
8b
9g
9b
10g
10b
11g
11b
12g
12b
13g
13b
14g
14b
15g
15b
1f
1a
2f
2a
3f
3a
4f
4a
5f
5a
6f
6a
7f
7a
8f
8a
9f
9a
10f
10a
11f
11a
12f
12a
13f
13a
14f
14a
15f
15a
A
B
G
2
0
3
Sn+1
28 Digit 15
26 Digit 14
18 Digit 10
16 Digit 9
14 Digit 8
12 Digit 7
10 Digit 6
8
6
4
Digit 5
Digit 4
Digit 3
2
Digit 2
0
Digit 1
A Parallel0
Serial
G
3
B Conversion
Sn
COM1
COM2
COM3
LCD_A Controller
26-19
LCD_A Controller Operation
4-Mux Mode Software Example
;
;
;
a
b
c
d
e
f
g
h
;
;
;
;
;
The 4mux rate supports eight segments for each digit.
All eight segments of a digit can often be located in
one display memory byte
EQU
080h
EQU
040h
EQU
020h
EQU
001h
EQU
002h
EQU
008h
EQU
004h
EQU
010h
The LSDigit of register Rx should be displayed.
The Table represents the ’on’−segments according to the
content of Rx.
MOV.B Table(Rx),&LCDn ;
;
;
;
...........
...........
Table DB
a+b+c+d+e+f
DB
b+c
...........
...........
DB
b+c+d+e+g
DB
a+d+e+f+g
DB
a+e+f+g
26-20
LCD_A Controller
n = 1 ..... 15
all eight segments are
written to the display
memory
; displays ”0”
; displays ”1”
; displays ”d”
; displays ”E”
; displays ”F”
LCD_A Controller Operation
26.3 LCD Controller Registers
The LCD Controller registers are listed in Table 26−2.
Table 26−2.LCD Controller Registers
Register
Short Form
Register Type Address
Initial State
LCD_A control register
LCDACTL
Read/write
090h
Reset with PUC
LCD memory 1
LCDM1
Read/write
091h
Unchanged
LCD memory 2
LCDM2
Read/write
092h
Unchanged
LCD memory 3
LCDM3
Read/write
093h
Unchanged
LCD memory 4
LCDM4
Read/write
094h
Unchanged
LCD memory 5
LCDM5
Read/write
095h
Unchanged
LCD memory 6
LCDM6
Read/write
096h
Unchanged
LCD memory 7
LCDM7
Read/write
097h
Unchanged
LCD memory 8
LCDM8
Read/write
098h
Unchanged
LCD memory 9
LCDM9
Read/write
099h
Unchanged
LCD memory 10
LCDM10
Read/write
09Ah
Unchanged
LCD memory 11
LCDM11
Read/write
09Bh
Unchanged
LCD memory 12
LCDM12
Read/write
09Ch
Unchanged
LCD memory 13
LCDM13
Read/write
09Dh
Unchanged
LCD memory 14
LCDM14
Read/write
09Eh
Unchanged
LCD memory 15
LCDM15
Read/write
09Fh
Unchanged
LCD memory 16
LCDM16
Read/write
0A0h
Unchanged
LCD memory 17
LCDM17
Read/write
0A1h
Unchanged
LCD memory 18
LCDM18
Read/write
0A2h
Unchanged
LCD memory 19
LCDM19
Read/write
0A3h
Unchanged
LCD memory 20
LCDM20
Read/write
0A4h
Unchanged
LCD_A port control 0
LCDAPCTL0
Read/write
0ACh
Reset with PUC
LCD_A port control 1
LCDAPCTL1
Read/write
0ADh
Reset with PUC
LCD_A voltage control 0
LCDAVCTL0
Read/write
0AEh
Reset with PUC
LCD_A voltage control 1
LCDAVCTL1
Read/write
0AFh
Reset with PUC
LCD_A Controller
26-21
LCD_A Controller Operation
LCDACTL, LCD_A Control Register
7
6
5
4
LCDFREQx
rw−0
rw−0
3
LCDMXx
rw−0
rw−0
rw−0
2
1
0
LCDSON
Unused
LCDON
rw−0
rw−0
rw−0
LCDFREQx
Bits
7-5
LCD frequency select. These bits select the ACLK divider for the LCD
frequency.
000 Divide by 32
001 Divide by 64
010 Divide by 96
011 Divide by 128
100 Divide by 192
101 Divide by 256
110 Divide by 384
111 Divide by 512
LCDMXx
Bits
4-3
LCD mux rate. These bits select the LCD mode.
00 Static
01 2-mux
10 3-mux
11 4-mux
LCDSON
Bit 2
LCD segments on. This bit supports flashing LCD applications by turning
off all segment lines, while leaving the LCD timing generator and R33
enabled.
0
All LCD segments are off
1
All LCD segments are enabled and on or off according to their
corresponding memory location.
Unused
Bit 1
Unused
LCDON
Bit 0
LCD On. This bit turns on the LCD_A module.
0
LCD_A module off.
1
LCD_A module on.
26-22
LCD_A Controller
LCD_A Controller Operation
LCDAPCTL0, LCD_A Port Control Register 0
†
7
6
5
4
3
2
1
0
LCDS28
LCDS24
LCDS20
LCDS16
LCDS12
LCDS8
LCDS4
LCDS0†
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
Segments S0−S3 on the MSP430FG461x devices are disabled from LCD functionality when charge pump is enabled.
LCDS28
Bit 7
LCD segment 28 to 31 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCDS24
Bit 6
LCD segment 24 to 27 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCDS20
Bit 5
LCD segment 20 to 23 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCDS16
Bit 4
LCD segment 16 to 19 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCDS12
Bit 3
LCD segment 12 to 15 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCDS8
Bit 2
LCD segment 8 to 11 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCDS4
Bit 1
LCD segment 4 to 7 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCDS0
Bit 0
LCD segment 0 to 3 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCD_A Controller
26-23
LCD_A Controller Operation
LCDAPCTL1, LCD_A Port Control Register 1
7
6
5
4
3
2
Unused
rw−0
rw−0
rw−0
rw−0
rw−0
rw−0
1
0
LCDS36
LCDS32
rw−0
rw−0
Unused
Bits
7−2
Unused
LCDS36
Bit 1
LCD segment 36 to 39 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
LCDS32
Bit 0
LCD segment 32 to 35 enable
This bit only affects pins with multiplexed functions. Dedicated LCD pins
are always LCD function.
0
Multiplexed pins are port functions.
1
Pins are LCD functions
26-24
LCD_A Controller
LCD_A Controller Operation
LCDAVCTL0, LCD_A Voltage Control Register 0
7
6
5
4
3
Unused
R03EXT
REXT
VLCDEXT
LCDCPEN
rw−0
rw−0
rw−0
rw−0
rw−0
2
1
VLCDREFx
rw−0
rw−0
0
LCD2B
rw−0
Unused
Bit 7
Unused
R03EXT
Bit 6
V5 voltage select. This bit selects the external connection for the lowest
LCD voltage. R03EXT is ignored if there is no R03 pin available.
0
V5 is AVSS
1
V5 is sourced from the R03 pin
REXT
Bit 5
V2 − V4 voltage select. This bit selects the external connections for
voltages V2 − V4.
0
V2 − V4 are generated internally
1
V2 − V4 are sourced externally and the internal bias generator is
switched off
VLCDEXT
Bit 4
VLCD source select
0
VLCD is generated internally
1
VLCD is sourced externally
LCDCPEN
Bit 3
Charge pump enable.
0
Charge pump disabled.
1
Charge pump enabled when VLCD is generated internally
(VLCDEXT = 0) and VLCDx > 0 or VLCDREFx > 0.
VLCDREFx
Bits
2−1
Charge pump reference select
00 Internal
01 External
10 Reserved
11 Reserved
LCD2B
Bit 0
Bias select. LCD2B is ignored when LCDMx = 00.
0
1/3 bias
1
1/2 bias
LCD_A Controller
26-25
LCD_A Controller Operation
LCDAVCTL1, LCD_A Voltage Control Register 1
7
6
5
4
3
Unused
rw−0
2
1
VLCDx
rw−0
rw−0
rw−0
rw−0
0
Unused
rw−0
rw−0
rw−0
Unused
Bits
7−5
Unused
VLCDx
Bits
4−1
Charge pump voltage select. LCDCPEN must be 1 for the charge pump to
be enabled. AVCC is used for VLCD when VLCDx = 0000 and VREFx = 00
and VLCDEXT = 0.
0000 Charge pump disabled
0001 VLCD = 2.60 V
0010 VLCD = 2.66 V
0011 VLCD = 2.72 V
0100 VLCD = 2.78 V
0101 VLCD = 2.84 V
0110 VLCD = 2.90 V
0111 VLCD = 2.96 V
1000 VLCD = 3.02 V
1001 VLCD = 3.08 V
1010 VLCD = 3.14 V
1011 VLCD = 3.20 V
1100 VLCD = 3.26 V
1101 VLCD = 3.32 V
1110 VLCD = 3.38 V
1111 VLCD = 3.44 V
Unused
Bit 0
Unused
26-26
LCD_A Controller
Chapter 27
ADC10
The ADC10 module is a high-performance 10-bit analog-to-digital converter.
This chapter describes the operation of the ADC10 module of the 4xx family.
The ADC10 is implemented on the MSP4340F41x2 devices.
Topic
Page
16.1 ADC10 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-2
16.2 ADC10 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-4
16.3 ADC10 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-24
ADC10
27-1
ADC10 Introduction
27.1 ADC10 Introduction
The ADC10 module supports fast, 10-bit analog-to-digital conversions. The
module implements a 10-bit SAR core, sample select control, reference
generator, and data transfer controller (DTC).
The DTC allows ADC10 samples to be converted and stored anywhere in
memory without CPU intervention. The module can be configured with user
software to support a variety of applications.
ADC10 features include:
- Greater than 200 ksps maximum conversion rate
- Monotonic10-bit converter with no missing codes
- Sample-and-hold with programmable sample periods
- Conversion initiation by software or Timer_A
- Software selectable on-chip reference voltage generation (1.5 V or 2.5 V)
- Software selectable internal or external reference
- Up to twelve external input channels
- Conversion channels for internal temperature sensor, VCC, and external
references
- Selectable conversion clock source
- Single-channel, repeated single-channel, sequence, and repeated
sequence conversion modes
- ADC core and reference voltage can be powered down separately
- Data transfer controller for automatic storage of conversion results
The block diagram of ADC10 is shown in Figure 27−1.
27-2
ADC10
ADC10 Introduction
Figure 27−1. ADC10 Block Diagram
Ve REF+
REFBURST
ADC10SR
REFOUT
SREF1
0
2_5V
VREF+
1
1
REFON
INCHx=0Ah
on
1.5V or 2.5V
Reference
0
VREF−/VeREF−
AVCC
Ref_x
AVCC
INCHx
Auto
A0
A1
A2
A3
A4
A5
A6
A7
A12†
A13†
A14†
A15†
SREF1
SREF0
11 10 01 00
4
CONSEQx
SREF2
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
ADC10OSC
AVSS
1
0
ADC10SSELx
ADC10ON
ADC10DIVx
Sample
and
Hold
VR−
VR+
00
Divider
/1 .. /8
10−bit SAR
Convert
S/H
ADC10CLK
01
ACLK
10
MCLK
11
SMCLK
SHSx
ISSH
BUSY
ENC
SAMPCON
AVCC
Sample Timer
/4/8/16/64
ADC10DF
SHI
0
1
Sync
00
ADC10SC
01
TA0_1
10
TA1_0
11
TA1_1
ADC10SHTx MSC
INCHx=0Bh
ADC10MEM
Ref_x
R
Data Transfer
Controller
n
RAM, Flash, Peripherials
ADC10SA
R
AVSS
ADC10CT
ADC10TB
ADC10B1
†Not all devices support all channels. See the devices specific datasheet for details.
ADC10
27-3
ADC10 Operation
27.2 ADC10 Operation
The ADC10 module is configured with user software. The setup and operation
of the ADC10 is discussed in the following sections.
27.2.1 10-Bit ADC Core
The ADC core converts an analog input to its 10-bit digital representation and
stores the result in the ADC10MEM register. The core uses two
programmable/selectable voltage levels (VR+ and VR−) to define the upper and
lower limits of the conversion. The digital output (NADC) is full scale (03FFh)
when the input signal is equal to or higher than VR+, and zero when the input
signal is equal to or lower than VR−. The input channel and the reference
voltage levels (VR+ and VR−) are defined in the conversion-control memory.
Conversion results may be in straight binary format or 2s-complement format.
The conversion formula for the ADC result when using straight binary format
is:
Vin – V R–
N ADC + 1023
V R)– V R–
The ADC10 core is configured by two control registers, ADC10CTL0 and
ADC10CTL1. The core is enabled with the ADC10ON bit. With few exceptions
the ADC10 control bits can only be modified when ENC = 0. ENC must be set
to 1 before any conversion can take place.
Conversion Clock Selection
The ADC10CLK is used both as the conversion clock and to generate the
sampling period. The ADC10 source clock is selected using the ADC10SSELx
bits and can be divided from 1-8 using the ADC10DIVx bits. Possible
ADC10CLK sources are SMCLK, MCLK, ACLK and an internal oscillator
ADC10OSC .
The ADC10OSC, generated internally, is in the 5-MHz range, but varies with
individual devices, supply voltage, and temperature. See the device-specific
datasheet for the ADC10OSC specification.
The user must ensure that the clock chosen for ADC10CLK remains active
until the end of a conversion. If the clock is removed during a conversion, the
operation will not complete, and any result will be invalid.
27-4
ADC10
ADC10 Operation
27.2.2 ADC10 Inputs and Multiplexer
The eight external and four internal analog signals are selected as the channel
for conversion by the analog input multiplexer. The input multiplexer is a
break-before-make type to reduce input-to-input noise injection resulting from
channel switching as shown in Figure 27−2. The input multiplexer is also a
T-switch to minimize the coupling between channels. Channels that are not
selected are isolated from the A/D and the intermediate node is connected to
analog ground (VSS) so that the stray capacitance is grounded to help
eliminate crosstalk.
The ADC10 uses the charge redistribution method. When the inputs are
internally switched, the switching action may cause transients on the input
signal. These transients decay and settle before causing errant conversion.
Figure 27−2. Analog Multiplexer
R ~ 100Ohm
INCHx
Input
Ax
ESD Protection
Analog Port Selection
The ADC10 external inputs Ax, VeREF+, and VREF− share terminals with
general purpose I/O ports, which are digital CMOS gates (see device-specific
datasheet). When analog signals are applied to digital CMOS gates, parasitic
current can flow from VCC to GND. This parasitic current occurs if the input
voltage is near the transition level of the gate. Disabling the port pin buffer
eliminates the parasitic current flow and therefore reduces overall current
consumption. The ADC10AEx bits provide the ability to disable the port pin
input and output buffers.
; P7.5 on MSP430x41x2 device configured for analog input
BIS.B #01h,&ADC10AE0 ; P7.5 ADC10 function and enable
ADC10
27-5
ADC10 Operation
27.2.3 Voltage Reference Generator
The ADC10 module contains a built-in voltage reference with two selectable
voltage levels. Setting REFON = 1 enables the internal reference. When
REF2_5V = 1, the internal reference is 2.5 V. When REF2_5V = 0, the
reference is 1.5 V. The internal reference voltage may be used internally and,
when REFOUT = 0, externally on pin VREF+.
External references may be supplied for VR+ and VR− through pins A4 and A3
respectively. When external references are used, or when VCC is used as the
reference, the internal reference may be turned off to save power.
An external positive reference VeREF+ can be buffered by setting SREF0 = 1
and SREF1 = 1. This allows using an external reference with a large internal
resistance at the cost of the buffer current. When REFBURST = 1 the
increased current consumption is limited to the sample and conversion period.
External storage capacitance is not required for the ADC10 reference source
as on the ADC12.
Internal Reference Low-Power Features
The ADC10 internal reference generator is designed for low power
applications. The reference generator includes a band-gap voltage source
and a separate buffer. The current consumption of each is specified separately
in the device-specific datasheet. When REFON = 1, both are enabled and
when REFON = 0 both are disabled. The total settling time when REFON
becomes set is 30 μs.
When REFON = 1, but no conversion is active, the buffer is automatically
disabled and automatically re-enabled when needed. When the buffer is
disabled, it consumes no current. In this case, the band-gap voltage source
remains enabled.
When REFOUT = 1, the REFBURST bit controls the operation of the internal
reference buffer. When REFBURST = 0, the buffer will be on continuously,
allowing the reference voltage to be present outside the device continuously.
When REFBURST = 1, the buffer is automatically disabled when the ADC10
is not actively converting, and automatically re-enabled when needed.
The internal reference buffer also has selectable speed vs. power settings.
When the maximum conversion rate is below 50 ksps, setting ADC10SR = 1
reduces the current consumption of the buffer approximately 50%.
27.2.4 Auto Power-Down
The ADC10 is designed for low power applications. When the ADC10 is not
actively converting, the core is automatically disabled and automatically
re-enabled when needed. The ADC10OSC is also automatically enabled
when needed and disabled when not needed. When the core or oscillator is
disabled, it consumes no current.
27-6
ADC10
ADC10 Operation
27.2.5 Sample and Conversion Timing
An analog-to-digital conversion is initiated with a rising edge of sample input
signal SHI. The source for SHI is selected with the SHSx bits and includes the
following for MSP430F41x2:
-
The ADC10SC bit
The Timer_A0 Output Unit 1
The Timer_A1 Output Unit 0
The Timer_A1 Output Unit 1
The polarity of the SHI signal source can be inverted with the ISSH bit. The
SHTx bits select the sample period tsample to be 4, 8, 16, or 64 ADC10CLK
cycles. The sampling timer sets SAMPCON high for the selected sample
period after synchronization with ADC10CLK. Total sampling time is tsample
plus tsync.The high-to-low SAMPCON transition starts the analog-to-digital
conversion, which requires 11 ADC10CLK cycles as shown in Figure 27−3.
Figure 27−3. Sample Timing
Start
Sampling
Stop
Sampling
Conversion
Complete
Start
Conversion
SHI
13 x ADC10CLKs
SAMPCON
tsample
tconvert
tsync
ADC10CLK
Sample Timing Considerations
When SAMPCON = 0 all Ax inputs are high impedance. When SAMPCON =
1, the selected Ax input can be modeled as an RC low-pass filter during the
sampling time tsample, as shown below in Figure 27−4. An internal MUX-on
input resistance RI (max. 2 kΩ) in series with capacitor CI (max. 27 pF) is seen
by the source. The capacitor CI voltage VC must be charged to within ½ LSB
of the source voltage VS for an accurate 10-bit conversion.
ADC10
27-7
ADC10 Operation
Figure 27−4. Analog Input Equivalent Circuit
MSP430
RS
VS
VI = Input voltage at pin Ax
VS = External source voltage
RS = External source resistance
RI = Internal MUX-on input resistance
CI = Input capacitance
VC = Capacitance-charging voltage
RI
VI
VC
CI
The resistance of the source RS and RI affect tsample.The following equations
can be used to calculate the minimum sampling time for a 10-bit conversion.
t
sample
u (R S ) R I)
ln(2 11)
CI
Substituting the values for RI and CI given above, the equation becomes:
t
sample
u (R S ) 2k)
7.625
27pF
For example, if RS is 10 kΩ, tsample must be greater than 2.47 μs.
When the reference buffer is used in burst mode, the sampling time must be
greater than the sampling time calculated and the settling time of the buffer,
tREFBURST:
t
sample
u
NJ
(R S ) R I)
ln(2 11)
CI
t REFBURST
For example, if VRef is 1.5 V and RS is 10 kΩ, tsample must be greater than 2.47
μs when ADC10SR = 0, or 2.5 μs when ADC10SR = 1. See the device-specific
datasheet for parameters.
To calculate the buffer settling time when using an external reference, the
formula is:
t REFBURST + SR
V Ref * 0.5s
Where:
SR:
Vref:
27-8
ADC10
Buffer slew rate
(~1 μs/V when ADC10SR = 0 and ~2 μs/V when ADC10SR = 1)
External reference voltage
ADC10 Operation
27.2.6 Conversion Modes
The ADC10 has four operating modes selected by the CONSEQx bits as
discussed in Table 27−1.
Table 27−1.Conversion Mode Summary
CONSEQx
Mode
Operation
00
Single channel
single-conversion
A single channel is converted once.
01
Sequence-ofchannels
A sequence of channels is converted once.
10
Repeat single
channel
A single channel is converted repeatedly.
11
Repeat sequenceof-channels
A sequence of channels is converted
repeatedly.
ADC10
27-9
ADC10 Operation
Single-Channel Single-Conversion Mode
A single channel selected by INCHx is sampled and converted once. The ADC
result is written to ADC10MEM. Figure 27−5 shows the flow of the
single-channel, single-conversion mode. When ADC10SC triggers a
conversion, successive conversions can be triggered by the ADC10SC bit.
When any other trigger source is used, ENC must be toggled between each
conversion.
Figure 27−5. Single-Channel Single-Conversion Mode
CONSEQx = 00
ADC10
Off
ENC =
ADC10ON = 1
x = INCHx
Wait for Enable
ENC =
SHS = 0
and
ENC = 1 or
and
ADC10SC =
ENC = 0
ENC =
Wait for Trigger
SAMPCON =
(4/8/16/64) x ADC10CLK
Sample, Input
Channel
ENC = 0†
12 x ADC10CLK
Convert
ENC = 0†
1 x ADC10CLK
Conversion
Completed,
Result to
ADC10MEM,
ADC10IFG is Set
†
x = input channel Ax
Conversion result is unpredictable
27-10
ADC10
ADC10 Operation
Sequence-of-Channels Mode
A sequence of channels is sampled and converted once. The sequence
begins with the channel selected by INCHx and decrements to channel A0.
Each ADC result is written to ADC10MEM. The sequence stops after
conversion of channel A0. Figure 27−6 shows the sequence-of-channels
mode. When ADC10SC triggers a sequence, successive sequences can be
triggered by the ADC10SC bit . When any other trigger source is used, ENC
must be toggled between each sequence.
Figure 27−6. Sequence-of-Channels Mode
CONSEQx = 01
ADC10
Off
ADC10ON = 1
ENC =
x = INCHx
Wait for Enable
ENC =
SHS = 0
and
ENC = 1 or
and
ADC10SC =
ENC =
Wait for Trigger
SAMPCON =
x=0
(4/8/16/64) x ADC10CLK
Sample,
Input Channel Ax
If x > 0 then x = x −1
If x > 0 then x = x −1
12 x ADC10CLK
MSC = 1
and
x≠0
Convert
MSC = 0
and
x≠0
1 x ADC10CLK
Conversion
Completed,
Result to ADC10MEM,
ADC10IFG is Set
x = input channel Ax
ADC10
27-11
ADC10 Operation
Repeat-Single-Channel Mode
A single channel selected by INCHx is sampled and converted continuously.
Each ADC result is written to ADC10MEM. Figure 27−7 shows the
repeat-single-channel mode.
Figure 27−7. Repeat-Single-Channel Mode
CONSEQx = 10
ADC10
Off
ADC10ON = 1
ENC =
x = INCHx
Wait for Enable
ENC =
SHS = 0
and
ENC = 1 or
and
ADC10SC =
ENC =
Wait for Trigger
SAMPCON =
ENC = 0
(4/8/16/64) × ADC10CLK
Sample,
Input Channel Ax
12 x ADC10CLK
MSC = 1
and
ENC = 1
MSC = 0
and
ENC = 1
Convert
1 x ADC10CLK
Conversion
Completed,
Result to ADC10MEM,
ADC10IFG is Set
x = input channel Ax
27-12
ADC10
ADC10 Operation
Repeat-Sequence-of-Channels Mode
A sequence of channels is sampled and converted repeatedly. The sequence
begins with the channel selected by INCHx and decrements to channel A0.
Each ADC result is written to ADC10MEM. The sequence ends after
conversion of channel A0, and the next trigger signal re-starts the sequence.
Figure 27−8 shows the repeat-sequence-of-channels mode.
Figure 27−8. Repeat-Sequence-of-Channels Mode
CONSEQx = 11
ADC10
Off
ADC10ON = 1
ENC =
x = INCHx
Wait for Enable
ENC =
SHS = 0
and
ENC = 1 or
and
ADC10SC =
ENC =
Wait for Trigger
SAMPCON =
(4/8/16/64) x ADC10CLK
Sample
Input Channel Ax
If x = 0 then x = INCH
else x = x −1
If x = 0 then x = INCH
else x = x −1
12 x ADC10CLK
Convert
MSC = 1
and
(ENC = 1
or
x ≠ 0)
1 x ADC10CLK
MSC = 0
and
(ENC = 1
or
x ≠ 0)
ENC = 0
and
x=0
Conversion
Completed,
Result to ADC10MEM,
ADC10IFG is Set
x = input channel Ax
ADC10
27-13
ADC10 Operation
Using the MSC Bit
To configure the converter to perform successive conversions automatically
and as quickly as possible, a multiple sample and convert function is available.
When MSC = 1 and CONSEQx > 0 the first rising edge of the SHI signal
triggers the first conversion. Successive conversions are triggered
automatically as soon as the prior conversion is completed. Additional rising
edges on SHI are ignored until the sequence is completed in the
single-sequence mode or until the ENC bit is toggled in repeat-single-channel,
or repeated-sequence modes. The function of the ENC bit is unchanged when
using the MSC bit.
Stopping Conversions
Stopping ADC10 activity depends on the mode of operation. The
recommended ways to stop an active conversion or conversion sequence are:
- Resetting ENC in single-channel single-conversion mode stops a
conversion immediately and the results are unpredictable. For correct
results, poll the ADC10BUSY bit until reset before clearing ENC.
- Resetting ENC during repeat-single-channel operation stops the
converter at the end of the current conversion.
- Resetting ENC during a sequence or repeat sequence mode stops the
converter at the end of the sequence.
- Any conversion mode may be stopped immediately by setting the
CONSEQx=0 and resetting the ENC bit. Conversion data is unreliable.
27-14
ADC10
ADC10 Operation
27.2.7 ADC10 Data Transfer Controller
The ADC10 includes a data transfer controller (DTC) to automatically transfer
conversion results from ADC10MEM to other on-chip memory locations. The
DTC is enabled by setting the ADC10DTC1 register to a nonzero value.
When the DTC is enabled, each time the ADC10 completes a conversion and
loads the result to ADC10MEM, a data transfer is triggered. No software
intervention is required to manage the ADC10 until the predefined amount of
conversion data has been transferred. Each DTC transfer requires one CPU
MCLK. To avoid any bus contention during the DTC transfer, the CPU is halted,
if active, for the one MCLK required for the transfer.
A DTC transfer must not be initiated while the ADC10 is busy. Software must
ensure that no active conversion or sequence is in progress when the DTC is
configured:
; ADC10 activity test
BIC.W #ENC,&ADC10CTL0 ;
busy_test BIT.W #BUSY,&ADC10CTL1;
JNZ
busy_test
;
MOV.W #xxx,&ADC10SA
; Safe
MOV.B #xx,&ADC10DTC1 ;
; continue setup
ADC10
27-15
ADC10 Operation
One-Block Transfer Mode
The one-block mode is selected if the ADC10TB is reset. The value n in
ADC10DTC1 defines the total number of transfers for a block. The block start
address is defined anywhere in the MSP430 address range using the 16-bit
register ADC10SA. The block ends at ADC10SA+2n–2. The one-block
transfer mode is shown in Figure 27−9.
Figure 27−9. One-Block Transfer
TB=0
’n’th transfer
ADC10SA+2n−2
ADC10SA+2n−4
DTC
2nd transfer
ADC10SA+2
1st transfer
ADC10SA
The internal address pointer is initially equal to ADC10SA and the internal
transfer counter is initially equal to ‘n’. The internal pointer and counter are not
visible to software. The DTC transfers the word-value of ADC10MEM to the
address pointer ADC10SA. After each DTC transfer, the internal address
pointer is incremented by two and the internal transfer counter is decremented
by one.
The DTC transfers continue with each loading of ADC10MEM, until the
internal transfer counter becomes equal to zero. No additional DTC transfers
will occur until a write to ADC10SA. When using the DTC in the one-block
mode, the ADC10IFG flag is set only after a complete block has been
transferred. Figure 27−10 shows a state diagram of the one-block mode.
27-16
ADC10
ADC10 Operation
Figure 27−10. State Diagram for Data Transfer Control in One-Block Transfer Mode
n=0 (ADC10DTC1)
DTC reset
n≠0
Wait for write to
ADC10SA
n=0
DTC init
Initialize
Start Address in ADC10SA
Prepare
DTC
Write to
ADC10SA
x=n
AD = SA
Write to ADC10SA
or
n=0
n is latched
in counter ’x’
Wait until ADC10MEM
is written
DTC idle
Write to ADC10MEM
completed
Write to ADC10SA
Wait
for
CPU ready
Synchronize
with MCLK
x>0
DTC
operation
Write to ADC10SA
1 x MCLK cycle
Transfer data to
Address AD
AD = AD + 2
x=x−1
x=0
ADC10IFG=1
ADC10TB = 0
and
ADC10CT = 1
ADC10TB = 0
and
ADC10CT = 0
ADC10
27-17
ADC10 Operation
Two-Block Transfer Mode
The two-block mode is selected if the ADC10TB bit is set. The value n in
ADC10DTC1 defines the number of transfers for one block. The address
range of the first block is defined anywhere in the MSP430 address range with
the 16-bit register ADC10SA. The first block ends at ADC10SA+2n–2. The
address range for the second block is defined as SA+2n to SA+4n–2. The
two-block transfer mode is shown in Figure 27−11.
Figure 27−11.Two-Block Transfer
TB=1
2 x ’n’th transfer
ADC10SA+4n−2
ADC10SA+4n−4
DTC
’n’th transfer
ADC10SA+2n−2
ADC10SA+2n−4
2nd transfer
ADC10SA+2
1st transfer
ADC10SA
The internal address pointer is initially equal to ADC10SA and the internal
transfer counter is initially equal to ‘n’. The internal pointer and counter are not
visible to software. The DTC transfers the word-value of ADC10MEM to the
address pointer ADC10SA. After each DTC transfer the internal address
pointer is incremented by two and the internal transfer counter is decremented
by one.
The DTC transfers continue, with each loading of ADC10MEM, until the
internal transfer counter becomes equal to zero. At this point, block one is full
and both the ADC10IFG flag the ADC10B1 bit are set. The user can test the
ADC10B1 bit to determine that block one is full.
The DTC continues with block two. The internal transfer counter is
automatically reloaded with ’n’. At the next load of the ADC10MEM, the DTC
begins transferring conversion results to block two. After n transfers have
completed, block two is full. The ADC10IFG flag is set and the ADC10B1 bit
is cleared. User software can test the cleared ADC10B1 bit to determine that
block two is full. Figure 27−12 shows a state diagram of the two-block mode.
27-18
ADC10
ADC10 Operation
Figure 27−12. State Diagram for Data Transfer Control in Two-Block Transfer Mode
n=0 (ADC10DTC1)
DTC reset
ADC10B1 = 0
ADC10TB = 1
n≠0
n=0
Wait for write to
ADC10SA
DTC init
Initialize
Start Address in ADC10SA
Prepare
DTC
Write to
ADC10SA
x=n
If ADC10B1 = 0
then AD = SA
Write to ADC10SA
or
n=0
n is latched
in counter ’x’
Wait until ADC10MEM
is written
DTC idle
Write to ADC10MEM
completed
Write to ADC10SA
Wait
for
CPU ready
Synchronize
with MCLK
x>0
DTC
operation
Write to ADC10SA
1 x MCLK cycle
Transfer data to
Address AD
AD = AD + 2
x=x−1
x=0
ADC10IFG=1
Toggle
ADC10B1
ADC10B1 = 1
or
ADC10CT=1
ADC10CT = 0
and
ADC10B1 = 0
ADC10
27-19
ADC10 Operation
Continuous Transfer
A continuous transfer is selected if ADC10CT bit is set. The DTC will not stop
after block one in (one-block mode) or block two (two-block mode) has been
transferred. The internal address pointer and transfer counter are set equal to
ADC10SA and n respectively. Transfers continue starting in block one. If the
ADC10CT bit is reset, DTC transfers cease after the current completion of
transfers into block one (in the one-block mode) or block two (in the two-block
mode) have been transfer.
DTC Transfer Cycle Time
For each ADC10MEM transfer, the DTC requires one or two MCLK clock
cycles to synchronize, one for the actual transfer (while the CPU is halted), and
one cycle of wait time. Because the DTC uses MCLK, the DTC cycle time is
dependent on the MSP430 operating mode and clock system setup.
If the MCLK source is active, but the CPU is off, the DTC uses the MCLK
source for each transfer, without re-enabling the CPU. If the MCLK source is
off, the DTC temporarily restarts MCLK, sourced with DCOCLK, only during
a transfer. The CPU remains off and after the DTC transfer, MCLK is again
turned off. The maximum DTC cycle time for all operating modes is show in
Table 27−2.
Table 27−2.Maximum DTC Cycle Time
†
27-20
ADC10
CPU Operating Mode
Clock Source
Maximum DTC Cycle Time
Active mode
MCLK=DCOCLK
3 MCLK cycles
Active mode
MCLK=LFXT1CLK
3 MCLK cycles
Low-power mode LPM0/1 MCLK=DCOCLK
4 MCLK cycles
Low-power mode LPM3/4 MCLK=DCOCLK
4 MCLK cycles + 2 μs†
Low-power mode LPM0/1 MCLK=LFXT1CLK
4 MCLK cycles
Low-power mode LPM3
MCLK=LFXT1CLK
4 MCLK cycles
Low-power mode LPM4
MCLK=LFXT1CLK
4 MCLK cycles + 2 μs†
The additional 2 μs are needed to start the DCOCLK. See device-datasheet for parameters.
ADC10 Operation
27.2.8 Using the Integrated Temperature Sensor
To use the on-chip temperature sensor, the user selects the analog input
channel INCHx = 1010. Any other configuration is done as if an external
channel was selected, including reference selection, conversion-memory
selection, etc.
The typical temperature sensor transfer function is shown in Figure 27−13.
When using the temperature sensor, the sample period must be greater than
30 μs. The temperature sensor offset error is large. Deriving absolute
temperature values in the application requires calibration. See the
device-specific datasheet for the parameters.
Selecting the temperature sensor automatically turns on the on-chip reference
generator as a voltage source for the temperature sensor. However, it does not
enable the VREF+ output or affect the reference selections for the conversion.
The reference choices for converting the temperature sensor are the same as
with any other channel.
Figure 27−13. Typical Temperature Sensor Transfer Function
Volts
1.300
1.200
1.100
1.000
0.900
VTEMP=0.00355(TEMPC)+0.986
0.800
0.700
Celsius
−50
0
50
100
ADC10
27-21
ADC10 Operation
27.2.9 ADC10 Grounding and Noise Considerations
As with any high-resolution ADC, appropriate printed-circuit-board layout and
grounding techniques should be followed to eliminate ground loops, unwanted
parasitic effects, and noise.
Ground loops are formed when return current from the A/D flows through paths
that are common with other analog or digital circuitry. If care is not taken, this
current can generate small, unwanted offset voltages that can add to or
subtract from the reference or input voltages of the A/D converter. The
connections shown in Figure 27--14 help avoid this.
In addition to grounding, ripple and noise spikes on the power supply lines due
to digital switching or switching power supplies can corrupt the conversion
result. A noise-free design is important to achieve high accuracy.
Figure 27-- 14. ADC10 Grounding and Noise Considerations (internal Vref).
DVCC
Digital
Power Supply
Decoupling
DVSS
10uF
100nF
AVCC
Analog
Power Supply
Decoupling
(if available)
AVSS
10uF
100nF
Figure 27-- 15. ADC10 Grounding and Noise Considerations (external Vref).
DVCC
Digital
Power Supply
Decoupling
DVSS
10uF
100nF
AVCC
Analog
Power Supply
Decoupling
(if available)
AVSS
10uF
Using an External
Positive Reference
Using an External
Negative Reference
27-22
ADC10
100nF
VREF+/VeREF+
VREF-/VeREF-
ADC10 Operation
27.2.10 ADC10 Interrupts
One interrupt and one interrupt vector are associated with the ADC10 as
shown in Figure 27−16. When the DTC is not used (ADC10DTC1 = 0)
ADC10IFG is set when conversion results are loaded into ADC10MEM. When
DTC is used (ADC10DTC1 > 0) ADC10IFG is set when a block transfer
completes and the internal transfer counter ’n’ = 0. If both the ADC10IE and
the GIE bits are set, then the ADC10IFG flag generates an interrupt request.
The ADC10IFG flag is automatically reset when the interrupt request is
serviced or may be reset by software.
Figure 27−16. ADC10 Interrupt System
ADC10IE
Set ADC10IFG
’n’ = 0
D
ADC10CLK
IRQ, Interrupt Service Requested
Q
Reset
IRACC, Interrupt Request Accepted
POR
ADC10
27-23
ADC10 Registers
27.3 ADC10 Registers
The ADC10 registers are listed in Table 27−3.
Table 27−3.ADC10 Registers
Register
Short Form
Register Type Address
Initial State
ADC10 Input enable register 0
ADC10AE0
Read/write
04Ah
Reset with POR
ADC10 Input enable register 1
ADC10AE1
Read/write
04Bh
Reset with POR
ADC10 control register 0
ADC10CTL0
Read/write
01B0h
Reset with POR
ADC10 control register 1
ADC10CTL1
Read/write
01B2h
Reset with POR
ADC10 memory
ADC10MEM
Read
01B4h
Unchanged
ADC10 data transfer control register 0
ADC10DTC0
Read/write
048h
Reset with POR
ADC10 data transfer control register 1
ADC10DTC1
Read/write
049h
Reset with POR
ADC10 data transfer start address
ADC10SA
Read/write
01BCh
0200h with POR
27-24
ADC10
ADC10 Registers
ADC10CTL0, ADC10 Control Register 0
15
14
13
12
SREFx
11
ADC10SHTx
10
9
8
ADC10SR
REFOUT
REFBURST
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
MSC
REF2_5V
REFON
ADC10ON
ADC10IE
ADC10IFG
ENC
ADC10SC
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
Modifiable only when ENC = 0
SREFx
Bits
15-13
Select reference
000 VR+ = VCC and VR− = VSS
001 VR+ = VREF+ and VR− = VSS
010 VR+ = VeREF+ and VR− = VSS
011 VR+ = Buffered VeREF+ and VR− = VSS
100 VR+ = VCC and VR− = VREF−/ VeREF−
101 VR+ = VREF+ and VR− = VREF−/ VeREF−
110 VR+ = VeREF+ and VR− = VREF−/ VeREF−
111 VR+ = Buffered VeREF+ and VR− = VREF−/ VeREF−
ADC10
SHTx
Bits
12-11
ADC10 sample-and-hold time
00 4 x ADC10CLKs
01 8 x ADC10CLKs
10 16 x ADC10CLKs
11 64 x ADC10CLKs
ADC10SR
Bit 10
ADC10 sampling rate. This bit selects the reference buffer drive capability for
the maximum sampling rate. Setting ADC10SR reduces the current
consumption of the reference buffer.
0
Reference buffer supports up to ~200 ksps
1
Reference buffer supports up to ~50 ksps
REFOUT
Bit 9
Reference output
0
Reference output off
1
Reference output on
REFBURST
Bit 8
Reference burst.
0
Reference buffer on continuously
1
Reference buffer on only during sample-and-conversion
ADC10
27-25
ADC10 Registers
MSC
Bit 7
Multiple sample and conversion. Valid only for sequence or repeated modes.
0
The sampling requires a rising edge of the SHI signal to trigger each
sample-and-conversion.
1
The first rising edge of the SHI signal triggers the sampling timer, but
further sample-and-conversions are performed automatically as soon
as the prior conversion is completed
REF2_5V
Bit 6
Reference-generator voltage. REFON must also be set.
0
1.5 V
1
2.5 V
REFON
Bit 5
Reference generator on
0
Reference off
1
Reference on
ADC10ON
Bit 4
ADC10 on
0
ADC10 off
1
ADC10 on
ADC10IE
Bit 3
ADC10 interrupt enable
0
Interrupt disabled
1
interrupt enabled
ADC10IFG
Bit 2
ADC10 interrupt flag. This bit is set if ADC10MEM is loaded with a conversion
result. It is automatically reset when the interrupt request is accepted, or it may
be reset by software. When using the DTC this flag is set when a block of
transfers is completed.
0
No interrupt pending
1
Interrupt pending
ENC
Bit 1
Enable conversion
0
ADC10 disabled
1
ADC10 enabled
ADC10SC
Bit 0
Start conversion. Software-controlled sample-and-conversion start.
ADC10SC and ENC may be set together with one instruction. ADC10SC is
reset automatically.
0
No sample-and-conversion start
1
Start sample-and-conversion
27-26
ADC10
ADC10 Registers
ADC10CTL1, ADC10 Control Register 1
15
14
13
12
11
INCHx
10
SHSx
9
8
ADC10DF
ISSH
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
ADC10DIVx
rw−(0)
rw−(0)
ADC10SSELx
rw−(0)
rw−(0)
rw−(0)
ADC10
BUSY
CONSEQx
rw−(0)
rw−(0)
r−0
Modifiable only when ENC = 0
INCHx
Bits
15-12
Input channel select. These bits select the channel for a single-conversion or
the highest channel for a sequence of conversions.
0000 A0
0001 A1
0010 A2
0011
A3
0100 A4
0101 A5
0110
A6
0111
A7
1000 VeREF+
1001 VREF− /VeREF−
1010 Temperature sensor
1011
(VCC – VSS) / 2
1100
(VCC – VSS) / 2, A12 on MSP430x22xx devices
1101
(VCC – VSS) / 2, A13 on MSP430x22xx devices
1110
(VCC – VSS) / 2, A14 on MSP430x22xx devices
1111
(VCC – VSS) / 2, A15 on MSP430x22xx devices
SHSx
Bits
11-10
Sample-and-hold source select.
For The MSP430F41x2 devices:
00 ADC10SC bit
01 Timer_A0.OUT1
10 Timer_A1.OUT0
11 Timer_A1.OUT1
ADC10DF
Bit 9
ADC10 data format
0
Straight binary
1
2’s complement
ISSH
Bit 8
Invert signal sample-and-hold
0
The sample-input signal is not inverted.
1
The sample-input signal is inverted.
ADC10
27-27
ADC10 Registers
ADC10DIVx
Bits
7-5
ADC10 clock divider
000 /1
001 /2
010 /3
011 /4
100 /5
101 /6
110 /7
111 /8
ADC10
SSELx
Bits
4-3
ADC10 clock source select
00 ADC10OSC
01 ACLK
10 MCLK
11 SMCLK
CONSEQx
Bits
2-1
Conversion sequence mode select
00 Single-channel-single-conversion
01 Sequence-of-channels
10 Repeat-single-channel
11 Repeat-sequence-of-channels
ADC10
BUSY
Bit 0
ADC10 busy. This bit indicates an active sample or conversion operation
0
No operation is active.
1
A sequence, sample, or conversion is active.
27-28
ADC10
ADC10 Registers
ADC10AE0, Analog (Input) Enable Control Register 0
7
6
5
4
3
2
1
0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
ADC10AE0x
rw−(0)
rw−(0)
ADC10AE0x Bits
rw−(0)
rw−(0)
ADC10 analog enable. These bits enable the corresponding pin for analog
input. BIT0 corresponds to A0, BIT1 corresponds to A1, etc.
0
Analog input disabled
1
Analog input enabled
7-0
ADC10AE1, Analog (Input) Enable Control Register 1
7
6
5
4
ADC10AE1x
rw−(0)
rw−(0)
ADC10AE1x Bits
7-4
rw−(0)
rw−(0)
3
2
1
0
Reserved
Reserved
Reserved
Reserved
rw−(0)
rw−(0)
rw−(0)
rw−(0)
ADC10 analog enable. These bits enable the corresponding pin for analog
input. BIT4 corresponds to A12, BIT5 corresponds to A13, BIT6 corresponds
to A14, and BIT7 corresponds to A15.
0
Analog input disabled
1
Analog input enabled
ADC10
27-29
ADC10 Registers
ADC10MEM, Conversion-Memory Register, Binary Format
15
14
13
12
11
10
9
8
0
0
0
0
0
0
r0
r0
r0
r0
r0
r0
r
r
7
6
5
4
3
2
1
0
r
r
r
Conversion Results
Conversion Results
r
r
Conversion
Results
Bits
15-0
r
r
r
The 10-bit conversion results are right justified, straight-binary format. Bit 9
is the MSB. Bits 15-10 are always 0.
ADC10MEM, Conversion-Memory Register, 2’s Complement Format
15
14
13
12
11
10
9
8
Conversion Results
r
r
r
r
r
r
r
r
7
6
5
4
3
2
1
0
0
0
0
0
0
0
r0
r0
r0
r0
r0
r0
Conversion Results
r
r
Conversion
Results
27-30
Bits
15-0
ADC10
The 10-bit conversion results are left-justified, 2’s complement format. Bit 15
is the MSB. Bits 5-0 are always 0.
ADC10 Registers
ADC10DTC0, Data Transfer Control Register 0
7
6
5
4
Reserved
r0
r0
r0
3
2
1
0
ADC10TB
ADC10CT
ADC10B1
ADC10
FETCH
rw−(0)
rw−(0)
r−(0)
rw−(0)
r0
Reserved
Bits
7-4
Reserved. Always read as 0.
ADC10TB
Bit 3
ADC10 two-block mode.
0
One-block transfer mode
1
Two-block transfer mode
ADC10CT
Bit 2
ADC10 continuous transfer.
0
Data transfer stops when one block (one-block mode) or two blocks
(two-block mode) have completed.
1
Data is transferred continuously. DTC operation is stopped only if
ADC10CT cleared, or ADC10SA is written to.
ADC10B1
Bit 1
ADC10 block one. This bit indicates for two-block mode which block is filled
with ADC10 conversion results. ADC10B1 is valid only after ADC10IFG has
been set the first time during DTC operation. ADC10TB must also be set.
0
Block 2 is filled
1
Block 1 is filled
ADC10
FETCH
Bit 0
This bit should normally be reset.
ADC10
27-31
ADC10 Registers
ADC10DTC1, Data Transfer Control Register 1
7
6
5
4
3
2
1
0
rw−(0)
rw−(0)
rw−(0)
DTC Transfers
rw−(0)
rw−(0)
DTC
Transfers
Bits
7-0
rw−(0)
rw−(0)
rw−(0)
DTC transfers. These bits define the number of transfers in each block.
0
DTC is disabled
01h-0FFh Number of transfers per block
ADC10SA, Start Address Register for Data Transfer
15
14
13
12
11
10
9
8
ADC10SAx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(1)
rw−(0)
7
6
5
4
3
2
1
0
ADC10SAx
rw−(0)
rw−(0)
rw−(0)
rw−(0)
0
rw−(0)
rw−(0)
rw−(0)
r0
ADC10SAx
Bits
15-1
ADC10 start address. These bits are the start address for the DTC. A write
to register ADC10SA is required to initiate DTC transfers.
Unused
Bit 0
Unused, Read only. Always read as 0.
27-32
ADC10
Chapter 28
ADC12
The ADC12 module is a high-performance 12-bit analog-to-digital converter
(ADC). This chapter describes the ADC12. The ADC12 is implemented in the
MSP430x43x MSP430x44x, and MSP430FG461x devices.
Topic
Page
28.1 ADC12 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-2
28.2 ADC12 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-4
28.3 ADC12 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-20
ADC12
28-1
ADC12 Introduction
28.1 ADC12 Introduction
The ADC12 module supports fast, 12-bit analog-to-digital conversions. The
module implements a 12-bit SAR core, sample select control, reference
generator and a 16 word conversion-and-control buffer. The
conversion-and-control buffer allows up to 16 independent ADC samples to be
converted and stored without any CPU intervention.
ADC12 features include:
- Greater than 200-ksps maximum conversion rate
- Monotonic 12-bit converter with no missing codes
- Sample-and-hold with programmable sampling periods controlled by
software or timers.
- Conversion initiation by software, Timer_A, or Timer_B
- Software selectable on-chip reference voltage generation (1.5 V or 2.5 V)
- Software selectable internal or external reference
- Eight individually configurable external input channels (twelve on
MSP430FG43x and MSP430FG461x devices)
- Conversion channels for internal temperature sensor, AVCC, and external
references
- Independent channel-selectable reference sources for both positive and
negative references
- Selectable conversion clock source
- Single-channel, repeat-single-channel, sequence, and repeat-sequence
conversion modes
- ADC core and reference voltage can be powered down separately
- Interrupt vector register for fast decoding of 18 ADC interrupts
- 16 conversion-result storage registers
The block diagram of ADC12 is shown in Figure 28−1.
28-2
ADC12
ADC12 Introduction
Figure 28−1. ADC12 Block Diagram
REFON
INCHx=0Ah
REF2_5V
Ve REF+
on
1.5 V or 2.5 V
Reference
VREF+
VREF− / Ve REF−
AVCC
INCHx
AVSS
4
A0
A1
A2
A3
A4
A5
A6
A7
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
A12†
A13†
A14†
A15†
SREF2
1
Ref_x
SREF1
SREF0
11 10 01 00
ADC12OSC
ADC12SSELx
ADC12ON
0
AVCC
ADC12DIVx
VR−
Sample
and
Hold
VR+
00
Divider
/1 .. /8
12−bit SAR
Convert
S/H
ADC12CLK
01
ACLK
10
MCLK
11
SMCLK
BUSY
SHP
SHSx
ISSH
SHT0x
ENC
4
1
SAMPCON
AVCC
Sample Timer
/4 .. /1024
0
SHI
0
1
Sync
4
SHT1x
00
ADC12SC
01
TA1
10
TB0
11
TB1
MSC
INCHx=0Bh
Ref_x
R
R
CSTARTADDx
CONSEQx
AVSS
†
ADC12MEM0
ADC12MCTL0
−
16 x 12
Memory
Buffer
−
−
16 x 8
Memory
Control
−
ADC12MEM15
ADC12MCTL15
MSP430FG43x and MSP430FG461x devices only
ADC12
28-3
ADC12 Operation
28.2 ADC12 Operation
The ADC12 module is configured with user software. The setup and operation
of the ADC12 is discussed in the following sections.
28.2.1 12-Bit ADC Core
The ADC core converts an analog input to its 12-bit digital representation and
stores the result in conversion memory. The core uses two
programmable/selectable voltage levels (VR+ and VR−) to define the upper and
lower limits of the conversion. The digital output (NADC) is full scale (0FFFh)
when the input signal is equal to or higher than VR+, and zero when the input
signal is equal to or lower than VR−. The input channel and the reference
voltage levels (VR+ and VR−) are defined in the conversion-control memory.
The conversion formula for the ADC result NADC is:
N ADC + 4095
Vin * V R*
V R) * V R*
The ADC12 core is configured by two control registers, ADC12CTL0 and
ADC12CTL1. The core is enabled with the ADC12ON bit. The ADC12 can be
turned off when not in use to save power. With few exceptions the ADC12
control bits can only be modified when ENC = 0. ENC must be set to 1 before
any conversion can take place.
Conversion Clock Selection
The ADC12CLK is used both as the conversion clock and to generate the
sampling period when the pulse sampling mode is selected. The ADC12
source clock is selected using the ADC12SSELx bits and can be divided by
1 to 8 using the ADC12DIVx bits. Possible ADC12CLK sources are SMCLK,
MCLK, ACLK, and an internal oscillator, ADC12OSC.
The ADC12OSC, generated internally, is in the 5-MHz range but varies with
individual devices, supply voltage, and temperature. See the device-specific
data sheet for the ADC12OSC specification.
The user must ensure that the clock chosen for ADC12CLK remains active
until the end of a conversion. If the clock is removed during a conversion, the
operation will not complete and any result will be invalid.
28-4
ADC12
ADC12 Operation
28.2.2 ADC12 Inputs and Multiplexer
The eight external and four internal analog signals are selected as the channel
for conversion by the analog input multiplexer. The input multiplexer is a
break-before-make type to reduce input-to-input noise injection resulting from
channel switching as shown in Figure 28−2. The input multiplexer is also a
T-switch to minimize the coupling between channels. Channels that are not
selected are isolated from the A/D and the intermediate node is connected to
analog ground (AVSS) so that the stray capacitance is grounded to help
eliminate crosstalk.
The ADC12 uses the charge redistribution method. When the inputs are
internally switched, the switching action may cause transients on the input
signal. These transients decay and settle before causing errant conversion.
Figure 28−2. Analog Multiplexer
R ~ 100 Ohm
ADC12MCTLx.0−3
Input
Ax
ESD Protection
Analog Port Selection
The ADC12 inputs are multiplexed with the port P6 pins, which are digital
CMOS gates. When analog signals are applied to digital CMOS gates,
parasitic current can flow from VCC to GND. This parasitic current occurs if the
input voltage is near the transition level of the gate. Disabling the port pin buffer
eliminates the parasitic current flow and therefore reduces overall current
consumption. The P6SELx bits provide the ability to disable the port pin input
and output buffers.
; P6.0 and P6.1 configured for analog input
BIS.B #3h,&P6SEL
; P6.1 and P6.0 ADC12 function
ADC12
28-5
ADC12 Operation
28.2.3 Voltage Reference Generator
The ADC12 module contains a built-in voltage reference with two selectable
voltage levels, 1.5 V and 2.5 V. Either of these reference voltages may be used
internally and externally on pin VREF+.
Setting REFON=1 enables the internal reference. When REF2_5V = 1, the
internal reference is 2.5 V, the reference is 1.5 V when REF2_5V = 0. The
reference can be turned off to save power when not in use.
For proper operation the internal voltage reference generator must be
supplied with storage capacitance across VREF+ and AVSS. The recommended
storage capacitance is a parallel combination of 10-μF and 0.1-μF capacitors.
From turn-on, a maximum of 17 ms must be allowed for the voltage reference
generator to bias the recommended storage capacitors. If the internal
reference generator is not used for the conversion, the storage capacitors are
not required.
Note: Reference Decoupling
Approximately 200 μA is required from any reference used by the ADC12
while the two LSBs are being resolved during a conversion. A parallel
combination of 10-μF and 0.1-μF capacitors is recommended for any
reference used as shown in Figure 28−11.
External references may be supplied for VR+ and VR− through pins VeREF+ and
VREF−/VeREF− respectively.
28.2.4 Auto Power-Down
The ADC12 is designed for low power applications. When the ADC12 is not
actively converting, the core is automatically disabled and automatically
re-enabled when needed. The ADC12OSC is also automatically enabled
when needed and disabled when not needed. The reference is not
automatically disabled, but can be disabled by setting REFON = 0. When the
core, oscillator, or reference are disabled, they consume no current.
28-6
ADC12
ADC12 Operation
28.2.5 Sample and Conversion Timing
An analog-to-digital conversion is initiated with a rising edge of the sample
input signal SHI. The source for SHI is selected with the SHSx bits and
includes the following:
-
The ADC12SC bit
The Timer_A Output Unit 1
The Timer_B Output Unit 0
The Timer_B Output Unit 1
The polarity of the SHI signal source can be inverted with the ISSH bit. The
SAMPCON signal controls the sample period and start of conversion. When
SAMPCON is high, sampling is active. The high-to-low SAMPCON transition
starts the analog-to-digital conversion, which requires 13 ADC12CLK cycles.
Two different sample-timing methods are defined by control bit SHP, extended
sample mode and pulse mode.
Extended Sample Mode
The extended sample mode is selected when SHP = 0. The SHI signal directly
controls SAMPCON and defines the length of the sample period tsample. When
SAMPCON is high, sampling is active. The high-to-low SAMPCON transition
starts the conversion after synchronization with ADC12CLK. See Figure 28−3.
Figure 28−3. Extended Sample Mode
Start
Sampling
Stop
Sampling
Start
Conversion
Conversion
Complete
SHI
13 x ADC12CLK
SAMPCON
tsample
tconvert
t sync
ADC12CLK
ADC12
28-7
ADC12 Operation
Pulse Sample Mode
The pulse sample mode is selected when SHP = 1. The SHI signal is used to
trigger the sampling timer. The SHT0x and SHT1x bits in ADC12CTL0 control
the interval of the sampling timer that defines the SAMPCON sample period
tsample. The sampling timer keeps SAMPCON high after synchronization with
AD12CLK for a programmed interval tsample. The total sampling time is tsample
plus tsync. See Figure 28−4.
The SHTx bits select the sampling time in 4x multiples of ADC12CLK. SHT0x
selects the sampling time for ADC12MCTL0 to 7 and SHT1x selects the
sampling time for ADC12MCTL8 to 15.
Figure 28−4. Pulse Sample Mode
Start
Sampling
Stop
Sampling
Conversion
Complete
Start
Conversion
SHI
13 x ADC12CLK
SAMPCON
tsample
tsync
ADC12CLK
28-8
ADC12
tconvert
ADC12 Operation
Sample Timing Considerations
When SAMPCON = 0 all Ax inputs are high impedance. When SAMPCON = 1,
the selected Ax input can be modeled as an RC low-pass filter during the
sampling time tsample, as shown below in Figure 28−5. An internal MUX-on
input resistance RI (maximum 2 kΩ) in series with capacitor CI (maximum
40 pF) is seen by the source. The capacitor CI voltage VC must be charged to
within 1/2 LSB of the source voltage VS for an accurate 12-bit conversion.
Figure 28−5. Analog Input Equivalent Circuit
MSP430
RS
VS
RI
VI
VC
CI
VI = Input voltage at pin Ax
VS = External source voltage
RS = External source resistance
RI = Internal MUX-on input resistance
CI = Input capacitance
VC = Capacitance-charging voltage
The resistance of the source RS and RI affect tsample. The following equation
can be used to calculate the minimum sampling time tsample for a 12-bit
conversion:
t
sample
u (R S ) R I)
ln(2 13)
C I ) 800ns
Substituting the values for RI and CI given above, the equation becomes:
t
sample
u (R S ) 2k)
9.011
40pF ) 800ns
For example, if RS is 10 kΩ, tsample must be greater than 5.13 μs.
ADC12
28-9
ADC12 Operation
28.2.6 Conversion Memory
There are 16 ADC12MEMx conversion memory registers to store conversion
results. Each ADC12MEMx is configured with an associated ADC12MCTLx
control register. The SREFx bits define the voltage reference and the INCHx
bits select the input channel. The EOS bit defines the end of sequence when
a sequential conversion mode is used. A sequence rolls over from
ADC12MEM15 to ADC12MEM0 when the EOS bit in ADC12MCTL15 is not
set.
The CSTARTADDx bits define the first ADC12MCTLx used for any
conversion. If the conversion mode is single-channel or repeat-single-channel
the CSTARTADDx points to the single ADC12MCTLx to be used.
If the conversion mode selected is either sequence-of-channels or
repeat-sequence-of-channels, CSTARTADDx points to the first
ADC12MCTLx location to be used in a sequence. A pointer, not visible to
software, is incremented automatically to the next ADC12MCTLx in a
sequence when each conversion completes. The sequence continues until an
EOS bit in ADC12MCTLx is processed - this is the last control byte processed.
When conversion results are written to a selected ADC12MEMx, the
corresponding flag in the ADC12IFGx register is set.
28.2.7 ADC12 Conversion Modes
The ADC12 has four operating modes selected by the CONSEQx bits as
discussed in Table 28−1.
Table 28−1.Conversion Mode Summary
CONSEQx
28-10
ADC12
Mode
Operation
00
Single channel
single-conversion
A single channel is converted once.
01
Sequence-ofchannels
A sequence of channels is converted once.
10
Repeat-singlechannel
A single channel is converted repeatedly.
11
Repeat-sequenceof-channels
A sequence of channels is converted
repeatedly.
ADC12 Operation
Single-Channel Single-Conversion Mode
A single channel is sampled and converted once. The ADC result is written to
the ADC12MEMx defined by the CSTARTADDx bits. Figure 28−6 shows the
flow of the Single-Channel, Single-Conversion mode. When ADC12SC
triggers a conversion, successive conversions can be triggered by the
ADC12SC bit. When any other trigger source is used, ENC must be toggled
between each conversion.
Figure 28−6. Single-Channel, Single-Conversion Mode
CONSEQx = 00
ADC12
off
ADC12ON = 1
ENC =
x = CSTARTADDx
Wait for Enable
ENC =
SHSx = 0
and
ENC = 1 or
and
ADC12SC =
ENC =
Wait for Trigger
SAMPCON =
ENC = 0
SAMPCON = 1
ENC = 0†
Sample, Input
Channel Defined in
ADC12MCTLx
SAMPCON =
12 x ADC12CLK
Convert
ENC = 0†
1 x ADC12CLK
Conversion
Completed,
Result Stored Into
ADC12MEMx,
ADC12IFG.x is Set
x = pointer to ADC12MCTLx
†Conversion result is unpredictable
ADC12
28-11
ADC12 Operation
Sequence-of-Channels Mode
A sequence of channels is sampled and converted once. The ADC results are
written to the conversion memories starting with the ADCMEMx defined by the
CSTARTADDx bits. The sequence stops after the measurement of the
channel with a set EOS bit. Figure 28−7 shows the sequence-of-channels
mode. When ADC12SC triggers a sequence, successive sequences can be
triggered by the ADC12SC bit. When any other trigger source is used, ENC
must be toggled between each sequence.
Figure 28−7. Sequence-of-Channels Mode
CONSEQx = 01
ADC12
off
ADC12ON = 1
ENC =
x = CSTARTADDx
Wait for Enable
ENC =
SHSx = 0
and
ENC = 1 or
and
ADC12SC =
ENC =
Wait for Trigger
EOS.x = 1
SAMPCON =
SAMPCON = 1
If x < 15 then x = x + 1
else x = 0
Sample, Input
Channel Defined in
ADC12MCTLx
If x < 15 then x = x + 1
else x = 0
SAMPCON =
MSC = 1
and
SHP = 1
and
EOS.x = 0
12 x ADC12CLK
Convert
1 x ADC12CLK
Conversion
Completed,
Result Stored Into
ADC12MEMx,
ADC12IFG.x is Set
x = pointer to ADC12MCTLx
28-12
ADC12
(MSC = 0
or
SHP = 0)
and
EOS.x = 0
ADC12 Operation
Repeat-Single-Channel Mode
A single channel is sampled and converted continuously. The ADC results are
written to the ADC12MEMx defined by the CSTARTADDx bits. It is necessary
to read the result after the completed conversion because only one
ADC12MEMx memory is used and is overwritten by the next conversion.
Figure 28−8 shows repeat-single-channel mode
Figure 28−8. Repeat-Single-Channel Mode
CONSEQx = 10
ADC12
off
ADC12ON = 1
ENC =
x = CSTARTADDx
Wait for Enable
ENC =
SHSx = 0
and
ENC = 1 or
and
ADC12SC =
ENC =
Wait for Trigger
ENC = 0
SAMPCON =
SAMPCON = 1
Sample, Input
Channel Defined in
ADC12MCTLx
SAMPCON =
12 x ADC12CLK
MSC = 1
and
SHP = 1
and
ENC = 1
Convert
1 x ADC12CLK
(MSC = 0
or
SHP = 0)
and
ENC = 1
Conversion
Completed,
Result Stored Into
ADC12MEMx,
ADC12IFG.x is Set
x = pointer to ADC12MCTLx
ADC12
28-13
ADC12 Operation
Repeat-Sequence-of-Channels Mode
A sequence of channels is sampled and converted repeatedly. The ADC
results are written to the conversion memories starting with the ADC12MEMx
defined by the CSTARTADDx bits. The sequence ends after the measurement
of the channel with a set EOS bit and the next trigger signal re-starts the
sequence. Figure 28−9 shows the repeat-sequence-of-channels mode.
Figure 28−9. Repeat-Sequence-of-Channels Mode
CONSEQx = 11
ADC12
off
ADC12ON = 1
ENC =
x = CSTARTADDx
Wait for Enable
ENC =
SHSx = 0
and
ENC = 1 or
and
ADC12SC =
ENC =
Wait for Trigger
ENC = 0
and
EOS.x = 1
SAMPCON =
SAMPCON = 1
Sample, Input
Channel Defined in
ADC12MCTLx
SAMPCON =
If EOS.x = 1 then
x = CSTARTADDx
else {if x < 15 then x = x + 1 else
x = 0}
MSC = 1
and
SHP = 1
and
(ENC = 1
or
EOS.x = 0)
x = pointer to ADC12MCTLx
28-14
ADC12
If EOS.x = 1 then
x = CSTARTADDx
else {if x < 15 then x = x + 1 else
x = 0}
12 x ADC12CLK
Convert
1 x ADC12CLK
Conversion
Completed,
Result Stored Into
ADC12MEMx,
ADC12IFG.x is Set
(MSC = 0
or
SHP = 0)
and
(ENC = 1
or
EOS.x = 0)
ADC12 Operation
Using the Multiple Sample and Convert (MSC) Bit
To configure the converter to perform successive conversions automatically
and as quickly as possible, a multiple sample and convert function is available.
When MSC = 1, CONSEQx > 0, and the sample timer is used, the first rising
edge of the SHI signal triggers the first conversion. Successive conversions
are triggered automatically as soon as the prior conversion is completed.
Additional rising edges on SHI are ignored until the sequence is completed in
the single-sequence mode or until the ENC bit is toggled in
repeat-single-channel, or repeated-sequence modes. The function of the ENC
bit is unchanged when using the MSC bit.
Stopping Conversions
Stopping ADC12 activity depends on the mode of operation. The
recommended ways to stop an active conversion or conversion sequence are:
- Resetting ENC in single-channel single-conversion mode stops a
conversion immediately and the results are unpredictable. For correct
results, poll the busy bit until reset before clearing ENC.
- Resetting ENC during repeat-single-channel operation stops the
converter at the end of the current conversion.
- Resetting ENC during a sequence or repeat-sequence mode stops the
converter at the end of the sequence.
- Any conversion mode may be stopped immediately by setting the
CONSEQx = 0 and resetting ENC bit. Conversion data are unreliable.
Note: No EOS Bit Set For Sequence
If no EOS bit is set and a sequence mode is selected, resetting the ENC bit
does not stop the sequence. To stop the sequence, first select a
single-channel mode and then reset ENC.
ADC12
28-15
ADC12 Operation
28.2.8 Using the Integrated Temperature Sensor
To use the on-chip temperature sensor, the user selects the analog input
channel INCHx = 1010. Any other configuration is done as if an external
channel was selected, including reference selection, conversion-memory
selection, etc.
The typical temperature sensor transfer function is shown in Figure 28−10.
When using the temperature sensor, the sample period must be greater than
30 μs. The temperature sensor offset error can be large, and may need to be
calibrated for most applications. See device-specific data sheet for
parameters.
Selecting the temperature sensor automatically turns on the on-chip reference
generator as a voltage source for the temperature sensor. However, it does not
enable the VREF+ output or affect the reference selections for the conversion.
The reference choices for converting the temperature sensor are the same as
with any other channel.
Figure 28−10. Typical Temperature Sensor Transfer Function
Volts
1.300
1.200
1.100
1.000
0.900
VTEMP=0.00355(TEMPC)+0.986
0.800
0.700
Celsius
−50
28-16
ADC12
0
50
100
ADC12 Operation
28.2.9 ADC12 Grounding and Noise Considerations
As with any high-resolution ADC, appropriate printed-circuit-board layout and
grounding techniques should be followed to eliminate ground loops, unwanted
parasitic effects, and noise.
Ground loops are formed when return current from the A/D flows through paths
that are common with other analog or digital circuitry. If care is not taken, this
current can generate small, unwanted offset voltages that can add to or
subtract from the reference or input voltages of the A/D converter. The
connections shown in Figure 28−11 help avoid this.
In addition to grounding, ripple and noise spikes on the power supply lines due
to digital switching or switching power supplies can corrupt the conversion
result. A noise-free design using separate analog and digital ground planes
with a single-point connection is recommend to achieve high accuracy.
Figure 28−11.ADC12 Grounding and Noise Considerations
Digital
Power Supply
Decoupling
DVCC
+
10 uF
Analog
Power Supply
Decoupling
100 nF
DVSS
AV CC
+
AV SS
10 uF
Using an External +
Positive
Reference
10 uF
Using the Internal +
Reference
Generator
10 uF
Using an External +
Negative
Reference
10 uF
100 nF
Ve REF+
100 nF
VREF+
100 nF
VREF− / Ve REF−
100 nF
ADC12
28-17
ADC12 Operation
28.2.10 ADC12 Interrupts
The ADC12 has 18 interrupt sources:
- ADC12IFG0-ADC12IFG15
- ADC12OV, ADC12MEMx overflow
- ADC12TOV, ADC12 conversion time overflow
The ADC12IFGx bits are set when their corresponding ADC12MEMx memory
register is loaded with a conversion result. An interrupt request is generated
if the corresponding ADC12IEx bit and the GIE bit are set. The ADC12OV
condition occurs when a conversion result is written to any ADC12MEMx
before its previous conversion result was read. The ADC12TOV condition is
generated when another sample-and-conversion is requested before the
current conversion is completed. The DMA is triggered after the conversion in
single channel modes or after the completion of a sequence−of−channel
modes.
ADC12IV, Interrupt Vector Generator
All ADC12 interrupt sources are prioritized and combined to source a single
interrupt vector. The interrupt vector register ADC12IV is used to determine
which enabled ADC12 interrupt source requested an interrupt.
The highest priority enabled ADC12 interrupt generates a number in the
ADC12IV register (see register description). This number can be evaluated or
added to the program counter to automatically enter the appropriate software
routine. Disabled ADC12 interrupts do not affect the ADC12IV value.
Any access, read or write, of the ADC12IV register automatically resets the
ADC12OV condition or the ADC12TOV condition if either was the highest
pending interrupt. Neither interrupt condition has an accessible interrupt flag.
The ADC12IFGx flags are not reset by an ADC12IV access. ADC12IFGx bits
are reset automatically by accessing their associated ADC12MEMx register
or may be reset with software.
If another interrupt is pending after servicing of an interrupt, another interrupt
is generated. For example, if the ADC12OV and ADC12IFG3 interrupts are
pending when the interrupt service routine accesses the ADC12IV register, the
ADC12OV interrupt condition is reset automatically. After the RETI instruction
of the interrupt service routine is executed, the ADC12IFG3 generates another
interrupt.
28-18
ADC12
ADC12 Operation
ADC12 Interrupt Handling Software Example
The following software example shows the recommended use of ADC12IV
and the handling overhead. The ADC12IV value is added to the PC to
automatically jump to the appropriate routine.
The numbers at the right margin show the necessary CPU cycles for each
instruction. The software overhead for different interrupt sources includes
interrupt latency and return-from-interrupt cycles, but not the task handling
itself. The latencies are:
- ADC12IFG0 - ADC12IFG14, ADC12TOV and ADC12OV
16 cycles
- ADC12IFG15
14 cycles
The interrupt handler for ADC12IFG15 shows a way to check immediately if
a higher prioritized interrupt occurred during the processing of ADC12IFG15.
This saves nine cycles if another ADC12 interrupt is pending.
; Interrupt handler for ADC12.
INT_ADC12
; Enter Interrupt Service Routine
6
ADD
&ADC12IV,PC; Add offset to PC
3
RETI
; Vector 0: No interrupt
5
JMP
ADOV
; Vector 2: ADC overflow
2
JMP
ADTOV
; Vector 4: ADC timing overflow
2
JMP
ADM0
; Vector 6: ADC12IFG0
2
...
; Vectors 8-32
2
JMP
ADM14
; Vector 34: ADC12IFG14
2
;
; Handler for ADC12IFG15 starts here. No JMP required.
;
ADM15
MOV &ADC12MEM15,xxx ; Move result, flag is reset
...
; Other instruction needed?
JMP INT_ADC12
; Check other int pending
;
;
ADC12IFG14-ADC12IFG1 handlers go here
;
ADM0
;
ADTOV
;
ADOV
MOV &ADC12MEM0,xxx ; Move result, flag is reset
...
; Other instruction needed?
RETI
; Return
5
...
RETI
; Handle Conv. time overflow
; Return
5
...
RETI
; Handle ADCMEMx overflow
; Return
5
ADC12
28-19
ADC12 Registers
28.3 ADC12 Registers
The ADC12 registers are listed in Table 28−2 .
Table 28−2.ADC12 Registers
Register
Short Form
Register Type Address
Initial State
ADC12 control register 0
ADC12CTL0
Read/write
01A0h
Reset with POR
ADC12 control register 1
ADC12CTL1
Read/write
01A2h
Reset with POR
ADC12 interrupt flag register
ADC12IFG
Read/write
01A4h
Reset with POR
ADC12 interrupt enable register
ADC12IE
Read/write
01A6h
Reset with POR
ADC12 interrupt vector word
ADC12IV
Read
01A8h
Reset with POR
ADC12 memory 0
ADC12MEM0
Read/write
0140h
Unchanged
ADC12 memory 1
ADC12MEM1
Read/write
0142h
Unchanged
ADC12 memory 2
ADC12MEM2
Read/write
0144h
Unchanged
ADC12 memory 3
ADC12MEM3
Read/write
0146h
Unchanged
ADC12 memory 4
ADC12MEM4
Read/write
0148h
Unchanged
ADC12 memory 5
ADC12MEM5
Read/write
014Ah
Unchanged
ADC12 memory 6
ADC12MEM6
Read/write
014Ch
Unchanged
ADC12 memory 7
ADC12MEM7
Read/write
014Eh
Unchanged
ADC12 memory 8
ADC12MEM8
Read/write
0150h
Unchanged
ADC12 memory 9
ADC12MEM9
Read/write
0152h
Unchanged
ADC12 memory 10
ADC12MEM10
Read/write
0154h
Unchanged
ADC12 memory 11
ADC12MEM11
Read/write
0156h
Unchanged
ADC12 memory 12
ADC12MEM12
Read/write
0158h
Unchanged
ADC12 memory 13
ADC12MEM13
Read/write
015Ah
Unchanged
ADC12 memory 14
ADC12MEM14
Read/write
015Ch
Unchanged
ADC12 memory 15
ADC12MEM15
Read/write
015Eh
Unchanged
ADC12 memory control 0
ADC12MCTL0
Read/write
080h
Reset with POR
ADC12 memory control 1
ADC12MCTL1
Read/write
081h
Reset with POR
ADC12 memory control 2
ADC12MCTL2
Read/write
082h
Reset with POR
ADC12 memory control 3
ADC12MCTL3
Read/write
083h
Reset with POR
ADC12 memory control 4
ADC12MCTL4
Read/write
084h
Reset with POR
ADC12 memory control 5
ADC12MCTL5
Read/write
085h
Reset with POR
ADC12 memory control 6
ADC12MCTL6
Read/write
086h
Reset with POR
ADC12 memory control 7
ADC12MCTL7
Read/write
087h
Reset with POR
ADC12 memory control 8
ADC12MCTL8
Read/write
088h
Reset with POR
ADC12 memory control 9
ADC12MCTL9
Read/write
089h
Reset with POR
ADC12 memory control 10
ADC12MCTL10
Read/write
08Ah
Reset with POR
ADC12 memory control 11
ADC12MCTL11
Read/write
08Bh
Reset with POR
ADC12 memory control 12
ADC12MCTL12
Read/write
08Ch
Reset with POR
ADC12 memory control 13
ADC12MCTL13
Read/write
08Dh
Reset with POR
ADC12 memory control 14
ADC12MCTL14
Read/write
08Eh
Reset with POR
ADC12 memory control 15
ADC12MCTL15
Read/write
08Fh
Reset with POR
28-20
ADC12
ADC12 Registers
ADC12CTL0, ADC12 Control Register 0
15
14
13
12
11
10
SHT1x
9
8
SHT0x
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
MSC
REF2_5V
REFON
ADC12ON
ADC12OVIE
ADC12
TOVIE
ENC
ADC12SC
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
Modifiable only when ENC = 0
SHT1x
Bits
15-12
Sample-and-hold time. These bits define the number of ADC12CLK cycles in
the sampling period for registers ADC12MEM8 to ADC12MEM15.
SHT0x
Bits
11-8
Sample-and-hold time. These bits define the number of ADC12CLK cycles in
the sampling period for registers ADC12MEM0 to ADC12MEM7.
SHTx Bits
ADC12CLK cycles
0000
4
0001
8
0010
16
0011
32
0100
64
0101
96
0110
128
0111
192
1000
256
1001
384
1010
512
1011
768
1100
1024
1101
1024
1110
1024
1111
1024
ADC12
28-21
ADC12 Registers
MSC
Bit 7
Multiple sample and conversion. Valid only for sequence or repeated modes.
0
The sampling timer requires a rising edge of the SHI signal to trigger
each sample-and-conversion.
1
The first rising edge of the SHI signal triggers the sampling timer, but
further sample-and-conversions are performed automatically as soon
as the prior conversion is completed.
REF2_5V
Bit 6
Reference generator voltage. REFON must also be set.
0
1.5 V
1
2.5 V
REFON
Bit 5
Reference generator on
0
Reference off
1
Reference on
ADC12ON
Bit 4
ADC12 on
0
ADC12 off
1
ADC12 on
ADC12OVIE Bit 3
ADC12MEMx overflow-interrupt enable. The GIE bit must also be set to
enable the interrupt.
0
Overflow interrupt disabled
1
Overflow interrupt enabled
ADC12
TOVIE
Bit 2
ADC12 conversion-time-overflow interrupt enable. The GIE bit must also be
set to enable the interrupt.
0
Conversion time overflow interrupt disabled
1
Conversion time overflow interrupt enabled
ENC
Bit 1
Enable conversion
0
ADC12 disabled
1
ADC12 enabled
ADC12SC
Bit 0
Start conversion. Software-controlled sample-and-conversion start.
ADC12SC and ENC may be set together with one instruction. ADC12SC is
reset automatically.
0
No sample-and-conversion-start
1
Start sample-and-conversion
28-22
ADC12
ADC12 Registers
ADC12CTL1, ADC12 Control Register 1
15
14
13
12
11
CSTARTADDx
10
SHSx
9
8
SHP
ISSH
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
ADC12DIVx
rw−(0)
rw−(0)
ADC12SSELx
rw−(0)
rw−(0)
rw−(0)
ADC12
BUSY
CONSEQx
rw−(0)
rw−(0)
r−(0)
Modifiable only when ENC = 0
CSTART
ADDx
Bits
15-12
Conversion start address. These bits select which ADC12
conversion-memory register is used for a single conversion or for the first
conversion in a sequence. The value of CSTARTADDx is 0 to 0Fh,
corresponding to ADC12MEM0 to ADC12MEM15.
SHSx
Bits
11-10
Sample-and-hold source select
00 ADC12SC bit
01 Timer_A.OUT1
10 Timer_B.OUT0
11 Timer_B.OUT1
SHP
Bit 9
Sample-and-hold pulse-mode select. This bit selects the source of the
sampling signal (SAMPCON) to be either the output of the sampling timer or
the sample-input signal directly.
0
SAMPCON signal is sourced from the sample-input signal.
1
SAMPCON signal is sourced from the sampling timer.
ISSH
Bit 8
Invert signal sample-and-hold
0
The sample-input signal is not inverted.
1
The sample-input signal is inverted.
ADC12DIVx
Bits
7-5
ADC12 clock divider
000 /1
001 /2
010 /3
011 /4
100 /5
101 /6
110 /7
111 /8
ADC12
28-23
ADC12 Registers
ADC12
SSELx
Bits
4-3
ADC12 clock source select
00 ADC12OSC
01 ACLK
10 MCLK
11 SMCLK
CONSEQx
Bits
2-1
Conversion sequence mode select
00 Single-channel, single-conversion
01 Sequence-of-channels
10 Repeat-single-channel
11 Repeat-sequence-of-channels
ADC12
BUSY
Bit 0
ADC12 busy. This bit indicates an active sample or conversion operation.
0
No operation is active.
1
A sequence, sample, or conversion is active.
ADC12MEMx, ADC12 Conversion Memory Registers
15
14
13
12
11
10
9
8
0
0
0
0
r0
r0
r0
r0
rw
rw
rw
rw
7
6
5
4
3
2
1
0
rw
rw
rw
Conversion Results
Conversion Results
rw
rw
Conversion
Results
28-24
Bits
15-0
ADC12
rw
rw
rw
The 12-bit conversion results are right-justified. Bit 11 is the MSB. Bits 15-12
are always 0. Writing to the conversion memory registers will corrupt the
results.
ADC12 Registers
ADC12MCTLx, ADC12 Conversion Memory Control Registers
7
6
EOS
rw−(0)
5
4
3
2
SREFx
rw−(0)
rw−(0)
1
0
rw−(0)
rw−(0)
INCHx
rw−(0)
rw−(0)
rw−(0)
Modifiable only when ENC = 0
EOS
Bit 7
End of sequence. Indicates the last conversion in a sequence.
0
Not end of sequence
1
End of sequence
SREFx
Bits
6-4
Select reference
000 VR+ = AVCC and VR− = AVSS
001 VR+ = VREF+ and VR− = AVSS
010 VR+ = VeREF+ and VR− = AVSS
011 VR+ = VeREF+ and VR− = AVSS
100 VR+ = AVCC and VR− = VREF−/ VeREF−
101 VR+ = VREF+ and VR− = VREF−/ VeREF−
110 VR+ = VeREF+ and VR− = VREF−/ VeREF−
111 VR+ = VeREF+ and VR− = VREF−/ VeREF−
INCHx
Bits
3-0
Input channel select
0000 A0
0001 A1
0010 A2
0011
A3
0100 A4
0101 A5
0110
A6
0111
A7
1000 VeREF+
1001 VREF− /VeREF−
1010 Temperature sensor
1011
(AVCC – AVSS) / 2
1100
(AVCC – AVSS) / 2, A12 on ’FG43x and ’FG461x devices
1101
(AVCC – AVSS) / 2, A13 on ’FG43x and ’FG461x devices
1110
(AVCC – AVSS) / 2, A14 on ’FG43x and ’FG461x devices
1111
(AVCC – AVSS) / 2, A15 on ’FG43x and ’FG461x devices
ADC12
28-25
ADC12 Registers
ADC12IE, ADC12 Interrupt Enable Register
15
14
13
12
11
10
9
8
ADC12IE15
ADC12IE14
ADC12IE13
ADC12IE12
ADC12IE11
ADC12IE10
ADC12IE9
ADC12IE8
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
ADC12IE7
ADC12IE6
ADC12IE5
ADC12IE4
ADC12IE3
ADC12IE2
ADC12IE1
ADC12IE0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
ADC12IEx
Bits
15-0
Interrupt enable. These bits enable or disable the interrupt request for the
ADC12IFGx bits.
0
Interrupt disabled
1
Interrupt enabled
ADC12IFG, ADC12 Interrupt Flag Register
15
14
13
12
11
10
9
8
ADC12
IFG15
ADC12
IFG14
ADC12
IFG13
ADC12
IFG12
ADC12
IFG11
ADC12
IFG10
ADC12
IFG9
ADC12
IFG8
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
7
6
5
4
3
2
1
0
ADC12
IFG7
ADC12
IFG6
ADC12
IFG5
ADC12
IFG4
ADC12
IFG3
ADC12
IFG2
ADC12
IFG1
ADC12
IFG0
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
rw−(0)
ADC12IFGx
28-26
Bits
15-0
ADC12
ADC12MEMx Interrupt flag. These bits are set when corresponding
ADC12MEMx is loaded with a conversion result. The ADC12IFGx bits are
reset if the corresponding ADC12MEMx is accessed, or may be reset with
software.
0
No interrupt pending
1
Interrupt pending
ADC12 Registers
ADC12IV, ADC12 Interrupt Vector Register
15
14
13
12
11
10
9
8
0
0
0
0
0
0
0
0
r0
r0
r0
r0
r0
r0
r0
r0
7
6
5
4
3
2
1
0
0
0
r0
r0
ADC12IVx
Bits
15-0
ADC12IVx
r−(0)
r−(0)
r−(0)
0
r−(0)
r−(0)
r0
ADC12 interrupt vector value
ADC12IV
Contents
Interrupt Source
Interrupt Flag
000h
No interrupt pending
−
002h
ADC12MEMx overflow
−
004h
Conversion time overflow
−
006h
ADC12MEM0 interrupt flag
ADC12IFG0
008h
ADC12MEM1 interrupt flag
ADC12IFG1
00Ah
ADC12MEM2 interrupt flag
ADC12IFG2
00Ch
ADC12MEM3 interrupt flag
ADC12IFG3
00Eh
ADC12MEM4 interrupt flag
ADC12IFG4
010h
ADC12MEM5 interrupt flag
ADC12IFG5
012h
ADC12MEM6 interrupt flag
ADC12IFG6
014h
ADC12MEM7 interrupt flag
ADC12IFG7
016h
ADC12MEM8 interrupt flag
ADC12IFG8
018h
ADC12MEM9 interrupt flag
ADC12IFG9
01Ah
ADC12MEM10 interrupt flag
ADC12IFG10
01Ch
ADC12MEM11 interrupt flag
ADC12IFG11
01Eh
ADC12MEM12 interrupt flag
ADC12IFG12
020h
ADC12MEM13 interrupt flag
ADC12IFG13
022h
ADC12MEM14 interrupt flag
ADC12IFG14
024h
ADC12MEM15 interrupt flag
ADC12IFG15
Interrupt
Priority
Highest
Lowest
ADC12
28-27
28-28
ADC12
Chapter 29
SD16
The SD16 module is a multichannel 16-bit sigma-delta analog-to-digital
converter. This chapter describes the SD16 of the MSP430x4xx family. The
SD16 module is implemented in the MSP430F42x, MSP430F42xA,
MSP430FE42x, MSP430FE42xA, and MSP430FE42x2 devices.
Topic
Page
29.1 SD16 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-2
29.2 SD16 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-4
29.3 SD16 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-19
SD16
29-1
SD16 Introduction
29.1 SD16 Introduction
The SD16 module consists of up to three independent sigma-delta
analog-to-digital converters and an internal voltage reference. Each channel
has up to 8 fully differential multiplexed analog input pairs including a built-in
temperature sensor. The converters are based on second-order oversampling
sigma-delta modulators and digital decimation filters. The decimation filters
are comb type filters with selectable oversampling ratios of up to 256.
Additional filtering can be done in software.
Features of the SD16 include:
- 16-bit sigma-delta architecture
- Up to three independent, simultaneously sampling ADC channels
(The number of channels is device dependent, see the device-specific
data sheet.)
- Up to eight multiplexed differential analog inputs per channel
(The number of inputs is device dependent, see the device-specific
data sheet.)
- Software selectable on-chip reference voltage generation (1.2 V)
- Software selectable internal or external reference
- Built-in temperature sensor accessible by all channels
- Up to 1.048576-MHz modulator input frequency
- Selectable low-power conversion mode
The block diagram of the SD16 module is shown in Figure 29−1.
29-2
SD16
SD16 Introduction
Figure 29−1. SD16 Block Diagram
SD16 Control Block
SD16REFON
Reference
1.2V
VREF
AV CC
SD16SSELx
SD16DIVx
Reference
AV SS
Divider
1/2/4/8
00
MCLK
01
SMCLK
10
ACLK
11
TACLK
SD16VMIDON
Temperature sensor
Reference
fM
Channel 0
Reference
Temperature sensor
fM
Group/Start
Conversion Logic
SD16INCHx
A1.0
A1.1
A1.2
A1.3
A1.4
A1.5
A1.6
A1.7
+
−
+
−
+
−
+
−
+
−
+
−
+
−
+
−
SD16GAINx
SD16OSRx
010
011
100
SD16GRP
SD16SC
SD16SNGL
Conversion Control
(from next channel)
000
001
Channel 1
Conversion Control
(to prior channel)
PGA
1..32
15
2nd Order
ΣΔ Modulator
0
SD16MEM1
101
7
110
111
SD16LP
0
SD16DF
SD16PRE1
Channel 2
SD16
29-3
SD16 Operation
29.2 SD16 Operation
The SD16 module is configured with user software. The setup and operation
of the SD16 is discussed in the following sections.
29.2.1 ADC Core
The analog-to-digital conversion is performed by a 1-bit, second-order
sigma-delta modulator. A single-bit comparator within the modulator quantizes
the input signal with the modulator frequency fM. The resulting 1-bit data
stream is averaged by the digital filter for the conversion result.
29.2.2 Analog Input Range and PGA
The full-scale input voltage range for each analog input pair is dependent on
the gain setting of the programmable gain amplifier of each channel. The
maximum full-scale range is ±VFSR where VFSR is defined by:
V FSR +
V REFń2
GAIN PGA
For a 1.2V reference, the maximum full-scale input range for a gain of 1 is:
1.2Vń2
+" 0.6V
1
Refer to the device-specific data sheet for full-scale input specifications.
" V FSR +
29.2.3 Voltage Reference Generator
The SD16 module has a built-in 1.2V reference that can be used for each SD16
channel and is enabled by the SD16REFON bit. When using the internal
reference an external 100nF capacitor connected from VREF to AVSS is
recommended to reduce noise. The internal reference voltage can be used
off-chip when SD16VMIDON = 1. The buffered output can provide up to 1mA
of drive. When using the internal reference off-chip, a 470nF capacitor
connected from VREF to AVSS is required. See device-specific data sheet for
parameters.
An external voltage reference can be applied to the VREF input when
SD16REFON and SD16VMIDON are both reset.
29.2.4 Auto Power-Down
The SD16 is designed for low power applications. When the SD16 is not
actively converting, it is automatically disabled and automatically re-enabled
when a conversion is started. The reference is not automatically disabled, but
can be disabled by setting SD16REFON = 0. When the SD16 or reference are
disabled, they consume no current.
29-4
SD16
SD16 Operation
29.2.5 Analog Input Pair Selection
Each SD16 channel can convert up to 8 differential input pairs multiplexed into
the PGA. Up to six input pairs (A0-A5) are available externally on the device.
See the device-specific data sheet for analog input pin information. An internal
temperature sensor is available to each channel using the A6 multiplexer
input.
Input A7 is a shorted connection between the + and − input pair and can
be used to calibrate the offset of each SD16 input stage. Note that the
measured offset depends on the impedance of the external
circuitry; thus, the actual offset seen at any of the analog inputs may be different.
Analog Input Setup
The analog input of each channel is configured using the SD16INCTLx
register. These settings can be independently configured for each SD16
channel.
The SD16INCHx bits select one of eight differential input pairs of the analog
multiplexer. The gain for each PGA is selected by the SD16GAINx bits. A total
of six gain settings are available.
During conversion any modification to the SD16INCHx and SD16GAINx bits
will become effective with the next decimation step of the digital filter. After
these bits are modified, the next three conversions may be invalid due to the
settling time of the digital filter. This can be handled automatically with the
SD16INTDLYx bits. When SD16INTDLY = 00h, conversion interrupt requests
will not begin until the 4th conversion after a start condition.
An external RC anti-aliasing filter is recommended for the SD16 to prevent
aliasing of the input signal. The cutoff frequency should be < 10 kHz for a
1-MHz modulator clock and OSR = 256. The cutoff frequency may set to a
lower frequency for applications that have lower bandwidth requirements.
SD16
29-5
SD16 Operation
29.2.6 Analog Input Characteristics
The SD16 uses a switched-capacitor input stage that appears as an
impedance to external circuitry as shown in Figure 29−2.
Figure 29−2. Analog Input Equivalent Circuit
MSP430
RS
VS+
VS−
RS
CS
1 k
VS+
= Positive external source voltage
= Negative external source voltage
= External source resistance
= Sampling capacitance
CS
AVCC / 2
CS
RS
1 k
VS−
The maximum modulator frequency fM may be calculated from the minimum
settling time tSettling of the sampling circuit given by:
t Settling w (R S ) 1kW)
CS
ǒ
ln
GAIN
2 17
V REF
V Ax
Ǔ
where
fM +
2
ǒŤ
ŤŤ
ŤǓ
AV CC
AV CC
1
and V Ax + max
* V S) ,
* VS* ,
t Settling
2
2
with VS+ and VS− referenced to AVSS.
CS varies with the gain setting as shown in Table 29−1.
Table 29−1.Sampling Capacitance
PGA Gain
29-6
SD16
Sampling Capacitance CS
1
1.25 pF
2, 4
2.5 pF
8
5 pF
16, 32
10 pF
SD16 Operation
29.2.7 Digital Filter
The digital filter processes the 1-bit data stream from the modulator using a
SINC3 comb filter. The transfer function is described in the z-Domain by:
H(z) +
1
ǒOSR
Ǔ
1 * z *OSR
1 * z *1
3
and in the frequency domain by:
ȱsincǒOSRp Ǔȳ ȡ 1
Hǒ f Ǔ +ȧ
ȧ +ȧOSR
ǒ
Ǔ
sinc
p
Ȳ
ȴ Ȣ
f
3
fM
f
fM
ǒ
sin OSR
ǒ
sin p
fM
f
fM
3
Ǔȣ
ȧ
Ǔ
Ȥ
f
p
where the oversampling rate, OSR, is the ratio of the modulator frequency fM
to the sample frequency fS. Figure 29−3 shows the filter’s frequency response
for an OSR of 32. The first filter notch is at fS = fM/OSR. The notch frequency
can be adjusted by changing the modulator frequency, fM, using SD16SSELx
and SD16DIVx and the oversampling rate using SD16OSRx.
The digital filter for each enabled ADC channel completes the decimation of
the digital bit-stream and outputs new conversion results to the corresponding
SD16MEMx register at the sample frequency fS.
Figure 29−3. Comb Filter’s Frequency Response with OSR = 32
0
−20
GAIN [dB]
−40
−60
−80
−100
−120
−140
fS
fM
Frequency
SD16
29-7
SD16 Operation
Figure 29−4 shows the digital filter step response and conversion points. For
step changes at the input after start of conversion a settling time must be
allowed before a valid conversion result is available. The SD16INTDLYx bits
can provide sufficient filter settling time for a full-scale change at the ADC
input. If the step occurs synchronously to the decimation of the digital filter the
valid data will be available on the third conversion. An asynchronous step will
require one additional conversion before valid data is available.
Figure 29−4. Digital Filter Step Response and Conversion Points
Asynchronous Step
4
1
Synchronous Step
3
1
3
2
0.8
0.8
0.6
% VFSR
0.6
2
0.4
0.4
0.2
0.2
1
1
0
0
Conversion
29-8
SD16
Conversion
SD16 Operation
Digital Filter Output
The number of bits output by each digital filter is dependent on the
oversampling ratio and ranges from 16 to 24 bits. Figure 29−5 shows the
digital filter output bits and their relation to SD16MEMx for each OSR. For
example, for OSR = 256 and LSBACC = 0, the SD16MEMx register contains
bits 23 − 8 of the digital filter output. When OSR = 32, the SD16MEMx LSB is
always zero.
The SD16LSBACC and SD16LSBTOG bits give access to the least significant
bits of the digital filter output. When SD16LSBACC = 1 the 16 least significant
bits of the digital filter’s output are read from SD16MEMx using word
instructions. The SD16MEMx register can also be accessed with byte
instructions returning only the 8 least significant bits of the digital filter output.
When SD16LSBTOG = 1 the SD16LSBACC bit is automatically toggled each
time the corresponding channel’s SD16MEMx register is read. This allows the
complete digital filter output result to be read with two read accesses of
SD16MEMx. Setting or clearing SD16LSBTOG does not change
SD16LSBACC until the next SD16MEMx access.
Figure 29−5. Used Bits of Digital Filter Output.
OSR=256, LSBACC=0
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
OSR=256, LSBACC=1
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
OSR=128, LSBACC=0
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
OSR=128, LSBACC=1
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
4
3
2
1
0
3
2
1
0
OSR=64, LSBACC=0
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
OSR=64, LSBACC=1
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
OSR=32, LSBACC=x
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
SD16
29-9
SD16 Operation
29.2.8 Conversion Memory Registers: SD16MEMx
One SD16MEMx register is associated with each SD16 channel. Conversion
results for each channel are moved to the corresponding SD16MEMx register
with each decimation step of the digital filter. The SD16IFG bit for a given
channel is set when new data is written to SD16MEMx. SD16IFG is
automatically cleared when SD16MEMx is read by the CPU or may be cleared
with software.
Output Data Format
The output data format is configurable in two’s complement or offset binary as
shown in Table 29−2.The data format is selected by the SD16DF bit.
Table 29−2.Data Format
SD16DF
Format
0
Offset
Binary
1
†
Analog Input
SD16MEMx†
Digital Filter Output
(OSR = 256)
+FSR
FFFF
FFFFFF
ZERO
8000
800000
−FSR
0000
000000
+FSR
7FFF
7FFFFF
ZERO
0000
000000
−FSR
8000
800000
Two’s
complement
Independent of SD16OSRx setting; SD16LSBACC = 0.
Figure 29−6 shows the relationship between the full-scale input voltage range
from −VFSR to +VFSR and the conversion result. The digital values for both data
formats are illustrated.
Figure 29−6. Input Voltage vs Digital Output
Offset Binary
2’s complement
SD16MEMx
SD16MEMx
FFFFh
7FFFh
Input
Voltage
−VFSR
8000h
0000h
+V FSR
Input
Voltage
0000h
−VFSR
29-10
SD16
8000h
+V FSR
SD16 Operation
29.2.9 Conversion Modes
The SD16 module can be configured for four modes of operation, listed in
Table 29−3. The SD16SNGL and SD16GRP bits for each channel selects the
conversion mode.
Table 29−3.Conversion Mode Summary
SD16SNGL SD16GRP{
†
Mode
Operation
1
0
Single channel,
Single conversion
A single channel is
converted once.
0
0
Single channel,
Continuous conversion
A single channel is
converted continuously.
1
1
Group of channels,
Single conversion
A group of channels is
converted once.
0
1
Group of channels,
Continuous conversion
A group of channels is
converted continuously.
A channel is grouped and is the master channel of the group when SD16GRP = 0 if SD16GRP
for the prior channel(s) is set.
Single Channel, Single Conversion
Setting the SD16SC bit of a channel initiates one conversion on that channel
when SD16SNGL = 1 and it is not grouped with any other channels. The
SD16SC bit is automatically cleared after conversion completion.
Clearing SD16SC before the conversion is completed immediately stops
conversion of the selected channel, the channel is powered down, and the
corresponding digital filter is turned off. The value in SD16MEMx can change
when SD16SC is cleared. It is recommended that the conversion data in
SD16MEMx be read prior to clearing SD16SC to avoid reading an invalid
result.
Single Channel, Continuous Conversion
When SD16SNGL = 0, continuous conversion mode is selected. Conversion
of the selected channel begins when SD16SC is set and continues until the
SD16SC bit is cleared by software when the channel is not grouped with any
other channel.
Clearing SD16SC immediately stops conversion of the selected channel, the
channel is powered downs and the corresponding digital filter is turned off. The
value in SD16MEMx can change when SD16SC is cleared. It is recommended
that the conversion data in SD16MEMx be read prior to clearing SD16SC to
avoid reading an invalid result.
Figure 29−7 shows single channel operation for single conversion mode and
continuous conversion mode.
SD16
29-11
SD16 Operation
Figure 29−7. Single Channel Operation − Example
Channel 0
SD16SNGL = 1
SD16GRP = 0
Channel 1
SD16SNGL = 1
SD16GRP = 0
Channel 2
SD16SNGL = 0
SD16GRP = 0
Conversion
SD16SC
Set by SW
Auto−clear
Conversion
SD16SC
Set by SW
Conversion
SD16SC
Set by SW
= Result written to SD16MEMx
Conversion
Auto−clear
Set by SW
Conversion
Conversion
Auto−clear
Conv
Cleared by SW
Time
Group of Channels, Single Conversion
Consecutive SD16 channels can be grouped together with the SD16GRP bit
to synchronize conversions. Setting SD16GRP for a channel groups that
channel with the next channel in the module. For example, setting SD16GRP
for channel 0 groups that channel with channel 1. In this case, channel 1 is the
master channel, enabling and disabling conversion of all channels in the group
with its SD16SC bit. The SD16GRP bit of the master channel is always 0. The
SD16GRP bit of last channel in SD16 has no function and is always 0.
When SD16SNGL = 1 for a channel in a group, single conversion mode is
selected. A single conversion of that channel will occur synchronously when
the master channel SD16SC bit is set. The SD16SC bit of all channels in the
group will automatically be set and cleared by SD16SC of the master channel.
SD16SC for each channel can also be cleared in software independently.
Clearing SD16SC of the master channel before the conversions are
completed immediately stops conversions of all channels in the group, the
channels are powered down and the corresponding digital filters are turned off.
Values in SD16MEMx can change when SD16SC is cleared. It is
recommended that the conversion data in SD16MEMx be read prior to
clearing SD16SC to avoid reading an invalid result.
29-12
SD16
SD16 Operation
Group of Channels, Continuous Conversion
When SD16SNGL = 0 for a channel in a group, continuous conversion mode
is selected. Continuous conversion of that channel occurs synchronously
when the master channel SD16SC bit is set. SD16SC bits for all grouped
channels are automatically set and cleared with the master channel’s SD16SC
bit. SD16SC for each channel in the group can also be cleared in software
independently.
When SD16SC of a grouped channel is set by software independently of the
master, conversion of that channel automatically synchronizes to conversions
of the master channel. This ensures that conversions for grouped channels
are always synchronous to the master.
Clearing SD16SC of the master channel immediately stops conversions of all
channels in the group the channels are powered down and the corresponding
digital filters are turned off. Values in SD16MEMx can change when SD16SC
is cleared. It is recommended that the conversion data in SD16MEMx be read
prior to clearing SD16SC to avoid reading an invalid result.
Figure 29−8 shows grouped channel operation for three SD16 channels.
Channel 0 is configured for single conversion mode, SD16SNGL = 1, and
channels 1 and 2 are in continuous conversion mode, SD16SNGL = 0.
Channel two, the last channel in the group, is the master channel. Conversions
of all channels in the group occur synchronously to the master channel
regardless of when each SD16SC bit is set using software.
Figure 29−8. Grouped Channel Operation − Example
(syncronized to master)
Channel 0
SD16SNGL = 1
SD16GRP = 1
Channel 1
SD16SNGL = 0
SD16GRP =1
Channel 2
SD16SNGL = 0
SD16GRP = 0
Conversion
SD16SC
Set by Ch2
Auto−clear
Conversion
SD16SC
Set by Ch2
Set by SW
= Result written to SD16MEMx
Set by SW
Auto−clear
(syncronized to master)
Conv
Cleared by SW
Conversion
SD16SC
Conversion
Conversion
Conversion
Set by SW
Conv
Cleared by Ch2
Conv
Conversion
Cleared by SW
Time
SD16
29-13
SD16 Operation
29.2.10 Conversion Operation Using Preload
When multiple channels are grouped the SD16PREx registers can be used to
delay the conversion time frame for each channel. Using SD16PREx, the
decimation time of the digital filter is increased by the specified number of fM
clock cycles and can range from 0 to 255. Figure 29−9 shows an example
using SD16PREx.
Figure 29−9. Conversion Delay using Preload − Example
SD16OSRx = 32
f M cycles:
32
40
32
Conversion
Delayed Conversion
Conversion
Load SD16PREx:
SD16PREx = 8
Delayed Conversion
Result
Preload
applied
Time
The SD16PREx delay is applied to the beginning of the next conversion cycle
after being written. The delay is used on the first conversion after SD16SC is
set and on the conversion cycle following each write to SD16PREx. Following
conversions are not delayed. After modifying SD16PREx, the next write to
SD16PREx should not occur until the next conversion cycle is completed,
otherwise the conversion results may be incorrect.
The accuracy of the result for the delayed conversion cycle using SD16PREx
is dependent on the length of the delay and the frequency of the analog signal
being sampled. For example, when measuring a DC signal, SD16PREx delay
has no effect on the conversion result regardless of the duration. The user
must determine when the delayed conversion result is useful in their
application.
Figure 29−10 shows the operation of grouped channels 0 and 1. The preload
register of channel 1 is loaded with zero resulting in immediate conversion
whereas the conversion cycle of channel 0 is delayed by setting
SD16PRE0 = 8. The first channel 0 conversion uses SD16PREx = 8, shifting
all subsequent conversions by 8 fM clock cycles.
29-14
SD16
SD16 Operation
Figure 29−10. Start of Conversion using Preload − Example
SD16OSRx = 32
f M cycles:
40
SD16PRE0 = 8
Delayed Conversion
32
32
Conversion
Conversion
1st Sample Ch0
SD16PRE1 = 0
32
32
32
Conversion
Conversion
Conversion
Conversion
1st Sample Ch1
Start of
Conversion
Time
When channels are grouped, care must be taken when a channel or channels
operate in single conversion mode or are disabled in software while the master
channel remains active. Each time channels in the group are re-enabled and
resynchronized with the master channel, the preload delay for that channel will
be reintroduced. Figure 29−11 shows the re-synchronization and preload
delays for channels in a group. It is recommended that SD16PREx = 0 for the
master channel to maintain a consistent delay between the master and
remaining channels in the group when they are re-enabled.
Figure 29−11.Preload and Channel Synchronization
(syncronized to master)
Channel 0
SD16SNGL = 0
SD16GRP = 1
Channel 1
SD16SNGL = 1
SD16GRP =1
Channel 2
SD16SNGL = 0
SD16GRP = 0
PRE0
SD16SC
Set by Ch2
PRE1
SD16SC
Conversion
PRE0
Conv
Cleared by SW
Set by SW
(syncronized to master)
Conversion
Set by Ch2
Conversion
SD16SC
Conv
PRE1
Auto−clear
Conversion
Conversion
Set by SW
Auto−clear
Conv
Conversion
Conversion
Set by SW
= Result written to SD16MEMx
Time
SD16
29-15
SD16 Operation
29.2.11 Using the Integrated Temperature Sensor
To use the on-chip temperature sensor, the user selects the analog input pair
SD16INCHx = 110 and sets SD16REFON = 1. Any other configuration is done
as if an external analog input pair was selected, including SD16INTDLYx and
SD16GAINx settings. Because the internal reference must be on to use the
temperature sensor, it is not possible to use an external reference for the
conversion of the temperature sensor voltage. Also, the internal reference will
be in contention with any used external reference. In this case, the
SD16VMIDON bit may be set to minimize the affects of the contention on the
conversion.
The typical temperature sensor transfer function is shown in Figure 29−12.
When switching inputs of an SD16 channel to the temperature sensor,
adequate delay must be provided using SD16INTDLYx to allow the digital filter
to settle and assure that conversion results are valid. The temperature sensor
offset error can be large, and may need to be calibrated for most applications.
See device-specific data sheet for temperature sensor parameters.
Figure 29−12. Typical Temperature Sensor Transfer Function
Volts
0.500
0.450
0.400
0.350
0.300
VSensor,typ = TCSensor(273 + T[oC]) + VOffset, sensor [mV]
0.250
0.200
Celsius
−50
29-16
SD16
0
50
100
SD16 Operation
29.2.12 Interrupt Handling
The SD16 has 2 interrupt sources for each ADC channel:
- SD16IFG
- SD16OVIFG
The SD16IFG bits are set when their corresponding SD16MEMx memory
register is written with a conversion result. An interrupt request is generated
if the corresponding SD16IE bit and the GIE bit are set. The SD16 overflow
condition occurs when a conversion result is written to any SD16MEMx
location before the previous conversion result was read.
SD16IV, Interrupt Vector Generator
All SD16 interrupt sources are prioritized and combined to source a single
interrupt vector. SD16IV is used to determine which enabled SD16 interrupt
source requested an interrupt. The highest priority SD16 interrupt request that
is enabled generates a number in the SD16IV register (see register
description). This number can be evaluated or added to the program counter
to automatically enter the appropriate software routine. Disabled SD16
interrupts do not affect the SD16IV value.
Any access, read or write, of the SD16IV register has no effect on the
SD16OVIFG or SD16IFG flags. The SD16IFG flags are reset by reading the
associated SD16MEMx register or by clearing the flags in software.
SD16OVIFG bits can only be reset with software.
If another interrupt is pending after servicing of an interrupt, another interrupt
is generated. For example, if the SD16OVIFG and one or more SD16IFG
interrupts are pending when the interrupt service routine accesses the SD16IV
register, the SD16OVIFG interrupt condition is serviced first and the
corresponding flag(s) must be cleared in software. After the RETI instruction
of the interrupt service routine is executed, the highest priority SD16IFG
pending generates another interrupt request.
Interrupt Delay Operation
The SD16INTDLYx bits control the timing for the first interrupt service request
for the corresponding channel. This feature delays the interrupt request for a
completed conversion by up to four conversion cycles allowing the digital filter
to settle prior to generating an interrupt request. The delay is applied each time
the SD16SC bit is set or when the SD16GAINx or SD16INCHx bits for the
channel are modified. SD16INTDLYx disables overflow interrupt generation
for the channel for the selected number of delay cycles. Interrupt requests for
the delayed conversions are not generated during the delay.
SD16
29-17
SD16 Operation
SD16 Interrupt Handling Software Example
The following software example shows the recommended use of SD16IV and
the handling overhead. The SD16IV value is added to the PC to automatically
jump to the appropriate routine.
The numbers at the right margin show the necessary CPU cycles for each
instruction. The software overhead for different interrupt sources includes
interrupt latency and return-from-interrupt cycles, but not the task handling
itself. The latencies are:
- SD16OVIFG, CH0 SD16IFG, CH1 SD16IFG
16 cycles
- CH2 SD16IFG
14 cycles
The interrupt handler for channel 2 SD16IFG shows a way to check
immediately if a higher prioritized interrupt occurred during the processing of
the ISR. This saves nine cycles if another SD16 interrupt is pending.
; Interrupt handler for SD16.
INT_SD16
; Enter Interrupt Service Routine
6
ADD
&SD16IV,PC; Add offset to PC
3
RETI
; Vector 0: No interrupt
5
JMP
ADOV
; Vector 2: ADC overflow
2
JMP
ADM0
; Vector 4: CH_0 SD16IFG
2
JMP
ADM1
; Vector 6: CH_1 SD16IFG
2
;
; Handler for CH_2 SD16IFG starts here. No JMP required.
;
ADM2
MOV &SD16MEM2,xxx ; Move result, flag is reset
...
; Other instruction needed?
JMP INT_SD16
; Check other int pending
2
;
; Remaining Handlers
;
ADM1
MOV &SD16MEM1,xxx
...
RETI
; Move result, flag is reset
; Other instruction needed?
; Return
5
;
ADM0
;
ADOV
29-18
SD16
MOV &SD16MEM0,xxx
; Move result, flag is reset
RETI
; Return
5
...
RETI
; Handle SD16MEMx overflow
; Return
5
SD16 Registers
29.3 SD16 Registers
The SD16 registers are listed in Table 29−4:
Table 29−4.SD16 Registers
Register
Short Form
Register Type Address
Initial State
SD16 Control
SD16CTL
Read/write
0100h
Reset with PUC
SD16 Interrupt Vector
SD16IV
Read/write
0110h
Reset with PUC
SD16 Channel 0 Control
SD16CCTL0
Read/write
0102h
Reset with PUC
SD16 Channel 0 Conversion Memory
SD16MEM0
Read/write
0112h
Reset with PUC
SD16 Channel 0 Input Control
SD16INCTL0
Read/write
0B0h
Reset with PUC
SD16 Channel 0 Preload
SD16PRE0
Read/write
0B8h
Reset with PUC
SD16 Channel 1 Control
SD16CCTL1
Read/write
0104h
Reset with PUC
SD16 Channel 1 Conversion Memory
SD16MEM1
Read/write
0114h
Reset with PUC
SD16 Channel 1 Input Control
SD16INCTL1
Read/write
0B1h
Reset with PUC
SD16 Channel 1 Preload
SD16PRE1
Read/write
0B9h
Reset with PUC
SD16 Channel 2 Control
SD16CCTL2
Read/write
0106h
Reset with PUC
SD16 Channel 2 Conversion Memory
SD16MEM2
Read/write
0116h
Reset with PUC
SD16 Channel 2 Input Control
SD16INCTL2
Read/write
0B2h
Reset with PUC
SD16 Channel 2 Preload
SD16PRE2
Read/write
0BAh
Reset with PUC
SD16
29-19
SD16 Registers
SD16CTL, SD16 Control Register
15
14
13
12
11
10
9
Reserved
8
SD16LP
r0
r0
r0
r0
r0
r0
r0
rw−0
7
6
5
4
3
2
1
0
SD16
VMIDON
SD16
REFON
SD16OVIE
Reserved
rw−0
rw−0
rw−0
r0
SD16DIVx
rw−0
rw−0
SD16SSELx
rw−0
rw−0
Reserved
Bits
15-9
Reserved
SD16LP
Bit 8
Low-power mode. This