C8051T630/1/2/3/4/5 Mixed-Signal Byte-Programmable EPROM MCU

C8051T630/1/2/3/4/5 Mixed-Signal Byte-Programmable EPROM MCU
C8051T630/1/2/3/4/5
Mixed-Signal Byte-Programmable EPROM MCU
High-Speed 8051 µC Core
- Pipelined instruction architecture; executes 70% of
Analog Peripherals
- 10-Bit ADC (‘T630/2/4 only)
•
•
•
•
•
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Up to 500 ksps
Up to 16 external inputs
VREF from on-chip VREF, external pin,
Internal Regulator or VDD
Internal or external start of conversion source
Built-in temperature sensor
instructions in 1 or 2 system clocks
Up to 25 MIPS throughput with 25 MHz clock
Expanded interrupt handler
-
Memory
- 768 Bytes internal data RAM (256 + 512)
- 8, 4, or 2 kB byte-programmable EPROM code
10-Bit Current Output DAC (‘T630/2/4 only)
Comparator
•
•
•
memory
Programmable hysteresis and response time
Configurable as interrupt or reset source
Low current (<0.5 µA)
Digital Peripherals
- 17 Port I/O with high sink current capability
- Hardware enhanced UART, SMBus™, and
On-Chip Debug
- C8051F336 can be used as code development 
-
platform; Complete development kit available
On-chip debug circuitry facilitates full speed, 
non-intrusive in-system debug
Provides breakpoints, single stepping, 
inspect/modify memory and registers
-
enhanced SPI™ serial ports
Four general purpose 16-bit counter/timers
Timer 3 supports real-time clock using external clock
source
•
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Supply Voltage 1.8 to 3.6 V
- On-chip LDO for internal core supply
- Built-in voltage supply monitor
Temperature Range: –40 to +85 °C
16-Bit programmable counter array (PCA) with three
capture/compare modules and enhanced PWM
functionality
Clock Sources
- Two internal oscillators:
24.5 MHz with ±2% accuracy supports crystal-less
UART operation and low-power suspend mode with
fast wake time
80/40/20/10 kHz low frequency, low power operation
•
•
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External oscillator: RC, C, or CMOS Clock
Can switch between clock sources on-the-fly; useful
in power saving modes
20-Pin QFN Package (4x4 mm)
ANALOG
PERIPHERALS
10-bit
500 ksps
ADC
10-bit
Current
DAC
+
TEMP
SENSOR
VREF
‘T630/2/4 Only
VOLTAGE
COMPARATOR
24.5 MHz PRECISION
INTERNAL OSCILLATOR
UART
SMBus
SPI
PCA
Timer 0
Timer 1
Timer 2
Timer 3
CROSSBAR
A
M
U
X
DIGITAL I/O
Port 0
Port 1
P2.0
LOW FREQUENCY INTERNAL
OSCILLATOR
HIGH-SPEED CONTROLLER CORE
2/4/8 kB
EPROM
FLEXIBLE
INTERRUPTS
Rev. 1.0 1/09
8051 CPU
(25 MIPS)
DEBUG
CIRCUITRY
768 B SRAM
POR
Copyright © 2009 by Silicon Laboratories
WDT
C8051T630/1/2/3/4/5
This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
C8051T630/1/2/3/4/5
2
Rev. 1.0
C8051T630/1/2/3/4/5
Table of Contents
1. System Overview ..................................................................................................... 15
2. Ordering Information ............................................................................................... 17
3. Pin Definitions.......................................................................................................... 18
4. QFN-20 Package Specifications ............................................................................. 21
5. Electrical Characteristics ........................................................................................ 23
5.1. Absolute Maximum Specifications..................................................................... 23
5.2. Electrical Characteristics ................................................................................... 24
5.3. Typical Performance Curves ............................................................................. 32
6. 10-Bit ADC (ADC0, C8051T630/2/4 only)................................................................ 33
6.1. Output Code Formatting .................................................................................... 34
6.2. 8-Bit Mode ......................................................................................................... 34
6.3. Modes of Operation ........................................................................................... 34
6.3.1. Starting a Conversion................................................................................ 34
6.3.2. Tracking Modes......................................................................................... 35
6.3.3. Settling Time Requirements...................................................................... 36
6.4. Programmable Window Detector....................................................................... 40
6.4.1. Window Detector Example........................................................................ 42
6.5. ADC0 Analog Multiplexer (C8051T630/2/4 only)............................................... 43
7. Temperature Sensor (C8051T630/2/4 only) ........................................................... 45
7.1. Calibration ......................................................................................................... 45
8. 10-Bit Current Mode DAC (IDA0, C8051T630/2/4 only) ......................................... 48
8.1. IDA0 Output Scheduling .................................................................................... 48
8.1.1. Update Output On-Demand ...................................................................... 48
8.1.2. Update Output Based on Timer Overflow ................................................. 49
8.1.3. Update Output Based on CNVSTR Edge ................................................. 49
8.2. IDAC Output Mapping ....................................................................................... 49
9. Voltage Reference Options ..................................................................................... 52
10. Voltage Regulator (REG0) ..................................................................................... 55
11. Comparator0........................................................................................................... 57
11.1. Comparator Multiplexer ................................................................................... 61
12. CIP-51 Microcontroller........................................................................................... 63
12.1. Instruction Set.................................................................................................. 64
12.1.1. Instruction and CPU Timing .................................................................... 64
12.2. CIP-51 Register Descriptions .......................................................................... 69
13. Memory Organization ............................................................................................ 72
13.1. Program Memory............................................................................................. 73
13.2. Data Memory ................................................................................................... 73
13.2.1. Internal RAM ........................................................................................... 73
13.2.1.1. General Purpose Registers ............................................................ 74
13.2.1.2. Bit Addressable Locations .............................................................. 74
13.2.1.3. Stack ............................................................................................ 74
13.2.2. External RAM .......................................................................................... 74
14. Special Function Registers................................................................................... 76
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C8051T630/1/2/3/4/5
15. Interrupts ................................................................................................................ 80
15.1. MCU Interrupt Sources and Vectors................................................................ 81
15.1.1. Interrupt Priorities.................................................................................... 81
15.1.2. Interrupt Latency ..................................................................................... 81
15.2. Interrupt Register Descriptions ........................................................................ 82
15.3. INT0 and INT1 External Interrupts................................................................... 87
16. EPROM Memory ..................................................................................................... 89
16.1. Programming and Reading the EPROM Memory ........................................... 89
16.1.1. EPROM Write Procedure ........................................................................ 89
16.1.2. EPROM Read Procedure........................................................................ 90
16.2. Security Options .............................................................................................. 90
16.3. Program Memory CRC .................................................................................... 91
16.3.1. Performing 32-bit CRCs on Full EPROM Content .................................. 91
16.3.2. Performing 16-bit CRCs on 256-Byte EPROM Blocks............................ 91
17. Power Management Modes................................................................................... 92
17.1. Idle Mode......................................................................................................... 92
17.2. Stop Mode ....................................................................................................... 93
17.3. Suspend Mode ................................................................................................ 93
18. Reset Sources ........................................................................................................ 95
18.1. Power-On Reset .............................................................................................. 96
18.2. Power-Fail Reset/VDD Monitor ....................................................................... 97
18.3. External Reset ................................................................................................. 98
18.4. Missing Clock Detector Reset ......................................................................... 98
18.5. Comparator0 Reset ......................................................................................... 99
18.6. PCA Watchdog Timer Reset ........................................................................... 99
18.7. EPROM Error Reset ........................................................................................ 99
18.8. Software Reset ................................................................................................ 99
19. Oscillators and Clock Selection ......................................................................... 101
19.1. System Clock Selection................................................................................. 101
19.2. Programmable Internal High-Frequency (H-F) Oscillator .............................. 103
19.2.1. Internal Oscillator Suspend Mode ......................................................... 103
19.3. Programmable Internal Low-Frequency (L-F) Oscillator ............................... 105
19.3.1. Calibrating the Internal L-F Oscillator.................................................... 105
19.4. External Oscillator Drive Circuit..................................................................... 106
19.4.1. External RC Example............................................................................ 108
19.4.2. External Capacitor Example.................................................................. 108
20. Port Input/Output ................................................................................................. 109
20.1. Port I/O Modes of Operation.......................................................................... 110
20.1.1. Port Pins Configured for Analog I/O...................................................... 110
20.1.2. Port Pins Configured For Digital I/O...................................................... 110
20.1.3. Interfacing Port I/O to 5V Logic ............................................................. 111
20.2. Assigning Port I/O Pins to Analog and Digital Functions............................... 112
20.2.1. Assigning Port I/O Pins to Analog Functions ........................................ 112
20.2.2. Assigning Port I/O Pins to Digital Functions.......................................... 112
20.2.3. Assigning Port I/O Pins to External Digital Event Capture Functions ... 113
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20.3. Priority Crossbar Decoder ............................................................................. 114
20.4. Port I/O Initialization ...................................................................................... 116
20.5. Port Match ..................................................................................................... 118
20.6. Special Function Registers for Accessing and Configuring Port I/O ............. 121
21. SMBus................................................................................................................... 127
21.1. Supporting Documents .................................................................................. 128
21.2. SMBus Configuration..................................................................................... 128
21.3. SMBus Operation .......................................................................................... 128
21.3.1. Transmitter Vs. Receiver....................................................................... 129
21.3.2. Arbitration.............................................................................................. 129
21.3.3. Clock Low Extension............................................................................. 129
21.3.4. SCL Low Timeout.................................................................................. 129
21.3.5. SCL High (SMBus Free) Timeout ......................................................... 130
21.4. Using the SMBus........................................................................................... 130
21.4.1. SMBus Configuration Register.............................................................. 130
21.4.2. SMB0CN Control Register .................................................................... 134
21.4.2.1. Software ACK Generation ............................................................ 134
21.4.2.2. Hardware ACK Generation ........................................................... 134
21.4.3. Hardware Slave Address Recognition .................................................. 136
21.4.4. Data Register ........................................................................................ 139
21.5. SMBus Transfer Modes................................................................................. 140
21.5.1. Write Sequence (Master) ...................................................................... 140
21.5.2. Read Sequence (Master) ...................................................................... 141
21.5.3. Write Sequence (Slave) ........................................................................ 142
21.5.4. Read Sequence (Slave) ........................................................................ 143
21.6. SMBus Status Decoding................................................................................ 143
22. UART0 ................................................................................................................... 148
22.1. Enhanced Baud Rate Generation.................................................................. 149
22.2. Operational Modes ........................................................................................ 150
22.2.1. 8-Bit UART ............................................................................................ 150
22.2.2. 9-Bit UART ............................................................................................ 151
22.3. Multiprocessor Communications ................................................................... 152
23. Enhanced Serial Peripheral Interface (SPI0) ..................................................... 156
23.1. Signal Descriptions........................................................................................ 157
23.1.1. Master Out, Slave In (MOSI)................................................................. 157
23.1.2. Master In, Slave Out (MISO)................................................................. 157
23.1.3. Serial Clock (SCK) ................................................................................ 157
23.1.4. Slave Select (NSS) ............................................................................... 157
23.2. SPI0 Master Mode Operation ........................................................................ 158
23.3. SPI0 Slave Mode Operation .......................................................................... 159
23.4. SPI0 Interrupt Sources .................................................................................. 160
23.5. Serial Clock Phase and Polarity .................................................................... 160
23.6. SPI Special Function Registers ..................................................................... 162
24. Timers ................................................................................................................... 169
24.1. Timer 0 and Timer 1 ...................................................................................... 171
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C8051T630/1/2/3/4/5
24.1.1. Mode 0: 13-bit Counter/Timer ............................................................... 171
24.1.2. Mode 1: 16-bit Counter/Timer ............................................................... 172
24.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload..................................... 173
24.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)................................ 174
24.2. Timer 2 .......................................................................................................... 179
24.2.1. 16-bit Timer with Auto-Reload............................................................... 179
24.2.2. 8-bit Timers with Auto-Reload............................................................... 180
24.2.3. Low-Frequency Oscillator (LFO) Capture Mode ................................... 181
24.3. Timer 3 .......................................................................................................... 185
24.3.1. 16-bit Timer with Auto-Reload............................................................... 185
24.3.2. 8-bit Timers with Auto-Reload............................................................... 186
24.3.3. Low-Frequency Oscillator (LFO) Capture Mode ................................... 187
25. Programmable Counter Array............................................................................. 191
25.1. PCA Counter/Timer ....................................................................................... 192
25.2. PCA0 Interrupt Sources................................................................................. 193
25.3. Capture/Compare Modules ........................................................................... 194
25.3.1. Edge-triggered Capture Mode............................................................... 195
25.3.2. Software Timer (Compare) Mode.......................................................... 196
25.3.3. High-Speed Output Mode ..................................................................... 197
25.3.4. Frequency Output Mode ....................................................................... 198
25.3.5. 8-bit, 9-bit, 10-bit and 11-bit Pulse Width Modulator Modes ................ 198
25.3.5.1. 8-bit Pulse Width Modulator Mode............................................... 199
25.3.5.2. 9/10/11-bit Pulse Width Modulator Mode..................................... 200
25.3.6. 16-Bit Pulse Width Modulator Mode..................................................... 201
25.4. Watchdog Timer Mode .................................................................................. 202
25.4.1. Watchdog Timer Operation ................................................................... 202
25.4.2. Watchdog Timer Usage ........................................................................ 203
25.5. Register Descriptions for PCA0..................................................................... 204
26. C2 Interface .......................................................................................................... 210
26.1. C2 Interface Registers................................................................................... 210
26.2. C2 Pin Sharing .............................................................................................. 217
Document Change List.............................................................................................. 218
Contact Information................................................................................................... 220
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C8051T630/1/2/3/4/5
List of Figures
1. System Overview
Figure 1.1. C8051T630/1/2/3/4/5 Block Diagram .................................................... 16
3. Pin Definitions
Figure 3.1. QFN-20 Pinout Diagram (Top View) ..................................................... 20
4. QFN-20 Package Specifications
Figure 4.1. QFN-20 Package Drawing .................................................................... 21
Figure 4.2. QFN-20 Recommended PCB Land Pattern .......................................... 22
5. Electrical Characteristics
Figure 5.1. Normal Mode Digital Supply Current vs. Frequency (MPCE = 1) ......... 32
Figure 5.2. Idle Mode Digital Supply Current vs. Frequency (MPCE = 1) ............... 32
6. 10-Bit ADC (ADC0, C8051T630/2/4 only)
Figure 6.1. ADC0 Functional Block Diagram ........................................................... 33
Figure 6.2. 10-Bit ADC Track and Conversion Example Timing ............................. 35
Figure 6.3. ADC0 Equivalent Input Circuits ............................................................. 36
Figure 6.4. ADC Window Compare Example: Right-Justified Data ......................... 42
Figure 6.5. ADC Window Compare Example: Left-Justified Data ........................... 42
Figure 6.6. ADC0 Multiplexer Block Diagram .......................................................... 43
7. Temperature Sensor (C8051T630/2/4 only)
Figure 7.1. Temperature Sensor Transfer Function ................................................ 45
Figure 7.2. Temperature Sensor Error with 1-Point Calibration at 0 Celsius ........... 46
8. 10-Bit Current Mode DAC (IDA0, C8051T630/2/4 only)
Figure 8.1. IDA0 Functional Block Diagram ............................................................ 48
Figure 8.2. IDA0 Data Word Mapping ..................................................................... 49
9. Voltage Reference Options
Figure 9.1. Voltage Reference Functional Block Diagram ....................................... 53
11. Comparator0
Figure 11.1. Comparator0 Functional Block Diagram ............................................. 57
Figure 11.2. Comparator Hysteresis Plot ................................................................ 58
Figure 11.3. Comparator Input Multiplexer Block Diagram ...................................... 61
12. CIP-51 Microcontroller
Figure 12.1. CIP-51 Block Diagram ......................................................................... 63
13. Memory Organization
Figure 13.1. Memory Map ....................................................................................... 72
Figure 13.2. Program Memory Map ......................................................................... 73
18. Reset Sources
Figure 18.1. Reset Sources ..................................................................................... 95
Figure 18.2. Power-On and VDD Monitor Reset Timing ......................................... 96
19. Oscillators and Clock Selection
Figure 19.1. Oscillator Options .............................................................................. 101
20. Port Input/Output
Figure 20.1. Port I/O Functional Block Diagram .................................................... 109
Figure 20.2. Port I/O Cell Block Diagram .............................................................. 111
Figure 20.3. Crossbar Priority Decoder with No Pins Skipped .............................. 114
Rev. 1.0
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C8051T630/1/2/3/4/5
Figure 20.4. Crossbar Priority Decoder with Crystal Pins Skipped ....................... 115
21. SMBus
Figure 21.1. SMBus Block Diagram ...................................................................... 127
Figure 21.2. Typical SMBus Configuration ............................................................ 128
Figure 21.3. SMBus Transaction ........................................................................... 129
Figure 21.4. Typical SMBus SCL Generation ........................................................ 131
Figure 21.5. Typical Master Write Sequence ........................................................ 140
Figure 21.6. Typical Master Read Sequence ........................................................ 141
Figure 21.7. Typical Slave Write Sequence .......................................................... 142
Figure 21.8. Typical Slave Read Sequence .......................................................... 143
22. UART0
Figure 22.1. UART0 Block Diagram ...................................................................... 148
Figure 22.2. UART0 Baud Rate Logic ................................................................... 149
Figure 22.3. UART Interconnect Diagram ............................................................. 150
Figure 22.4. 8-Bit UART Timing Diagram .............................................................. 150
Figure 22.5. 9-Bit UART Timing Diagram .............................................................. 151
Figure 22.6. UART Multi-Processor Mode Interconnect Diagram ......................... 152
23. Enhanced Serial Peripheral Interface (SPI0)
Figure 23.1. SPI Block Diagram ............................................................................ 156
Figure 23.2. Multiple-Master Mode Connection Diagram ...................................... 158
Figure 23.3. 3-Wire Single Master and 3-Wire
Single Slave Mode Connection Diagram .......................................... 159
Figure 23.4. 4-Wire Single Master Mode
and 4-Wire Slave Mode Connection Diagram ................................... 159
Figure 23.5. Master Mode Data/Clock Timing ....................................................... 161
Figure 23.6. Slave Mode Data/Clock Timing (CKPHA = 0) ................................... 161
Figure 23.7. Slave Mode Data/Clock Timing (CKPHA = 1) ................................... 162
Figure 23.8. SPI Master Timing (CKPHA = 0) ....................................................... 166
Figure 23.9. SPI Master Timing (CKPHA = 1) ....................................................... 166
Figure 23.10. SPI Slave Timing (CKPHA = 0) ....................................................... 167
Figure 23.11. SPI Slave Timing (CKPHA = 1) ....................................................... 167
24. Timers
Figure 24.1. T0 Mode 0 Block Diagram ................................................................. 172
Figure 24.2. T0 Mode 2 Block Diagram ................................................................. 173
Figure 24.3. T0 Mode 3 Block Diagram ................................................................. 174
Figure 24.4. Timer 2 16-Bit Mode Block Diagram ................................................. 179
Figure 24.5. Timer 2 8-Bit Mode Block Diagram ................................................... 180
Figure 24.6. Timer 2 Low-Frequency Oscillation Capture Mode Block Diagram ... 181
Figure 24.7. Timer 3 16-Bit Mode Block Diagram ................................................. 185
Figure 24.8. Timer 3 8-Bit Mode Block Diagram ................................................... 186
Figure 24.9. Timer 3 Low-Frequency Oscillation Capture Mode Block Diagram ... 187
25. Programmable Counter Array
Figure 25.1. PCA Block Diagram ........................................................................... 191
Figure 25.2. PCA Counter/Timer Block Diagram ................................................... 192
Figure 25.3. PCA Interrupt Block Diagram ............................................................ 193
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Figure 25.4. PCA Capture Mode Diagram ............................................................. 195
Figure 25.5. PCA Software Timer Mode Diagram ................................................. 196
Figure 25.6. PCA High-Speed Output Mode Diagram ........................................... 197
Figure 25.7. PCA Frequency Output Mode ........................................................... 198
Figure 25.8. PCA 8-Bit PWM Mode Diagram ........................................................ 199
Figure 25.9. PCA 9, 10 and 11-Bit PWM Mode Diagram ...................................... 200
Figure 25.10. PCA 16-Bit PWM Mode ................................................................... 201
Figure 25.11. PCA Module 2 with Watchdog Timer Enabled ................................ 202
26. C2 Interface
Figure 26.1. Typical C2 Pin Sharing ...................................................................... 217
Rev. 1.0
9
C8051T630/1/2/3/4/5
List of Tables
2. Ordering Information
Table 2.1. Product Selection Guide ......................................................................... 17
3. Pin Definitions
Table 3.1. Pin Definitions for the C8051T630/1/2/3/4/5 ........................................... 18
4. QFN-20 Package Specifications
Table 4.1. QFN-20 Package Dimensions ................................................................ 21
Table 4.2. QFN-20 PCB Land Pattern Dimesions ................................................... 22
5. Electrical Characteristics
Table 5.1. Absolute Maximum Ratings .................................................................... 23
Table 5.2. Global Electrical Characteristics ............................................................. 24
Table 5.3. Port I/O DC Electrical Characteristics ..................................................... 25
Table 5.4. Reset Electrical Characteristics .............................................................. 26
Table 5.5. Internal Voltage Regulator Electrical Characteristics ............................. 26
Table 5.6. EPROM Electrical Characteristics .......................................................... 26
Table 5.7. Internal High-Frequency Oscillator Electrical Characteristics ................. 27
Table 5.8. Internal Low-Frequency Oscillator Electrical Characteristics ................. 27
Table 5.9. ADC0 Electrical Characteristics .............................................................. 28
Table 5.10. Temperature Sensor Electrical Characteristics .................................... 29
Table 5.11. Voltage Reference Electrical Characteristics ....................................... 29
Table 5.12. IDAC Electrical Characteristics ............................................................. 30
Table 5.13. Comparator Electrical Characteristics .................................................. 31
6. 12. CIP-51 Microcontroller
Table 12.1. CIP-51 Instruction Set Summary .......................................................... 65
14. Special Function Registers
Table 14.1. Special Function Register (SFR) Memory Map .................................... 76
Table 14.2. Special Function Registers ................................................................... 77
15. Interrupts
Table 15.1. Interrupt Summary ................................................................................ 82
16. EPROM Memory
Table 16.1. Security Byte Decoding ........................................................................ 90
20. Port Input/Output
Table 20.1. Port I/O Assignment for Analog Functions ......................................... 112
Table 20.2. Port I/O Assignment for Digital Functions ........................................... 112
Table 20.3. Port I/O Assignment for External Digital Event Capture Functions .... 113
21. SMBus
Table 21.1. SMBus Clock Source Selection .......................................................... 131
Table 21.2. Minimum SDA Setup and Hold Times ................................................ 132
Table 21.3. Sources for Hardware Changes to SMB0CN ..................................... 136
Table 21.4. Hardware Address Recognition Examples (EHACK = 1) ................... 137
Table 21.5. SMBus Status Decoding With Hardware ACK Generation Disabled
(EHACK = 0) ....................................................................................... 144
Table 21.6. SMBus Status Decoding With Hardware ACK Generation Enabled
(EHACK = 1) ....................................................................................... 146
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22. UART0
Table 22.1. Timer Settings for Standard Baud Rates 
Using The Internal 24.5 MHz Oscillator .............................................. 155
Table 22.2. Timer Settings for Standard Baud Rates 
Using an External 22.1184 MHz Oscillator ......................................... 155
23. Enhanced Serial Peripheral Interface (SPI0)
Table 23.1. SPI Slave Timing Parameters ............................................................ 168
25. Programmable Counter Array
Table 25.1. PCA Timebase Input Options ............................................................. 192
Table 25.2. PCA0CPM and PCA0PWM Bit Settings
for PCA Capture/Compare Modules ................................................... 194
Table 25.3. Watchdog Timer Timeout Intervals1 ................................................... 203
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11
C8051T630/1/2/3/4/5
List of Registers
SFR Definition 6.1. ADC0CF: ADC0 Configuration ...................................................... 37
SFR Definition 6.2. ADC0H: ADC0 Data Word MSB .................................................... 38
SFR Definition 6.3. ADC0L: ADC0 Data Word LSB ...................................................... 38
SFR Definition 6.4. ADC0CN: ADC0 Control ................................................................ 39
SFR Definition 6.5. ADC0GTH: ADC0 Greater-Than Data High Byte .......................... 40
SFR Definition 6.6. ADC0GTL: ADC0 Greater-Than Data Low Byte ............................ 40
SFR Definition 6.7. ADC0LTH: ADC0 Less-Than Data High Byte ................................ 41
SFR Definition 6.8. ADC0LTL: ADC0 Less-Than Data Low Byte ................................. 41
SFR Definition 6.9. AMX0P: AMUX0 Positive Channel Select ..................................... 44
SFR Definition 7.1. TOFFH: Temperature Offset Measurement High Byte .................. 47
SFR Definition 7.2. TOFFL: Temperature Offset Measurement Low Byte ................... 47
SFR Definition 8.1. IDA0CN: IDA0 Control ................................................................... 50
SFR Definition 8.2. IDA0H: IDA0 Data Word MSB ....................................................... 51
SFR Definition 8.3. IDA0L: IDA0 Data Word LSB ......................................................... 51
SFR Definition 9.1. REF0CN: Reference Control ......................................................... 54
SFR Definition 10.1. REG0CN: Voltage Regulator Control .......................................... 56
SFR Definition 11.1. CPT0CN: Comparator0 Control ................................................... 59
SFR Definition 11.2. CPT0MD: Comparator0 Mode Selection ..................................... 60
SFR Definition 11.3. CPT0MX: Comparator0 MUX Selection ...................................... 62
SFR Definition 12.1. DPL: Data Pointer Low Byte ........................................................ 69
SFR Definition 12.2. DPH: Data Pointer High Byte ....................................................... 69
SFR Definition 12.3. SP: Stack Pointer ......................................................................... 70
SFR Definition 12.4. ACC: Accumulator ....................................................................... 70
SFR Definition 12.5. B: B Register ................................................................................ 70
SFR Definition 12.6. PSW: Program Status Word ........................................................ 71
SFR Definition 13.1. EMI0CN: External Memory Interface Control .............................. 75
SFR Definition 15.1. IE: Interrupt Enable ...................................................................... 83
SFR Definition 15.2. IP: Interrupt Priority ...................................................................... 84
SFR Definition 15.3. EIE1: Extended Interrupt Enable 1 .............................................. 85
SFR Definition 15.4. EIP1: Extended Interrupt Priority 1 .............................................. 86
SFR Definition 15.5. IT01CF: INT0/INT1 Configuration ................................................ 88
SFR Definition 17.1. PCON: Power Control .................................................................. 94
SFR Definition 18.1. VDM0CN: VDD Monitor Control .................................................. 98
SFR Definition 18.2. RSTSRC: Reset Source ............................................................ 100
SFR Definition 19.1. CLKSEL: Clock Select ............................................................... 102
SFR Definition 19.2. OSCICL: Internal H-F Oscillator Calibration .............................. 103
SFR Definition 19.3. OSCICN: Internal H-F Oscillator Control ................................... 104
SFR Definition 19.4. OSCLCN: Internal L-F Oscillator Control ................................... 105
SFR Definition 19.5. OSCXCN: External Oscillator Control ........................................ 107
SFR Definition 20.1. XBR0: Port I/O Crossbar Register 0 .......................................... 117
SFR Definition 20.2. XBR1: Port I/O Crossbar Register 1 .......................................... 118
SFR Definition 20.3. P0MASK: Port 0 Mask Register ................................................. 119
SFR Definition 20.4. P0MAT: Port 0 Match Register .................................................. 119
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SFR Definition 20.5. P1MASK: Port 1 Mask Register ................................................. 120
SFR Definition 20.6. P1MAT: Port 1 Match Register .................................................. 120
SFR Definition 20.7. P0: Port 0 ................................................................................... 121
SFR Definition 20.8. P0MDIN: Port 0 Input Mode ....................................................... 122
SFR Definition 20.9. P0MDOUT: Port 0 Output Mode ................................................ 122
SFR Definition 20.10. P0SKIP: Port 0 Skip ................................................................. 123
SFR Definition 20.11. P1: Port 1 ................................................................................. 123
SFR Definition 20.12. P1MDIN: Port 1 Input Mode ..................................................... 124
SFR Definition 20.13. P1MDOUT: Port 1 Output Mode .............................................. 124
SFR Definition 20.14. P1SKIP: Port 1 Skip ................................................................. 125
SFR Definition 20.15. P2: Port 2 ................................................................................. 125
SFR Definition 20.16. P2MDOUT: Port 2 Output Mode .............................................. 126
SFR Definition 21.1. SMB0CF: SMBus Clock/Configuration ...................................... 133
SFR Definition 21.2. SMB0CN: SMBus Control .......................................................... 135
SFR Definition 21.3. SMB0ADR: SMBus Slave Address ............................................ 137
SFR Definition 21.4. SMB0ADM: SMBus Slave Address Mask .................................. 138
SFR Definition 21.5. SMB0DAT: SMBus Data ............................................................ 139
SFR Definition 22.1. SCON0: Serial Port 0 Control .................................................... 153
SFR Definition 22.2. SBUF0: Serial (UART0) Port Data Buffer .................................. 154
SFR Definition 23.1. SPI0CFG: SPI0 Configuration ................................................... 163
SFR Definition 23.2. SPI0CN: SPI0 Control ............................................................... 164
SFR Definition 23.3. SPI0CKR: SPI0 Clock Rate ....................................................... 165
SFR Definition 23.4. SPI0DAT: SPI0 Data ................................................................. 165
SFR Definition 24.1. CKCON: Clock Control .............................................................. 170
SFR Definition 24.2. TCON: Timer Control ................................................................. 175
SFR Definition 24.3. TMOD: Timer Mode ................................................................... 176
SFR Definition 24.4. TL0: Timer 0 Low Byte ............................................................... 177
SFR Definition 24.5. TL1: Timer 1 Low Byte ............................................................... 177
SFR Definition 24.6. TH0: Timer 0 High Byte ............................................................. 178
SFR Definition 24.7. TH1: Timer 1 High Byte ............................................................. 178
SFR Definition 24.8. TMR2CN: Timer 2 Control ......................................................... 182
SFR Definition 24.9. TMR2RLL: Timer 2 Reload Register Low Byte .......................... 183
SFR Definition 24.10. TMR2RLH: Timer 2 Reload Register High Byte ...................... 183
SFR Definition 24.11. TMR2L: Timer 2 Low Byte ....................................................... 183
SFR Definition 24.12. TMR2H Timer 2 High Byte ....................................................... 184
SFR Definition 24.13. TMR3CN: Timer 3 Control ....................................................... 188
SFR Definition 24.14. TMR3RLL: Timer 3 Reload Register Low Byte ........................ 189
SFR Definition 24.15. TMR3RLH: Timer 3 Reload Register High Byte ...................... 189
SFR Definition 24.16. TMR3L: Timer 3 Low Byte ....................................................... 189
SFR Definition 24.17. TMR3H Timer 3 High Byte ....................................................... 190
SFR Definition 25.1. PCA0CN: PCA Control .............................................................. 204
SFR Definition 25.2. PCA0MD: PCA Mode ................................................................ 205
SFR Definition 25.3. PCA0PWM: PCA PWM Configuration ....................................... 206
SFR Definition 25.4. PCA0CPMn: PCA Capture/Compare Mode .............................. 207
SFR Definition 25.5. PCA0L: PCA Counter/Timer Low Byte ...................................... 208
Rev. 1.0
13
C8051T630/1/2/3/4/5
SFR Definition 25.6. PCA0H: PCA Counter/Timer High Byte ..................................... 208
SFR Definition 25.7. PCA0CPLn: PCA Capture Module Low Byte ............................. 209
SFR Definition 25.8. PCA0CPHn: PCA Capture Module High Byte ........................... 209
C2 Register Definition 26.1. C2ADD: C2 Address ...................................................... 210
C2 Register Definition 26.2. DEVICEID: C2 Device ID ............................................... 211
C2 Register Definition 26.3. REVID: C2 Revision ID .................................................. 211
C2 Register Definition 26.4. DEVCTL: C2 Device Control .......................................... 212
C2 Register Definition 26.5. EPCTL: EPROM Programming Control Register ........... 212
C2 Register Definition 26.6. EPDAT: C2 EPROM Data .............................................. 213
C2 Register Definition 26.7. EPSTAT: C2 EPROM Status ......................................... 213
C2 Register Definition 26.8. EPADDRH: C2 EPROM Address High Byte .................. 214
C2 Register Definition 26.9. EPADDRL: C2 EPROM Address Low Byte ................... 214
C2 Register Definition 26.10. CRC0: CRC Byte 0 ...................................................... 215
C2 Register Definition 26.11. CRC1: CRC Byte 1 ...................................................... 215
C2 Register Definition 26.12. CRC2: CRC Byte 2 ...................................................... 216
C2 Register Definition 26.13. CRC3: CRC Byte 3 ...................................................... 216
14
Rev. 1.0
C8051T630/1/2/3/4/5
1. System Overview
C8051T630/1/2/3/4/5 devices are fully integrated, mixed-signal, system-on-a-chip MCUs. Highlighted features are listed below. Refer to Table 2.1 for specific product feature selection and part ordering numbers.












High-speed pipelined 8051-compatible microcontroller core (up to 25 MIPS)
In-system, full-speed, non-intrusive debug interface (on-chip)
C8051F336 ISP Flash device is available for quick in-system code development
10-bit 500 ksps Single-ended ADC with analog multiplexer and integrated temperature sensor
10-bit Current Output DAC
Precision calibrated 24.5 MHz internal oscillator
8/4/2 kB of on-chip Byte-Programmable EPROM—(512 bytes are reserved on 8k version)
768 bytes of on-chip RAM
SMBus/I2C, Enhanced UART, and Enhanced SPI serial interfaces implemented in hardware
Four general-purpose 16-bit timers
Programmable Counter/Timer Array (PCA) with three capture/compare modules and Watchdog Timer
function
On-chip Power-On Reset, VDD Monitor, and Temperature Sensor

On-chip Voltage Comparator
 17 Port I/O
With on-chip power-on reset, VDD monitor, watchdog timer, and clock oscillator, the C8051T630/1/2/3/4/5
devices are truly stand-alone, system-on-a-chip solutions. User software has complete control of all
peripherals, and may individually shut down any or all peripherals for power savings.
Code written for the C8051T630/1/2/3/4/5 family of processors will run on the C8051F336 Mixed-Signal
ISP Flash microcontroller, providing a quick, cost-effective way to develop code without requiring special
emulator circuitry. The C8051T630/1/2/3/4/5 processors include Silicon Laboratories’ 2-Wire C2 Debug
and Programming interface, which allows non-intrusive (uses no on-chip resources), full speed, in-circuit
debugging using the production MCU installed in the final application. This debug logic supports inspection
of memory, viewing and modification of special function registers, setting breakpoints, single stepping, and
run and halt commands. All analog and digital peripherals are fully functional while debugging using C2.
The two C2 interface pins can be shared with user functions, allowing in-system debugging without occupying package pins.
Each device is specified for 1.8–3.6 V operation over the industrial temperature range (–45 to +85 °C). An
internal LDO is used to supply the processor core voltage at 1.8 V. The Port I/O and RST pins are tolerant
of input signals up to 5 V. The C8051T630/1/2/3/4/5 are available in 20-pin QFN RoHS compliant packaging. See Table 2.1 for ordering information. A block diagram is shown in Figure 1.1.
Rev. 1.0
15
C8051T630/1/2/3/4/5
Power On
Reset
Reset
C2CK/RST
Port I/O Configuration
CIP-51 8051
Controller Core
Debug /
Programming
Hardware
8/4/2k Byte EPROM
Program Memory
UART
256 Byte SRAM
Timers 0,
1, 2, 3
512 Byte XRAM
PCA/
WDT
C2D
SPI
SYSCLK
Regulator
Core Power
Crossbar Control
SFR
Bus
Analog Peripherals
GND
Precision
24.5 MHz
Oscillator
VDD
External
Oscillator
Circuit
10-bit
VREF IDAC IDA0
Voltage
Reference
Low-Freq.
Oscillator
EXTCLK
Port 1
Drivers
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Priority
Crossbar
Decoder
SMBus
Peripheral Power
VDD
Port 0
Drivers
P0.0/VREF
P0.1/IDA0
P0.2/VPP
P0.3/EXTCLK
P0.4/TX
P0.5/RX
P0.6/CNVSTR
P0.7
Digital Peripherals
Port 2
Drivers
VREF
VDD
A
M
U
X
10-bit
500ksps
ADC
Temp
Sensor
‘T630/2/4 Only
CP0, CP0A
System Clock
Configuration
+
-
Comparator
Figure 1.1. C8051T630/1/2/3/4/5 Block Diagram
16
Rev. 1.0
P2.0/C2D
C8051T630/1/2/3/4/5
2. Ordering Information
SMBus/I2C
Enhanced SPI
UART
Timers (16-bit)
Programmable Counter Array
Digital Port I/Os
10-bit 500ksps ADC
10-bit Current Output DAC
Internal Voltage Reference
Temperature Sensor
Analog Comparator
Lead-free (RoHS Compliant)
Y
Y
Y
4
Y
17
Y
Y
Y
Y
Y
Y QFN-20
C8051T631-GM 25
8k* 768
Y
Y
Y
Y
Y
4
Y
17 — — — —
Y
Y QFN-20
C8051T632-GM 25
4k 768
Y
Y
Y
Y
Y
4
Y
17
Y
Y
Y QFN-20
C8051T633-GM 25
4k 768
Y
Y
Y
Y
Y
4
Y
17 — — — —
Y
Y QFN-20
C8051T634-GM 25
2k 768
Y
Y
Y
Y
Y
4
Y
17
Y
Y
Y QFN-20
C8051T635-GM 25
2k 768
Y
Y
Y
Y
Y
4
Y
17 — — — —
Y
Y QFN-20
Y
Y
Y
Y
Y
Y
Package
Internal 80 kHz Oscillator
Y
RAM (Bytes)
Y
EPROM Memory (Bytes)
8k* 768
MIPS (Peak)
C8051T630-GM 25
Ordering Part Number
Calibrated Internal 24.5 MHz Oscillator
Table 2.1. Product Selection Guide
* 512 Bytes Reserved for Factory Use
Rev. 1.0
17
C8051T630/1/2/3/4/5
3. Pin Definitions
Table 3.1. Pin Definitions for the C8051T630/1/2/3/4/5
Name
Pin
VDD
3
Power Supply Voltage.
GND
2
Ground.
RST/
4
C2CK
P2.0/
5
C2D
P0.0/
1
VREF
P0.1
20
IDA0
P0.2/
19
VPP
P0.3/
18
EXTCLK
Type
Description
D I/O
Device Reset. Open-drain output of internal POR or VDD monitor. An
external source can initiate a system reset by driving this pin low for at
least 10 µs.
D I/O
Clock signal for the C2 Debug Interface.
D I/O
Port 2.0.
D I/O
Bi-directional data signal for the C2 Debug Interface.
D I/O or
A In
Port 0.0.
A In
External VREF input.
D I/O or
A In
Port 0.1.
AOut
IDA0 Output.
D I/O or
A In
Port 0.2.
A In
VPP Programming Supply Voltage
D I/O or
A In
Port 0.3.
A I/O or
D In
External Clock Pin. This pin can be used as the external clock input for
CMOS, capacitor, or RC oscillator configurations.
P0.4
17
D I/O or
A In
Port 0.4.
P0.5
16
D I/O or
A In
Port 0.5.
P0.6/
15
D I/O or
A In
Port 0.6.
D In
ADC0 External Convert Start or IDA0 Update Source Input.
CNVSTR
18
Rev. 1.0
C8051T630/1/2/3/4/5
Table 3.1. Pin Definitions for the C8051T630/1/2/3/4/5 (Continued)
Name
Pin
Type
Description
P0.7
14
D I/O or
A In
Port 0.7.
P1.0
13
D I/O or
A In
Port 1.0.
P1.1
12
D I/O or
A In
Port 1.1.
P1.2
11
D I/O or
A In
Port 1.2.
P1.3
10
D I/O or
A In
Port 1.3.
P1.4
9
D I/O or
A In
Port 1.4.
P1.5
8
D I/O or
A In
Port 1.5.
P1.6
7
D I/O or
A In
Port 1.6.
P1.7
6
D I/O or
A In
Port 1.7.
Rev. 1.0
19
P0.1
P0.2/VPP
P0.3/
EXTCLK
P0.4
P0.5
20
19
18
17
16
C8051T630/1/2/3/4/5
P0.0
1
15
P0.6/
CNVSTR
GND
2
14
P0.7
VDD
3
13
P1.0
RST/C2CK
4
12
P1.1
P2.0/C2D
5
11
P1.2
C8051T630/1/2/3/4/5
Top View
8
9
10
P1.4
P1.3
7
P1.6
P1.5
6
P1.7
GND
Figure 3.1. QFN-20 Pinout Diagram (Top View)
20
Rev. 1.0
C8051T630/1/2/3/4/5
4. QFN-20 Package Specifications
Figure 4.1. QFN-20 Package Drawing
Table 4.1. QFN-20 Package Dimensions
Dimension
Min
Typ
Max
Dimension
Min
Typ
Max
A
A1
b
D
D2
e
E
E2
0.80
0.00
0.18
0.90
0.02
0.25
4.00 BSC.
2.15
0.50 BSC.
4.00 BSC.
2.15
1.00
0.05
0.30
L
L1
aaa
bbb
ddd
eee
Z
Y
0.45
0.00
—
—
—
—
—
—
0.55
—
—
—
—
—
0.43
0.18
0.65
0.15
0.15
0.10
0.05
0.08
—
—
2.00
2.00
2.25
2.25
Notes:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to the JEDEC Solid State Outline MO-220, variation VGGD except for
custom features D2, E2, Z, Y, and L which are toleranced per supplier designation.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for Small
Body Components.
Rev. 1.0
21
C8051T630/1/2/3/4/5
Figure 4.2. QFN-20 Recommended PCB Land Pattern
Table 4.2. QFN-20 PCB Land Pattern Dimesions
Dimension
C1
C2
E
X1
Min
Max
Dimension
Min
Max
X2
Y1
Y2
2.15
0.90
2.15
2.25
1.00
2.25
3.70
3.70
0.50
0.20
0.30
Notes:
General
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification.
3. This Land Pattern Design is based on the IPC-7351 guidelines.
Solder Mask Design
4. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder
mask and the metal pad is to be 60m minimum, all the way around the pad.
Stencil Design
5. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used
to assure good solder paste release.
6. The stencil thickness should be 0.125mm (5 mils).
7. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pins.
8. A 2x2 array of 0.95mm openings on a 1.1mm pitch should be used for the center pad to
assure the proper paste volume (71% Paste Coverage).
Card Assembly
9. A No-Clean, Type-3 solder paste is recommended.
10. The recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for
Small Body Components.
22
Rev. 1.0
C8051T630/1/2/3/4/5
5. Electrical Characteristics
5.1. Absolute Maximum Specifications
Table 5.1. Absolute Maximum Ratings
Parameter
Conditions
Min
Typ
Max
Units
Ambient temperature under bias
–55
—
125
°C
Storage Temperature
–65
—
150
°C
Voltage on RST or any Port I/O Pin
VDD > 2.2 V
(except VPP during programming) with VDD < 2.2 V
respect to GND
–0.3
–0.3
—
—
5.8
VDD + 3.6
V
V
Voltage on VPP with respect to GND
during a programming operation
VDD > 2.4 V
–0.3
—
7.0
V
Duration of High-voltage on VPP pin
(cumulative)
VPP > (VDD + 3.6 V)
—
—
10
s
Voltage on VDD with respect to GND
Regulator in Normal Mode
Regulator in Bypass Mode
–0.3
–0.3
—
—
4.2
1.98
V
V
Maximum Total current through VDD
and GND
—
—
500
mA
Maximum output current sunk by RST
or any Port pin
—
—
100
mA
Note: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of the devices at those or any other conditions above
those indicated in the operation listings of this specification is not implied. Exposure to maximum rating
conditions for extended periods may affect device reliability.
Rev. 1.0
23
C8051T630/1/2/3/4/5
5.2. Electrical Characteristics
Table 5.2. Global Electrical Characteristics
–40 to +85 °C, 25 MHz system clock unless otherwise specified.
Parameter
Conditions
Min
Typ
Max
Units
Supply Voltage (Note 1)
Regulator in Normal Mode
Regulator in Bypass Mode
1.8
1.7
3.0
1.8
3.6
1.9
V
V
Digital Supply Current with
CPU Active
VDD = 1.8 V, Clock = 25 MHz
VDD = 1.8 V, Clock = 1 MHz
VDD = 3.0 V, Clock = 25 MHz
VDD = 3.0 V, Clock = 1 MHz
—
—
—
—
6.2
2.7
7
2.9
8.8
—
8.9
—
mA
mA
mA
mA
Digital Supply Current with
CPU Inactive (not accessing
EPROM)
VDD = 1.8 V, Clock = 25 MHz
VDD = 1.8 V, Clock = 1 MHz
VDD = 3.0 V, Clock = 25 MHz
VDD = 3.0 V, Clock = 1 MHz
—
—
—
—
2.2
0.41
2.3
0.42
3
—
3.1
—
mA
mA
mA
mA
Digital Supply Current 
(shutdown)
Oscillator not running (stop mode),
Internal Regulator Off
—
0.2
2
µA
Oscillator not running (stop or suspend mode), Internal Regulator On
—
350
400
µA
—
1.5
—
V
–40
—
+85
°C
0
—
25
MHz
Tsysl (SYSCLK low time)
18
—
—
ns
Tsysh (SYSCLK high time)
18
—
—
ns
Digital Supply RAM Data
Retention Voltage
Specified Operating Temperature Range
SYSCLK (system clock 
frequency)
(Note 2)
Notes:
1. Analog performance is not guaranteed when VDD is below 1.8 V.
2. SYSCLK must be at least 32 kHz to enable debugging.
24
Rev. 1.0
C8051T630/1/2/3/4/5
Table 5.3. Port I/O DC Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +85 °C unless otherwise specified.
Parameters
Conditions
Output High Voltage IOH = –3 mA, Port I/O push-pull
IOH = –10 µA, Port I/O push-pull
IOH = –10 mA, Port I/O push-pull
Output Low Voltage IOL = 8.5 mA
IOL = 10 µA
IOL = 25 mA
Input High Voltage
Input Low Voltage
Input Leakage 
Weak Pullup Off
Current
Weak Pullup On, VIN = 0 V
Rev. 1.0
Min
Typ
Max
Units
VDD - 0.2
VDD - 0.1
—
—
—
—
0.7 x VDD
—
-1
—
—
—
VDD - 0.4
—
—
0.6
—
—
—
25
—
—
—
0.4
0.1
—
—
0.6
1
50
V
V
V
V
V
V
V
V
µA
µA
25
C8051T630/1/2/3/4/5
Table 5.4. Reset Electrical Characteristics
–40 to +85 °C unless otherwise specified.
Parameter
Conditions
Min
Typ
Max
Units
—
—
0.6
V
RST Input High Voltage
0.75 x VDD
—
—
V
RST Input Low Voltage
—
—
0.6
VDD
IOL = 8.5 mA, 
VDD = 1.8 V to 3.6 V
RST Output Low Voltage
—
25
50
µA
VDD POR Ramp Time
RST Input Pullup Current
RST = 0.0 V
—
—
1
ms
VDD Monitor Threshold (VRST)
1.7
1.75
1.8
V
500
625
750
µs
—
—
60
µs
15
—
—
µs
—
50
—
µs
—
20
30
µA
Missing Clock Detector 
Timeout
Time from last system clock
rising edge to reset initiation
Reset Time Delay
Delay between release of any
reset source and code 
execution at location 0x0000
Minimum RST Low Time to
Generate a System Reset
VDD Monitor Turn-on Time
VDD = VRST - 0.1 V
VDD Monitor Supply Current
Table 5.5. Internal Voltage Regulator Electrical Characteristics
–40 to +85 °C unless otherwise specified.
Parameter
Conditions
Input Voltage Range
Bias Current
Normal Mode
Min
Typ
Max
Units
1.8
—
3.6
V
—
30
50
µA
Table 5.6. EPROM Electrical Characteristics
Parameter
Conditions
Min
Typ
Max
Units
1
—
—
bytes
—
—
bytes
EPROM Size
C8051T630/1
8192
EPROM Size
C8051T632/3
4096
EPROM Size
C8051T634/5
2048
—
—
bytes
105
155
205
µs
Date Code 0935 and later
5.75
6.0
6.25
V
Date Code prior to 0935
6.25
6.375
6.5
V
Write Cycle Time (per Byte)
Programming Voltage2 (VPP)
Notes:
1. 512 bytes at location 0x1E00 to 0x1FFF are not available for program storage.
2. Refer to device errata for details.
26
Rev. 1.0
C8051T630/1/2/3/4/5
Table 5.7. Internal High-Frequency Oscillator Electrical Characteristics
VDD = 1.8 to 3.6 V; TA = –40 to +85 °C unless otherwise specified. Use factory-calibrated settings.
Parameter
Oscillator Frequency
Oscillator Supply Current 
(from VDD)
Power Supply Variance
Temperature Variance
Conditions
IFCN = 11b
25 °C, VDD = 3.0 V,
OSCICN.7 = 1,
OCSICN.5 = 0
Constant Temperature
Constant Supply
Min
Typ
Max
Units
24
—
24.5
450
25
700
MHz
µA
—
—
±0.02
±20
—
—
%/V
ppm/°C
Table 5.8. Internal Low-Frequency Oscillator Electrical Characteristics
VDD = 1.8 to 3.6 V; TA = –40 to +85 °C unless otherwise specified. Use factory-calibrated settings.
Parameter
Oscillator Frequency
Oscillator Supply Current 
(from VDD)
Power Supply Variance
Temperature Variance
Conditions
OSCLD = 11b
25 °C, VDD = 3.0 V,
OSCLCN.7 = 1
Constant Temperature
Constant Supply
Rev. 1.0
Min
Typ
Max
Units
72
—
80
3
88
6
kHz
µA
—
—
±0.02
±50
—
—
%/V
ppm/°C
27
C8051T630/1/2/3/4/5
Table 5.9. ADC0 Electrical Characteristics
VDD = 3.0 V, VREF = 2.40 V (REFSL=0), –40 to +85 °C unless otherwise specified.
Parameter
Conditions
Min
Typ
Max
Units
—
—
–2
–2
—
10
±0.5
±0.5
0
0
45
±1
±1
2
2
—
bits
LSB
LSB
LSB
LSB
ppm/°C
DC Accuracy
Resolution
Integral Nonlinearity
Differential Nonlinearity
Offset Error
Full Scale Error
Offset Temperature Coefficient
Guaranteed Monotonic
Dynamic performance (10 kHz sine-wave single-ended input, 1 dB below Full Scale, 200 ksps)
Signal-to-Noise Plus Distortion
Total Harmonic Distortion
Spurious-Free Dynamic Range
Up to the 5th harmonic
56
—
—
60
72
–75
—
—
—
dB
dB
dB
10-bit Mode
8-bit Mode
VDD >= 2.0 V
VDD < 2.0 V
—
13
11
300
2.0
—
—
—
—
—
—
—
8.33
—
—
—
—
500
MHz
clocks
clocks
ns
µs
ksps
1x Gain
0.5x Gain
0
—
—
—
—
5
3
5
VREF
—
—
—
V
pF
pF
k
Operating Mode, 200 ksps
—
600
900
µA
—
–70
—
dB
Conversion Rate
SAR Conversion Clock
Conversion Time in SAR Clocks
Track/Hold Acquisition Time
Throughput Rate
Analog Inputs
ADC Input Voltage Range
Sampling Capacitance
Input Multiplexer Impedance
Power Specifications
Power Supply Current 
(VDD supplied to ADC0)
Power Supply Rejection
28
Rev. 1.0
C8051T630/1/2/3/4/5
Table 5.10. Temperature Sensor Electrical Characteristics
VDD = 3.0 V, –40 to +85 °C unless otherwise specified.
Parameter
Conditions
Linearity
Slope
Slope Error*
Offset
Offset Error*
Temp = 0 °C
Temp = 0 °C
Min
Typ
Max
Units
—
—
—
—
—
±0.5
3.49
±40
930
±12
—
—
—
—
—
°C
mV/°C
µV/°C
mV
mV
Note: Represents one standard deviation from the mean.
Table 5.11. Voltage Reference Electrical Characteristics
VDD = 3.0 V; –40 to +85 °C unless otherwise specified.
Parameter
Conditions
Min
Typ
Max
Units
1.195
2.3
1.2
2.35
1.205
2.4
V
V
VREF Short-Circuit Current
—
4.5
6
mA
VREF Temperature 
Coefficient
—
±15
—
ppm/°C
Load = 0 to 200 µA to GND, 1.2 V setting
—
3.7
—
µV/µA
Load = 0 to 200 µA to GND, 2.4 V setting
—
5.0
—
µV/µA
VREF Turn-On Time 
(1.2 V setting)
4.7 µF tantalum, 0.1 µF ceramic bypass
—
1.2
—
ms
0.1 µF ceramic bypass
—
25
—
µs
VREF Turn-On Time 
(2.4 V setting)
4.7 µF tantalum, 0.1 µF ceramic bypass
—
4.3
—
ms
0.1 µF ceramic bypass
—
90
—
µs
Power Supply Rejection
1.2 V setting
—
120
—
µV/V
2.4 V setting
—
360
—
µV/V
0
—
VDD
V
Sample Rate = 500 ksps; VREF = 2.5 V
—
12
—
µA
REFBE = 1, 2.4 V setting
—
75
100
µA
On-Chip Reference (REFBE = 1)
Output Voltage
Load Regulation
1.2 V Setting, 25 °C ambient
2.4 V Setting 25 °C ambient
External Reference (REFBE = 0)
Input Voltage Range
Input Current
Power Specifications
Reference Bias Generator
Rev. 1.0
29
C8051T630/1/2/3/4/5
Table 5.12. IDAC Electrical Characteristics
VDD = 3.0 V, –40 to +85 °C Full-scale output current set to 2 mA unless otherwise specified.
Parameter
Conditions
Min
Typ
Max
Units
Static Performance
Resolution
10
Integral Nonlinearity
bits
—
±1
±2.5
LSB
—
±0.5
±1
LSB
Output Compliance Range
—
—
VDD – 1.2
V
Offset Error
–1
0
1
µA
–30
0
30
µA
—
50
—
ppm/°C
—
1
—
µA/V
Output Settling Time to 1/2 IDA0H:L = 0x3FF to 0x000
LSB
—
5
—
µs
Startup Time
—
5
—
µs
1 mA Full Scale Output Current
0.5 mA Full Scale Output Current
—
—
±1
±1
—
—
%
%
2 mA Full Scale Output Current
1 mA Full Scale Output Current
0.5 mA Full Scale Output Current
—
—
—
2100
1100
600
2500
1500
1000
µA
µA
µA
Differential Nonlinearity
Full Scale Error
Guaranteed Monotonic
2 mA Full-Scale Output Current
25 °C
Full Scale Error Tempco
VDD Power Supply 
Rejection Ratio
2 mA Full-Scale Output Current
25 °C
Dynamic Performance
Gain Variation
Power Specifications
Power Supply Current 
(VDD supplied to IDAC)
30
Rev. 1.0
C8051T630/1/2/3/4/5
Table 5.13. Comparator Electrical Characteristics
VDD = 3.0 V, –40 to +85 °C unless otherwise noted.
Parameter
Conditions
Min
Typ
Max
Units
Response Time:
Mode 0, Vcm* = 1.5 V
CP0+ – CP0– = 100 mV
—
240
—
ns
CP0+ – CP0– = –100 mV
—
240
—
ns
Response Time:
Mode 1, Vcm* = 1.5 V
CP0+ – CP0– = 100 mV
—
400
—
ns
CP0+ – CP0– = –100 mV
—
400
—
ns
Response Time:
Mode 2, Vcm* = 1.5 V
CP0+ – CP0– = 100 mV
—
650
—
ns
CP0+ – CP0– = –100 mV
—
1100
—
ns
Response Time:
Mode 3, Vcm* = 1.5 V
CP0+ – CP0– = 100 mV
—
2000
—
ns
CP0+ – CP0– = –100 mV
—
5500
—
ns
Common-Mode Rejection Ratio
—
1
4
mV/V
Positive Hysteresis 1
CP0HYP1–0 = 00
—
0
1
mV
Positive Hysteresis 2
CP0HYP1–0 = 01
2
5
8
mV
Positive Hysteresis 3
CP0HYP1–0 = 10
6
10
14
mV
Positive Hysteresis 4
CP0HYP1–0 = 11
12
20
28
mV
Negative Hysteresis 1
CP0HYN1–0 = 00
—
0
1
mV
Negative Hysteresis 2
CP0HYN1–0 = 01
2
5
8
mV
Negative Hysteresis 3
CP0HYN1–0 = 10
6
10
14
mV
Negative Hysteresis 4
CP0HYN1–0 = 11
12
20
28
mV
Inverting or Non-Inverting Input
Voltage Range
–0.25
—
VDD + 0.25
V
Input Offset Voltage
–7.5
—
7.5
mV
Power Supply Rejection
—
0.5
—
mV/V
Powerup Time
—
10
—
µs
Mode 0
—
26
50
µA
Mode 1
—
10
20
µA
Mode 2
—
3
6
µA
Mode 3
—
0.5
2
µA
Power Specifications
Supply Current at DC
Note: Vcm is the common-mode voltage on CP0+ and CP0–.
Rev. 1.0
31
C8051T630/1/2/3/4/5
5.3. Typical Performance Curves
8.0
7.0
6.0
VDD > 1.8 V
IDD (mA)
5.0
VDD = 1.8 V
4.0
3.0
2.0
1.0
0.0
0
5
10
15
20
25
SYSCLK (MHz)
Figure 5.1. Normal Mode Digital Supply Current vs. Frequency (MPCE = 1)
2.5
2.0
IDD (mA)
VDD > 1.8 V
1.5
VDD = 1.8 V
1.0
0.5
0.0
0
5
10
15
20
SYSCLK (MHz)
Figure 5.2. Idle Mode Digital Supply Current vs. Frequency (MPCE = 1)
32
Rev. 1.0
25
C8051T630/1/2/3/4/5
6. 10-Bit ADC (ADC0, C8051T630/2/4 only)
ADC0 on the C8051T630/2/4 is a 500 ksps, 10-bit successive-approximation-register (SAR) ADC with
integrated track-and-hold, a gain stage programmable to 1x or 0.5x, and a programmable window detector.
The ADC is fully configurable under software control via Special Function Registers. The ADC may be configured to measure various different signals using the analog multiplexer described in Section “6.5. ADC0
Analog Multiplexer (C8051T630/2/4 only)” on page 43. The voltage reference for the ADC is selected as
described in Section “9. Voltage Reference Options” on page 52. The ADC0 subsystem is enabled only
when the AD0EN bit in the ADC0 Control register (ADC0CN) is set to logic 1. The ADC0 subsystem is in
low power shutdown when this bit is logic 0.
AD0CM2
AD0CM1
AD0CM0
AD0EN
AD0TM
AD0INT
AD0BUSY
AD0WINT
ADC0CN
VDD
X1 or
X0.5
AIN
10-Bit
SAR
000
001
010
011
100
101
AD0BUSY (W)
Timer 0 Overflow
Timer 2 Overflow
Timer 1 Overflow
CNVSTR Input
Timer 3 Overflow
ADC0H
ADC
AD0SC2
AD0SC1
AD0SC0
AD0LJST
AD08BE
AMP0GN0
SYSCLK
REF
AMP0GN0
AD0SC4
AD0SC3
From
AMUX0
ADC0L
Start
Conversion
ADC0LTH ADC0LTL
ADC0CF
ADC0GTH ADC0GTL
AD0WINT
32
Window
Compare
Logic
Figure 6.1. ADC0 Functional Block Diagram
Rev. 1.0
33
C8051T630/1/2/3/4/5
6.1. Output Code Formatting
The ADC measures the input voltage with reference to GND. The registers ADC0H and ADC0L contain the
high and low bytes of the output conversion code from the ADC at the completion of each conversion. Data
can be right-justified or left-justified, depending on the setting of the AD0LJST bit. Conversion codes are
represented as 10-bit unsigned integers. Inputs are measured from 0 to VREF x 1023/1024. Example
codes are shown below for both right-justified and left-justified data. Unused bits in the ADC0H and ADC0L
registers are set to 0.
Input Voltage
Right-Justified ADC0H:ADC0L
(AD0LJST = 0)
Left-Justified ADC0H:ADC0L
(AD0LJST = 1)
VREF x 1023/1024
VREF x 512/1024
VREF x 256/1024
0
0x03FF
0x0200
0x0100
0x0000
0xFFC0
0x8000
0x4000
0x0000
6.2. 8-Bit Mode
Setting the ADC08BE bit in register ADC0CF to 1 will put the ADC in 8-bit mode. In 8-bit mode, only the 8
MSBs of data are converted, and the ADC0H register holds the results. The AD0LJST bit is ignored for 8bit mode. 8-bit conversions take two fewer SAR clock cycles than 10-bit conversions, so the conversion is
completed faster, and a 500 ksps sampling rate can be achieved with a slower SAR clock.
6.3. Modes of Operation
ADC0 has a maximum conversion speed of 500 ksps. The ADC0 conversion clock is a divided version of
the system clock, determined by the AD0SC bits in the ADC0CF register.
6.3.1. Starting a Conversion
A conversion can be initiated in one of six ways, depending on the programmed states of the ADC0 Start of
Conversion Mode bits (AD0CM2–0) in register ADC0CN. Conversions may be initiated by one of the following:
1. Writing a 1 to the AD0BUSY bit of register ADC0CN
2. A Timer 0 overflow (i.e., timed continuous conversions)
3. A Timer 2 overflow
4. A Timer 1 overflow
5. A rising edge on the CNVSTR input signal
6. A Timer 3 overflow
Writing a 1 to AD0BUSY provides software control of ADC0 whereby conversions are performed "ondemand". During conversion, the AD0BUSY bit is set to logic 1 and reset to logic 0 when the conversion is
complete. The falling edge of AD0BUSY triggers an interrupt (when enabled) and sets the ADC0 interrupt
flag (AD0INT). Note: When polling for ADC conversion completions, the ADC0 interrupt flag (AD0INT)
should be used. Converted data is available in the ADC0 data registers, ADC0H:ADC0L, when bit AD0INT
is logic 1. Note that when Timer 2 or Timer 3 overflows are used as the conversion source, Low Byte overflows are used if Timer 2/3 is in 8-bit mode; High byte overflows are used if Timer 2/3 is in 16-bit mode.
See Section “24. Timers” on page 169 for timer configuration.
Important Note About Using CNVSTR: The CNVSTR input pin also functions as a Port I/O pin. When the
CNVSTR input is used as the ADC0 conversion source, the associated pin should be skipped by the Digital Crossbar. See Section “20. Port Input/Output” on page 109 for details on Port I/O configuration.
34
Rev. 1.0
C8051T630/1/2/3/4/5
6.3.2. Tracking Modes
The AD0TM bit in register ADC0CN enables "delayed conversions", and will delay the actual conversion
start by three SAR clock cycles, during which time the ADC will continue to track the input. If AD0TM is left
at logic 0, a conversion will begin immediately, without the extra tracking time. For internal start-of-conversion sources, the ADC will track anytime it is not performing a conversion. When the CNVSTR signal is
used to initiate conversions, ADC0 will track either when AD0TM is logic 1, or when AD0TM is logic 0 and
CNVSTR is held low. See Figure 6.2 for track and convert timing details. Delayed conversion mode is useful when AMUX settings are frequently changed, due to the settling time requirements described in Section
“6.3.3. Settling Time Requirements” on page 36.
A. ADC Timing for External Trigger Source
CNVSTR
(AD0CM[2:0]=1xx)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15* 16 17
SAR
Clocks
AD0TM=1
Track
Convert
Track
*Conversion Ends at rising edge of 15th clock in 8-bit Mode
1 2 3 4 5 6 7 8 9 10 11 12* 13 14
SAR Clocks
AD0TM=0
N/C
Track
Convert
N/C
*Conversion Ends at rising edge of 12th clock in 8-bit Mode
B. ADC Timing for Internal Trigger Source
Write '1' to AD0BUSY,
Timer 0, Timer 2, Timer 1 Overflow
(AD0CM[2:0]=000, 001, 010, 011)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15* 16 17
SAR
Clocks
AD0TM=1
Track
Convert
Track
*Conversion Ends at rising edge of 15th clock in 8-bit Mode
1 2 3 4 5 6 7 8 9 10 11 12* 13 14
SAR
Clocks
AD0TM=0
Track
Convert
Track
th
*Conversion Ends at rising edge of 12 clock in 8-bit Mode
Figure 6.2. 10-Bit ADC Track and Conversion Example Timing
Rev. 1.0
35
C8051T630/1/2/3/4/5
6.3.3. Settling Time Requirements
A minimum tracking time is required before each conversion to ensure that an accurate conversion is performed. This tracking time is determined by any series impedance, including the AMUX0 resistance, the
the ADC0 sampling capacitance, and the accuracy required for the conversion. Note that in delayed tracking mode, three SAR clocks are used for tracking at the start of every conversion. For many applications,
these three SAR clocks will meet the minimum tracking time requirements.
Figure 6.3 shows the equivalent ADC0 input circuit. The required ADC0 settling time for a given settling
accuracy (SA) may be approximated by Equation 6.1. See Table 5.9 for ADC0 minimum settling time
requirements as well as the mux impedance and sampling capacitor values.
n
2
t = ln  -------  R TOTAL C SAMPLE
 SA
Equation 6.1. ADC0 Settling Time Requirements
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required settling time in seconds
RTOTAL is the sum of the AMUX0 resistance and any external source resistance.
n is the ADC resolution in bits (10).
MUX Select
Input Pin
RMUX
CSAMPLE
RCInput= RMUX * CSAMPLE
Note: See electrical specification tables for RMUX and CSAMPLE parameters.
Figure 6.3. ADC0 Equivalent Input Circuits
36
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 6.1. ADC0CF: ADC0 Configuration
Bit
7
6
5
4
3
2
1
0
Name
AD0SC[4:0]
AD0LJST
AD08BE
AMP0GN0
Type
R/W
R/W
R/W
R/W
0
0
1
Reset
1
1
1
1
SFR Address = 0xBC
Bit
Name
7:3
1
Function
AD0SC[4:0] ADC0 SAR Conversion Clock Period Bits.
SAR Conversion clock is derived from system clock by the following equation, where
AD0SC refers to the 5-bit value held in bits AD0SC4–0. SAR Conversion clock
requirements are given in the ADC specification table.
SYSCLK
AD0SC = ----------------------- – 1
CLK SAR
Note: If the Memory Power Controller is enabled (MPCE = '1'), AD0SC must be set to at least
"00001" for proper ADC operation.
2
AD0LJST
ADC0 Left Justify Select.
0: Data in ADC0H:ADC0L registers are right-justified.
1: Data in ADC0H:ADC0L registers are left-justified.
Note: The AD0LJST bit is only valid for 10-bit mode (AD08BE = 0).
1
AD08BE
8-Bit Mode Enable.
0: ADC operates in 10-bit mode (normal).
1: ADC operates in 8-bit mode.
Note: When AD08BE is set to 1, the AD0LJST bit is ignored.
0
AMP0GN0 ADC Gain Control Bit.
0: Gain = 0.5
1: Gain = 1
Rev. 1.0
37
C8051T630/1/2/3/4/5
SFR Definition 6.2. ADC0H: ADC0 Data Word MSB
Bit
7
6
5
4
3
Name
ADC0H[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0xBE
Bit
Name
2
1
0
0
0
0
Function
7:0 ADC0H[7:0] ADC0 Data Word High-Order Bits.
For AD0LJST = 0: Bits 7–2 will read 000000b. Bits 1–0 are the upper 2 bits of the 10bit ADC0 Data Word.
For AD0LJST = 1: Bits 7–0 are the most-significant bits of the 10-bit ADC0 Data
Word.
Note: In 8-bit mode AD0LJST is ignored, and ADC0H holds the 8-bit data word.
SFR Definition 6.3. ADC0L: ADC0 Data Word LSB
Bit
7
6
5
4
3
Name
ADC0L[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xBD
Bit
Name
7:0
0
2
1
0
0
0
0
Function
ADC0L[7:0] ADC0 Data Word Low-Order Bits.
For AD0LJST = 0: Bits 7–0 are the lower 8 bits of the 10-bit Data Word.
For AD0LJST = 1: Bits 7–6 are the lower 2 bits of the 10-bit Data Word. Bits 5–0 will
read 000000b.
Note: In 8-bit mode AD0LJST is ignored, and ADC0L will read back 00000000b.
38
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 6.4. ADC0CN: ADC0 Control
Bit
7
6
5
4
Name
AD0EN
AD0TM
AD0INT
Type
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
AD0EN
2
AD0BUSY AD0WINT
SFR Address = 0xE8; Bit-Addressable
Bit
Name
7
3
1
0
AD0CM[2:0]
R/W
0
0
0
Function
ADC0 Enable Bit.
0: ADC0 Disabled. ADC0 is in low-power shutdown.
1: ADC0 Enabled. ADC0 is active and ready for data conversions.
6
AD0TM
ADC0 Track Mode Bit.
0: Normal Track Mode: When ADC0 is enabled, tracking is continuous unless a conversion is in progress. Conversion begins immediately on start-of-conversion event,
as defined by AD0CM[2:0].
1: Delayed Track Mode: When ADC0 is enabled, input is tracked when a conversion
is not in progress. A start-of-conversion signal initiates three SAR clocks of additional
tracking, and then begins the conversion.
5
AD0INT
ADC0 Conversion Complete Interrupt Flag.
0: ADC0 has not completed a data conversion since AD0INT was last cleared.
1: ADC0 has completed a data conversion.
4
3
AD0BUSY
AD0WINT
ADC0 Busy Bit.
Read:
Write:
0: ADC0 conversion is not in
progress.
1: ADC0 conversion is in progress.
0: No Effect.
1: Initiates ADC0 Conversion if
AD0CM[2:0] = 000b
ADC0 Window Compare Interrupt Flag.
0: ADC0 Window Comparison Data match has not occurred since this flag was last
cleared.
1: ADC0 Window Comparison Data match has occurred.
2:0 AD0CM[2:0] ADC0 Start of Conversion Mode Select.
000: ADC0 start-of-conversion source is write of 1 to AD0BUSY.
001: ADC0 start-of-conversion source is overflow of Timer 0.
010: ADC0 start-of-conversion source is overflow of Timer 2.
011: ADC0 start-of-conversion source is overflow of Timer 1.
100: ADC0 start-of-conversion source is rising edge of external CNVSTR.
101: ADC0 start-of-conversion source is overflow of Timer 3.
11x: Reserved.
Rev. 1.0
39
C8051T630/1/2/3/4/5
6.4. Programmable Window Detector
The ADC Programmable Window Detector continuously compares the ADC0 output registers to user-programmed limits, and notifies the system when a desired condition is detected. This is especially effective in
an interrupt-driven system, saving code space and CPU bandwidth while delivering faster system
response times. The window detector interrupt flag (AD0WINT in register ADC0CN) can also be used in
polled mode. The ADC0 Greater-Than (ADC0GTH, ADC0GTL) and Less-Than (ADC0LTH, ADC0LTL)
registers hold the comparison values. The window detector flag can be programmed to indicate when measured data is inside or outside of the user-programmed limits, depending on the contents of the ADC0
Less-Than and ADC0 Greater-Than registers.
SFR Definition 6.5. ADC0GTH: ADC0 Greater-Than Data High Byte
Bit
7
6
5
4
3
Name
ADC0GTH[7:0]
Type
R/W
Reset
1
1
1
1
1
SFR Address = 0xC4
Bit
Name
2
1
0
1
1
1
2
1
0
1
1
1
Function
7:0 ADC0GTH[7:0] ADC0 Greater-Than Data Word High-Order Bits.
SFR Definition 6.6. ADC0GTL: ADC0 Greater-Than Data Low Byte
Bit
7
6
5
4
3
Name
ADC0GTL[7:0]
Type
R/W
Reset
1
1
1
1
SFR Address = 0xC3
Bit
Name
7:0
40
1
Function
ADC0GTL[7:0] ADC0 Greater-Than Data Word Low-Order Bits.
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 6.7. ADC0LTH: ADC0 Less-Than Data High Byte
Bit
7
6
5
4
3
Name
ADC0LTH[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0xC6
Bit
Name
7:0
2
1
0
0
0
0
2
1
0
0
0
0
Function
ADC0LTH[7:0] ADC0 Less-Than Data Word High-Order Bits.
SFR Definition 6.8. ADC0LTL: ADC0 Less-Than Data Low Byte
Bit
7
6
5
4
3
Name
ADC0LTL[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xC5
Bit
Name
7:0
0
Function
ADC0LTL[7:0] ADC0 Less-Than Data Word Low-Order Bits.
Rev. 1.0
41
C8051T630/1/2/3/4/5
6.4.1. Window Detector Example
Figure 6.4
shows
two
example
window
comparisons
for
right-justified
data,
with
ADC0LTH:ADC0LTL = 0x0080 (128d) and ADC0GTH:ADC0GTL = 0x0040 (64d). The input voltage can
range from 0 to VREF x (1023/1024) with respect to GND, and is represented by a 10-bit unsigned integer
value. In the left example, an AD0WINT interrupt will be generated if the ADC0 conversion word
(ADC0H:ADC0L) is within the range defined by ADC0GTH:ADC0GTL and ADC0LTH:ADC0LTL
(if 0x0040 < ADC0H:ADC0L < 0x0080). In the right example, and AD0WINT interrupt will be generated if
the ADC0 conversion word is outside of the range defined by the ADC0GT and ADC0LT registers
(if ADC0H:ADC0L < 0x0040 or ADC0H:ADC0L > 0x0080). Figure 6.5 shows an example using left-justified data with the same comparison values.
ADC0H:ADC0L
ADC0H:ADC0L
Input Voltage
(AIN - GND)
Input Voltage
(AIN - GND)
VREF x (1023/
1024)
0x03FF
VREF x (1023/
1024)
0x03FF
AD0WINT
not affected
AD0WINT=1
0x0081
VREF x (128/1024)
0x0080
0x0081
ADC0LTH:ADC0LTL
VREF x (128/1024)
0x007F
0x0080
0x007F
AD0WINT=1
VREF x (64/1024)
0x0041
0x0040
ADC0GTH:ADC0GTL
VREF x (64/1024)
0x003F
0x0041
0x0040
ADC0GTH:ADC0GTL
AD0WINT
not affected
ADC0LTH:ADC0LTL
0x003F
AD0WINT=1
AD0WINT
not affected
0x0000
0
0
0x0000
Figure 6.4. ADC Window Compare Example: Right-Justified Data
ADC0H:ADC0L
ADC0H:ADC0L
Input Voltage
(AIN - GND)
Input Voltage
(AIN - GND)
VREF x (1023/
1024)
VREF x (1023/
1024)
0xFFC0
0xFFC0
AD0WINT
not affected
AD0WINT=1
0x2040
VREF x (128/1024)
0x2000
0x2040
ADC0LTH:ADC0LTL
VREF x (128/1024)
0x1FC0
0x2000
0x1FC0
AD0WINT=1
0x1040
VREF x (64/1024)
0x1000
0x1040
ADC0GTH:ADC0GTL
VREF x (64/1024)
0x0FC0
0x1000
ADC0GTH:ADC0GTL
AD0WINT
not affected
ADC0LTH:ADC0LTL
0x0FC0
AD0WINT=1
AD0WINT
not affected
0
0x0000
0
0x0000
Figure 6.5. ADC Window Compare Example: Left-Justified Data
42
Rev. 1.0
C8051T630/1/2/3/4/5
6.5. ADC0 Analog Multiplexer (C8051T630/2/4 only)
ADC0 on the C8051T630/2/4 uses an analog input multiplexer to select the positive input to the ADC. Any
of the following may be selected as the positive input: Port 0 and 1 I/O pins, the on-chip temperature sensor, or the positive power supply (VDD). The ADC0 input channel is selected in the AMX0P register
described in SFR Definition 6.9.
AMX0P4
AMX0P3
AMX0P2
AMX0P1
AMX0P0
AMX0P
P0.0
AMUX
ADC0
P1.7
Temp
Sensor
VDD
Figure 6.6. ADC0 Multiplexer Block Diagram
Important Note About ADC0 Input Configuration: Port pins selected as ADC0 inputs should be configured as analog inputs, and should be skipped by the Digital Crossbar. To configure a Port pin for analog
input, set to 0 the corresponding bit in register PnMDIN. To force the Crossbar to skip a Port pin, set to 1
the corresponding bit in register PnSKIP. See Section “20. Port Input/Output” on page 109 for more Port
I/O configuration details.
Rev. 1.0
43
C8051T630/1/2/3/4/5
SFR Definition 6.9. AMX0P: AMUX0 Positive Channel Select
Bit
7
6
5
4
3
1
0
1
1
AMX0P[4:0]
Name
Type
R
R
R
Reset
0
0
0
R/W
1
SFR Address = 0xBB
Bit
Name
1
Function
7:5
Unused
Unused. Read = 000b; Write = Don’t Care.
4:0 AMX0P[4:0] AMUX0 Positive Input Selection.
00000:
00001:
00010:
00011:
00100:
00101:
00110:
00111:
01000:
01001:
01010:
01011:
01100:
01101:
01110:
01111:
10000:
10001:
10010 – 11111:
44
2
P0.0
P0.1
P0.2
P0.3
P0.4
P0.5
P0.6
P0.7
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Temp Sensor
VDD
no input selected
Rev. 1.0
1
C8051T630/1/2/3/4/5
7. Temperature Sensor (C8051T630/2/4 only)
An on-chip temperature sensor is included on the C8051T630/2/4 which can be directly accessed via the
ADC multiplexer. To use the ADC to measure the temperature sensor, the ADC mux channel should be
configured to connect to the temperature sensor. The temperature sensor transfer function is shown in
Figure 7.1. The output voltage (VTEMP) is the positive ADC input when the ADC multiplexer is set correctly.
The TEMPE bit in register REF0CN enables/disables the temperature sensor, as described in SFR Definition 9.1. While disabled, the temperature sensor defaults to a high impedance state and any ADC measurements performed on the sensor will result in meaningless data. Refer to Table 5.10 for the slope and
offset parameters of the temperature sensor.
VTEMP = (Slope x TempC) + Offset
TempC = (VTEMP - Offset) / Slope
Voltage
Slope (V / deg C)
Offset (V at 0 Celsius)
Temperature
Figure 7.1. Temperature Sensor Transfer Function
7.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature measurements (see Table 5.10 on page 29 for specifications). For absolute temperature measurements, offset
and/or gain calibration is recommended. A single-point offset measurement of the temperature sensor is
performed on each device during production test. The registers TOFFH and TOFFL, shown in SFR Definition 7.1 and SFR Definition 7.2 represent the output of the ADC when reading the temperature sensor at 0
degrees Celsius, and using the internal regulator as a voltage reference.
Figure 7.2 shows the typical temperature sensor error assuming a 1-point calibration at 0 °C. Parameters
that affect ADC measurement, in particular the voltage reference value, will also affect temperature
measurement.
Rev. 1.0
45
Error (degrees C)
C8051T630/1/2/3/4/5
5.00
5.00
4.00
4.00
3.00
3.00
2.00
2.00
1.00
1.00
0.00
-40.00
-20.00
0.00
20.00
40.00
60.00
80.00
-1.00
-1.00
-2.00
-2.00
-3.00
-3.00
-4.00
-4.00
-5.00
-5.00
Temperature (degrees C)
Figure 7.2. Temperature Sensor Error with 1-Point Calibration at 0 Celsius
46
0.00
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 7.1. TOFFH: Temperature Offset Measurement High Byte
Bit
7
6
5
4
3
2
1
0
Varies
Varies
Varies
Varies
Name
TOFF[9:2]
Type
R/W
Reset
Varies
Varies
Varies
Varies
SFR Address = 0x86
Bit
Name
7:0
TOFF[9:2]
Function
Temperature Sensor Offset High Order Bits.
The temperature sensor offset registers represent the output of the ADC when measuring the temperature sensor at 0 °C, with the voltage reference set to the internal
regulator. The temperature sensor offset information is left-justified. One LSB of this
measurement is equivalent to one LSB of the ADC output under the measurement
conditions.
SFR Definition 7.2. TOFFL: Temperature Offset Measurement Low Byte
Bit
7
6
Name
TOFF[1:0]
Type
R/W
Reset
Varies
Varies
5
4
3
2
1
0
R
R
R
R
R
R
0
0
0
0
0
0
SFR Address = 0x85
Bit
Name
7:6
TOFF[1:0]
Function
Temperature Sensor Offset Low Order Bits.
The temperature sensor offset registers represent the output of the ADC when measuring the temperature sensor at 0 °C, with the voltage reference set to the internal
regulator. The temperature sensor offset information is left-justified. One LSB of this
measurement is equivalent to one LSB of the ADC output under the measurement
conditions.
5:0
Unused
Unused. Read = 000000b; Write = Don’t Care.
Rev. 1.0
47
C8051T630/1/2/3/4/5
8. 10-Bit Current Mode DAC (IDA0, C8051T630/2/4 only)
The C8051T630/2/4 device includes a 10-bit current-mode Digital-to-Analog Converter (IDAC). The maximum current output of the IDAC can be adjusted for three different current settings; 0.5 mA, 1 mA, and
2 mA. The IDAC is enabled or disabled with the IDA0EN bit in the IDA0 Control Register (see SFR Definition 8.1). When IDA0EN is set to 0, the IDAC port pin (P0.1) behaves as a normal GPIO pin. When
IDA0EN is set to 1, the digital output drivers and weak pullup for the IDAC pin are automatically disabled,
and the pin is connected to the IDAC output. An internal bandgap bias generator is used to generate a reference current for the IDAC whenever it is enabled. When using the IDAC, bit 1 in the P0SKIP register
should be set to 1, to force the Crossbar to skip the IDAC pin.
8.1. IDA0 Output Scheduling
IDA0 features a flexible output update mechanism which allows for seamless full-scale changes and supports jitter-free updates for waveform generation. Three update modes are provided, allowing IDAC output
updates on a write to IDA0H, on a Timer overflow, or on an external pin edge.
8.1.1. Update Output On-Demand
IDA0CN
CNVSTR
Timer 3
Timer 2
Timer 1
IDA0EN
IDA0CM2
IDA0CM1
IDA0CM0
Timer 0
IDA0H
In its default mode (IDA0CN.[6:4] = 111) the IDA0 output is updated “on-demand” on a write to the highbyte of the IDA0 data register (IDA0H). It is important to note that writes to IDA0L are held in this mode,
and have no effect on the IDA0 output until a write to IDA0H takes place. If writing a full 10-bit word to the
IDAC data registers, the 10-bit data word is written to the low byte (IDA0L) and high byte (IDA0H) data registers. Data is latched into IDA0 after a write to the IDA0H register, so the write sequence should be
IDA0L followed by IDA0H if the full 10-bit resolution is required. The IDAC can be used in 8-bit mode by
initializing IDA0L to the desired value (typically 0x00), and writing data to only IDA0H (see Section 8.2 for
information on the format of the 10-bit IDAC data word within the 16-bit SFR space).
IDA0H
8
IDA0L
IDA0OMD1
IDA0OMD0
2
10
Latch
IDA0
Figure 8.1. IDA0 Functional Block Diagram
48
Rev. 1.0
IDA0
C8051T630/1/2/3/4/5
8.1.2. Update Output Based on Timer Overflow
Similar to the ADC operation, in which an ADC conversion can be initiated by a timer overflow independently of the processor, the IDAC outputs can use a Timer overflow to schedule an output update event.
This feature is useful in systems where the IDAC is used to generate a waveform of a defined sampling
rate by eliminating the effects of variable interrupt latency and instruction execution on the timing of the
IDAC output. When the IDA0CM bits (IDA0CN.[6:4]) are set to 000, 001, 010 or 011, writes to both IDAC
data registers (IDA0L and IDA0H) are held until an associated Timer overflow event (Timer 0, Timer 1,
Timer 2 or Timer 3, respectively) occurs, at which time the IDA0H:IDA0L contents are copied to the IDAC
input latches, allowing the IDAC output to change to the new value.
8.1.3. Update Output Based on CNVSTR Edge
The IDAC output can also be configured to update on a rising edge, falling edge, or both edges of the
external CNVSTR signal. When the IDA0CM bits (IDA0CN.[6:4]) are set to 100, 101, or 110, writes to both
IDAC data registers (IDA0L and IDA0H) are held until an edge occurs on the CNVSTR input pin. The particular setting of the IDA0CM bits determines whether IDAC outputs are updated on rising, falling, or both
edges of CNVSTR. When a corresponding edge occurs, the IDA0H:IDA0L contents are copied to the IDAC
input latches, allowing the IDAC output to change to the new value.
8.2. IDAC Output Mapping
The IDAC data registers (IDA0H and IDA0L) are left-justified, meaning that the eight MSBs of the IDAC
output word are mapped to bits 7–0 of the IDA0H register, and the two LSBs of the IDAC output word are
mapped to bits 7 and 6 of the IDA0L register. The data word mapping for the IDAC is shown in Figure 8.2.
B9
B8
B7
IDA0H
B6
B5
IDA0L
B4
B3
B2
B1
B0
Input Data Word
(IDA09–IDA00)
Output Current
IDA0OMD[1:0] = 1x
Output Current
IDA0OMD[1:0] = 01
Output Current
IDA0OMD[1:0] = 00
0x000
0x001
0x200
0x3FF
0 mA
1/1024 x 2 mA
512/1024 x 2 mA
1023/1024 x 2 mA
0 mA
1/1024 x 1 mA
512/1024 x 1 mA
1023/1024 x 1 mA
0 mA
1/1024 x 0.5 mA
512/1024 x 0.5 mA
1023/1024 x 0.5 mA
Figure 8.2. IDA0 Data Word Mapping
The full-scale output current of the IDAC is selected using the IDA0OMD bits (IDA0CN[1:0]). By default,
the IDAC is set to a full-scale output current of 2 mA. The IDA0OMD bits can also be configured to provide
full-scale output currents of 1 mA or 0.5 mA, as shown in SFR Definition 8.1.
Rev. 1.0
49
C8051T630/1/2/3/4/5
SFR Definition 8.1. IDA0CN: IDA0 Control
Bit
7
6
5
Name
IDA0EN
IDA0CM[2:0]
Type
R/W
R/W
Reset
0
1
1
4
IDA0EN
2
1
R
R
0
0
Function
IDA0 Enable.
0: IDA0 Disabled.
1: IDA0 Enabled.
6:4
IDA0CM[2:0]
IDA0 Update Source Select bits.
000: DAC output updates on Timer 0 overflow.
001: DAC output updates on Timer 1 overflow.
010: DAC output updates on Timer 2 overflow.
011: DAC output updates on Timer 3 overflow.
100: DAC output updates on rising edge of CNVSTR.
101: DAC output updates on falling edge of CNVSTR.
110: DAC output updates on any edge of CNVSTR.
111: DAC output updates on write to IDA0H.
3:2
Unused
Unused. Read = 00b. Write = Don’t care.
1:0 IDA0OMD[1:0] IDA0 Output Mode Select bits.
00: 0.5 mA full-scale output current.
01: 1.0 mA full-scale output current.
1x: 2.0 mA full-scale output current.
50
1
0
IDA0OMD[1:0]
SFR Address = 0xB9
Bit
Name
7
3
Rev. 1.0
R/W
1
0
C8051T630/1/2/3/4/5
SFR Definition 8.2. IDA0H: IDA0 Data Word MSB
Bit
7
6
5
4
Name
IDA0[9:2]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x97
Bit
Name
7:0
IDA0[9:2]
3
2
1
0
0
0
0
0
Function
IDA0 Data Word High-Order Bits.
Upper 8 bits of the 10-bit IDA0 Data Word.
SFR Definition 8.3. IDA0L: IDA0 Data Word LSB
Bit
7
6
Name
IDA0[1:0]
Type
R/W
Reset
0
0
5
4
3
2
1
0
R
R
R
R
R
R
0
0
0
0
0
0
SFR Address = 0x96
Bit
Name
7:6
IDA0[1:0]
Function
IDA0 Data Word Low-Order Bits.
Lower 2 bits of the 10-bit IDA0 Data Word.
5:0
Unused
Unused. Read = 000000b. Write = Don’t care.
Rev. 1.0
51
C8051T630/1/2/3/4/5
9. Voltage Reference Options
The Voltage reference multiplexer for the ADC is configurable to use an externally connected voltage reference, the on-chip reference voltage generator routed to the VREF pin, the unregulated power supply voltage (VDD), or the regulated 1.8 V internal supply (see Figure 9.1). The REFSL bit in the Reference Control
register (REF0CN, SFR Definition 9.1) selects the reference source for the ADC. For an external source or
the on-chip reference, REFSL should be set to 0 to select the VREF pin. To use VDD as the reference
source, REFSL should be set to 1. To override this selection and use the internal regulator as the reference
source, the REGOVR bit can be set to 1.
The BIASE bit enables the internal voltage bias generator, which is used by many of the analog peripherals
on the device. This bias is automatically enabled when any peripheral which requires it is enabled, and it
does not need to be enabled manually. The bias generator may be enabled manually by writing a 1 to the
BIASE bit in register REF0CN. The electrical specifications for the voltage reference circuit are given in
Table 5.11.
The C8051T630/2/4 devices also include an on-chip voltage reference circuit which consists of a 1.2 V,
temperature stable bandgap voltage reference generator and a selectable-gain output buffer amplifier. The
buffer is configured for 1x or 2x gain using the REFBGS bit in register REF0CN. On the 1x gain setting the
output voltage is nominally 1.2 V, and on the 2x gain setting the output voltage is nominally 2.4 V. The onchip voltage reference can be driven on the VREF pin by setting the REFBE bit in register REF0CN to a 1.
The maximum load seen by the VREF pin must be less than 200 µA to GND. Bypass capacitors of 0.1 µF
and 4.7 µF are recommended from the VREF pin to GND, and a minimum of 0.1uF is required. If the onchip reference is not used, the REFBE bit should be cleared to 0. Electrical specifications for the on-chip
voltage reference are given in Table 5.11.
Important Note about the VREF Pin: When using either an external voltage reference or the on-chip reference circuitry, the VREF pin should be configured as an analog pin and skipped by the Digital Crossbar.
Refer to Section “20. Port Input/Output” on page 109 for the location of the VREF pin, as well as details of
how to configure the pin in analog mode and to be skipped by the crossbar.
52
Rev. 1.0
C8051T630/1/2/3/4/5
REGOVR
REFSL
TEMPE
BIASE
REFBE
REFBGS
REF0CN
EN
To ADC, IDAC,
Internal Oscillators,
Reference,
TempSensor
Bias Generator
IOSCEN
VDD
EN
External
Voltage
Reference
Circuit
R1
VREF
1x/2x
Temp Sensor
1.2V Reference
To Analog Mux
EN
REFBE
REFBGS
GND
0
0
4.7F
+
0.1F
Recommended Bypass
Capacitors
VDD
VREF
(to ADC)
1
Internal
Regulator
1
REGOVR
Figure 9.1. Voltage Reference Functional Block Diagram
Rev. 1.0
53
C8051T630/1/2/3/4/5
SFR Definition 9.1. REF0CN: Reference Control
Bit
7
6
Name
REFBGS
Type
R/W
R
Reset
0
0
5
4
3
2
1
0
REGOVR
REFSL
TEMPE
BIASE
REFBE
R
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
SFR Address = 0xD1
Bit
Name
7
Function
REFBGS Reference Buffer Gain Select.
This bit selects between 1x and 2x gain for the on-chip voltage reference buffer.
0: 2x Gain
1: 1x Gain
6:5
4
Unused Unused. Read = 00b; Write = don’t care.
REGOVR Regulator Reference Override.
This bit “overrides” the REFSL bit, and allows the internal regulator to be used as a reference source.
0: The voltage reference source is selected by the REFSL bit.
1: The internal regulator is used as the voltage reference.
3
REFSL
Voltage Reference Select.
This bit selects the ADCs voltage reference.
0: VREF pin used as voltage reference.
1: VDD used as voltage reference.
2
TEMPE
Temperature Sensor Enable Bit.
0: Internal Temperature Sensor off.
1: Internal Temperature Sensor on.
1
BIASE
Internal Analog Bias Generator Enable Bit.
0: Internal Bias Generator off.
1: Internal Bias Generator on.
0
REFBE
On-chip Reference Buffer Enable Bit.
0: On-chip Reference Buffer off.
1: On-chip Reference Buffer on. Internal voltage reference driven on the VREF pin.
54
Rev. 1.0
C8051T630/1/2/3/4/5
10. Voltage Regulator (REG0)
C8051T630/1/2/3/4/5 devices include an internal voltage regulator (REG0) to regulate the internal core
supply to 1.8 V from a VDD supply of 1.8 to 3.6 V. Two power-saving modes are built into the regulator to
help reduce current consumption in low-power applications. These modes are accessed through the
REG0CN register (SFR Definition 10.1). Electrical characteristics for the on-chip regulator are specified in
Table 5.5 on page 26
If an external regulator is used to power the device, the internal regulator may be put into bypass mode
using the BYPASS bit. The internal regulator should never be placed in bypass mode unless an
external 1.8 V regulator is used to supply VDD. Doing so could cause permanent damage to the
device.
Under default conditions, when the device enters STOP mode the internal regulator will remain on. This
allows any enabled reset source to generate a reset for the device and bring the device out of STOP mode.
For additional power savings, the STOPCF bit can be used to shut down the regulator and the internal
power network of the device when the part enters STOP mode. When STOPCF is set to 1, the RST pin or
a full power cycle of the device are the only methods of generating a reset.
Rev. 1.0
55
C8051T630/1/2/3/4/5
SFR Definition 10.1. REG0CN: Voltage Regulator Control
Bit
7
6
5
4
Name
STOPCF
BYPASS
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
2
1
0
MPCE
SFR Address = 0xC7
Bit
Name
7
3
Function
STOPCF Stop Mode Configuration.
This bit configures the regulator’s behavior when the device enters STOP mode.
0: Regulator is still active in STOP mode. Any enabled reset source will reset the
device.
1: Regulator is shut down in STOP mode. Only the RST pin or power cycle can reset
the device.
6
BYPASS
Bypass Internal Regulator.
This bit places the regulator in bypass mode, turning off the regulator, and allowing the
core to run directly from the VDD supply pin.
0: Normal Mode—Regulator is on.
1: Bypass Mode—Regulator is off, and the microcontroller core operates directly from
the VDD supply voltage.
IMPORTANT: Bypass mode is for use with an external regulator as the supply
voltage only. Never place the regulator in bypass mode when the VDD supply
voltage is greater than the specifications given in Table 5.1 on page 23. Doing so
may cause permanent damage to the device.
5:1
0
Reserved Reserved. Must Write 00000b
MPCE
Memory Power Controller Enable.
This bit can help the system save power at slower system clock frequencies (about
2.0 MHz or less) by automatically shutting down the EPROM memory between clocks
when information is not being fetched from the EPROM memory.
0: Normal Mode—Memory power controller disabled (EPROM memory is always on).
1: Low Power Mode—Memory power controller enabled (EPROM memory turns on/off
as needed).
Note: If an external clock source is used with the Memory Power Controller enabled, and the
clock frequency changes from slow (<2.0 MHz) to fast (> 2.0 MHz), the EPROM power
will turn on, and up to 20 clocks may be "skipped" to ensure that the EPROM power is
stable before reading memory.
56
Rev. 1.0
C8051T630/1/2/3/4/5
11. Comparator0
C8051T630/1/2/3/4/5 devices include an on-chip programmable voltage comparator, Comparator0, shown
in Figure 11.1.
The Comparator offers programmable response time and hysteresis, an analog input multiplexer, and two
outputs that are optionally available at the Port pins: a synchronous “latched” output (CP0), or an asynchronous “raw” output (CP0A). The asynchronous CP0A signal is available even when the system clock is
not active. This allows the Comparator to operate and generate an output with the device in STOP mode.
When assigned to a Port pin, the Comparator output may be configured as open drain or push-pull (see
Section “20.4. Port I/O Initialization” on page 116). Comparator0 may also be used as a reset source (see
Section “18.5. Comparator0 Reset” on page 99).
The Comparator0 inputs are selected by the comparator input multiplexer, as detailed in Section
“11.1. Comparator Multiplexer” on page 61.
CPT0CN
CP0EN
CP0OUT
CP0RIF
CP0FIF
CP0HYP1
CP0HYP0
CP0HYN1
CP0HYN0
VDD
CP0 +
Comparator
Input Mux
+
CP0 -
CP0
D
-
SET
CLR
D
Q
Q
SET
CLR
Q
Q
Crossbar
(SYNCHRONIZER)
CP0A
GND
CPT0MD
CP0RIE
CP0FIE
CP0MD1
CP0MD0
Reset
Decision
Tree
0
CP0RIF
CP0FIF
CP0EN
EA
1
0
0
0
1
1
CP0
Interrupt
1
Figure 11.1. Comparator0 Functional Block Diagram
The Comparator output can be polled in software, used as an interrupt source, and/or routed to a Port pin.
When routed to a Port pin, the Comparator output is available asynchronous or synchronous to the system
clock; the asynchronous output is available even in STOP mode (with no system clock active). When disabled, the Comparator output (if assigned to a Port I/O pin via the Crossbar) defaults to the logic low state,
and the power supply to the comparator is turned off. See Section “20.3. Priority Crossbar Decoder” on
page 114 for details on configuring Comparator outputs via the digital Crossbar. Comparator inputs can be
externally driven from –0.25 V to (VDD) + 0.25 V without damage or upset. The complete Comparator electrical specifications are given in Section “5. Electrical Characteristics” on page 23.
Rev. 1.0
57
C8051T630/1/2/3/4/5
The Comparator response time may be configured in software via the CPT0MD register (see SFR Definition 11.2). Selecting a longer response time reduces the Comparator supply current.
VIN+
VIN-
CP0+
CP0-
+
CP0
_
OUT
CIRCUIT CONFIGURATION
Positive Hysteresis Voltage
(Programmed with CP0HYP Bits)
VIN-
INPUTS
Negative Hysteresis Voltage
(Programmed by CP0HYN Bits)
VIN+
VOH
OUTPUT
VOL
Negative Hysteresis
Disabled
Positive Hysteresis
Disabled
Maximum
Negative Hysteresis
Maximum
Positive Hysteresis
Figure 11.2. Comparator Hysteresis Plot
The Comparator hysteresis is software-programmable via its Comparator Control register CPT0CN. The
user can program both the amount of hysteresis voltage (referred to the input voltage) and the positive and
negative-going symmetry of this hysteresis around the threshold voltage.
The Comparator hysteresis is programmed using Bits3–0 in the Comparator Control Register CPT0CN
(shown in SFR Definition 11.1). The amount of negative hysteresis voltage is determined by the settings of
the CP0HYN bits. As shown in Figure 11.2, settings of 20, 10 or 5 mV of negative hysteresis can be programmed, or negative hysteresis can be disabled. In a similar way, the amount of positive hysteresis is
determined by the setting the CP0HYP bits.
Comparator interrupts can be generated on both rising-edge and falling-edge output transitions. (For Interrupt enable and priority control, see Section “15.1. MCU Interrupt Sources and Vectors” on page 81). The
CP0FIF flag is set to logic 1 upon a Comparator falling-edge occurrence, and the CP0RIF flag is set to
logic 1 upon the Comparator rising-edge occurrence. Once set, these bits remain set until cleared by software. The Comparator rising-edge interrupt mask is enabled by setting CP0RIE to a logic 1. The
Comparator0 falling-edge interrupt mask is enabled by setting CP0FIE to a logic 1.
The output state of the Comparator can be obtained at any time by reading the CP0OUT bit. The Comparator is enabled by setting the CP0EN bit to logic 1, and is disabled by clearing this bit to logic 0.
Note that false rising edges and falling edges can be detected when the comparator is first powered on or
if changes are made to the hysteresis or response time control bits. Therefore, it is recommended that the
rising-edge and falling-edge flags be explicitly cleared to logic 0 a short time after the comparator is
enabled or its mode bits have been changed.
58
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 11.1. CPT0CN: Comparator0 Control
Bit
7
6
5
4
Name
CP0EN
CP0OUT
CP0RIF
CP0FIF
CP0HYP[1:0]
CP0HYN[1:0]
Type
R/W
R
R/W
R/W
R/W
R/W
Reset
0
0
0
0
SFR Address = 0x9B
Bit
Name
7
CP0EN
3
2
0
0
1
0
0
0
Function
Comparator0 Enable Bit.
0: Comparator0 Disabled.
1: Comparator0 Enabled.
6
CP0OUT
Comparator0 Output State Flag.
0: Voltage on CP0+ < CP0–.
1: Voltage on CP0+ > CP0–.
5
CP0RIF
Comparator0 Rising-Edge Flag. Must be cleared by software.
0: No Comparator0 Rising Edge has occurred since this flag was last cleared.
1: Comparator0 Rising Edge has occurred.
4
CP0FIF
Comparator0 Falling-Edge Flag. Must be cleared by software.
0: No Comparator0 Falling-Edge has occurred since this flag was last cleared.
1: Comparator0 Falling-Edge has occurred.
3:2 CP0HYP[1:0] Comparator0 Positive Hysteresis Control Bits.
00: Positive Hysteresis Disabled.
01: Positive Hysteresis = 5 mV.
10: Positive Hysteresis = 10 mV.
11: Positive Hysteresis = 20 mV.
1:0 CP0HYN[1:0] Comparator0 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hysteresis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
Rev. 1.0
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C8051T630/1/2/3/4/5
SFR Definition 11.2. CPT0MD: Comparator0 Mode Selection
Bit
7
6
Name
5
4
CP0RIE
CP0FIE
3
2
R
R
R/W
R/W
R
R
Reset
0
0
0
0
0
0
Unused
CP0RIE
Unused. Read = 00b, Write = Don’t Care.
4
CP0FIE
Comparator0 Falling-Edge Interrupt Enable.
0: Comparator0 Falling-edge interrupt disabled.
1: Comparator0 Falling-edge interrupt enabled.
60
R/W
1
Function
7:6
5
3:2
1:0
0
CP0MD[1:0]
Type
SFR Address = 0x9D
Bit
Name
1
Comparator0 Rising-Edge Interrupt Enable.
0: Comparator0 Rising-edge interrupt disabled.
1: Comparator0 Rising-edge interrupt enabled.
Unused
Unused. Read = 00b, Write = don’t care.
CP0MD[1:0] Comparator0 Mode Select.
These bits affect the response time and power consumption for Comparator0.
00: Mode 0 (Fastest Response Time, Highest Power Consumption)
01: Mode 1
10: Mode 2
11: Mode 3 (Slowest Response Time, Lowest Power Consumption)
Rev. 1.0
0
C8051T630/1/2/3/4/5
11.1. Comparator Multiplexer
C8051T630/1/2/3/4/5 devices include an analog input multiplexer to connect Port I/O pins to the comparator inputs. The Comparator0 inputs are selected in the CPT0MX register (SFR Definition 11.3). The
CMX0P3–CMX0P0 bits select the Comparator0 positive input; the CMX0N3–CMX0N0 bits select the
Comparator0 negative input. Important Note About Comparator Inputs: The Port pins selected as comparator inputs should be configured as analog inputs in their associated Port configuration register, and
configured to be skipped by the Crossbar (for details on Port configuration, see Section “20.6. Special
Function Registers for Accessing and Configuring Port I/O” on page 121).
P0.0
P0.2
P0.4
P0.6
P1.0
P1.2
P1.4
P1.6
VDD
CP0 +
+
CP0 P0.1
P0.3
P0.5
P0.7
P1.1
P1.3
P1.5
P1.7
-
CMX0P1
CMX0P0
CMX0P3
CMX0P2
CMX0N1
CMX0N0
CMX0N3
CMX0N2
GND
CPT0MX
Figure 11.3. Comparator Input Multiplexer Block Diagram
Rev. 1.0
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C8051T630/1/2/3/4/5
SFR Definition 11.3. CPT0MX: Comparator0 MUX Selection
Bit
7
6
5
4
3
2
1
Name
CMX0N[3:0]
CMX0P[3:0]
Type
R/W
R/W
Reset
1
1
1
1
SFR Address = 0x9F
Bit
Name
7:4
P0.1
P0.3
P0.5
P0.7
P1.1
P1.3
P1.5
P1.7
None
CMX0P[3:0] Comparator0 Positive Input MUX Selection.
0000:
0001:
0010:
0011:
0100:
0101:
0110:
0111:
1xxx:
62
Function
CMX0N[3:0] Comparator0 Negative Input MUX Selection.
0000:
0001:
0010:
0011:
0100:
0101:
0110:
0111:
1xxx:
3:0
1
P0.0
P0.2
P0.4
P0.6
P1.0
P1.2
P1.4
P1.6
None
Rev. 1.0
1
1
0
1
C8051T630/1/2/3/4/5
12. CIP-51 Microcontroller
The MCU system controller core is the CIP-51 microcontroller. The CIP-51 is fully compatible with the
MCS-51™ instruction set; standard 803x/805x assemblers and compilers can be used to develop software. The MCU family has a superset of all the peripherals included with a standard 8051. The CIP-51
also includes on-chip debug hardware (see description in Section 26), and interfaces directly with the analog and digital subsystems providing a complete data acquisition or control-system solution in a single integrated circuit.
The CIP-51 Microcontroller core implements the standard 8051 organization and peripherals as well as
additional custom peripherals and functions to extend its capability (see Figure 12.1 for a block diagram).
The CIP-51 includes the following features:
Fully
Reset
25
Compatible with MCS-51 Instruction Set
MIPS Peak Throughput with 25 MHz Clock
0 to 25 MHz Clock Frequency
Extended Interrupt Handler
Power
Input
Management Modes
On-chip Debug Logic
Program and Data Memory Security
Performance
The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the standard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system
clock cycles to execute, and usually have a maximum system clock of 12 MHz. By contrast, the CIP-51
core executes 70% of its instructions in one or two system clock cycles, with no instructions taking more
than eight system clock cycles.
D8
D8
ACCUMULATOR
STACK POINTER
TMP1
TMP2
SRAM
ADDRESS
REGISTER
PSW
D8
D8
D8
ALU
SRAM
D8
DATA BUS
B REGISTER
D8
D8
D8
DATA BUS
DATA BUS
SFR_ADDRESS
BUFFER
D8
D8
DATA POINTER
D8
SFR
BUS
INTERFACE
SFR_CONTROL
SFR_WRITE_DATA
SFR_READ_DATA
DATA BUS
PC INCREMENTER
PROGRAM COUNTER (PC)
PRGM. ADDRESS REG.
MEM_ADDRESS
D8
MEM_CONTROL
A16
MEMORY
INTERFACE
MEM_WRITE_DATA
MEM_READ_DATA
PIPELINE
RESET
D8
CONTROL
LOGIC
SYSTEM_IRQs
CLOCK
D8
STOP
IDLE
POWER CONTROL
REGISTER
INTERRUPT
INTERFACE
EMULATION_IRQ
D8
Figure 12.1. CIP-51 Block Diagram
Rev. 1.0
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C8051T630/1/2/3/4/5
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. The CIP-51 has
a total of 109 instructions. The table below shows the total number of instructions that require each execution time.
Clocks to Execute
1
2
2/3
3
3/4
4
4/5
5
8
Number of Instructions
26
50
5
14
7
3
1
2
1
12.1. Instruction Set
The instruction set of the CIP-51 System Controller is fully compatible with the standard MCS-51™ instruction set. Standard 8051 development tools can be used to develop software for the CIP-51. All CIP-51
instructions are the binary and functional equivalent of their MCS-51™ counterparts, including opcodes,
addressing modes and effect on PSW flags. However, instruction timing is different than that of the standard 8051.
12.1.1. Instruction and CPU Timing
In many 8051 implementations, a distinction is made between machine cycles and clock cycles, with
machine cycles varying from 2 to 12 clock cycles in length. However, the CIP-51 implementation is based
solely on clock cycle timing. All instruction timings are specified in terms of clock cycles.
Due to the pipelined architecture of the CIP-51, most instructions execute in the same number of clock
cycles as there are program bytes in the instruction. Conditional branch instructions take one less clock
cycle to complete when the branch is not taken as opposed to when the branch is taken. Table 12.1 is the
CIP-51 Instruction Set Summary, which includes the mnemonic, number of bytes, and number of clock
cycles for each instruction.
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Table 12.1. CIP-51 Instruction Set Summary
Mnemonic
Description
Bytes
Clock
Cycles
Add register to A
Add direct byte to A
Add indirect RAM to A
Add immediate to A
Add register to A with carry
Add direct byte to A with carry
Add indirect RAM to A with carry
Add immediate to A with carry
Subtract register from A with borrow
Subtract direct byte from A with borrow
Subtract indirect RAM from A with borrow
Subtract immediate from A with borrow
Increment A
Increment register
Increment direct byte
Increment indirect RAM
Decrement A
Decrement register
Decrement direct byte
Decrement indirect RAM
Increment Data Pointer
Multiply A and B
Divide A by B
Decimal adjust A
1
2
1
2
1
2
1
2
1
2
1
2
1
1
2
1
1
1
2
1
1
1
1
1
1
2
2
2
1
2
2
2
1
2
2
2
1
1
2
2
1
1
2
2
1
4
8
1
AND Register to A
AND direct byte to A
AND indirect RAM to A
AND immediate to A
AND A to direct byte
AND immediate to direct byte
OR Register to A
OR direct byte to A
OR indirect RAM to A
OR immediate to A
OR A to direct byte
OR immediate to direct byte
Exclusive-OR Register to A
Exclusive-OR direct byte to A
Exclusive-OR indirect RAM to A
Exclusive-OR immediate to A
Exclusive-OR A to direct byte
1
2
1
2
2
3
1
2
1
2
2
3
1
2
1
2
2
1
2
2
2
2
3
1
2
2
2
2
3
1
2
2
2
2
Arithmetic Operations
ADD A, Rn
ADD A, direct
ADD A, @Ri
ADD A, #data
ADDC A, Rn
ADDC A, direct
ADDC A, @Ri
ADDC A, #data
SUBB A, Rn
SUBB A, direct
SUBB A, @Ri
SUBB A, #data
INC A
INC Rn
INC direct
INC @Ri
DEC A
DEC Rn
DEC direct
DEC @Ri
INC DPTR
MUL AB
DIV AB
DA A
Logical Operations
ANL A, Rn
ANL A, direct
ANL A, @Ri
ANL A, #data
ANL direct, A
ANL direct, #data
ORL A, Rn
ORL A, direct
ORL A, @Ri
ORL A, #data
ORL direct, A
ORL direct, #data
XRL A, Rn
XRL A, direct
XRL A, @Ri
XRL A, #data
XRL direct, A
Rev. 1.0
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C8051T630/1/2/3/4/5
Table 12.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic
Description
Bytes
Clock
Cycles
XRL direct, #data
CLR A
CPL A
RL A
RLC A
RR A
RRC A
SWAP A
Exclusive-OR immediate to direct byte
Clear A
Complement A
Rotate A left
Rotate A left through Carry
Rotate A right
Rotate A right through Carry
Swap nibbles of A
3
1
1
1
1
1
1
1
3
1
1
1
1
1
1
1
Move Register to A
Move direct byte to A
Move indirect RAM to A
Move immediate to A
Move A to Register
Move direct byte to Register
Move immediate to Register
Move A to direct byte
Move Register to direct byte
Move direct byte to direct byte
Move indirect RAM to direct byte
Move immediate to direct byte
Move A to indirect RAM
Move direct byte to indirect RAM
Move immediate to indirect RAM
Load DPTR with 16-bit constant
Move code byte relative DPTR to A
Move code byte relative PC to A
Move external data (8-bit address) to A
Move A to external data (8-bit address)
Move external data (16-bit address) to A
Move A to external data (16-bit address)
Push direct byte onto stack
Pop direct byte from stack
Exchange Register with A
Exchange direct byte with A
Exchange indirect RAM with A
Exchange low nibble of indirect RAM with A
1
2
1
2
1
2
2
2
2
3
2
3
1
2
2
3
1
1
1
1
1
1
2
2
1
2
1
1
1
2
2
2
1
2
2
2
2
3
2
3
2
2
2
3
3
3
3
3
3
3
2
2
1
2
2
2
Clear Carry
Clear direct bit
Set Carry
Set direct bit
Complement Carry
Complement direct bit
1
2
1
2
1
2
1
2
1
2
1
2
Data Transfer
MOV A, Rn
MOV A, direct
MOV A, @Ri
MOV A, #data
MOV Rn, A
MOV Rn, direct
MOV Rn, #data
MOV direct, A
MOV direct, Rn
MOV direct, direct
MOV direct, @Ri
MOV direct, #data
MOV @Ri, A
MOV @Ri, direct
MOV @Ri, #data
MOV DPTR, #data16
MOVC A, @A+DPTR
MOVC A, @A+PC
MOVX A, @Ri
MOVX @Ri, A
MOVX A, @DPTR
MOVX @DPTR, A
PUSH direct
POP direct
XCH A, Rn
XCH A, direct
XCH A, @Ri
XCHD A, @Ri
Boolean Manipulation
CLR C
CLR bit
SETB C
SETB bit
CPL C
CPL bit
66
Rev. 1.0
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Table 12.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic
Description
Bytes
Clock
Cycles
ANL C, bit
ANL C, /bit
ORL C, bit
ORL C, /bit
MOV C, bit
MOV bit, C
JC rel
JNC rel
JB bit, rel
JNB bit, rel
JBC bit, rel
AND direct bit to Carry
AND complement of direct bit to Carry
OR direct bit to carry
OR complement of direct bit to Carry
Move direct bit to Carry
Move Carry to direct bit
Jump if Carry is set
Jump if Carry is not set
Jump if direct bit is set
Jump if direct bit is not set
Jump if direct bit is set and clear bit
2
2
2
2
2
2
2
2
3
3
3
2
2
2
2
2
2
2/3
2/3
3/4
3/4
3/4
Absolute subroutine call
Long subroutine call
Return from subroutine
Return from interrupt
Absolute jump
Long jump
Short jump (relative address)
Jump indirect relative to DPTR
Jump if A equals zero
Jump if A does not equal zero
Compare direct byte to A and jump if not equal
Compare immediate to A and jump if not equal
Compare immediate to Register and jump if not
equal
Compare immediate to indirect and jump if not
equal
Decrement Register and jump if not zero
Decrement direct byte and jump if not zero
No operation
2
3
1
1
2
3
2
1
2
2
3
3
3
3
4
5
5
3
4
3
3
2/3
2/3
3/4
3/4
3/4
3
4/5
2
3
1
2/3
3/4
1
Program Branching
ACALL addr11
LCALL addr16
RET
RETI
AJMP addr11
LJMP addr16
SJMP rel
JMP @A+DPTR
JZ rel
JNZ rel
CJNE A, direct, rel
CJNE A, #data, rel
CJNE Rn, #data, rel
CJNE @Ri, #data, rel
DJNZ Rn, rel
DJNZ direct, rel
NOP
Rev. 1.0
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Notes on Registers, Operands and Addressing Modes:
Rn - Register R0–R7 of the currently selected register bank.
@Ri - Data RAM location addressed indirectly through R0 or R1.
rel - 8-bit, signed (twos complement) offset relative to the first byte of the following instruction. Used by
SJMP and all conditional jumps.
direct - 8-bit internal data location’s address. This could be a direct-access Data RAM location (0x00–
0x7F) or an SFR (0x80–0xFF).
#data - 8-bit constant
#data16 - 16-bit constant
bit - Direct-accessed bit in Data RAM or SFR
addr11 - 11-bit destination address used by ACALL and AJMP. The destination must be within the same
2 kB page of program memory as the first byte of the following instruction.
addr16 - 16-bit destination address used by LCALL and LJMP. The destination may be anywhere within
the 8 kB program memory space.
There is one unused opcode (0xA5) that performs the same function as NOP.
All mnemonics copyrighted © Intel Corporation 1980.
68
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12.2. CIP-51 Register Descriptions
Following are descriptions of SFRs related to the operation of the CIP-51 System Controller. Reserved bits
should always be written to the value indicated in the SFR description. Future product versions may use
these bits to implement new features in which case the reset value of the bit will be the indicated value,
selecting the feature's default state. Detailed descriptions of the remaining SFRs are included in the sections of the data sheet associated with their corresponding system function.
SFR Definition 12.1. DPL: Data Pointer Low Byte
Bit
7
6
5
4
Name
DPL[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x82
Bit
Name
7:0
DPL[7:0]
3
2
1
0
0
0
0
0
3
2
1
0
0
0
0
0
Function
Data Pointer Low.
The DPL register is the low byte of the 16-bit DPTR.
SFR Definition 12.2. DPH: Data Pointer High Byte
Bit
7
6
5
4
Name
DPH[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x83
Bit
Name
7:0
DPH[7:0]
Function
Data Pointer High.
The DPH register is the high byte of the 16-bit DPTR.
Rev. 1.0
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C8051T630/1/2/3/4/5
SFR Definition 12.3. SP: Stack Pointer
Bit
7
6
5
4
Name
SP[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x81
Bit
Name
7:0
SP[7:0]
3
2
1
0
0
1
1
1
Function
Stack Pointer.
The Stack Pointer holds the location of the top of the stack. The stack pointer is incremented before every PUSH operation. The SP register defaults to 0x07 after reset.
SFR Definition 12.4. ACC: Accumulator
Bit
7
6
5
4
Name
ACC[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xE0; Bit-Addressable
Bit
Name
7:0
ACC[7:0]
3
2
1
0
0
0
0
0
Function
Accumulator.
This register is the accumulator for arithmetic operations.
SFR Definition 12.5. B: B Register
Bit
7
6
5
4
Name
B[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xF0; Bit-Addressable
Bit
Name
7:0
B[7:0]
3
2
1
0
0
0
0
0
Function
B Register.
This register serves as a second accumulator for certain arithmetic operations.
70
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SFR Definition 12.6. PSW: Program Status Word
Bit
7
6
5
Name
CY
AC
F0
Type
R/W
R/W
R/W
Reset
0
0
0
4
3
2
1
0
RS[1:0]
OV
F1
PARITY
R/W
R/W
R/W
R
0
0
0
0
SFR Address = 0xD0; Bit-Addressable
Bit
Name
7
CY
0
Function
Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry (addition) or a borrow (subtraction). It is cleared to logic 0 by all other arithmetic operations.
6
AC
Auxiliary Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry into (addition) or a
borrow from (subtraction) the high order nibble. It is cleared to logic 0 by all other arithmetic operations.
5
F0
User Flag 0.
This is a bit-addressable, general purpose flag for use under software control.
4:3
RS[1:0]
Register Bank Select.
These bits select which register bank is used during register accesses.
00: Bank 0, Addresses 0x00-0x07
01: Bank 1, Addresses 0x08-0x0F
10: Bank 2, Addresses 0x10-0x17
11: Bank 3, Addresses 0x18-0x1F
2
OV
Overflow Flag.
This bit is set to 1 under the following circumstances:
An
ADD, ADDC, or SUBB instruction causes a sign-change overflow.
MUL instruction results in an overflow (result is greater than 255).
A DIV instruction causes a divide-by-zero condition.
A
The OV bit is cleared to 0 by the ADD, ADDC, SUBB, MUL, and DIV instructions in all
other cases.
1
F1
User Flag 1.
This is a bit-addressable, general purpose flag for use under software control.
0
PARITY
Parity Flag.
This bit is set to logic 1 if the sum of the eight bits in the accumulator is odd and cleared
if the sum is even.
Rev. 1.0
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13. Memory Organization
The memory organization of the CIP-51 System Controller is similar to that of a standard 8051. There are
two separate memory spaces: program memory and data memory. Program and data memory share the
same address space but are accessed via different instruction types. The memory organization of the
C8051T630/1/2/3/4/5 device family is shown in Figure 13.1
C8051T630/1
CODE MEMORY
DATA MEMORY (RAM)
INTERNAL DATA ADDRESS SPACE
0xFF
0x1E00
0x1DFF
8k Bytes EPROM
0x0000
C8051T632/3
CODE MEMORY
0x1000
Upper 128 RAM
(Indirect Addressing
Only)
RESERVED
0x80
0x7F
(Direct and Indirect
Addressing)
0x30
0x2F
0x20
0x1F
0x00
Bit Addressable
RESERVED
EXTERNAL DATA ADDRESS SPACE
4k Bytes EPROM
0xFFFF
0x0000
Same 512 bytes as from
0x0000 to 0x01FF, wrapped
on 512-byte boundaries
C8051T634/5
CODE MEMORY
RESERVED
0x07FF
0x0200
0x01FF
2k Bytes EPROM
0x0000
XRAM - 512 Bytes
(accessable using MOVX
instruction)
0x0000
Figure 13.1. Memory Map
72
Lower 128 RAM
(Direct and Indirect
Addressing)
General Purpose
Registers
0x0FFF
0x0800
Special Function
Register's
(Direct Addressing Only)
Rev. 1.0
C8051T630/1/2/3/4/5
13.1. Program Memory
The CIP-51 core has a 64 kB program memory space. The C8051T630/1 implements 8192 bytes of this
program memory space as in-system, Byte-Programmable EPROM, organized in a contiguous block from
addresses 0x0000 to 0x1FFF. Note that 512 bytes (0x1E00 – 0x1FFF) of this memory are reserved for factory use and are not available for user program storage. The C8051T632/3 implements 4096 bytes of
EPROM program memory space; the C8051T634/5 implements 2048 bytes of EPROM program memory
space. C2 Register Definition 13.2 shows the program memory maps for C8051T630/1/2/3/4/5 devices.
C8051T630/1
C8051T632/3
Security Byte
0x1FFF
Reserved
0x1FFE
0x1E00
0x1DFF
Security Byte
C8051T634/5
0x1FFF
Security Byte
0x1FFE
0x1FFF
0x1FFE
Reserved
Reserved
0x1000
0x0FFF
7680 Bytes
EPROM Memory
4096 Bytes
EPROM Memory
0x0800
0x07FF
2048 Bytes
EPROM Memory
0x0000
0x0000
0x0000
Figure 13.2. Program Memory Map
Program memory is read-only from within firmware. Individual program memory bytes can be read using
the MOVC instruction. This facilitates the use of EPROM space for constant storage.
13.2. Data Memory
The C8051T630/1/2/3/4/5 device family includes 768 bytes of RAM data memory. 256 bytes of this memory is mapped into the internal RAM space of the 8051. 512 bytes of this memory is on-chip “external”
memory. The data memory map is shown in Figure 13.1 for reference.
13.2.1. Internal RAM
There are 256 bytes of internal RAM mapped into the data memory space from 0x00 through 0xFF. The
lower 128 bytes of data memory are used for general purpose registers and scratch pad memory. Either
direct or indirect addressing may be used to access the lower 128 bytes of data memory. Locations 0x00
through 0x1F are addressable as four banks of general purpose registers, each bank consisting of eight
byte-wide registers. The next 16 bytes, locations 0x20 through 0x2F, may either be addressed as bytes or
as 128 bit locations accessible with the direct addressing mode.
The upper 128 bytes of data memory are accessible only by indirect addressing. This region occupies the
same address space as the Special Function Registers (SFR) but is physically separate from the SFR
space. The addressing mode used by an instruction when accessing locations above 0x7F determines
whether the CPU accesses the upper 128 bytes of data memory space or the SFRs. Instructions that use
direct addressing will access the SFR space. Instructions using indirect addressing above 0x7F access the
upper 128 bytes of data memory. Figure 13.1 illustrates the data memory organization of the
C8051T630/1/2/3/4/5.
Rev. 1.0
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13.2.1.1. General Purpose Registers
The lower 32 bytes of data memory, locations 0x00 through 0x1F, may be addressed as four banks of general-purpose registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only
one of these banks may be enabled at a time. Two bits in the program status word, RS0 (PSW.3) and RS1
(PSW.4), select the active register bank (see description of the PSW in SFR Definition 12.6). This allows
fast context switching when entering subroutines and interrupt service routines. Indirect addressing modes
use registers R0 and R1 as index registers.
13.2.1.2. Bit Addressable Locations
In addition to direct access to data memory organized as bytes, the sixteen data memory locations at 0x20
through 0x2F are also accessible as 128 individually addressable bits. Each bit has a bit address from
0x00 to 0x7F. Bit 0 of the byte at 0x20 has bit address 0x00 while bit7 of the byte at 0x20 has bit address
0x07. Bit 7 of the byte at 0x2F has bit address 0x7F. A bit access is distinguished from a full byte access by
the type of instruction used (bit source or destination operands as opposed to a byte source or destination).
The MCS-51™ assembly language allows an alternate notation for bit addressing of the form XX.B where
XX is the byte address and B is the bit position within the byte. For example, the instruction:
MOV
C, 22.3h
moves the Boolean value at 0x13 (bit 3 of the byte at location 0x22) into the Carry flag.
13.2.1.3. Stack
A programmer's stack can be located anywhere in the 256-byte data memory. The stack area is designated using the Stack Pointer (SP) SFR. The SP will point to the last location used. The next value pushed
on the stack is placed at SP+1 and then SP is incremented. A reset initializes the stack pointer to location
0x07. Therefore, the first value pushed on the stack is placed at location 0x08, which is also the first register (R0) of register bank 1. Thus, if more than one register bank is to be used, the SP should be initialized
to a location in the data memory not being used for data storage. The stack depth can extend up to
256 bytes.
13.2.2. External RAM
There are 512 bytes of on-chip RAM mapped into the external data memory space. All of these address
locations may be accessed using the external move instruction (MOVX) and the data pointer (DPTR), or
using MOVX indirect addressing mode. If the MOVX instruction is used with an 8-bit address operand
(such as @R1), then the high byte of the 16-bit address is provided by the External Memory Interface Control Register (EMI0CN as shown in SFR Definition 13.1).
For a 16-bit MOVX operation (@DPTR), the upper 7 bits of the 16-bit external data memory address word
are "don't cares". As a result, the 512-byte RAM is mapped modulo style over the entire 64 k external data
memory address range. For example, the XRAM byte at address 0x0000 is shadowed at addresses
0x0200, 0x0400, 0x0600, 0x0800, etc. This is a useful feature when performing a linear memory fill, as the
address pointer doesn't have to be reset when reaching the RAM block boundary.
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Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 13.1. EMI0CN: External Memory Interface Control
Bit
7
6
5
4
3
2
1
0
PGSEL
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xAA
Bit
Name
7:1
0
Unused
PGSEL
Function
Unused. Read = 0000000b; Write = Don’t Care
XRAM Page Select.
The EMI0CN register provides the high byte of the 16-bit external data memory
address when using an 8-bit MOVX command, effectively selecting a 256-byte page
of RAM. Since the upper (unused) bits of the register are always zero, the PGSEL
determines which page of XRAM is accessed.
For Example: If EMI0CN = 0x01, addresses 0x0100 through 0x01FF will be
accessed.
Rev. 1.0
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C8051T630/1/2/3/4/5
14. Special Function Registers
The direct-access data memory locations from 0x80 to 0xFF constitute the special function registers
(SFRs). The SFRs provide control and data exchange with the C8051T630/1/2/3/4/5's resources and
peripherals. The CIP-51 controller core duplicates the SFRs found in a typical 8051 implementation as well
as implementing additional SFRs used to configure and access the sub-systems unique to the
C8051T630/1/2/3/4/5. This allows the addition of new functionality while retaining compatibility with the
MCS-51™ instruction set. Table 14.1 lists the SFRs implemented in the C8051T630/1/2/3/4/5 device family.
The SFR registers are accessed anytime the direct addressing mode is used to access memory locations
from 0x80 to 0xFF. SFRs with addresses ending in 0x0 or 0x8 (e.g. P0, TCON, SCON0, IE, etc.) are bitaddressable as well as byte-addressable. All other SFRs are byte-addressable only. Unoccupied
addresses in the SFR space are reserved for future use. Accessing these areas will have an indeterminate
effect and should be avoided. Refer to the corresponding pages of the data sheet, as indicated in
Table 14.2, for a detailed description of each register.
Table 14.1. Special Function Register (SFR) Memory Map
F8
F0
E8
E0
D8
D0
C8
C0
B8
B0
A8
A0
98
90
88
80
76
SPI0CN
PCA0L
PCA0H PCA0CPL0 PCA0CPH0 P0MAT
P0MASK
VDM0CN
B
P0MDIN
P1MDIN
EIP1
PCA0PWM
ADC0CN PCA0CPL1 PCA0CPH1 PCA0CPL2 PCA0CPH2 P1MAT
P1MASK
RSTSRC
ACC
XBR0
XBR1
OSCLCN
IT01CF
EIE1
SMB0ADM
PCA0CN PCA0MD PCA0CPM0 PCA0CPM1 PCA0CPM2
PSW
REF0CN
P0SKIP
P1SKIP
SMB0ADR
TMR2CN
TMR2RLL TMR2RLH
TMR2L
TMR2H
SMB0CN SMB0CF SMB0DAT ADC0GTL ADC0GTH ADC0LTL ADC0LTH
REG0CN
IP
IDA0CN
AMX0P
ADC0CF
ADC0L
ADC0H
OSCXCN OSCICN
OSCICL
IE
CLKSEL
EMI0CN
P2
SPI0CFG SPI0CKR SPI0DAT P0MDOUT P1MDOUT P2MDOUT
SCON0
SBUF0
CPT0CN
CPT0MD
CPT0MX
P1
TMR3CN TMR3RLL TMR3RLH
TMR3L
TMR3H
IDA0L
IDA0H
TCON
TMOD
TL0
TL1
TH0
TH1
CKCON
P0
SP
DPL
DPH
TOFFL
TOFFH
PCON
0(8)
1(9)
2(A)
3(B)
4(C)
5(D)
6(E)
7(F)
(bit addressable)
Rev. 1.0
C8051T630/1/2/3/4/5
Table 14.2. Special Function Registers
SFRs are listed in alphabetical order. All undefined SFR locations are reserved
Register
Address
Description
Page
ACC
0xE0
Accumulator
70
ADC0CF
0xBC
ADC0 Configuration
37
ADC0CN
0xE8
ADC0 Control
39
ADC0GTH
0xC4
ADC0 Greater-Than Compare High
40
ADC0GTL
0xC3
ADC0 Greater-Than Compare Low
40
ADC0H
0xBE
ADC0 High
38
ADC0L
0xBD
ADC0 Low
38
ADC0LTH
0xC6
ADC0 Less-Than Compare Word High
41
ADC0LTL
0xC5
ADC0 Less-Than Compare Word Low
41
AMX0P
0xBB
AMUX0 Positive Channel Select
44
B
0xF0
B Register
70
CKCON
0x8E
Clock Control
170
CLKSEL
0xA9
Clock Select
102
CPT0CN
0x9B
Comparator0 Control
59
CPT0MD
0x9D
Comparator0 Mode Selection
60
CPT0MX
0x9F
Comparator0 MUX Selection
62
DPH
0x83
Data Pointer High
69
DPL
0x82
Data Pointer Low
69
EIE1
0xE6
Extended Interrupt Enable 1
85
EIP1
0xF6
Extended Interrupt Priority 1
86
EMI0CN
0xAA
External Memory Interface Control
75
IDA0CN
0xB9
Current Mode DAC0 Control
50
IDA0H
0x97
Current Mode DAC0 High
51
IDA0L
0x96
Current Mode DAC0 Low
51
IE
0xA8
Interrupt Enable
83
IP
0xB8
Interrupt Priority
84
IT01CF
0xE4
INT0/INT1 Configuration
88
OSCICL
0xB3
Internal Oscillator Calibration
103
OSCICN
0xB2
Internal Oscillator Control
104
OSCLCN
0xE3
Low-Frequency Oscillator Control
105
OSCXCN
0xB1
External Oscillator Control
107
P0
0x80
Port 0 Latch
121
P0MASK
0xFE
Port 0 Mask Configuration
119
Rev. 1.0
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C8051T630/1/2/3/4/5
Table 14.2. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved
Register
Address
Description
Page
P0MAT
0xFD
Port 0 Match Configuration
119
P0MDIN
0xF1
Port 0 Input Mode Configuration
122
P0MDOUT
0xA4
Port 0 Output Mode Configuration
122
P0SKIP
0xD4
Port 0 Skip
123
P1
0x90
Port 1 Latch
123
P1MASK
0xEE
Port 1Mask Configuration
120
P1MAT
0xED
Port 1 Match Configuration
120
P1MDIN
0xF2
Port 1 Input Mode Configuration
124
P1MDOUT
0xA5
Port 1 Output Mode Configuration
124
P1SKIP
0xD5
Port 1 Skip
125
P2
0xA0
Port 2 Latch
125
P2MDOUT
0xA6
Port 2 Output Mode Configuration
126
PCA0CN
0xD8
PCA Control
204
PCA0CPH0
0xFC
PCA Capture 0 High
209
PCA0CPH1
0xEA
PCA Capture 1 High
209
PCA0CPH2
0xEC
PCA Capture 2 High
209
PCA0CPL0
0xFB
PCA Capture 0 Low
209
PCA0CPL1
0xE9
PCA Capture 1 Low
209
PCA0CPL2
0xEB
PCA Capture 2 Low
209
PCA0CPM0
0xDA
PCA Module 0 Mode Register
207
PCA0CPM1
0xDB
PCA Module 1 Mode Register
207
PCA0CPM2
0xDC
PCA Module 2 Mode Register
207
PCA0H
0xFA
PCA Counter High
208
PCA0L
0xF9
PCA Counter Low
208
PCA0MD
0xD9
PCA Mode
205
PCA0PWM
0xF7
PCA PWM Configuration
206
PCON
0x87
Power Control
94
PSW
0xD0
Program Status Word
71
REF0CN
0xD1
Voltage Reference Control
54
REG0CN
0xC7
Voltage Regulator Control
56
RSTSRC
0xEF
Reset Source Configuration/Status
100
SBUF0
0x99
UART0 Data Buffer
154
SCON0
0x98
UART0 Control
153
SMB0ADM
0xE7
SMBus Slave Address Mask
138
78
Rev. 1.0
C8051T630/1/2/3/4/5
Table 14.2. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved
Register
Address
Description
Page
SMB0ADR
0xD7
SMBus Slave Address
137
SMB0CF
0xC1
SMBus Configuration
133
SMB0CN
0xC0
SMBus Control
135
SMB0DAT
0xC2
SMBus Data
139
SP
0x81
Stack Pointer
70
SPI0CFG
0xA1
SPI Configuration
163
SPI0CKR
0xA2
SPI Clock Rate Control
165
SPI0CN
0xF8
SPI Control
164
SPI0DAT
0xA3
SPI Data
165
TCON
0x88
Timer/Counter Control
175
TH0
0x8C
Timer/Counter 0 High
178
TH1
0x8D
Timer/Counter 1 High
178
TL0
0x8A
Timer/Counter 0 Low
177
TL1
0x8B
Timer/Counter 1 Low
177
TMOD
0x89
Timer/Counter Mode
176
TMR2CN
0xC8
Timer/Counter 2 Control
182
TMR2H
0xCD
Timer/Counter 2 High
184
TMR2L
0xCC
Timer/Counter 2 Low
183
TMR2RLH
0xCB
Timer/Counter 2 Reload High
183
TMR2RLL
0xCA
Timer/Counter 2 Reload Low
183
TMR3CN
0x91
Timer/Counter 3Control
188
TMR3H
0x95
Timer/Counter 3 High
190
TMR3L
0x94
Timer/Counter 3Low
189
TMR3RLH
0x93
Timer/Counter 3 Reload High
189
TMR3RLL
0x92
Timer/Counter 3 Reload Low
189
TOFFH
0x86
Temperature Sensor Offset Measurement High
47
TOFFL
0x85
Temperature Sensor Offset Measurement Low
47
VDM0CN
0xFF
VDD Monitor Control
98
XBR0
0xE1
Port I/O Crossbar Control 0
117
XBR1
0xE2
Port I/O Crossbar Control 1
118
Rev. 1.0
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C8051T630/1/2/3/4/5
15. Interrupts
The C8051T630/1/2/3/4/5 includes an extended interrupt system supporting a total of 14 interrupt sources
with two priority levels. The allocation of interrupt sources between on-chip peripherals and external input
pins varies according to the specific version of the device. Each interrupt source has one or more associated interrupt-pending flag(s) located in an SFR. When a peripheral or external source meets a valid interrupt condition, the associated interrupt-pending flag is set to logic 1.
If interrupts are enabled for the source, an interrupt request is generated when the interrupt-pending flag is
set. As soon as execution of the current instruction is complete, the CPU generates an LCALL to a predetermined address to begin execution of an interrupt service routine (ISR). Each ISR must end with an RETI
instruction, which returns program execution to the next instruction that would have been executed if the
interrupt request had not occurred. If interrupts are not enabled, the interrupt-pending flag is ignored by the
hardware and program execution continues as normal. (The interrupt-pending flag is set to logic 1 regardless of the interrupt's enable/disable state.)
Each interrupt source can be individually enabled or disabled through the use of an associated interrupt
enable bit in an SFR (IE–EIE1). However, interrupts must first be globally enabled by setting the EA bit
(IE.7) to logic 1 before the individual interrupt enables are recognized. Setting the EA bit to logic 0 disables
all interrupt sources regardless of the individual interrupt-enable settings.
Note: Any instruction that clears a bit to disable an interrupt should be immediately followed by an instruction that has two or more opcode bytes. Using EA (global interrupt enable) as an example:
// in 'C':
EA = 0; // clear EA bit.
EA = 0; // this is a dummy instruction with two-byte opcode.
; in assembly:
CLR EA ; clear EA bit.
CLR EA ; this is a dummy instruction with two-byte opcode.
For example, if an interrupt is posted during the execution phase of a "CLR EA" opcode (or any instruction
which clears a bit to disable an interrupt source), and the instruction is followed by a single-cycle instruction, the interrupt may be taken. However, a read of the enable bit will return a '0' inside the interrupt service routine. When the bit-clearing opcode is followed by a multi-cycle instruction, the interrupt will not be
taken.
Some interrupt-pending flags are automatically cleared by the hardware when the CPU vectors to the ISR.
However, most are not cleared by the hardware and must be cleared by software before returning from the
ISR. If an interrupt-pending flag remains set after the CPU completes the return-from-interrupt (RETI)
instruction, a new interrupt request will be generated immediately and the CPU will re-enter the ISR after
the completion of the next instruction.
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15.1. MCU Interrupt Sources and Vectors
The C8051T630/1/2/3/4/5 MCUs support 14 interrupt sources. Software can simulate an interrupt by setting any interrupt-pending flag to logic 1. If interrupts are enabled for the flag, an interrupt request will be
generated and the CPU will vector to the ISR address associated with the interrupt-pending flag. MCU
interrupt sources, associated vector addresses, priority order and control bits are summarized in
Table 15.1. Refer to the datasheet section associated with a particular on-chip peripheral for information
regarding valid interrupt conditions for the peripheral and the behavior of its interrupt-pending flag(s).
15.1.1. Interrupt Priorities
Each interrupt source can be individually programmed to one of two priority levels: low or high. A low priority interrupt service routine can be preempted by a high priority interrupt. A high priority interrupt cannot be
preempted. Each interrupt has an associated interrupt priority bit in an SFR (IP or EIP1) used to configure
its priority level. Low priority is the default. If two interrupts are recognized simultaneously, the interrupt with
the higher priority is serviced first. If both interrupts have the same priority level, a fixed priority order is
used to arbitrate, given in Table 15.1.
15.1.2. Interrupt Latency
Interrupt response time depends on the state of the CPU when the interrupt occurs. Pending interrupts are
sampled and priority decoded each system clock cycle. Therefore, the fastest possible response time is 5
system clock cycles: 1 clock cycle to detect the interrupt and 4 clock cycles to complete the LCALL to the
ISR. If an interrupt is pending when a RETI is executed, a single instruction is executed before an LCALL
is made to service the pending interrupt. Therefore, the maximum response time for an interrupt (when no
other interrupt is currently being serviced or the new interrupt is of greater priority) occurs when the CPU is
performing an RETI instruction followed by a DIV as the next instruction. In this case, the response time is
18 system clock cycles: 1 clock cycle to detect the interrupt, 5 clock cycles to execute the RETI, 8 clock
cycles to complete the DIV instruction and 4 clock cycles to execute the LCALL to the ISR. If the CPU is
executing an ISR for an interrupt with equal or higher priority, the new interrupt will not be serviced until the
current ISR completes, including the RETI and following instruction.
Rev. 1.0
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C8051T630/1/2/3/4/5
Interrupt
Vector
Priority
Order
Pending Flag
Reset
0x0000
Top
None
External Interrupt 0
(INT0)
Timer 0 Overflow
External Interrupt 1
(INT1)
Timer 1 Overflow
UART0
0x0003
0
IE0 (TCON.1)
N/A N/A Always
Always
Enabled
Highest
Y
Y
EX0 (IE.0) PX0 (IP.0)
0x000B
0x0013
1
2
TF0 (TCON.5)
IE1 (TCON.3)
Y
Y
Y
Y
ET0 (IE.1) PT0 (IP.1)
EX1 (IE.2) PX1 (IP.2)
0x001B
0x0023
3
4
Y
Y
Y
N
ET1 (IE.3) PT1 (IP.3)
ES0 (IE.4) PS0 (IP.4)
Timer 2 Overflow
0x002B
5
Y
N
ET2 (IE.5) PT2 (IP.5)
SPI0
0x0033
6
Y
N
ESPI0
(IE.6)
SMB0
0x003B
7
TF1 (TCON.7)
RI0 (SCON0.0)
TI0 (SCON0.1)
TF2H (TMR2CN.7)
TF2L (TMR2CN.6)
SPIF (SPI0CN.7)
WCOL (SPI0CN.6)
MODF (SPI0CN.5)
RXOVRN (SPI0CN.4)
SI (SMB0CN.0)
Y
N
Port Match
0x0043
8
None
ADC0 Window Compare
ADC0 Conversion
Complete
Programmable Counter Array
0x004B
9
0x0053
10
AD0WINT
(ADC0CN.3)
AD0INT (ADC0CN.5)
0x005B
11
Comparator0
0x0063
12
RESERVED
Timer 3 Overflow
0x006B
0x0073
13
14
Cleared by HW?
Interrupt Source
Bit addressable?
Table 15.1. Interrupt Summary
Enable
Flag
ESMB0
(EIE1.0)
N/A N/A EMAT
(EIE1.1)
Y
N
EWADC0
(EIE1.2)
Y
N
EADC0
(EIE1.3)
Y
N
EPCA0
(EIE1.4)
CF (PCA0CN.7)
CCFn (PCA0CN.n)
COVF (PCA0PWM.6)
CP0FIF (CPT0CN.4) N
N
CP0RIF (CPT0CN.5)
N/A
N/A N/A
TF3H (TMR3CN.7)
N
N
TF3L (TMR3CN.6)
ECP0
(EIE1.5)
N/A
ET3
(EIE1.7)
Priority
Control
PSPI0
(IP.6)
PSMB0
(EIP1.0)
PMAT
(EIP1.1)
PWADC0
(EIP1.2)
PADC0
(EIP1.3)
PPCA0
(EIP1.4)
PCP0
(EIP1.5)
N/A
PT3
(EIP1.7)
15.2. Interrupt Register Descriptions
The SFRs used to enable the interrupt sources and set their priority level are described in this section.
Refer to the data sheet section associated with a particular on-chip peripheral for information regarding
valid interrupt conditions for the peripheral and the behavior of its interrupt-pending flag(s).
82
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SFR Definition 15.1. IE: Interrupt Enable
Bit
7
6
5
4
3
2
1
0
Name
EA
ESPI0
ET2
ES0
ET1
EX1
ET0
EX0
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xA8; Bit-Addressable
Bit
Name
Function
7
EA
6
ESPI0
5
ET2
Enable Timer 2 Interrupt.
This bit sets the masking of the Timer 2 interrupt.
0: Disable Timer 2 interrupt.
1: Enable interrupt requests generated by the TF2L or TF2H flags.
4
ES0
Enable UART0 Interrupt.
This bit sets the masking of the UART0 interrupt.
0: Disable UART0 interrupt.
1: Enable UART0 interrupt.
3
ET1
Enable Timer 1 Interrupt.
This bit sets the masking of the Timer 1 interrupt.
0: Disable all Timer 1 interrupt.
1: Enable interrupt requests generated by the TF1 flag.
2
EX1
Enable External Interrupt 1.
This bit sets the masking of External Interrupt 1.
0: Disable external interrupt 1.
1: Enable interrupt requests generated by the /INT1 input.
1
ET0
Enable Timer 0 Interrupt.
This bit sets the masking of the Timer 0 interrupt.
0: Disable all Timer 0 interrupt.
1: Enable interrupt requests generated by the TF0 flag.
0
EX0
Enable External Interrupt 0.
This bit sets the masking of External Interrupt 0.
0: Disable external interrupt 0.
1: Enable interrupt requests generated by the INT0 input.
Enable All Interrupts.
Globally enables/disables all interrupts. It overrides individual interrupt mask settings.
0: Disable all interrupt sources.
1: Enable each interrupt according to its individual mask setting.
Enable Serial Peripheral Interface (SPI0) Interrupt.
This bit sets the masking of the SPI0 interrupts.
0: Disable all SPI0 interrupts.
1: Enable interrupt requests generated by SPI0.
Rev. 1.0
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C8051T630/1/2/3/4/5
SFR Definition 15.2. IP: Interrupt Priority
Bit
7
Name
6
5
4
3
2
1
0
PSPI0
PT2
PS0
PT1
PX1
PT0
PX0
Type
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
1
0
0
0
0
0
0
0
SFR Address = 0xB8; Bit-Addressable
Bit
Name
84
Function
7
6
Unused
PSPI0
Unused. Read = 1, Write = Don't Care.
5
PT2
Timer 2 Interrupt Priority Control.
This bit sets the priority of the Timer 2 interrupt.
0: Timer 2 interrupt set to low priority level.
1: Timer 2 interrupt set to high priority level.
4
PS0
UART0 Interrupt Priority Control.
This bit sets the priority of the UART0 interrupt.
0: UART0 interrupt set to low priority level.
1: UART0 interrupt set to high priority level.
3
PT1
Timer 1 Interrupt Priority Control.
This bit sets the priority of the Timer 1 interrupt.
0: Timer 1 interrupt set to low priority level.
1: Timer 1 interrupt set to high priority level.
2
PX1
External Interrupt 1 Priority Control.
This bit sets the priority of the External Interrupt 1 interrupt.
0: External Interrupt 1 set to low priority level.
1: External Interrupt 1 set to high priority level.
1
PT0
Timer 0 Interrupt Priority Control.
This bit sets the priority of the Timer 0 interrupt.
0: Timer 0 interrupt set to low priority level.
1: Timer 0 interrupt set to high priority level.
0
PX0
External Interrupt 0 Priority Control.
This bit sets the priority of the External Interrupt 0 interrupt.
0: External Interrupt 0 set to low priority level.
1: External Interrupt 0 set to high priority level.
Serial Peripheral Interface (SPI0) Interrupt Priority Control.
This bit sets the priority of the SPI0 interrupt.
0: SPI0 interrupt set to low priority level.
1: SPI0 interrupt set to high priority level.
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 15.3. EIE1: Extended Interrupt Enable 1
Bit
7
6
5
4
3
2
1
0
Name
ET3
Reserved
ECP0
EPCA0
EADC0
EWADC0
EMAT
ESMB0
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xE6
Bit
Name
7
6
5
ET3
Function
Enable Timer 3 Interrupt.
This bit sets the masking of the Timer 3 interrupt.
0: Disable Timer 3 interrupts.
1: Enable interrupt requests generated by the TF3L or TF3H flags.
Reserved Reserved. Must Write 0.
ECP0
Enable Comparator0 (CP0) Interrupt.
This bit sets the masking of the CP0 interrupt.
0: Disable CP0 interrupts.
1: Enable interrupt requests generated by the CP0RIF or CP0FIF flags.
4
EPCA0
Enable Programmable Counter Array (PCA0) Interrupt.
This bit sets the masking of the PCA0 interrupts.
0: Disable all PCA0 interrupts.
1: Enable interrupt requests generated by PCA0.
3
EADC0
Enable ADC0 Conversion Complete Interrupt.
This bit sets the masking of the ADC0 Conversion Complete interrupt.
0: Disable ADC0 Conversion Complete interrupt.
1: Enable interrupt requests generated by the AD0INT flag.
2
EWADC0 Enable Window Comparison ADC0 Interrupt.
This bit sets the masking of ADC0 Window Comparison interrupt.
0: Disable ADC0 Window Comparison interrupt.
1: Enable interrupt requests generated by ADC0 Window Compare flag (AD0WINT).
1
EMAT
0
ESMB0
Enable Port Match Interrupts.
This bit sets the masking of the Port Match Event interrupt.
0: Disable all Port Match interrupts.
1: Enable interrupt requests generated by a Port Match.
Enable SMBus (SMB0) Interrupt.
This bit sets the masking of the SMB0 interrupt.
0: Disable all SMB0 interrupts.
1: Enable interrupt requests generated by SMB0.
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SFR Definition 15.4. EIP1: Extended Interrupt Priority 1
Bit
7
6
5
4
3
2
1
0
Name
PT3
Reserved
PCP0
PPCA0
PADC0
PWADC0
PMAT
PSMB0
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xF6
Bit
Name
7
6
5
Timer 3 Interrupt Priority Control.
This bit sets the priority of the Timer 3 interrupt.
0: Timer 3 interrupts set to low priority level.
1: Timer 3 interrupts set to high priority level.
Reserved Reserved. Must Write 0.
PCP0
Comparator0 (CP0) Interrupt Priority Control.
This bit sets the priority of the CP0 interrupt.
0: CP0 interrupt set to low priority level.
1: CP0 interrupt set to high priority level.
4
PPCA0
Programmable Counter Array (PCA0) Interrupt Priority Control.
This bit sets the priority of the PCA0 interrupt.
0: PCA0 interrupt set to low priority level.
1: PCA0 interrupt set to high priority level.
3
PADC0
ADC0 Conversion Complete Interrupt Priority Control.
This bit sets the priority of the ADC0 Conversion Complete interrupt.
0: ADC0 Conversion Complete interrupt set to low priority level.
1: ADC0 Conversion Complete interrupt set to high priority level.
2
86
PT3
Function
PWADC0 ADC0 Window Comparator Interrupt Priority Control.
This bit sets the priority of the ADC0 Window interrupt.
0: ADC0 Window interrupt set to low priority level.
1: ADC0 Window interrupt set to high priority level.
1
PMAT
0
PSMB0
Port Match Interrupt Priority Control.
This bit sets the priority of the Port Match Event interrupt.
0: Port Match interrupt set to low priority level.
1: Port Match interrupt set to high priority level.
SMBus (SMB0) Interrupt Priority Control.
This bit sets the priority of the SMB0 interrupt.
0: SMB0 interrupt set to low priority level.
1: SMB0 interrupt set to high priority level.
Rev. 1.0
C8051T630/1/2/3/4/5
15.3. INT0 and INT1 External Interrupts
The INT0 and INT1 external interrupt sources are configurable as active high or low, edge or level sensitive. The IN0PL (INT0 Polarity) and IN1PL (INT1 Polarity) bits in the IT01CF register select active high or
active low; the IT0 and IT1 bits in TCON (Section “24.1. Timer 0 and Timer 1” on page 171) select level or
edge sensitive. The table below lists the possible configurations.
IT0
IN0PL
/INT0 Interrupt
IT1
IN1PL
/INT1 Interrupt
1
1
0
0
0
1
0
1
Active low, edge sensitive
Active high, edge sensitive
Active low, level sensitive
Active high, level sensitive
1
1
0
0
0
1
0
1
Active low, edge sensitive
Active high, edge sensitive
Active low, level sensitive
Active high, level sensitive
INT0 and INT1 are assigned to Port pins as defined in the IT01CF register (see SFR Definition 15.5). Note
that INT0 and INT0 Port pin assignments are independent of any Crossbar assignments. INT0 and INT1
will monitor their assigned Port pins without disturbing the peripheral that was assigned the Port pin via the
Crossbar. To assign a Port pin only to INT0 and/or INT1, configure the Crossbar to skip the selected pin(s).
This is accomplished by setting the associated bit in register XBR0 (see Section “20.3. Priority Crossbar
Decoder” on page 114 for complete details on configuring the Crossbar).
IE0 (TCON.1) and IE1 (TCON.3) serve as the interrupt-pending flags for the INT0 and INT1 external interrupts, respectively. If an INT0 or INT1 external interrupt is configured as edge-sensitive, the corresponding
interrupt-pending flag is automatically cleared by the hardware when the CPU vectors to the ISR. When
configured as level sensitive, the interrupt-pending flag remains logic 1 while the input is active as defined
by the corresponding polarity bit (IN0PL or IN1PL); the flag remains logic 0 while the input is inactive. The
external interrupt source must hold the input active until the interrupt request is recognized. It must then
deactivate the interrupt request before execution of the ISR completes or another interrupt request will be
generated.
Rev. 1.0
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SFR Definition 15.5. IT01CF: INT0/INT1 Configuration
Bit
7
6
Name
IN1PL
IN1SL[2:0]
IN0PL
IN0SL[2:0]
Type
R/W
R/W
R/W
R/W
Reset
0
0
5
0
4
0
3
0
2
0
1
0
0
1
SFR Address = 0xE4
Bit
Name
7
IN1PL
6:4
3
2:0
88
Function
INT1 Polarity.
0: /INT1 input is active low.
1: /INT1 input is active high.
IN1SL[2:0] INT1 Port Pin Selection Bits.
These bits select which Port pin is assigned to /INT1. Note that this pin assignment is
independent of the Crossbar; /INT1 will monitor the assigned Port pin without disturbing the peripheral that has been assigned the Port pin via the Crossbar. The Crossbar
will not assign the Port pin to a peripheral if it is configured to skip the selected pin.
000: Select P0.0
001: Select P0.1
010: Select P0.2
011: Select P0.3
100: Select P0.4
101: Select P0.5
110: Select P0.6
111: Select P0.7
IN0PL
INT0 Polarity.
0: /INT0 input is active low.
1: /INT0 input is active high.
IN0SL[2:0] INT0 Port Pin Selection Bits.
These bits select which Port pin is assigned to /INT0. Note that this pin assignment is
independent of the Crossbar; /INT0 will monitor the assigned Port pin without disturbing the peripheral that has been assigned the Port pin via the Crossbar. The Crossbar
will not assign the Port pin to a peripheral if it is configured to skip the selected pin.
000: Select P0.0
001: Select P0.1
010: Select P0.2
011: Select P0.3
100: Select P0.4
101: Select P0.5
110: Select P0.6
111: Select P0.7
Rev. 1.0
C8051T630/1/2/3/4/5
16. EPROM Memory
Electrically programmable read-only memory (EPROM) is included on-chip for program code storage. The
EPROM memory can be programmed via the C2 debug and programming interface when a special programming voltage is applied to the VPP pin. Each location in EPROM memory is programmable only once
(i.e., non-erasable). Table 5.6 on page 26 shows the EPROM specifications.
16.1. Programming and Reading the EPROM Memory
Reading and writing the EPROM memory is accomplished through the C2 programming and debug interface. When creating hardware to program the EPROM, it is necessary to follow the programming steps
listed below. Refer to the “C2 Interface Specification” available at http://www.silabs.com for details on communicating via the C2 interface. Section “26. C2 Interface” on page 210 has information about C2 register
addresses for the C8051T630/1/2/3/4/5.
16.1.1. EPROM Write Procedure
1. Reset the device using the RST pin.
2. Wait at least 20 µs before sending the first C2 command.
3. Place the device in core reset: Write 0x04 to the DEVCTL register.
4. Set the device to program mode (1st step): Write 0x40 to the EPCTL register.
5. Set the device to program mode (2nd step): Write 0x58 to the EPCTL register.
6. Apply the VPP programming Voltage.
7. Write the first EPROM address for programming to EPADDRH and EPADDRL.
8. Write a data byte to EPDAT. EPADDRH:L will increment by 1 after this write.
9. Use a C2 Address Read command to poll for write completion.
10.(Optional) Check the ERROR bit in register EPSTAT and abort the programming operation if necessary.
11. If programming is not finished, return to Step 8 to write the next address in sequence, or return to
Step 7 to program a new address.
12.Remove the VPP programming Voltage
13.Remove program mode (1st step): Write 0x40 to the EPCTL register.
14.Remove program mode (2nd step): Write 0x00 to the EPCTL register.
15.Reset the device: Write 0x02 and then 0x00 to the DEVCTL register.
Important Note: There is a finite amount of time which VPP can be applied without damaging the device,
which is cumulative over the life of the device. Refer to Table 5.1 on page 23 for the VPP timing specification.
Rev. 1.0
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16.1.2. EPROM Read Procedure
1. Reset the device using the /RST pin.
2. Wait at least 20 µs before sending the first C2 command.
3. Place the device in core reset: Write 0x04 to the DEVCTL register.
4. Write 0x00 to the EPCTL register.
5. Write the first EPROM address for reading to EPADDRH and EPADDRL.
6. Read a data byte from EPDAT. EPADDRH:L will increment by 1 after this read.
7. (Optional) Check the ERROR bit in register EPSTAT and abort the memory read operation if necessary.
8. If reading is not finished, return to Step 6 to read the next address in sequence, or return to Step 5 to
select a new address.
9. Remove read mode (1st step): Write 0x40 to the EPCTL register.
10.Remove read mode (2nd step): Write 0x00 to the EPCTL register.
11. Reset the device: Write 0x02 and then 0x00 to the DEVCTL register.
16.2. Security Options
The C8051T630/1/2/3/4/5 devices provide security options to prevent unauthorized viewing of proprietary
program code and constants. A security byte in EPROM address space can be used to lock the program
memory from being read or written across the C2 interface. When read, the RDLOCK and WRLOCK bits in
register EPSTAT will indicate the lock status of the location currently addressed by EPADDR. Table 16.1
shows the security byte decoding. See Section “13. Memory Organization” on page 72 for the security byte
location and EPROM memory map.
Important Note: Once the security byte has been written, there are no means of unlocking the
device. Locking memory from write access should be performed only after all other code has been
successfully programmed to memory.
Table 16.1. Security Byte Decoding
Bits
Description
7–4
Write Lock: Clearing any of these bits to logic 0 prevents all code
memory from being written across the C2 interface.
Read Lock: Clearing any of these bits to logic 0 prevents all code
memory from being read across the C2 interface.
3–0
90
Rev. 1.0
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16.3. Program Memory CRC
A CRC engine is included on-chip which provides a means of verifying EPROM contents once the device
has been programmed. The CRC engine is available for EPROM verification even if the device is fully read
and write locked, allowing for verification of code contents at any time.
The CRC engine is operated through the C2 debug and programming interface, and performs 16-bit CRCs
on individual 256-Byte blocks of program memory, or a 32-bit CRC on the entire memory space. To prevent
hacking and extrapolation of security-locked source code, the CRC engine will only allow CRCs to be performed on contiguous 256-Byte blocks beginning on 256-Byte boundaries (lowest 8-bits of address are
0x00). For example, the CRC engine can perform a CRC for locations 0x0400 through 0x04FF, but it cannot perform a CRC for locations 0x0401 through 0x0500, or on block sizes smaller or larger than
256 bytes.
16.3.1. Performing 32-bit CRCs on Full EPROM Content
A 32-bit CRC on the entire EPROM space is initiated by writing to the CRC1 byte over the C2 interface.
The CRC calculation begins at address 0x0000 and ends at the end of user EPROM space. The EPBusy
bit in register C2ADD will be set during the CRC operation, and cleared once the operation is complete.
The 32-bit results will be available in the CRC3-0 registers. CRC3 is the MSB, and CRC0 is the LSB. The
polynomial used for the 32-bit CRC calculation is 0x04C11DB7.
Note: If a 16-bit CRC has been performed since the last device reset, a device reset should be initiated before
performing a 32-bit CRC operation.
16.3.2. Performing 16-bit CRCs on 256-Byte EPROM Blocks
A 16-bit CRC of individual 256-byte blocks of EPROM can be initiated by writing to the CRC0 byte over the
C2 interface. The value written to CRC0 is the high byte of the beginning address for the CRC. For example, if CRC0 is written to 0x02, the CRC will be performed on the 256-bytes beginning at address 0x0200,
and ending at address 0x2FF. The EPBusy bit in register C2ADD will be set during the CRC operation, and
cleared once the operation is complete. The 16-bit results will be available in the CRC1-0 registers. CRC1
is the MSB, and CRC0 is the LSB. The polynomial for the 16-bit CRC calculation is 0x1021
Rev. 1.0
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C8051T630/1/2/3/4/5
17. Power Management Modes
The C8051T630/1/2/3/4/5 devices have three software programmable power management modes: idle,
stop, and suspend. Idle mode and stop mode are part of the standard 8051 architecture, while suspend
mode is an enhanced power-saving mode implemented by the high-speed oscillator peripheral.
Idle mode halts the CPU while leaving the peripherals and clocks active. In stop mode, the CPU is halted,
all interrupts and timers (except the missing clock detector) are inactive, and the internal oscillator is
stopped (analog peripherals remain in their selected states; the external oscillator is not affected). Suspend mode is similar to stop mode in that the internal oscillator and CPU are halted, but the device can
wake on events such as a port mismatch, comparator low output, or a Timer 3 overflow. Since clocks are
running in idle mode, power consumption is dependent upon the system clock frequency and the number
of peripherals left in active mode before entering Idle. Stop mode and Suspend mode consume the least
power because the majority of the device is shut down with no clocks active. SFR Definition 17.1 describes
the Power Control Register (PCON) used to control the C8051T630/1/2/3/4/5's stop and idle power management modes. Suspend mode is controlled by the SUSPEND bit in the OSCICN register (SFR Definition
19.3).
Although the C8051T630/1/2/3/4/5 has idle, stop, and suspend modes available, more control over the
device power can be achieved by enabling/disabling individual peripherals as needed. Each analog
peripheral can be disabled when not in use and placed in low power mode. Digital peripherals, such as timers or serial buses, draw little power when they are not in use. Turning off oscillators lowers power consumption considerably, at the expense of reduced functionality.
17.1. Idle Mode
Setting the Idle Mode Select bit (PCON.0) causes the hardware to halt the CPU and enter idle mode as
soon as the instruction that sets the bit completes execution. All internal registers and memory maintain
their original data. All analog and digital peripherals can remain active during idle mode.
Idle mode is terminated when an enabled interrupt is asserted or a reset occurs. The assertion of an
enabled interrupt will cause the Idle Mode Selection bit (PCON.0) to be cleared and the CPU to resume
operation. The pending interrupt will be serviced and the next instruction to be executed after the return
from interrupt (RETI) will be the instruction immediately following the one that set the Idle Mode Select bit.
If Idle mode is terminated by an internal or external reset, the CIP-51 performs a normal reset sequence
and begins program execution at address 0x0000.
If the instruction following the write of the IDLE bit is a single-byte instruction and an interrupt occurs during
the execution phase of the instruction that sets the IDLE bit, the CPU may not wake from idle mode when
a future interrupt occurs. Therefore, instructions that set the IDLE bit should be followed by an instruction
that has two or more opcode bytes, for example:
// in ‘C’:
PCON |= 0x01;
PCON = PCON;
// set IDLE bit
// ... followed by a 3-cycle dummy instruction
; in assembly:
ORL PCON, #01h
MOV PCON, PCON
; set IDLE bit
; ... followed by a 3-cycle dummy instruction
If enabled, the watchdog timer (WDT) will eventually cause an internal watchdog reset and thereby terminate the idle mode. This feature protects the system from an unintended permanent shutdown in the event
of an inadvertent write to the PCON register. If this behavior is not desired, the WDT may be disabled by
92
Rev. 1.0
C8051T630/1/2/3/4/5
software prior to entering the idle mode if the WDT was initially configured to allow this operation. This provides the opportunity for additional power savings, allowing the system to remain in the idle mode indefinitely, waiting for an external stimulus to wake up the system. Refer to Section “18.6. PCA Watchdog Timer
Reset” on page 99 for more information on the use and configuration of the WDT.
17.2. Stop Mode
Setting the Stop Mode Select bit (PCON.1) causes the controller core to enter stop mode as soon as the
instruction that sets the bit completes execution. In stop mode the internal oscillator, CPU, and all digital
peripherals are stopped; the state of the external oscillator circuit is not affected. Each analog peripheral
(including the external oscillator circuit) may be shut down individually prior to entering stop mode. Stop
mode can only be terminated by an internal or external reset. On reset, the device performs the normal
reset sequence and begins program execution at address 0x0000.
If enabled, the missing clock detector will cause an internal reset and thereby terminate the stop mode.
The missing clock detector should be disabled if the CPU is to be put to in stop mode for longer than the
MCD timeout.
By default, when in stop mode the internal regulator is still active. However, the regulator can be configured to shut down while in stop mode to save power. To shut down the regulator in stop mode, the
STOPCF bit in register REG0CN should be set to 1 prior to setting the STOP bit (see SFR Definition 10.1).
If the regulator is shut down using the STOPCF bit, only the RST pin or a full power cycle are capable of
resetting the device.
17.3. Suspend Mode
Setting the SUSPEND bit (OSCICN.5) causes the hardware to halt the CPU and the high-frequency internal oscillator, and go into suspend mode as soon as the instruction that sets the bit completes execution.
All internal registers and memory maintain their original data. Most digital peripherals are not active in suspend mode. The exception to this is the Port Match feature and Timer 3, when it is run from an external
oscillator source or the internal low-frequency oscillator.
Suspend mode can be terminated by four types of events, a port match (described in Section “20.5. Port
Match” on page 118), a Timer 3 overflow (described in Section “24.3. Timer 3” on page 185), a comparator
low output (if enabled), or a device reset event. To run Timer 3 in suspend mode, the timer must be configured to clock from either the external clock source or the internal low-frequency oscillator source. When
suspend mode is terminated, the device will continue execution on the instruction following the one that set
the SUSPEND bit. If the wake event (port match or Timer 3 overflow) was configured to generate an interrupt, the interrupt will be serviced upon waking the device. If suspend mode is terminated by an internal or
external reset, the CIP-51 performs a normal reset sequence and begins program execution at address
0x0000.
Rev. 1.0
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SFR Definition 17.1. PCON: Power Control
Bit
7
6
5
4
3
2
1
0
Name
GF[5:0]
STOP
IDLE
Type
R/W
R/W
R/W
0
0
Reset
0
0
0
0
SFR Address = 0x87
Bit
Name
7:2
GF[5:0]
0
0
Function
General Purpose Flags 5–0.
These are general purpose flags for use under software control.
94
1
STOP
Stop Mode Select.
Setting this bit will place the CIP-51 in Stop mode. This bit will always be read as 0.
1: CPU goes into Stop mode (internal oscillator stopped).
0
IDLE
Idle Mode Select.
Setting this bit will place the CIP-51 in Idle mode. This bit will always be read as 0.
1: CPU goes into Idle mode. (Shuts off clock to CPU, but clock to Timers, Interrupts,
Serial Ports, and Analog Peripherals are still active.)
Rev. 1.0
C8051T630/1/2/3/4/5
18. Reset Sources
Reset circuitry allows the controller to be easily placed in a predefined default condition. On entry to this
reset state, the following occur:

CIP-51 halts program execution
Special Function Registers (SFRs) are initialized to their defined reset values
 External Port pins are forced to a known state
 Interrupts and timers are disabled
All SFRs are reset to the predefined values noted in the SFR detailed descriptions. The contents of internal
data memory are unaffected during a reset; any previously stored data is preserved. However, since the
stack pointer SFR is reset, the stack is effectively lost, even though the data on the stack is not altered.

The Port I/O latches are reset to 0xFF (all logic ones) in open-drain mode. Weak pullups are enabled during and after the reset. For VDD Monitor and power-on resets, the RST pin is driven low until the device
exits the reset state.
On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the internal oscillator. The Watchdog Timer is enabled with the system clock divided by 12 as its clock source. Program execution begins at location 0x0000.
VDD
Power On
Reset
Supply
Monitor
Px.x
Px.x
+
-
Comparator 0
'0'
Enable
(wired-OR)
/RST
+
C0RSEF
Missing
Clock
Detector
(oneshot)
EN
Reset
Funnel
PCA
WDT
(Software Reset)
SWRSF
Illegal
EPROM
Operation
Internal
Oscillator
EXTCLK
External
Oscillator
Drive
MCD
Enable
System
Clock
Clock Select
WDT
Enable
EN
Low
Frequency
Oscillator
CIP-51
Microcontroller
Core
System Reset
Extended Interrupt
Handler
Figure 18.1. Reset Sources
Rev. 1.0
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C8051T630/1/2/3/4/5
18.1. Power-On Reset
During power-up, the device is held in a reset state and the RST pin is driven low until VDD settles above
VRST. A delay occurs before the device is released from reset; the delay decreases as the VDD ramp time
increases (VDD ramp time is defined as how fast VDD ramps from 0 V to VRST). Figure 18.2. plots the
power-on and VDD monitor event timing. The maximum VDD ramp time is 1 ms; slower ramp times may
cause the device to be released from reset before VDD reaches the VRST level. For ramp times less than
1 ms, the power-on reset delay (TPORDelay) is typically less than 0.3 ms.
Supply Voltage
On exit from a power-on or VDD monitor reset, the PORSF flag (RSTSRC.1) is set by hardware to logic 1.
When PORSF is set, all of the other reset flags in the RSTSRC Register are indeterminate (PORSF is
cleared by all other resets). Since all resets cause program execution to begin at the same location
(0x0000) software can read the PORSF flag to determine if a power-up was the cause of reset. The content of internal data memory should be assumed to be undefined after a power-on reset. The VDD monitor
is enabled following a power-on reset.
VDD
VD
D
VRST
t
Logic HIGH
/RST
TPORDelay
Logic LOW
VDD
Monitor
Reset
Power-On
Reset
Figure 18.2. Power-On and VDD Monitor Reset Timing
96
Rev. 1.0
C8051T630/1/2/3/4/5
18.2. Power-Fail Reset/VDD Monitor
When a power-down transition or power irregularity causes VDD to drop below VRST, the power supply
monitor will drive the RST pin low and hold the CIP-51 in a reset state (see Figure 18.2). When VDD returns
to a level above VRST, the CIP-51 will be released from the reset state. Note that even though internal data
memory contents are not altered by the power-fail reset, it is impossible to determine if VDD dropped below
the level required for data retention. If the PORSF flag reads 1, the data may no longer be valid. The VDD
monitor is enabled after power-on resets. Its defined state (enabled/disabled) is not altered by any other
reset source. For example, if the VDD monitor is disabled by code and a software reset is performed, the
VDD monitor will still be disabled after the reset.
Important Note: If the VDD monitor is being turned on from a disabled state, it should be enabled before it
is selected as a reset source. Selecting the VDD monitor as a reset source before it is enabled and stabilized may cause a system reset. In some applications, this reset may be undesirable. If this is not desirable
in the application, a delay should be introduced between enabling the monitor and selecting it as a reset
source. The procedure for enabling the VDD monitor and configuring it as a reset source from a disabled
state is shown below:
1. Enable the VDD monitor (VDMEN bit in VDM0CN = 1).
2. If necessary, wait for the VDD monitor to stabilize (see Table 5.4 for the VDD Monitor turn-on time).
3. Select the VDD monitor as a reset source (PORSF bit in RSTSRC = 1).
See Figure 18.2 for VDD monitor timing; note that the power-on-reset delay is not incurred after a VDD
monitor reset. See Table 5.4 for complete electrical characteristics of the VDD monitor.
Rev. 1.0
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C8051T630/1/2/3/4/5
SFR Definition 18.1. VDM0CN: VDD Monitor Control
Bit
7
6
5
4
3
2
1
0
Name
VDMEN
VDDSTAT
Type
R/W
R
R
R
R
R
R
R
Reset
Varies
Varies
0
0
0
0
0
0
SFR Address = 0xFF
Bit
Name
7
VDMEN
Function
VDD Monitor Enable.
This bit turns the VDD monitor circuit on/off. The VDD Monitor cannot generate system resets until it is also selected as a reset source in register RSTSRC (SFR Definition 18.2). Selecting the VDD monitor as a reset source before it has stabilized
may generate a system reset. In systems where this reset would be undesirable, a
delay should be introduced between enabling the VDD Monitor and selecting it as a
reset source. See Table 5.4 for the minimum VDD Monitor turn-on time.
0: VDD Monitor Disabled.
1: VDD Monitor Enabled.
6
VDDSTAT
VDD Status.
This bit indicates the current power supply status (VDD Monitor output).
0: VDD is at or below the VDD monitor threshold.
1: VDD is above the VDD monitor threshold.
5:0
Unused
Unused. Read = 000000b; Write = Don’t care.
18.3. External Reset
The external RST pin provides a means for external circuitry to force the device into a reset state. Asserting an active-low signal on the RST pin generates a reset; an external pullup and/or decoupling of the RST
pin may be necessary to avoid erroneous noise-induced resets. See Table 5.4 for complete RST pin specifications. The PINRSF flag (RSTSRC.0) is set on exit from an external reset.
18.4. Missing Clock Detector Reset
The Missing Clock Detector (MCD) is a one-shot circuit that is triggered by the system clock. If the system
clock remains high or low for more than 100 µs, the one-shot will time out and generate a reset. After a
MCD reset, the MCDRSF flag (RSTSRC.2) will read 1, signifying the MCD as the reset source; otherwise,
this bit reads 0. Writing a 1 to the MCDRSF bit enables the Missing Clock Detector; writing a 0 disables it.
The state of the RST pin is unaffected by this reset.
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18.5. Comparator0 Reset
Comparator0 can be configured as a reset source by writing a 1 to the C0RSEF flag (RSTSRC.5).
Comparator0 should be enabled and allowed to settle prior to writing to C0RSEF to prevent any turn-on
chatter on the output from generating an unwanted reset. The Comparator0 reset is active-low: if the noninverting input voltage (on CP0+) is less than the inverting input voltage (on CP0-), the device is put into
the reset state. After a Comparator0 reset, the C0RSEF flag (RSTSRC.5) will read 1 signifying
Comparator0 as the reset source; otherwise, this bit reads 0. The state of the RST pin is unaffected by this
reset.
18.6. PCA Watchdog Timer Reset
The programmable watchdog timer (WDT) function of the programmable counter array (PCA) can be used
to prevent software from running out of control during a system malfunction. The PCA WDT function can
be enabled or disabled by software as described in Section “25.4. Watchdog Timer Mode” on page 202;
the WDT is enabled and clocked by SYSCLK/12 following any reset. If a system malfunction prevents user
software from updating the WDT, a reset is generated and the WDTRSF bit (RSTSRC.5) is set to 1. The
state of the RST pin is unaffected by this reset.
18.7. EPROM Error Reset
If an EPROM read or write targets an illegal address, a system reset is generated. This may occur due to
any of the following:

Programming hardware attempts to write or read an EPROM location which is above the user code
space address limit.
 An EPROM read from firmware is attempted above user code space. This occurs when a MOVC
operation is attempted above the user code space address limit.
 A Program read is attempted above user code space. This occurs when user code attempts to branch
to an address above the user code space address limit.
The MEMERR bit (RSTSRC.6) is set following an EPROM error reset. The state of the RST pin is unaffected by this reset.
18.8. Software Reset
Software may force a reset by writing a 1 to the SWRSF bit (RSTSRC.4). The SWRSF bit will read 1 following a software forced reset. The state of the RST pin is unaffected by this reset.
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SFR Definition 18.2. RSTSRC: Reset Source
Bit
7
Name
6
5
4
3
2
1
0
MEMERR
C0RSEF
SWRSF
WDTRSF
MCDRSF
PORSF
PINRSF
Type
R
R
R/W
R/W
R
R/W
R/W
R
Reset
0
Varies
Varies
Varies
Varies
Varies
Varies
Varies
SFR Address = 0xEF
Bit
Name
7
Unused
Description
Unused.
Write
Don’t care.
0
Set to 1 if EPROM
read/write error caused
the last reset.
Set to 1 if Comparator0
caused the last reset.
6
MEMERR EPROM Error Reset Flag.
N/A
5
C0RSEF Comparator0 Reset Enable
and Flag.
4
SWRSF
Writing a 1 enables
Comparator0 as a reset
source (active-low).
Writing a 1 forces a system reset.
Software Reset Force and
Flag.
3
WDTRSF Watchdog Timer Reset Flag. N/A
2
MCDRSF Missing Clock Detector
Enable and Flag.
1
PORSF
0
PINRSF
Writing a 1 enables the
Missing Clock Detector.
The MCD triggers a reset
if a missing clock condition
is detected.
Writing
a 1 enables the
Power-On/VDD Monitor
monitor
as a reset
V
Reset Flag, and VDD monitor DD
source.
Reset Enable.
Writing 1 to this bit
before the VDD monitor
is enabled and stabilized
may cause a system
reset.
N/A
HW Pin Reset Flag.
Note: Do not use read-modify-write operations on this register
100
Read
Rev. 1.0
Set to 1 if last reset was
caused by a write to
SWRSF.
Set to 1 if Watchdog Timer
overflow caused the last
reset.
Set to 1 if Missing Clock
Detector timeout caused
the last reset.
Set to 1 anytime a poweron or VDD monitor reset
occurs.
When set to 1 all other
RSTSRC flags are indeterminate.
Set to 1 if RST pin caused
the last reset.
C8051T630/1/2/3/4/5
19. Oscillators and Clock Selection
C8051T630/1/2/3/4/5 devices include a programmable internal high-frequency oscillator, a programmable
internal low-frequency oscillator, and an external oscillator drive circuit. The internal high-frequency oscillator can be enabled/disabled and calibrated using the OSCICN and OSCICL registers, as shown in
Figure 19.1. The internal low-frequency oscillator can be enabled/disabled and calibrated using the
OSCLCN register. The system clock can be sourced by the external oscillator circuit or either internal oscillator. Both internal oscillators offer a selectable post-scaling feature.
OSCLEN
OSCLRDY
OSCLF3
OSCLF2
OSCLF1
OSCLF0
OSCLD1
OSCLD0
RC Mode
VDD
OSCLCN
IFCN1
IFCN0
OSCICN
IOSCEN
IFRDY
SUSPEND
OSCICL
OSCLF OSCLD
EXTCLK
Programmable
Internal Clock
Generator
EN
n
OSCLF
C Mode
EXTCLK
EN
Low Frequency
Oscillator
SYSCLK
n
OSCLD
Input
Circuit
EXTCLK
OSC
OSCXCN
SEL1
SEL0
XFCN2
XFCN1
XFCN0
XOSCMD2
XOSCMD1
XOSCMD0
CMOS Mode
EXTCLK
CLKSEL
Figure 19.1. Oscillator Options
19.1. System Clock Selection
The CLKSL[1:0] bits in register CLKSEL select which oscillator source is used as the system clock.
CLKSL[1:0] must be set to 01b for the system clock to run from the external oscillator; however the external oscillator may still clock certain peripherals (timers, PCA) when the internal oscillator is selected as the
system clock. The system clock may be switched on-the-fly between the internal oscillator, external oscillator, and Clock Multiplier so long as the selected clock source is enabled and running.
The internal high-frequency and low-frequency oscillators require little start-up time and may be selected
as the system clock immediately following the register write which enables the oscillator. The external RC
and C modes also typically require no startup time.
Rev. 1.0
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SFR Definition 19.1. CLKSEL: Clock Select
Bit
7
6
5
4
3
2
0
CLKSL[1:0]
Name
Type
R
R
R
R
R
R
Reset
0
0
0
0
0
0
SFR Address = 0xA9
Bit
Name
7:2
1:0
1
R/W
0
0
Function
Unused
Unused. Read = 000000b; Write = Don’t Care
CLKSL[1:0] System Clock Source Select Bits.
00: SYSCLK derived from the Internal High-Frequency Oscillator and scaled per the
IFCN bits in register OSCICN.
01: SYSCLK derived from the External Oscillator circuit.
10: SYSCLK derived from the Internal Low-Frequency Oscillator and scaled per the
OSCLD bits in register OSCLCN.
11: reserved.
102
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19.2. Programmable Internal High-Frequency (H-F) Oscillator
All C8051T630/1/2/3/4/5 devices include a programmable internal high-frequency oscillator that defaults
as the system clock after a system reset. The internal oscillator period caPara1n be adjusted via the
OSCICL register as defined by SFR Definition 19.2.
On C8051T630/1/2/3/4/5 devices, OSCICL is factory calibrated to obtain a 24.5 MHz base frequency.
The system clock may be derived from the programmed internal oscillator divided by 1, 2, 4, or 8, as
defined by the IFCN bits in register OSCICN. The divide value defaults to 8 following a reset.
19.2.1. Internal Oscillator Suspend Mode
When software writes a logic 1 to SUSPEND (OSCICN.5), the internal oscillator is suspended. If the system clock is derived from the internal oscillator, the input clock to the peripheral or CIP-51 will be stopped
until one of the following events occur:

Port 0 Match Event.
Port 1 Match Event.
 Comparator 0 enabled and output is logic 0.
 Timer3 Overflow Event.

When one of the oscillator awakening events occur, the internal oscillator, CIP-51, and affected peripherals
resume normal operation, regardless of whether the event also causes an interrupt. The CPU resumes
execution at the instruction following the write to SUSPEND.
SFR Definition 19.2. OSCICL: Internal H-F Oscillator Calibration
Bit
7
6
5
4
3
1
0
Varies
Varies
Varies
OSCICL[6:0]
Name
Type
R
Reset
0
R/W
Varies
Varies
Varies
SFR Address = 0xB3
Bit
Name
7
6:0
2
Varies
Function
Unused
Unused. Read = 0; Write = Don’t Care
OSCICL[6:0] Internal Oscillator Calibration Bits.
These bits determine the internal oscillator period. When set to 0000000b, the H-F
oscillator operates at its fastest setting. When set to 1111111b, the H-F oscillator
operates at its slowest setting. The reset value is factory calibrated to generate an
internal oscillator frequency of 24.5 MHz.
Rev. 1.0
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SFR Definition 19.3. OSCICN: Internal H-F Oscillator Control
Bit
7
6
5
4
Name
IOSCEN
IFRDY
SUSPEND
STSYNC
Type
R/W
R
R/W
R
R
R
Reset
1
1
0
0
0
0
SFR Address = 0xB2
Bit
Name
7
IOSCEN
3
2
1
0
IFCN[1:0]
R/W
0
0
Function
Internal H-F Oscillator Enable Bit.
0: Internal H-F Oscillator Disabled.
1: Internal H-F Oscillator Enabled.
6
IFRDY
Internal H-F Oscillator Frequency Ready Flag.
0: Internal H-F Oscillator is not running at programmed frequency.
1: Internal H-F Oscillator is running at programmed frequency.
5
SUSPEND
Internal Oscillator Suspend Enable Bit.
Setting this bit to logic 1 places the internal oscillator in SUSPEND mode. The internal oscillator resumes operation when one of the SUSPEND mode awakening
events occurs.
4
STSYNC
Suspend Timer Synchronization Bit.
This bit is used to indicate when it is safe to read and write the registers associated
with the suspend wake-up timer. If a suspend wake-up source other than the timer
has brought the oscillator out of suspend mode, it may take up to three timer clocks
before the timer can be read or written. When STSYNC reads '1', reads and writes of
the timer register should not be performed. When STSYNC reads '0', it is safe to
read and write the timer registers.
3:2
1:0
Unused
IFCN[1:0]
Unused. Read = 00b; Write = Don’t Care
Internal H-F Oscillator Frequency Divider Control Bits.
00: SYSCLK derived from Internal H-F Oscillator divided by 8.
01: SYSCLK derived from Internal H-F Oscillator divided by 4.
10: SYSCLK derived from Internal H-F Oscillator divided by 2.
11: SYSCLK derived from Internal H-F Oscillator divided by 1.
104
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19.3. Programmable Internal Low-Frequency (L-F) Oscillator
All C8051T630/1/2/3/4/5 devices include a programmable low-frequency internal oscillator, which is calibrated to a nominal frequency of 80 kHz. The low-frequency oscillator circuit includes a divider that can be
changed to divide the clock by 1, 2, 4, or 8, using the OSCLD bits in the OSCLCN register (see SFR Definition 19.4). Additionally, the OSCLF[3:0] bits can be used to adjust the oscillator’s output frequency.
19.3.1. Calibrating the Internal L-F Oscillator
Timers 2 and 3 include capture functions that can be used to capture the oscillator frequency, when running from a known time base. When either Timer 2 or Timer 3 is configured for L-F Oscillator Capture
Mode, a falling edge (Timer 2) or rising edge (Timer 3) of the low-frequency oscillator’s output will cause a
capture event on the corresponding timer. As a capture event occurs, the current timer value
(TMRnH:TMRnL) is copied into the timer reload registers (TMRnRLH:TMRnRLL). By recording the difference between two successive timer capture values, the low-frequency oscillator’s period can be calculated. The OSCLF bits can then be adjusted to produce the desired oscillator frequency.
SFR Definition 19.4. OSCLCN: Internal L-F Oscillator Control
Bit
7
6
5
Name
OSCLEN
OSCLRDY
OSCLF[3:0]
OSCLD[1:0]
Type
R/W
R
R.W
R/W
Reset
0
0
Varies
4
3
Varies
SFR Address = 0xE3
Bit
Name
7
OSCLEN
Varies
2
Varies
1
0
0
0
Function
Internal L-F Oscillator Enable.
0: Internal L-F Oscillator Disabled.
1: Internal L-F Oscillator Enabled.
6
OSCLRDY
Internal L-F Oscillator Ready.
0: Internal L-F Oscillator frequency not stabilized.
1: Internal L-F Oscillator frequency stabilized.
Note: OSCLRDY is only set back to 0 in the event of a device reset or a change to the
OSCLD[1:0] bits.
5:2
OSCLF[3:0] Internal L-F Oscillator Frequency Control Bits.
Fine-tune control bits for the Internal L-F oscillator frequency. When set to 0000b, the
L-F oscillator operates at its fastest setting. When set to 1111b, the L-F oscillator
operates at its slowest setting.
1:0
OSCLD[1:0] Internal L-F Oscillator Divider Select.
00: Divide by 8 selected.
01: Divide by 4 selected.
10: Divide by 2 selected.
11: Divide by 1 selected.
Rev. 1.0
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19.4. External Oscillator Drive Circuit
The external oscillator circuit may drive an external capacitor or RC network. A CMOS clock may also provide a clock input. In RC, capacitor, or CMOS clock configuration, the clock source should be wired to the
EXTCLK pin as shown in Figure 19.1. The type of external oscillator must be selected in the OSCXCN register, and the frequency control bits (XFCN) must be selected appropriately (see SFR Definition 19.5).
Important Note on External Oscillator Usage: Port pins must be configured when using the external
oscillator circuit. When the external oscillator drive circuit is enabled in capacitor, RC, or CMOS clock
mode, Port pin P0.3 is used as EXTCLK. The Port I/O Crossbar should be configured to skip the Port pin
used by the oscillator circuit; see Section “20.3. Priority Crossbar Decoder” on page 114 for Crossbar configuration. Additionally, when using the external oscillator circuit in capacitor or RC mode, the associated
Port pin should be configured as an analog input. In CMOS clock mode, the associated pin should be
configured as a digital input. See Section “20.4. Port I/O Initialization” on page 116 for details on Port
input mode selection.
106
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 19.5. OSCXCN: External Oscillator Control
Bit
7
6
5
4
2
XOSCMD[2:0]
Name
Type
R
Reset
0
R/W
0
0
1
0
XFCN[2:0]
R
0
SFR Address = 0xB1
Bit
Name
7
6:4
3
R/W
0
0
0
0
Function
Unused
Read = 0; Write = Don’t Care
XOSCMD[2:0] External Oscillator Mode Select.
00x: External Oscillator circuit off.
010: External CMOS Clock Mode.
011: External CMOS Clock Mode with divide by 2 stage.
100: RC Oscillator Mode with divide by 2 stage.
101: Capacitor Oscillator Mode with divide by 2 stage.
11x: Reserved.
3
2:0
Unused
XFCN[2:0]
Read = 0; Write = Don’t Care
External Oscillator Frequency Control Bits.
Set according to the desired frequency range for RC mode.
Set according to the desired K Factor for C mode.
XFCN
RC Mode
C Mode
000
001
010
011
100
101
110
111
f 25 kHz
25 kHz f 50 kHz
50 kHz f 100 kHz
100 kHz f 200 kHz
200 kHz f 400 kHz
400 kHz f 800 kHz
800 kHz f 1.6 MHz
1.6 MHz f 3.2 MHz
K Factor = 0.87
K Factor = 2.6
K Factor = 7.7
K Factor = 22
K Factor = 65
K Factor = 180
K Factor = 664
K Factor = 1590
Rev. 1.0
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19.4.1. External RC Example
If an RC network is used as an external oscillator source for the MCU, the circuit should be configured as
shown in Figure 19.1, “RC Mode”. The capacitor should be no greater than 100 pF; however for very small
capacitors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. To determine the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, first
select the RC network value to produce the desired frequency of oscillation, according to Equation 19.1,
where f = the frequency of oscillation in MHz, C = the capacitor value in pF, and R = the pull-up resistor
value in k.
Equation 19.1. RC Mode Oscillator Frequency
3
f = 1.23  10   R  C 
For example: If the frequency desired is 100 kHz, let R = 246 k and C = 50 pF:
f = 1.23( 103 ) / RC = 1.23 ( 103 ) / [ 246 x 50 ] = 0.1 MHz = 100 kHz
Referring to the table in SFR Definition 19.5, the required XFCN setting is 010b.
19.4.2. External Capacitor Example
If a capacitor is used as an external oscillator for the MCU, the circuit should be configured as shown in
Figure 19.1, “C Mode”. The capacitor should be no greater than 100 pF; however for very small capacitors,
the total capacitance may be dominated by parasitic capacitance in the PCB layout. To determine the
required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, select the capacitor to be used and find the frequency of oscillation according to Equation 19.2, where f = the frequency of
oscillation in MHz, C = the capacitor value in pF, and VDD = the MCU power supply in Volts.
Equation 19.2. C Mode Oscillator Frequency
f =  KF    R  V DD 
For example: Assume VDD = 3.0 V and f = 150 kHz:
f = KF / (C x VDD)
0.150 MHz = KF / (C x 3.0)
Since the frequency of roughly 150 kHz is desired, select the K Factor from the table in SFR Definition 19.5
(OSCXCN) as KF = 22:
0.150 MHz = 22 / (C x 3.0)
C x 3.0 = 22 / 0.150 MHz
C = 146.6 / 3.0 pF = 48.8 pF
Therefore, the XFCN value to use in this example is 011b and C = 50 pF.
108
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20. Port Input/Output
Digital and analog resources are available through 17 I/O pins. Port pins P0.0-P1.7 can be defined as general-purpose I/O (GPIO), assigned to one of the internal digital resources,Para1 or assigned to an analog
function as shown in Figure 20.3. Port pin P2.0 on can be used as GPIO and is shared with the C2 Interface Data signal (C2D). The designer has complete control over which functions are assigned, limited only
by the number of physical I/O pins. This resource assignment flexibility is achieved through the use of a
Priority Crossbar Decoder. Note that the state of a Port I/O pin can always be read in the corresponding
Port latch, regardless of the Crossbar settings.
The Crossbar assigns the selected internal digital resources to the I/O pins based on the Priority Decoder
(Figure 20.3 and Figure 20.4). The registers XBR0 and XBR1, defined in SFR Definition 20.1 and SFR
Definition 20.2, are used to select internal digital functions.
All Port I/Os are 5 V tolerant (refer to Figure 20.2 for the Port cell circuit). The Port I/O cells are configured
as either push-pull or open-drain in the Port Output Mode registers (PnMDOUT, where n = 0,1). Complete
Electrical Specifications for Port I/O are given in Table 5.3 on page 25.
Port Match
P0MASK, P0MAT
P1MASK, P1MAT
XBR0, XBR1,
PnSKIP Registers
External Interrupts
EX0 and EX1
Priority
Decoder
Highest
Priority
UART
4
(Internal Digital Signals)
SPI
P0.0
2
SMBus
Digital
Crossbar
P1.0
8
P1
I/O
Cells
4
P1.7
2
T0, T1
8
(Port Latches)
P0
I/O
Cells
P0.7
SYSCLK
P0
8
2
CP0
Outputs
PCA
Lowest
Priority
PnMDOUT,
PnMDIN Registers
2
P2
I/O
Cell
(P0.0-P0.7)
P2.0
8
P1
(P1.0-P1.7)
1
P2
To Analog Peripherals
(ADC0, CP0, VREF, EXTCLK)
(P2.0)
Figure 20.1. Port I/O Functional Block Diagram
Rev. 1.0
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C8051T630/1/2/3/4/5
20.1. Port I/O Modes of Operation
Port pins use the Port I/O cell shown in Figure 20.2. Each Port I/O cell can be configured by software for
analog I/O or digital I/O using the PnMDIN registers. On reset, all Port I/O cells default to a high impedance
state with weak pull-ups enabled until the Crossbar is enabled (XBARE = 1).
20.1.1. Port Pins Configured for Analog I/O
Any pins to be used as Comparator or ADC input, external oscillator input/output, VREF, or IDAC output
should be configured for analog I/O (PnMDIN.n = 1). When a pin is configured for analog I/O, its weak pullup, digital driver, and digital receiver are disabled. Port pins configured for analog I/O will always read
back a value of 0.
Configuring pins as analog I/O saves power and isolates the Port pin from digital interference. Port pins
configured as digital inputs may still be used by analog peripherals; however, this practice is not recommended and may result in measurement errors.
20.1.2. Port Pins Configured For Digital I/O
Any pins to be used by digital peripherals (UART, SPI, SMBus, etc.), external digital event capture functions, or as GPIO should be configured as digital I/O (PnMDIN.n = 1). For digital I/O pins, one of two output
modes (push-pull or open-drain) must be selected using the PnMDOUT registers.
Push-pull outputs (PnMDOUT.n = 1) drive the Port pad to the VDD/DC+ or GND supply rails based on the
output logic value of the Port pin. Open-drain outputs have the high side driver disabled; therefore, they
only drive the Port pad to GND when the output logic value is 0 and become high impedance inputs (both
high low drivers turned off) when the output logic value is 1.
When a digital I/O cell is placed in the high impedance state, a weak pull-up transistor pulls the Port pad to
the VDD supply voltage to ensure the digital input is at a defined logic state. Weak pull-ups are disabled
when the I/O cell is driven to GND to minimize power consumption and may be globally disabled by setting
WEAKPUD to 1. The user should ensure that digital I/O are always internally or externally pulled or driven
to a valid logic state to minimize power consumption. Port pins configured for digital I/O always read back
the logic state of the Port pad, regardless of the output logic value of the Port pin.
110
Rev. 1.0
C8051T630/1/2/3/4/5
WEAKPUD
(Weak Pull-Up Disable)
PxMDOUT.x
(1 for push-pull)
(0 for open-drain)
VDD
XBARE
(Crossbar
Enable)
VDD
(WEAK)
PORT
PAD
Px.x – Output
Logic Value
(Port Latch or
Crossbar)
PxMDIN.x
(1 for digital)
(0 for analog)
To/From Analog
Peripheral
GND
Px.x – Input Logic Value
(Reads 0 when pin is configured as an analog I/O)
Figure 20.2. Port I/O Cell Block Diagram
20.1.3. Interfacing Port I/O to 5V Logic
All Port I/O configured for digital, open-drain operation are capable of interfacing to digital logic operating at
a supply voltage higher than VDD and less than 5.25 V. An external pullup resistor to the higher supply
voltage is typically required for most systems.
Important Note: In a multi-voltage interface, the external pullup resistor should be sized to allow a current
of at least 150 µA to flow into the Port pin when the supply voltage is between (VDD + 0.6 V) and (VDD +
1.0 V). Once the Port pin voltage increases beyond this range, the current flowing into the Port pin is minimal.
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20.2. Assigning Port I/O Pins to Analog and Digital Functions
Port I/O pins can be assigned to various analog, digital, and external interrupt functions. The Port pins
assigned to analog functions should be configured for analog I/O, and Port pins assigned to digital or external interrupt functions should be configured for digital I/O.
20.2.1. Assigning Port I/O Pins to Analog Functions
Table 20.1 shows all available analog functions that require Port I/O assignments. Port pins selected for
these analog functions should have their corresponding bit in PnSKIP set to 1. This reserves the pin
for use by the analog function and does not allow it to be claimed by the Crossbar. Table 20.1 shows the
potential mapping of Port I/O to each analog function.
Table 20.1. Port I/O Assignment for Analog Functions
Analog Function
Potentially Assignable
Port Pins
SFR(s) used for
Assignment
ADC Input
P0.0–P1.7
AMX0P, AMX0N,
PnSKIP
Comparator0 Input
P0.0–P1.7
CPT0MX, PnSKIP
Voltage Reference (VREF0)
P0.0
REF0CN, PnSKIP
Current DAC Output (IDA0)
P0.1
IDA0CN, PnSKIP
External Oscillator in RC or C Mode (EXTCLK)
P0.3
OSCXCN, PnSKIP
20.2.2. Assigning Port I/O Pins to Digital Functions
Any Port pins not assigned to analog functions may be assigned to digital functions or used as GPIO. Most
digital functions rely on the Crossbar for pin assignment; however, some digital functions bypass the
Crossbar in a manner similar to the analog functions listed above. Port pins used by these digital functions and any Port pins selected for use as GPIO should have their corresponding bit in PnSKIP set
to 1. Table 20.2 shows all available digital functions and the potential mapping of Port I/O to each digital
function.
Table 20.2. Port I/O Assignment for Digital Functions
Digital Function
Potentially Assignable Port Pins
UART0, SPI0, SMBus, CP0, Any Port pin available for assignment by the
CP0A, SYSCLK, PCA0
Crossbar. This includes P0.0 - P1.7 pins which
(CEX0-2 and ECI), T0 or T1. have their PnSKIP bit set to 0.
Note: The Crossbar will always assign UART0
pins to P0.4 and P0.5.
Any pin used for GPIO
112
P0.0–P2.0
Rev. 1.0
SFR(s) used for
Assignment
XBR0, XBR1
PnSKIP
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20.2.3. Assigning Port I/O Pins to External Digital Event Capture Functions
External digital event capture functions can be used to trigger an interrupt or wake the device from a low
power mode when a transition occurs on a digital I/O pin. The digital event capture functions do not require
dedicated pins and will function on both GPIO pins (PnSKIP = 1) and pins in use by the Crossbar (PnSKIP
= 0). External digital event capture functions cannot be used on pins configured for analog I/O. Table 20.3
shows all available external digital event capture functions.
Table 20.3. Port I/O Assignment for External Digital Event Capture Functions
Digital Function
Potentially Assignable Port Pins
SFR(s) used for
Assignment
External Interrupt 0
P0.0–P0.7
IT01CF
External Interrupt 1
P0.0–P0.7
IT01CF
Port Match
P0.0–P1.7
P0MASK, P0MAT
P1MASK, P1MAT
Rev. 1.0
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20.3. Priority Crossbar Decoder
The Priority Crossbar Decoder (Figure 20.3) assigns a priority to each I/O function, starting at the top with
UART0. When a digital resource is selected, the least-significant unassigned Port pin is assigned to that
resource (excluding UART0, which is always at pins 4 and 5). If a Port pin is assigned, the Crossbar skips
that pin when assigning the next selected resource. Additionally, the Crossbar will skip Port pins whose
associated bits in the PnSKIP registers are set. The PnSKIP registers allow software to skip Port pins that
are to be used for analog input, dedicated functions, or GPIO.
Important Note on Crossbar Configuration: If a Port pin is claimed by a peripheral without use of the
Crossbar, its corresponding PnSKIP bit should be set. This applies to P0.0 if VREF is used, P0.3 if the
external oscillator circuit is enabled, P0.6 if the ADC or IDAC is configured to use the external conversion
start signal (CNVSTR), and any selected ADC or Comparator inputs. The Crossbar skips selected pins as
if they were already assigned, and moves to the next unassigned pin. Figure 20.3 shows the Crossbar
Decoder priority with no Port pins skipped (P0SKIP, P1SKIP = 0x00); Figure 20.4 shows the Crossbar
Decoder priority with the VPP (P0.2) and EXTCLK(P0.3) pins skipped (P0SKIP = 0x0C).
P0
SF Signals
PIN I/O
VREF IDA
0
1
P1
EXTCLK
2
3
4
CNVSTR
5
6
7
0
1
2
3
P2
4
5
6
7
0
0
0
TX0
RX0
SCK
MISO
MOSI
*NSS is only pinned out in 4-wire SPI Mode
NSS*
SDA
SCL
CP0
CP0A
SYSCLK
CEX0
CEX1
CEX2
ECI
T0
T1
0
0
0
0
0
0
0
0
0
0
0
P0SKIP[0:7]
0
0
P1SKIP[0:7]
Port pin potentially available to peripheral
SF Signals
Special Function Signals are not assigned by the crossbar.
When these signals are enabled, the CrossBar must be
manually configured to skip their corresponding port pins.
Figure 20.3. Crossbar Priority Decoder with No Pins Skipped
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P0
SF Signals
PIN I/O
VREF IDA
0
1
2
P1
EXTCLK
3
4
5
CNVSTR
6
7
0
1
2
3
P2
4
5
6
7
0
TX0
RX0
SCK
MISO
MOSI
*NSS is only pinned out in 4-wire SPI Mode
NSS*
SDA
SCL
CP0
CP0A
SYSCLK
CEX0
CEX1
CEX2
ECI
T0
T1
0
0
1
1
0
0
0
0
0
0
0
P0SKIP[0:7]
0
0
0
0
0
P1SKIP[0:7]
Port pin potentially available to peripheral
SF Signals
Special Function Signals are not assigned by the crossbar.
When these signals are enabled, the CrossBar must be
manually configured to skip their corresponding port pins.
Figure 20.4. Crossbar Priority Decoder with Crystal Pins Skipped
Registers XBR0 and XBR1 are used to assign the digital I/O resources to the physical I/O Port pins. Note
that when the SMBus is selected, the Crossbar assigns both pins associated with the SMBus (SDA and
SCL); when the UART is selected, the Crossbar assigns both pins associated with the UART (TX and RX).
UART0 pin assignments are fixed for bootloading purposes: UART TX0 is always assigned to P0.4; UART
RX0 is always assigned to P0.5. Standard Port I/Os appear contiguously after the prioritized functions
have been assigned.
Important Note: The SPI can be operated in either 3-wire or 4-wire modes, pending the state of the
NSSMD1–NSSMD0 bits in register SPI0CN. According to the SPI mode, the NSS signal may or may not
be routed to a Port pin.
Rev. 1.0
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20.4. Port I/O Initialization
Port I/O initialization consists of the following steps:
1. Select the input mode (analog or digital) for all Port pins, using the Port Input Mode register (PnMDIN).
2. Select the output mode (open-drain or push-pull) for all Port pins, using the Port Output Mode register
(PnMDOUT).
3. Select any pins to be skipped by the I/O Crossbar using the Port Skip registers (PnSKIP).
4. Assign Port pins to desired peripherals.
5. Enable the Crossbar (XBARE = 1).
All Port pins must be configured as either analog or digital inputs. Any pins to be used as Comparator or
ADC inputs should be configured as an analog inputs. When a pin is configured as an analog input, its
weak pullup, digital driver, and digital receiver are disabled. This process saves power and reduces noise
on the analog input. Pins configured as digital inputs may still be used by analog peripherals; however this
practice is not recommended.
Additionally, all analog input pins should be configured to be skipped by the Crossbar (accomplished by
setting the associated bits in PnSKIP). Port input mode is set in the PnMDIN register, where a 1 indicates a
digital input, and a 0 indicates an analog input. All pins default to digital inputs on reset. See SFR Definition
20.8 for the PnMDIN register details.
The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMDOUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is
required even for the digital resources selected in the XBRn registers, and is not automatic. The only
exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the
PnMDOUT settings. When the WEAKPUD bit in XBR1 is 0, a weak pullup is enabled for all Port I/O configured as open-drain. WEAKPUD does not affect the push-pull Port I/O. Furthermore, the weak pullup is
turned off on an output that is driving a 0 to avoid unnecessary power dissipation.
Registers XBR0 and XBR1 must be loaded with the appropriate values to select the digital I/O functions
required by the design. Setting the XBARE bit in XBR1 to 1 enables the Crossbar. Until the Crossbar is
enabled, the external pins remain as standard Port I/O (in input mode), regardless of the XBRn Register
settings. For given XBRn Register settings, one can determine the I/O pin-out using the Priority Decode
Table; as an alternative, the Configuration Wizard utility of the Silicon Labs IDE software will determine the
Port I/O pin-assignments based on the XBRn Register settings.
The Crossbar must be enabled to use Port pins as standard Port I/O in output mode. Port output drivers
are disabled while the Crossbar is disabled.
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SFR Definition 20.1. XBR0: Port I/O Crossbar Register 0
Bit
7
6
Name
5
4
3
2
1
0
CP0AE
CP0E
SYSCKE
SMB0E
SPI0E
URT0E
Type
R
R
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xE1
Bit
Name
7:6
5
Unused
CP0AE
Function
Unused. Read = 00b; Write = Don’t Care.
Comparator0 Asynchronous Output Enable.
0: Asynchronous CP0 unavailable at Port pin.
1: Asynchronous CP0 routed to Port pin.
4
CP0E
Comparator0 Output Enable.
0: CP0 unavailable at Port pin.
1: CP0 routed to Port pin.
3
SYSCKE
/SYSCLK Output Enable.
0: /SYSCLK unavailable at Port pin.
1: /SYSCLK output routed to Port pin.
2
SMB0E
SMBus I/O Enable.
0: SMBus I/O unavailable at Port pins.
1: SMBus I/O routed to Port pins.
1
SPI0E
SPI I/O Enable.
0: SPI I/O unavailable at Port pins.
1: SPI I/O routed to Port pins. Note that the SPI can be assigned either 3 or 4 GPIO
pins.
0
URT0E
UART I/O Output Enable.
0: UART I/O unavailable at Port pin.
1: UART TX0, RX0 routed to Port pins P0.4 and P0.5.
Rev. 1.0
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SFR Definition 20.2. XBR1: Port I/O Crossbar Register 1
Bit
7
Name WEAKPUD
6
5
4
3
XBARE
T1E
T0E
ECIE
2
1
0
PCA0ME[1:0]
Type
R/W
R/W
R/W
R/W
R/W
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xE2
Bit
Name
7
WEAKPUD
Function
Port I/O Weak Pullup Disable.
0: Weak Pullups enabled (except for Ports whose I/O are configured for analog
mode).
1: Weak Pullups disabled.
6
XBARE
Crossbar Enable.
0: Crossbar disabled.
1: Crossbar enabled.
5
T1E
T1 Enable.
0: T1 unavailable at Port pin.
1: T1 routed to Port pin.
4
T0E
T0 Enable.
0: T0 unavailable at Port pin.
1: T0 routed to Port pin.
3
ECIE
PCA0 External Counter Input Enable.
0: ECI unavailable at Port pin.
1: ECI routed to Port pin.
2
Unused
Unused. Read = 0b; Write = Don’t Care.
1:0 PCA0ME[1:0] PCA Module I/O Enable Bits.
00: All PCA I/O unavailable at Port pins.
01: CEX0 routed to Port pin.
10: CEX0, CEX1 routed to Port pins.
11: CEX0, CEX1, CEX2 routed to Port pins.
20.5. Port Match
Port match functionality allows system events to be triggered by a logic value change on P0 or P1. A software controlled value stored in the PnMATCH registers specifies the expected or normal logic values of P0
and P1. A Port mismatch event occurs if the logic levels of the Port’s input pins no longer match the software controlled value. This allows Software to be notified if a certain change or pattern occurs on P0 or P1
input pins regardless of the XBRn settings.
The PnMASK registers can be used to individually select which P0 and P1 pins should be compared
against the PnMATCH registers. A Port mismatch event is generated if (P0 & P0MASK) does not equal
(P0MATCH & P0MASK) or if (P1 & P1MASK) does not equal (P1MATCH & P1MASK).
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A Port mismatch event may be used to generate an interrupt or wake the device from a low power mode,
such as IDLE or SUSPEND. See the Interrupts and Power Options chapters for more details on interrupt
and wake-up sources.
SFR Definition 20.3. P0MASK: Port 0 Mask Register
Bit
7
6
5
4
3
Name
P0MASK[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0xFE
Bit
Name
7:0
P0MASK[7:0]
2
1
0
0
0
0
Function
Port 0 Mask Value.
Selects P0 pins to be compared to the corresponding bits in P0MAT.
0: P0.n pin logic value is ignored and cannot cause a Port Mismatch event.
1: P0.n pin logic value is compared to P0MAT.n.
SFR Definition 20.4. P0MAT: Port 0 Match Register
Bit
7
6
5
4
3
Name
P0MAT[7:0]
Type
R/W
Reset
1
1
1
1
SFR Address = 0xFD
Bit
Name
7:0
P0MAT[7:0]
1
2
1
0
1
1
1
Function
Port 0 Match Value.
Match comparison value used on Port 0 for bits in P0MASK which are set to 1.
0: P0.n pin logic value is compared with logic LOW.
1: P0.n pin logic value is compared with logic HIGH.
Rev. 1.0
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SFR Definition 20.5. P1MASK: Port 1 Mask Register
Bit
7
6
5
4
3
Name
P1MASK[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0xEE
Bit
Name
7:0
P1MASK[7:0]
2
1
0
0
0
0
Function
Port 1 Mask Value.
Selects P1 pins to be compared to the corresponding bits in P1MAT.
0: P1.n pin logic value is ignored and cannot cause a Port Mismatch event.
1: P1.n pin logic value is compared to P1MAT.n.
SFR Definition 20.6. P1MAT: Port 1 Match Register
Bit
7
6
5
4
3
Name
P1MAT[7:0]
Type
R/W
Reset
1
1
1
1
SFR Address = 0xED
Bit
Name
7:0
P1MAT[7:0]
1
2
1
0
1
1
1
Function
Port 1 Match Value.
Match comparison value used on Port 1 for bits in P1MASK which are set to 1.
0: P1.n pin logic value is compared with logic LOW.
1: P1.n pin logic value is compared with logic HIGH.
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20.6. Special Function Registers for Accessing and Configuring Port I/O
All Port I/O are accessed through corresponding special function registers (SFRs) that are both byte
addressable and bit addressable. When writing to a Port, the value written to the SFR is latched to maintain the output data value at each pin. When reading, the logic levels of the Port's input pins are returned
regardless of the XBRn settings (i.e., even when the pin is assigned to another signal by the Crossbar, the
Port register can always read its corresponding Port I/O pin). The exception to this is the execution of the
read-modify-write instructions that target a Port Latch register as the destination. The read-modify-write
instructions when operating on a Port SFR are the following: ANL, ORL, XRL, JBC, CPL, INC, DEC, DJNZ
and MOV, CLR or SETB, when the destination is an individual bit in a Port SFR. For these instructions, the
value of the latch register (not the pin) is read, modified, and written back to the SFR.
Each Port has a corresponding PnSKIP register which allows its individual Port pins to be assigned to digital functions or skipped by the Crossbar. All Port pins used for analog functions, GPIO, or dedicated digital
functions such as the EMIF should have their PnSKIP bit set to 1.
The Port input mode of the I/O pins is defined using the Port Input Mode registers (PnMDIN). Each Port
cell can be configured for analog or digital I/O. This selection is required even for the digital resources
selected in the XBRn registers, and is not automatic. The only exception to this is P2.4, which can only be
used for digital I/O.
The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMDOUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is
required even for the digital resources selected in the XBRn registers, and is not automatic. The only
exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the
PnMDOUT settings.
SFR Definition 20.7. P0: Port 0
Bit
7
6
5
4
Name
P0[7:0]
Type
R/W
Reset
1
1
1
1
SFR Address = 0x80; Bit-Addressable
Bit
Name
Description
7:0
P0[7:0]
Port 0 Data.
Sets the Port latch logic
value or reads the Port pin
logic state in Port cells configured for digital I/O.
3
2
1
0
1
1
1
1
Write
0: Set output latch to logic
LOW.
1: Set output latch to logic
HIGH.
Rev. 1.0
Read
0: P0.n Port pin is logic
LOW.
1: P0.n Port pin is logic
HIGH.
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SFR Definition 20.8. P0MDIN: Port 0 Input Mode
Bit
7
6
5
4
3
Name
P0MDIN[7:0]
Type
R/W
Reset
1
1
1
1
1
SFR Address = 0xF1
Bit
Name
7:0
P0MDIN[7:0]
2
1
0
1
1
1
Function
Analog Configuration Bits for P0.7–P0.0 (respectively).
Port pins configured for analog mode have their weak pullup, digital driver, and
digital receiver disabled.
0: Corresponding P0.n pin is configured for analog mode.
1: Corresponding P0.n pin is not configured for analog mode.
SFR Definition 20.9. P0MDOUT: Port 0 Output Mode
Bit
7
6
5
4
3
Name
P0MDOUT[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xA4
Bit
Name
0
2
1
0
0
0
0
Function
7:0 P0MDOUT[7:0] Output Configuration Bits for P0.7–P0.0 (respectively).
These bits are ignored if the corresponding bit in register P0MDIN is logic 0.
0: Corresponding P0.n Output is open-drain.
1: Corresponding P0.n Output is push-pull.
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SFR Definition 20.10. P0SKIP: Port 0 Skip
Bit
7
6
5
4
3
Name
P0SKIP[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0xD4
Bit
Name
7:0
P0SKIP[7:0]
2
1
0
0
0
0
Function
Port 0 Crossbar Skip Enable Bits.
These bits select Port 0 pins to be skipped by the Crossbar Decoder. Port pins
used for analog, special functions or GPIO should be skipped by the Crossbar.
0: Corresponding P0.n pin is not skipped by the Crossbar.
1: Corresponding P0.n pin is skipped by the Crossbar.
SFR Definition 20.11. P1: Port 1
Bit
7
6
5
4
Name
P1[7:0]
Type
R/W
Reset
1
1
1
1
SFR Address = 0x90; Bit-Addressable
Bit
Name
Description
7:0
P1[7:0]
Port 1 Data.
Sets the Port latch logic
value or reads the Port pin
logic state in Port cells configured for digital I/O.
3
2
1
0
1
1
1
1
Write
0: Set output latch to logic
LOW.
1: Set output latch to logic
HIGH.
Rev. 1.0
Read
0: P1.n Port pin is logic
LOW.
1: P1.n Port pin is logic
HIGH.
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SFR Definition 20.12. P1MDIN: Port 1 Input Mode
Bit
7
6
5
4
3
Name
P1MDIN[7:0]
Type
R/W
Reset
1
1
1
1
1
SFR Address = 0xF2
Bit
Name
7:0
P1MDIN[7:0]
2
1
0
1
1
1
Function
Analog Configuration Bits for P1.7–P1.0 (respectively).
Port pins configured for analog mode have their weak pullup, digital driver, and
digital receiver disabled.
0: Corresponding P1.n pin is configured for analog mode.
1: Corresponding P1.n pin is not configured for analog mode.
SFR Definition 20.13. P1MDOUT: Port 1 Output Mode
Bit
7
6
5
4
3
Name
P1MDOUT[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xA5
Bit
Name
0
2
1
0
0
0
0
Function
7:0 P1MDOUT[7:0] Output Configuration Bits for P1.7–P1.0 (respectively).
These bits are ignored if the corresponding bit in register P1MDIN is logic 0.
0: Corresponding P1.n Output is open-drain.
1: Corresponding P1.n Output is push-pull.
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SFR Definition 20.14. P1SKIP: Port 1 Skip
Bit
7
6
5
4
Name
3
1
0
0
0
0
P1SKIP[6:0]
Type
R
Reset
0
R/W
0
0
0
SFR Address = 0xD5
Bit
Name
7
6:0
2
Unused
P1SKIP[6:0]
0
Function
Unused. Read = 0b; Write = Don’t Care.
Port 1 Crossbar Skip Enable Bits.
These bits select Port 1 pins to be skipped by the Crossbar Decoder. Port pins
used for analog, special functions or GPIO should be skipped by the Crossbar.
0: Corresponding P1.n pin is not skipped by the Crossbar.
1: Corresponding P1.n pin is skipped by the Crossbar.
SFR Definition 20.15. P2: Port 2
Bit
7
6
5
4
3
2
1
0
P2[0]
Name
Type
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
1
SFR Address = 0xA0; Bit-Addressable
Bit
Name
Description
7:1
Unused
0
P2[0]
Write
Read
Unused.
Don’t Care
000000b
Port 2 Data.
0: Set output latch to logic
LOW.
1: Set output latch to logic
HIGH.
0: P2.0 Port pin is logic
LOW.
1: P2.0 Port pin is logic
HIGH.
Sets the Port latch logic
value or reads the Port pin
logic state in Port cells configured for digital I/O.
Rev. 1.0
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SFR Definition 20.16. P2MDOUT: Port 2 Output Mode
Bit
7
6
5
4
3
2
1
0
P2MDOUT[0]
Name
Type
R
R
R
R
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xA6
Bit
Name
7:1
0
Unused
P2MDOUT[0]
Function
Unused. Read = 000000b; Write = Don’t Care
Output Configuration Bits for P2.0.
0: P2.0 Output is open-drain.
1: P2.0 Output is push-pull.
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21. SMBus
The SMBus I/O interface is a two-wire, bi-directional serial bus. The SMBus is compliant with the System
Management Bus Specification, version 1.1, and compatible with the I2C serial bus. Reads and writes to
the interface by the system controller are byte oriented with the SMBus interface autonomously controlling
the serial transfer of the data. Data can be transferred at up to 1/20th of the system clock as a master or
slave (this can be faster than allowed by the SMBus specification, depending on the system clock used). A
method of extending the clock-low duration is available to accommodate devices with different speed
capabilities on the same bus.
The SMBus interface may operate as a master and/or slave, and may function on a bus with multiple masters. The SMBus provides control of SDA (serial data), SCL (serial clock) generation and synchronization,
arbitration logic, and START/STOP control and generation. The SMBus peripheral can be fully driven by
software (i.e., software accepts/rejects slave addresses, and generates ACKs), or hardware slave address
recognition and automatic ACK generation can be enabled to minimize software overhead. A block diagram of the SMBus peripheral and the associated SFRs is shown in Figure 21.1.
SMB0CN
M T S S A A A S
A X T T C RC I
SMAOK B K
T O
R L
E D
QO
R E
S
T
SMB0CF
E I B E S S S S
N N U XMMMM
S H S T B B B B
M Y H T F C C
B
OO T S S
L E E 1 0
D
SMBUS CONTROL LOGIC
Arbitration
SCL Synchronization
SCL Generation (Master Mode)
SDA Control
Hardware Slave Address Recognition
Hardware ACK Generation
Data Path
IRQ Generation
Control
Interrupt
Request
00
T0 Overflow
01
T1 Overflow
10
TMR2H Overflow
11
TMR2L Overflow
SCL
Control
S
L
V
5
S
L
V
4
S
L
V
3
S
L
V
2
S
L
V
1
SMB0ADR
SG
L C
V
0
S S S S S S S
L L L L L L L
V V V V V V V
MMMMMMM
6 5 4 3 2 1 0
SMB0ADM
C
R
O
S
S
B
A
R
N
SDA
Control
SMB0DAT
7 6 5 4 3 2 1 0
S
L
V
6
SCL
FILTER
Port I/O
SDA
FILTER
E
H
A
C
K
N
Figure 21.1. SMBus Block Diagram
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21.1. Supporting Documents
It is assumed the reader is familiar with or has access to the following supporting documents:
1. The I2C-Bus and How to Use It (including specifications), Philips Semiconductor.
2. The I2C-Bus Specification—Version 2.0, Philips Semiconductor.
3. System Management Bus Specification—Version 1.1, SBS Implementers Forum.
21.2. SMBus Configuration
Figure 21.2 shows a typical SMBus configuration. The SMBus specification allows any recessive voltage
between 3.0 V and 5.0 V; different devices on the bus may operate at different voltage levels. The bi-directional SCL (serial clock) and SDA (serial data) lines must be connected to a positive power supply voltage
through a pullup resistor or similar circuit. Every device connected to the bus must have an open-drain or
open-collector output for both the SCL and SDA lines, so that both are pulled high (recessive state) when
the bus is free. The maximum number of devices on the bus is limited only by the requirement that the rise
and fall times on the bus not exceed 300 ns and 1000 ns, respectively.
VDD = 5V
VDD = 3V
VDD = 5V
VDD = 3V
Master
Device
Slave
Device 1
Slave
Device 2
SDA
SCL
Figure 21.2. Typical SMBus Configuration
21.3. SMBus Operation
Two types of data transfers are possible: data transfers from a master transmitter to an addressed slave
receiver (WRITE), and data transfers from an addressed slave transmitter to a master receiver (READ).
The master device initiates both types of data transfers and provides the serial clock pulses on SCL. The
SMBus interface may operate as a master or a slave, and multiple master devices on the same bus are
supported. If two or more masters attempt to initiate a data transfer simultaneously, an arbitration scheme
is employed with a single master always winning the arbitration. Note that it is not necessary to specify one
device as the Master in a system; any device who transmits a START and a slave address becomes the
master for the duration of that transfer.
A typical SMBus transaction consists of a START condition followed by an address byte (Bits7–1: 7-bit
slave address; Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Bytes that are
received (by a master or slave) are acknowledged (ACK) with a low SDA during a high SCL (see
Figure 21.3). If the receiving device does not ACK, the transmitting device will read a NACK (not acknowledge), which is a high SDA during a high SCL.
The direction bit (R/W) occupies the least-significant bit position of the address byte. The direction bit is set
to logic 1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation.
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All transactions are initiated by a master, with one or more addressed slave devices as the target. The
master generates the START condition and then transmits the slave address and direction bit. If the transaction is a WRITE operation from the master to the slave, the master transmits the data a byte at a time
waiting for an ACK from the slave at the end of each byte. For READ operations, the slave transmits the
data waiting for an ACK from the master at the end of each byte. At the end of the data transfer, the master
generates a STOP condition to terminate the transaction and free the bus. Figure 21.3 illustrates a typical
SMBus transaction.
SCL
SDA
SLA6
START
SLA5-0
Slave Address + R/W
R/W
D7
ACK
D6-0
Data Byte
NACK
STOP
Figure 21.3. SMBus Transaction
21.3.1. Transmitter Vs. Receiver
On the SMBus communications interface, a device is the “transmitter” when it is sending an address or
data byte to another device on the bus. A device is a “receiver” when an address or data byte is being sent
to it from another device on the bus. The transmitter controls the SDA line during the address or data byte.
After each byte of address or data information is sent by the transmitter, the receiver sends an ACK or
NACK bit during the ACK phase of the transfer, during which time the receiver controls the SDA line.
21.3.2. Arbitration
A master may start a transfer only if the bus is free. The bus is free after a STOP condition or after the SCL
and SDA lines remain high for a specified time (see Section “21.3.5. SCL High (SMBus Free) Timeout” on
page 130). In the event that two or more devices attempt to begin a transfer at the same time, an arbitration scheme is employed to force one master to give up the bus. The master devices continue transmitting
until one attempts a HIGH while the other transmits a LOW. Since the bus is open-drain, the bus will be
pulled LOW. The master attempting the HIGH will detect a LOW SDA and lose the arbitration. The winning
master continues its transmission without interruption; the losing master becomes a slave and receives the
rest of the transfer if addressed. This arbitration scheme is non-destructive: one device always wins, and
no data is lost.
21.3.3. Clock Low Extension
SMBus provides a clock synchronization mechanism, similar to I2C, which allows devices with different
speed capabilities to coexist on the bus. A clock-low extension is used during a transfer in order to allow
slower slave devices to communicate with faster masters. The slave may temporarily hold the SCL line
LOW to extend the clock low period, effectively decreasing the serial clock frequency.
21.3.4. SCL Low Timeout
If the SCL line is held low by a slave device on the bus, no further communication is possible. Furthermore,
the master cannot force the SCL line high to correct the error condition. To solve this problem, the SMBus
protocol specifies that devices participating in a transfer must detect any clock cycle held low longer than
25 ms as a “timeout” condition. Devices that have detected the timeout condition must reset the communication no later than 10 ms after detecting the timeout condition.
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When the SMBTOE bit in SMB0CF is set, Timer 3 is used to detect SCL low timeouts. Timer 3 is forced to
reload when SCL is high, and allowed to count when SCL is low. With Timer 3 enabled and configured to
overflow after 25 ms (and SMBTOE set), the Timer 3 interrupt service routine can be used to reset (disable
and re-enable) the SMBus in the event of an SCL low timeout.
21.3.5. SCL High (SMBus Free) Timeout
The SMBus specification stipulates that if the SCL and SDA lines remain high for more that 50 µs, the bus
is designated as free. When the SMBFTE bit in SMB0CF is set, the bus will be considered free if SCL and
SDA remain high for more than 10 SMBus clock source periods (as defined by the timer configured for the
SMBus clock source). If the SMBus is waiting to generate a Master START, the START will be generated
following this timeout. A clock source is required for free timeout detection, even in a slave-only implementation.
21.4. Using the SMBus
The SMBus can operate in both Master and Slave modes. The interface provides timing and shifting control for serial transfers; higher level protocol is determined by user software. The SMBus interface provides
the following application-independent features:








Byte-wise serial data transfers
Clock signal generation on SCL (Master Mode only) and SDA data synchronization
Timeout/bus error recognition, as defined by the SMB0CF configuration register
START/STOP timing, detection, and generation
Bus arbitration
Interrupt generation
Status information
Optional hardware recognition of slave address and automatic acknowledgement of address/data
SMBus interrupts are generated for each data byte or slave address that is transferred. When hardware
acknowledgement is disabled, the point at which the interrupt is generated depends on whether the hardware is acting as a data transmitter or receiver. When a transmitter (i.e., sending address/data, receiving
an ACK), this interrupt is generated after the ACK cycle so that software may read the received ACK value;
when receiving data (i.e., receiving address/data, sending an ACK), this interrupt is generated before the
ACK cycle so that software may define the outgoing ACK value. If hardware acknowledgement is enabled,
these interrupts are always generated after the ACK cycle. See Section 21.5 for more details on transmission sequences.
Interrupts are also generated to indicate the beginning of a transfer when a master (START generated), or
the end of a transfer when a slave (STOP detected). Software should read the SMB0CN (SMBus Control
register) to find the cause of the SMBus interrupt. The SMB0CN register is described in Section 21.4.2;
Table 21.5 provides a quick SMB0CN decoding reference.
21.4.1. SMBus Configuration Register
The SMBus Configuration register (SMB0CF) is used to enable the SMBus Master and/or Slave modes,
select the SMBus clock source, and select the SMBus timing and timeout options. When the ENSMB bit is
set, the SMBus is enabled for all master and slave events. Slave events may be disabled by setting the
INH bit. With slave events inhibited, the SMBus interface will still monitor the SCL and SDA pins; however,
the interface will NACK all received addresses and will not generate any slave interrupts. When the INH bit
is set, all slave events will be inhibited following the next START (interrupts will continue for the duration of
the current transfer).
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Table 21.1. SMBus Clock Source Selection
SMBCS1
SMBCS0
SMBus Clock Source
0
0
1
1
0
1
0
1
Timer 0 Overflow
Timer 1 Overflow
Timer 2 High Byte Overflow
Timer 2 Low Byte Overflow
The SMBCS1–0 bits select the SMBus clock source, which is used only when operating as a master or
when the Free Timeout detection is enabled. When operating as a master, overflows from the selected
source determine the absolute minimum SCL low and high times as defined in Equation 21.1. Note that the
selected clock source may be shared by other peripherals so long as the timer is left running at all times.
For example, Timer 1 overflows may generate the SMBus and UART baud rates simultaneously. Timer
configuration is covered in Section “24. Timers” on page 169.
1
T HighMin = T LowMin = ---------------------------------------------f ClockSourceOverflow
Equation 21.1. Minimum SCL High and Low Times
The selected clock source should be configured to establish the minimum SCL High and Low times as per
Equation 21.1. When the interface is operating as a master (and SCL is not driven or extended by any
other devices on the bus), the typical SMBus bit rate is approximated by Equation 21.2.
f ClockSourceOverflow
BitRate = ---------------------------------------------3
Equation 21.2. Typical SMBus Bit Rate
Figure 21.4 shows the typical SCL generation described by Equation 21.2. Notice that THIGH is typically
twice as large as TLOW. The actual SCL output may vary due to other devices on the bus (SCL may be
extended low by slower slave devices, or driven low by contending master devices). The bit rate when
operating as a master will never exceed the limits defined by equation Equation 21.1.
Timer Source
Overflows
SCL
TLow
THigh
SCL High Timeout
Figure 21.4. Typical SMBus SCL Generation
Setting the EXTHOLD bit extends the minimum setup and hold times for the SDA line. The minimum SDA
setup time defines the absolute minimum time that SDA is stable before SCL transitions from low-to-high.
The minimum SDA hold time defines the absolute minimum time that the current SDA value remains stable
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after SCL transitions from high-to-low. EXTHOLD should be set so that the minimum setup and hold times
meet the SMBus Specification requirements of 250 ns and 300 ns, respectively. Table 21.2 shows the minimum setup and hold times for the two EXTHOLD settings. Setup and hold time extensions are typically
necessary when SYSCLK is above 10 MHz.
Table 21.2. Minimum SDA Setup and Hold Times
EXTHOLD
0
1
Minimum SDA Setup Time
Tlow – 4 system clocks
or
1 system clock + s/w delay*
11 system clocks
Minimum SDA Hold Time
3 system clocks
12 system clocks
Note: Setup Time for ACK bit transmissions and the MSB of all data transfers. When using
software acknowledgement, the s/w delay occurs between the time SMB0DAT or
ACK is written and when SI is cleared. Note that if SI is cleared in the same write
that defines the outgoing ACK value, s/w delay is zero.
With the SMBTOE bit set, Timer 3 should be configured to overflow after 25 ms in order to detect SCL low
timeouts (see Section “21.3.4. SCL Low Timeout” on page 129). The SMBus interface will force Timer 3 to
reload while SCL is high, and allow Timer 3 to count when SCL is low. The Timer 3 interrupt service routine
should be used to reset SMBus communication by disabling and re-enabling the SMBus.
SMBus Free Timeout detection can be enabled by setting the SMBFTE bit. When this bit is set, the bus will
be considered free if SDA and SCL remain high for more than 10 SMBus clock source periods (see
Figure 21.4).
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SFR Definition 21.1. SMB0CF: SMBus Clock/Configuration
Bit
7
6
5
4
Name
ENSMB
INH
BUSY
Type
R/W
R/W
R
R/W
Reset
0
0
0
0
EXTHOLD SMBTOE
SFR Address = 0xC1
Bit
Name
7
ENSMB
3
2
1
0
SMBFTE
SMBCS[1:0]
R/W
R/W
R/W
0
0
0
0
Function
SMBus Enable.
This bit enables the SMBus interface when set to 1. When enabled, the interface
constantly monitors the SDA and SCL pins.
6
INH
SMBus Slave Inhibit.
When this bit is set to logic 1, the SMBus does not generate an interrupt when slave
events occur. This effectively removes the SMBus slave from the bus. Master Mode
interrupts are not affected.
5
BUSY
SMBus Busy Indicator.
This bit is set to logic 1 by hardware when a transfer is in progress. It is cleared to
logic 0 when a STOP or free-timeout is sensed.
4
EXTHOLD
SMBus Setup and Hold Time Extension Enable.
This bit controls the SDA setup and hold times according to Table 21.2.
0: SDA Extended Setup and Hold Times disabled.
1: SDA Extended Setup and Hold Times enabled.
3
SMBTOE
SMBus SCL Timeout Detection Enable.
This bit enables SCL low timeout detection. If set to logic 1, the SMBus forces
Timer 3 to reload while SCL is high and allows Timer 3 to count when SCL goes low.
If Timer 3 is configured to Split Mode, only the High Byte of the timer is held in reload
while SCL is high. Timer 3 should be programmed to generate interrupts at 25 ms,
and the Timer 3 interrupt service routine should reset SMBus communication.
2
SMBFTE
SMBus Free Timeout Detection Enable.
When this bit is set to logic 1, the bus will be considered free if SCL and SDA remain
high for more than 10 SMBus clock source periods.
1:0 SMBCS[1:0] SMBus Clock Source Selection.
These two bits select the SMBus clock source, which is used to generate the SMBus
bit rate. The selected device should be configured according to Equation 21.1.
00: Timer 0 Overflow
01: Timer 1 Overflow
10: Timer 2 High Byte Overflow
11: Timer 2 Low Byte Overflow
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21.4.2. SMB0CN Control Register
SMB0CN is used to control the interface and to provide status information (see SFR Definition 21.2). The
higher four bits of SMB0CN (MASTER, TXMODE, STA, and STO) form a status vector that can be used to
jump to service routines. MASTER indicates whether a device is the master or slave during the current
transfer. TXMODE indicates whether the device is transmitting or receiving data for the current byte.
STA and STO indicate that a START and/or STOP has been detected or generated since the last SMBus
interrupt. STA and STO are also used to generate START and STOP conditions when operating as a master. Writing a 1 to STA will cause the SMBus interface to enter Master Mode and generate a START when
the bus becomes free (STA is not cleared by hardware after the START is generated). Writing a 1 to STO
while in Master Mode will cause the interface to generate a STOP and end the current transfer after the
next ACK cycle. If STO and STA are both set (while in Master Mode), a STOP followed by a START will be
generated.
The ARBLOST bit indicates that the interface has lost an arbitration. This may occur anytime the interface
is transmitting (master or slave). A lost arbitration while operating as a slave indicates a bus error condition. ARBLOST is cleared by hardware each time SI is cleared.
The SI bit (SMBus Interrupt Flag) is set at the beginning and end of each transfer, after each byte frame, or
when an arbitration is lost; see Table 21.3 for more details.
Important Note About the SI Bit: The SMBus interface is stalled while SI is set; thus SCL is held low, and
the bus is stalled until software clears SI.
21.4.2.1. Software ACK Generation
When the EHACK bit in register SMB0ADM is cleared to 0, the firmware on the device must detect incoming slave addresses and ACK or NACK the slave address and incoming data bytes. As a receiver, writing
the ACK bit defines the outgoing ACK value; as a transmitter, reading the ACK bit indicates the value
received during the last ACK cycle. ACKRQ is set each time a byte is received, indicating that an outgoing
ACK value is needed. When ACKRQ is set, software should write the desired outgoing value to the ACK
bit before clearing SI. A NACK will be generated if software does not write the ACK bit before clearing SI.
SDA will reflect the defined ACK value immediately following a write to the ACK bit; however SCL will
remain low until SI is cleared. If a received slave address is not acknowledged, further slave events will be
ignored until the next START is detected.
21.4.2.2. Hardware ACK Generation
When the EHACK bit in register SMB0ADM is set to 1, automatic slave address recognition and ACK generation is enabled. More detail about automatic slave address recognition can be found in Section 21.4.3.
As a receiver, the value currently specified by the ACK bit will be automatically sent on the bus during the
ACK cycle of an incoming data byte. As a transmitter, reading the ACK bit indicates the value received on
the last ACK cycle. The ACKRQ bit is not used when hardware ACK generation is enabled. If a received
slave address is NACKed by hardware, further slave events will be ignored until the next START is
detected, and no interrupt will be generated.
Table 21.3 lists all sources for hardware changes to the SMB0CN bits. Refer to Table 21.5 for SMBus status decoding using the SMB0CN register.
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SFR Definition 21.2. SMB0CN: SMBus Control
Bit
7
6
5
4
3
2
1
0
Name
MASTER
TXMODE
STA
STO
ACKRQ
ARBLOST
ACK
SI
Type
R
R
R/W
R/W
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xC0; Bit-Addressable
Bit
Name
Description
Read
Write
7
MASTER SMBus Master/Slave
Indicator. This read-only bit
indicates when the SMBus is
operating as a master.
0: SMBus operating in
slave mode.
1: SMBus operating in
master mode.
N/A
6
TXMODE SMBus Transmit Mode
Indicator. This read-only bit
indicates when the SMBus is
operating as a transmitter.
0: SMBus in Receiver
Mode.
1: SMBus in Transmitter
Mode.
N/A
0: No Start generated.
1: When Configured as a
Master, initiates a START
or repeated START.
0: No STOP condition is
transmitted.
1: When configured as a
Master, causes a STOP
condition to be transmitted after the next ACK
cycle.
Cleared by Hardware.
N/A
5
STA
SMBus Start Flag.
4
STO
SMBus Stop Flag.
0: No Start or repeated
Start detected.
1: Start or repeated Start
detected.
0: No Stop condition
detected.
1: Stop condition detected
(if in Slave Mode) or pending (if in Master Mode).
3
ACKRQ
SMBus Acknowledge
Request.
0: No Ack requested
1: ACK requested
2
ARBLOST SMBus Arbitration Lost
Indicator.
1
ACK
0
SI
SMBus Acknowledge.
0: No arbitration error.
1: Arbitration Lost
N/A
0: NACK received.
1: ACK received.
0: Send NACK
1: Send ACK
0: No interrupt pending
SMBus Interrupt Flag.
This bit is set by hardware
1: Interrupt Pending
under the conditions listed in
Table 15.3. SI must be cleared
by software. While SI is set,
SCL is held low and the
SMBus is stalled.
Rev. 1.0
0: Clear interrupt, and initiate next state machine
event.
1: Force interrupt.
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Table 21.3. Sources for Hardware Changes to SMB0CN
Bit
MASTER
Set by Hardware When:


A START is generated.
START is generated.
 SMB0DAT is written before the start of an
SMBus frame.



A STOP is generated.
Arbitration is lost.
A START is detected.
Arbitration is lost.
SMB0DAT is not written before the
start of an SMBus frame.
Must be cleared by software.

A pending STOP is generated.

After each ACK cycle.

Each time SI is cleared.


TXMODE
STA

STO


ACKRQ

ARBLOST


ACK




SI
Cleared by Hardware When:



A START followed by an address byte is
received.
A STOP is detected while addressed as a
slave.
Arbitration is lost due to a detected STOP.
A byte has been received and an ACK
response value is needed (only when
hardware ACK is not enabled).
A repeated START is detected as a
MASTER when STA is low (unwanted
repeated START).
SCL is sensed low while attempting to
generate a STOP or repeated START
condition.
SDA is sensed low while transmitting a 1
(excluding ACK bits).
The incoming ACK value is low 
(ACKNOWLEDGE).
A START has been generated.
Lost arbitration.
A byte has been transmitted and an
ACK/NACK received.
A byte has been received.
A START or repeated START followed by a
slave address + R/W has been received.
A STOP has been received.



The incoming ACK value is high
(NOT ACKNOWLEDGE).
 Must be cleared by software.
21.4.3. Hardware Slave Address Recognition
The SMBus hardware has the capability to automatically recognize incoming slave addresses and send an
ACK without software intervention. Automatic slave address recognition is enabled by setting the EHACK
bit in register SMB0ADM to 1. This will enable both automatic slave address recognition and automatic
hardware ACK generation for received bytes (as a master or slave). More detail on automatic hardware
ACK generation can be found in Section 21.4.2.2.
The registers used to define which address(es) are recognized by the hardware are the SMBus Slave
Address register (SFR Definition 21.3) and the SMBus Slave Address Mask register (SFR Definition 21.4).
A single address or range of addresses (including the General Call Address 0x00) can be specified using
these two registers. The most-significant seven bits of the two registers are used to define which
addresses will be ACKed. A 1 in bit positions of the slave address mask SLVM[6:0] enable a comparison
between the received slave address and the hardware’s slave address SLV[6:0] for those bits. A 0 in a bit
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of the slave address mask means that bit will be treated as a “don’t care” for comparison purposes. In this
case, either a 1 or a 0 value are acceptable on the incoming slave address. Additionally, if the GC bit in
register SMB0ADR is set to 1, hardware will recognize the General Call Address (0x00). Table 21.4 shows
some example parameter settings and the slave addresses that will be recognized by hardware under
those conditions.
Table 21.4. Hardware Address Recognition Examples (EHACK = 1)
Hardware Slave Address
SLV[6:0]
Slave Address Mask
SLVM[6:0]
GC bit
Slave Addresses Recognized by
Hardware
0x34
0x34
0x34
0x34
0x70
0x7F
0x7F
0x7E
0x7E
0x73
0
1
0
1
0
0x34
0x34, 0x00 (General Call)
0x34, 0x35
0x34, 0x35, 0x00 (General Call)
0x70, 0x74, 0x78, 0x7C
SFR Definition 21.3. SMB0ADR: SMBus Slave Address
Bit
7
6
5
4
3
2
1
0
Name
SLV[6:0]
GC
Type
R/W
R/W
Reset
0
0
0
0
SFR Address = 0xD7
Bit
Name
7:1
SLV[6:0]
0
0
0
0
Function
SMBus Hardware Slave Address.
Defines the SMBus Slave Address(es) for automatic hardware acknowledgement.
Only address bits which have a 1 in the corresponding bit position in SLVM[6:0]
are checked against the incoming address. This allows multiple addresses to be
recognized.
0
GC
General Call Address Enable.
When hardware address recognition is enabled (EHACK = 1), this bit will determine whether the General Call Address (0x00) is also recognized by hardware.
0: General Call Address is ignored.
1: General Call Address is recognized.
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SFR Definition 21.4. SMB0ADM: SMBus Slave Address Mask
Bit
7
6
5
4
3
2
1
0
Name
SLVM[6:0]
EHACK
Type
R/W
R/W
Reset
1
1
1
1
SFR Address = 0xE7
Bit
Name
7:1
SLVM[6:0]
1
1
1
0
Function
SMBus Slave Address Mask.
Defines which bits of register SMB0ADR are compared with an incoming address
byte, and which bits are ignored. Any bit set to 1 in SLVM[6:0] enables comparisons with the corresponding bit in SLV[6:0]. Bits set to 0 are ignored (can be either
0 or 1 in the incoming address).
0
EHACK
Hardware Acknowledge Enable.
Enables hardware acknowledgement of slave address and received data bytes.
0: Firmware must manually acknowledge all incoming address and data bytes.
1: Automatic Slave Address Recognition and Hardware Acknowledge is Enabled.
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21.4.4. Data Register
The SMBus Data register SMB0DAT holds a byte of serial data to be transmitted or one that has just been
received. Software may safely read or write to the data register when the SI flag is set. Software should not
attempt to access the SMB0DAT register when the SMBus is enabled and the SI flag is cleared to logic 0,
as the interface may be in the process of shifting a byte of data into or out of the register.
Data in SMB0DAT is always shifted out MSB first. After a byte has been received, the first bit of received
data is located at the MSB of SMB0DAT. While data is being shifted out, data on the bus is simultaneously
being shifted in. SMB0DAT always contains the last data byte present on the bus. In the event of lost arbitration, the transition from master transmitter to slave receiver is made with the correct data or address in
SMB0DAT.
SFR Definition 21.5. SMB0DAT: SMBus Data
Bit
7
6
5
4
3
Name
SMB0DAT[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xC2
Bit
Name
0
2
1
0
0
0
0
Function
7:0 SMB0DAT[7:0] SMBus Data.
The SMB0DAT register contains a byte of data to be transmitted on the SMBus
serial interface or a byte that has just been received on the SMBus serial interface.
The CPU can read from or write to this register whenever the SI serial interrupt flag
(SMB0CN.0) is set to logic 1. The serial data in the register remains stable as long
as the SI flag is set. When the SI flag is not set, the system may be in the process
of shifting data in/out and the CPU should not attempt to access this register.
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21.5. SMBus Transfer Modes
The SMBus interface may be configured to operate as master and/or slave. At any particular time, it will be
operating in one of the following four modes: Master Transmitter, Master Receiver, Slave Transmitter, or
Slave Receiver. The SMBus interface enters Master Mode any time a START is generated, and remains in
Master Mode until it loses an arbitration or generates a STOP. An SMBus interrupt is generated at the end
of all SMBus byte frames. Note that the position of the ACK interrupt when operating as a receiver
depends on whether hardware ACK generation is enabled. As a receiver, the interrupt for an ACK occurs
before the ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is enabled. As a transmitter, interrupts occur after the ACK, regardless of whether hardware ACK generation is enabled or not.
21.5.1. Write Sequence (Master)
During a write sequence, an SMBus master writes data to a slave device. The master in this transfer will be
a transmitter during the address byte, and a transmitter during all data bytes. The SMBus interface generates the START condition and transmits the first byte containing the address of the target slave and the
data direction bit. In this case the data direction bit (R/W) will be logic 0 (WRITE). The master then transmits one or more bytes of serial data. After each byte is transmitted, an acknowledge bit is generated by
the slave. The transfer is ended when the STO bit is set and a STOP is generated. Note that the interface
will switch to Master Receiver Mode if SMB0DAT is not written following a Master Transmitter interrupt.
Figure 21.5 shows a typical master write sequence. Two transmit data bytes are shown, though any number of bytes may be transmitted. Notice that all of the “data byte transferred” interrupts occur after the ACK
cycle in this mode, regardless of whether hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
W
A
Data Byte
A
Data Byte
A
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 21.5. Typical Master Write Sequence
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21.5.2. Read Sequence (Master)
During a read sequence, an SMBus master reads data from a slave device. The master in this transfer will
be a transmitter during the address byte, and a receiver during all data bytes. The SMBus interface generates the START condition and transmits the first byte containing the address of the target slave and the
data direction bit. In this case the data direction bit (R/W) will be logic 1 (READ). Serial data is then
received from the slave on SDA while the SMBus outputs the serial clock. The slave transmits one or more
bytes of serial data.
If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each
received byte. Software must write the ACK bit at that time to ACK or NACK the received byte.
With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK,
and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be
set up by the software prior to receiving the byte when hardware ACK generation is enabled.
Writing a 1 to the ACK bit generates an ACK; writing a 0 generates a NACK. Software should write a 0 to
the ACK bit for the last data transfer, to transmit a NACK. The interface exits Master Receiver Mode after
the STO bit is set and a STOP is generated. The interface will switch to Master Transmitter Mode if
SMB0DAT is written while an active Master Receiver. Figure 21.6 shows a typical master read sequence.
Two received data bytes are shown, though any number of bytes may be received. Notice that the ‘data
byte transferred’ interrupts occur at different places in the sequence, depending on whether hardware ACK
generation is enabled. The interrupt occurs before the ACK with hardware ACK generation disabled, and
after the ACK when hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
R
A
Data Byte
A
Data Byte
N
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 21.6. Typical Master Read Sequence
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21.5.3. Write Sequence (Slave)
During a write sequence, an SMBus master writes data to a slave device. The slave in this transfer will be
a receiver during the address byte, and a receiver during all data bytes. When slave events are enabled
(INH = 0), the interface enters Slave Receiver Mode when a START followed by a slave address and direction bit (WRITE in this case) is received. If hardware ACK generation is disabled, upon entering Slave
Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The software must respond to the
received slave address with an ACK, or ignore the received slave address with a NACK. If hardware ACK
generation is enabled, the hardware will apply the ACK for a slave address which matches the criteria set
up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK cycle.
If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the
next START is detected. If the received slave address is acknowledged, zero or more data bytes are
received.
If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each
received byte. Software must write the ACK bit at that time to ACK or NACK the received byte.
With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK,
and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be
set up by the software prior to receiving the byte when hardware ACK generation is enabled.
The interface exits Slave Receiver Mode after receiving a STOP. Note that the interface will switch to Slave
Transmitter Mode if SMB0DAT is written while an active Slave Receiver. Figure 21.7 shows a typical slave
write sequence. Two received data bytes are shown, though any number of bytes may be received. Notice
that the ‘data byte transferred’ interrupts occur at different places in the sequence, depending on whether
hardware ACK generation is enabled. The interrupt occurs before the ACK with hardware ACK generation
disabled, and after the ACK when hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 21.7. Typical Slave Write Sequence
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21.5.4. Read Sequence (Slave)
During a read sequence, an SMBus master reads data from a slave device. The slave in this transfer will
be a receiver during the address byte, and a transmitter during all data bytes. When slave events are
enabled (INH = 0), the interface enters Slave Receiver Mode (to receive the slave address) when a START
followed by a slave address and direction bit (READ in this case) is received. If hardware ACK generation
is disabled, upon entering Slave Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The
software must respond to the received slave address with an ACK, or ignore the received slave address
with a NACK. If hardware ACK generation is enabled, the hardware will apply the ACK for a slave address
which matches the criteria set up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK
cycle.
If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the
next START is detected. If the received slave address is acknowledged, zero or more data bytes are transmitted. If the received slave address is acknowledged, data should be written to SMB0DAT to be transmitted. The interface enters slave transmitter mode, and transmits one or more bytes of data. After each byte
is transmitted, the master sends an acknowledge bit; if the acknowledge bit is an ACK, SMB0DAT should
be written with the next data byte. If the acknowledge bit is a NACK, SMB0DAT should not be written to
before SI is cleared (an error condition may be generated if SMB0DAT is written following a received
NACK while in slave transmitter mode). The interface exits slave transmitter mode after receiving a STOP.
Note that the interface will switch to slave receiver mode if SMB0DAT is not written following a Slave
Transmitter interrupt. Figure 21.8 shows a typical slave read sequence. Two transmitted data bytes are
shown, though any number of bytes may be transmitted. Notice that all of the “data byte transferred” interrupts occur after the ACK cycle in this mode, regardless of whether hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
R
A
Data Byte
A
Data Byte
N
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 21.8. Typical Slave Read Sequence
21.6. SMBus Status Decoding
The current SMBus status can be easily decoded using the SMB0CN register. The appropriate actions to
take in response to an SMBus event depend on whether hardware slave address recognition and ACK
generation is enabled or disabled. Table 21.5 describes the typical actions when hardware slave address
recognition and ACK generation is disabled. Table 21.6 describes the typical actions when hardware slave
address recognition and ACK generation is enabled. In the tables, STATUS VECTOR refers to the four
upper bits of SMB0CN: MASTER, TXMODE, STA, and STO. The shown response options are only the typical responses; application-specific procedures are allowed as long as they conform to the SMBus specification. Highlighted responses are allowed by hardware but do not conform to the SMBus specification.
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144
ARBLOST
0
0 X
0
0
1000
1
0
ACK
STO
0
STA
1100
Typical Response Options
ACK
ACKRQ
Vector
Status
Mode
Master Receiver
Master Transmitter
1110
Current SMbus State
Vector Expected
Values to
Write
Values Read
Next Status
Table 21.5. SMBus Status Decoding With Hardware ACK Generation Disabled
(EHACK = 0)
0
0 X
1100
1
0 X
1110
0
1 X
—
Load next data byte into
SMB0DAT.
0
0 X
1100
End transfer with STOP.
0
1 X
—
A master data or address byte End transfer with STOP and start 1
1 was transmitted; ACK
another transfer.
received.
Send repeated START.
1
1 X
—
0 X
1110
Switch to Master Receiver Mode 0
(clear SI without writing new data
to SMB0DAT).
0 X
1000
Acknowledge received byte;
Read SMB0DAT.
0
0
1
1000
Send NACK to indicate last byte, 0
and send STOP.
1
0
—
Send NACK to indicate last byte, 1
and send STOP followed by
START.
1
0
1110
Send ACK followed by repeated
START.
1
0
1
1110
Send NACK to indicate last byte, 1
and send repeated START.
0
0
1110
Send ACK and switch to Master
Transmitter Mode (write to
SMB0DAT before clearing SI).
0
0
1
1100
Send NACK and switch to Master Transmitter Mode (write to
SMB0DAT before clearing SI).
0
0
0
1100
A master START was generated.
Load slave address + R/W into
SMB0DAT.
A master data or address byte Set STA to restart transfer.
0 was transmitted; NACK
Abort transfer.
received.
0 X
A master data byte was
received; ACK requested.
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ARBLOST
ACK
STA
STO
0101
ACKRQ
0
0
0
A slave byte was transmitted; No action required (expecting
NACK received.
STOP condition).
0
0 X
0001
0
0
1
A slave byte was transmitted; Load SMB0DAT with next data
ACK received.
byte to transmit.
0
0 X
0100
0
1 X
A Slave byte was transmitted; No action required (expecting
error detected.
Master to end transfer).
0
0 X
0001
0
0 X
—
0
0
1
0000
If Read, Load SMB0DAT with
0
data byte; ACK received address
0
1
0100
NACK received address.
0
0
0
—
If Write, Acknowledge received
address
0
0
1
0000
If Read, Load SMB0DAT with
0
Lost arbitration as master;
1 X slave address + R/W received; data byte; ACK received address
ACK requested.
NACK received address.
0
0
1
0100
0
0
—
1
0
0
1110
0
0 X
—
Current SMbus State
Typical Response Options
An illegal STOP or bus error
0 X X was detected while a Slave
Clear STO.
Transmission was in progress.
If Write, Acknowledge received
address
1
0 X
A slave address + R/W was
received; ACK requested.
Slave Receiver
0010
1
Reschedule failed transfer;
NACK received address.
0
A STOP was detected while
0 X addressed as a Slave Transmitter or Slave Receiver.
1
1 X
Lost arbitration while attempt- No action required (transfer
ing a STOP.
complete/aborted).
0
0
0
—
Acknowledge received byte;
Read SMB0DAT.
0
1
0000
0 X
A slave byte was received;
ACK requested.
0
1
NACK received byte.
0
0
0
—
0
0 X
—
1
0 X
1110
Abort failed transfer.
0
0 X
—
1110
0001
Bus Error Condition
0000
ACK
Vector
Status
Mode
Slave Transmitter
0100
Vector Expected
Values to
Write
Values Read
Next Status
Table 21.5. SMBus Status Decoding With Hardware ACK Generation Disabled
(EHACK = 0) (Continued)
Clear STO.
0010
0
1 X
Lost arbitration while attempt- Abort failed transfer.
ing a repeated START.
Reschedule failed transfer.
0001
0
1 X
Lost arbitration due to a
detected STOP.
Reschedule failed transfer.
1
0 X
0
0
—
1
1 X
Lost arbitration while transmit- Abort failed transfer.
ting a data byte as master.
Reschedule failed transfer.
0
0000
1
0
0
1110
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ARBLOST
0
0 X
0
0
Master Receiver
0
0
ACK
0
0 X
1100
1
0 X
1110
0
1 X
—
Load next data byte into
SMB0DAT.
0
0 X
1100
End transfer with STOP.
0
1 X
—
End transfer with STOP and start 1
A master data or address byte
another transfer.
1 was transmitted; ACK
Send repeated START.
1
received.
Switch to Master Receiver Mode 0
(clear SI without writing new data
to SMB0DAT). Set ACK for initial
data byte.
1 X
—
0 X
1110
0
1
1000
A master START was generated.
0
Load slave address + R/W into
SMB0DAT.
A master data or address byte Set STA to restart transfer.
0 was transmitted; NACK
Abort transfer.
received.
1
A master data byte was
received; ACK sent.
1000
0
146
0
STO
0
STA
1100
Typical Response Options
ACK
ACKRQ
Vector
Status
Mode
Master Transmitter
1110
Current SMbus State
Vector Expected
Values to
Write
Values Read
Next Status
Table 21.6. SMBus Status Decoding With Hardware ACK Generation Enabled
(EHACK = 1)
A master data byte was
0 received; NACK sent (last
byte).
Set ACK for next data byte;
Read SMB0DAT.
0
0
1
1000
Set NACK to indicate next data
byte as the last data byte;
Read SMB0DAT.
0
0
0
1000
Initiate repeated START.
1
0
0
1110
Switch to Master Transmitter
0
Mode (write to SMB0DAT before
clearing SI).
0 X
1100
Read SMB0DAT; send STOP.
0
1
0
—
Read SMB0DAT; Send STOP
followed by START.
1
1
0
1110
Initiate repeated START.
1
0
0
1110
0 X
1100
Switch to Master Transmitter
0
Mode (write to SMB0DAT before
clearing SI).
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ARBLOST
ACK
STA
STO
0101
ACKRQ
0
0
0
A slave byte was transmitted; No action required (expecting
NACK received.
STOP condition).
0
0 X
0001
0
0
1
A slave byte was transmitted; Load SMB0DAT with next data
ACK received.
byte to transmit.
0
0 X
0100
0
1 X
A Slave byte was transmitted; No action required (expecting
error detected.
Master to end transfer).
0
0 X
0001
0
0 X
—
If Write, Set ACK for first data
byte.
0
0
1
0000
If Read, Load SMB0DAT with
data byte
0
0 X
0100
If Write, Set ACK for first data
byte.
0
0
1
0000
0
0 X
0100
1
0 X
1110
0
0 X
—
Lost arbitration while attempt- No action required (transfer
ing a STOP.
complete/aborted).
0
0
0
—
Set ACK for next data byte;
Read SMB0DAT.
0
0
1
0000
Set NACK for next data byte;
Read SMB0DAT.
0
0
0
0000
0
0 X
—
1
0 X
1110
Abort failed transfer.
0
0 X
—
Current SMbus State
Typical Response Options
An illegal STOP or bus error
0 X X was detected while a Slave
Clear STO.
Transmission was in progress.
0
A slave address + R/W was
0 X
received; ACK sent.
Bus Error Condition
Slave Receiver
0010
0
Lost arbitration as master;
1 X slave address + R/W received; If Read, Load SMB0DAT with
ACK sent.
data byte
Reschedule failed transfer
0
A STOP was detected while
0 X addressed as a Slave Transmitter or Slave Receiver.
0
1 X
0001
ACK
Vector
Status
Mode
Slave Transmitter
0100
Vector Expected
Values to
Write
Values Read
Next Status
Table 21.6. SMBus Status Decoding With Hardware ACK Generation Enabled
(EHACK = 1) (Continued)
Clear STO.
0000
0
0 X A slave byte was received.
0010
0
1 X
Lost arbitration while attempt- Abort failed transfer.
ing a repeated START.
Reschedule failed transfer.
0001
0
1 X
Lost arbitration due to a
detected STOP.
Reschedule failed transfer.
1
0 X
1110
0 X
—
0
1 X
Lost arbitration while transmit- Abort failed transfer.
ting a data byte as master.
Reschedule failed transfer.
0
0000
1
0 X
1110
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22. UART0
UART0 is an asynchronous, full duplex serial port offering modes 1 and 3 of the standard 8051 UART.
Enhanced baud rate support allows a wide range of clock sources to generate standard baud rates (details
in Section “22.1. Enhanced Baud Rate Generation” on page 149). Received data buffering allows UART0
to start reception of a second incoming data byte before software has finished reading the previous data
byte.
UART0 has two associated SFRs: Serial Control Register 0 (SCON0) and Serial Data Buffer 0 (SBUF0).
The single SBUF0 location provides access to both transmit and receive registers. Writes to SBUF0
always access the Transmit register. Reads of SBUF0 always access the buffered Receive register;
it is not possible to read data from the Transmit register.
With UART0 interrupts enabled, an interrupt is generated each time a transmit is completed (TI0 is set in
SCON0), or a data byte has been received (RI0 is set in SCON0). The UART0 interrupt flags are not
cleared by hardware when the CPU vectors to the interrupt service routine. They must be cleared manually
by software, allowing software to determine the cause of the UART0 interrupt (transmit complete or receive
complete).
SFR Bus
Write to
SBUF
TB8
SBUF
(TX Shift)
SET
D
Q
TX
CLR
Crossbar
Zero Detector
Stop Bit
Shift
Start
Data
Tx Control
Tx Clock
Send
Tx IRQ
SCON
TI
Serial
Port
Interrupt
MCE
REN
TB8
RB8
TI
RI
SMODE
UART Baud
Rate Generator
Port I/O
RI
Rx IRQ
Rx Clock
Rx Control
Start
Shift
0x1FF
RB8
Load
SBUF
Input Shift Register
(9 bits)
Load SBUF
SBUF
(RX Latch)
Read
SBUF
SFR Bus
RX
Crossbar
Figure 22.1. UART0 Block Diagram
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22.1. Enhanced Baud Rate Generation
The UART0 baud rate is generated by Timer 1 in 8-bit auto-reload mode. The TX clock is generated by
TL1; the RX clock is generated by a copy of TL1 (shown as RX Timer in Figure 22.2), which is not useraccessible. Both TX and RX Timer overflows are divided by two to generate the TX and RX baud rates.
The RX Timer runs when Timer 1 is enabled, and uses the same reload value (TH1). However, an
RX Timer reload is forced when a START condition is detected on the RX pin. This allows a receive to
begin any time a START is detected, independent of the TX Timer state.
Timer 1
TL1
UART
Overflow
2
TX Clock
Overflow
2
RX Clock
TH1
Start
Detected
RX Timer
Figure 22.2. UART0 Baud Rate Logic
Timer 1 should be configured for Mode 2, 8-bit auto-reload (see Section “24.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload” on page 173). The Timer 1 reload value should be set so that overflows will
occur at two times the desired UART baud rate frequency. Note that Timer 1 may be clocked by one of six
sources: SYSCLK, SYSCLK/4, SYSCLK/12, SYSCLK/48, the external oscillator clock/8, or an external
input T1. For any given Timer 1 clock source, the UART0 baud rate is determined by Equation 22.1-A and
Equation 22.1-B.
A)
1
UartBaudRate = ---  T1_Overflow_Rate
2
B)
T1 CLK
T1_Overflow_Rate = -------------------------256 – TH1
Equation 22.1. UART0 Baud Rate
Where T1CLK is the frequency of the clock supplied to Timer 1, and T1H is the high byte of Timer 1 (reload
value). Timer 1 clock frequency is selected as described in Section “24. Timers” on page 169. A quick reference for typical baud rates and system clock frequencies is given in Table 22.1 through Table 22.2. The
internal oscillator may still generate the system clock when the external oscillator is driving Timer 1.
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22.2. Operational Modes
UART0 provides standard asynchronous, full duplex communication. The UART mode (8-bit or 9-bit) is
selected by the S0MODE bit (SCON0.7). Typical UART connection options are shown in Figure 22.3.
TX
RS-232
LEVEL
XLTR
RS-232
RX
C8051xxxx
OR
TX
TX
RX
RX
MCU
C8051xxxx
Figure 22.3. UART Interconnect Diagram
22.2.1. 8-Bit UART
8-Bit UART mode uses a total of 10 bits per data byte: one start bit, eight data bits (LSB first), and one stop
bit. Data are transmitted LSB first from the TX0 pin and received at the RX0 pin. On receive, the eight data
bits are stored in SBUF0 and the stop bit goes into RB80 (SCON0.2).
Data transmission begins when software writes a data byte to the SBUF0 register. The TI0 Transmit Interrupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to logic 1. After the stop bit is
received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met:
RI0 must be logic 0, and if MCE0 is logic 1, the stop bit must be logic 1. In the event of a receive data overrun, the first received 8 bits are latched into the SBUF0 receive register and the following overrun data bits
are lost.
If these conditions are met, the eight bits of data is stored in SBUF0, the stop bit is stored in RB80 and the
RI0 flag is set. If these conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not
be set. An interrupt will occur if enabled when either TI0 or RI0 is set.
MARK
SPACE
START
BIT
D0
D1
D2
D3
D4
D5
D6
BIT TIMES
BIT SAMPLING
Figure 22.4. 8-Bit UART Timing Diagram
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STOP
BIT
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22.2.2. 9-Bit UART
9-bit UART mode uses a total of eleven bits per data byte: a start bit, 8 data bits (LSB first), a programmable ninth data bit, and a stop bit. The state of the ninth transmit data bit is determined by the value in TB80
(SCON0.3), which is assigned by user software. It can be assigned the value of the parity flag (bit P in register PSW) for error detection, or used in multiprocessor communications. On receive, the ninth data bit
goes into RB80 (SCON0.2) and the stop bit is ignored.
Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI0 Transmit
Interrupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data
reception can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to 1. After the stop bit is
received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met:
(1) RI0 must be logic 0, and (2) if MCE0 is logic 1, the 9th bit must be logic 1 (when MCE0 is logic 0, the
state of the ninth data bit is unimportant). If these conditions are met, the eight bits of data are stored in
SBUF0, the ninth bit is stored in RB80, and the RI0 flag is set to 1. If the above conditions are not met,
SBUF0 and RB80 will not be loaded and the RI0 flag will not be set to 1. A UART0 interrupt will occur if
enabled when either TI0 or RI0 is set to 1.
MARK
SPACE
START
BIT
D0
D1
D2
D3
D4
D5
D6
D7
D8
STOP
BIT
BIT TIMES
BIT SAMPLING
Figure 22.5. 9-Bit UART Timing Diagram
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22.3. Multiprocessor Communications
9-Bit UART mode supports multiprocessor communication between a master processor and one or more
slave processors by special use of the ninth data bit. When a master processor wants to transmit to one or
more slaves, it first sends an address byte to select the target(s). An address byte differs from a data byte
in that its ninth bit is logic 1; in a data byte, the ninth bit is always set to logic 0.
Setting the MCE0 bit (SCON0.5) of a slave processor configures its UART such that when a stop bit is
received, the UART will generate an interrupt only if the ninth bit is logic 1 (RB80 = 1) signifying an address
byte has been received. In the UART interrupt handler, software will compare the received address with
the slave's own assigned 8-bit address. If the addresses match, the slave will clear its MCE0 bit to enable
interrupts on the reception of the following data byte(s). Slaves that weren't addressed leave their MCE0
bits set and do not generate interrupts on the reception of the following data bytes, thereby ignoring the
data. Once the entire message is received, the addressed slave resets its MCE0 bit to ignore all transmissions until it receives the next address byte.
Multiple addresses can be assigned to a single slave and/or a single address can be assigned to multiple
slaves, thereby enabling "broadcast" transmissions to more than one slave simultaneously. The master
processor can be configured to receive all transmissions or a protocol can be implemented such that the
master/slave role is temporarily reversed to enable half-duplex transmission between the original master
and slave(s).
Master
Device
Slave
Device
Slave
Device
Slave
Device
V+
RX
TX
RX
TX
RX
TX
RX
TX
Figure 22.6. UART Multi-Processor Mode Interconnect Diagram
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SFR Definition 22.1. SCON0: Serial Port 0 Control
Bit
7
6
Name
S0MODE
Type
R/W
Reset
0
5
4
3
2
1
0
MCE0
REN0
TB80
RB80
TI0
RI0
R
R/W
R/W
R/W
R/W
R/W
R/W
1
0
0
0
0
0
0
SFR Address = 0x98; Bit-Addressable
Bit
Name
7
6
5
Function
S0MODE Serial Port 0 Operation Mode.
Selects the UART0 Operation Mode.
0: 8-bit UART with Variable Baud Rate.
1: 9-bit UART with Variable Baud Rate.
Unused
MCE0
Unused. Read = 1b, Write = Don’t Care.
Multiprocessor Communication Enable.
The function of this bit is dependent on the Serial Port 0 Operation Mode:
Mode 0: Checks for valid stop bit.
0: Logic level of stop bit is ignored.
1: RI0 will only be activated if stop bit is logic level 1.
Mode 1: Multiprocessor Communications Enable.
0: Logic level of ninth bit is ignored.
1: RI0 is set and an interrupt is generated only when the ninth bit is logic 1.
4
REN0
Receive Enable.
0: UART0 reception disabled.
1: UART0 reception enabled.
3
TB80
Ninth Transmission Bit.
The logic level of this bit will be sent as the ninth transmission bit in 9-bit UART Mode
(Mode 1). Unused in 8-bit mode (Mode 0).
2
RB80
Ninth Receive Bit.
RB80 is assigned the value of the STOP bit in Mode 0; it is assigned the value of the
9th data bit in Mode 1.
1
TI0
Transmit Interrupt Flag.
Set by hardware when a byte of data has been transmitted by UART0 (after the 8th bit
in 8-bit UART Mode, or at the beginning of the STOP bit in 9-bit UART Mode). When
the UART0 interrupt is enabled, setting this bit causes the CPU to vector to the UART0
interrupt service routine. This bit must be cleared manually by software.
0
RI0
Receive Interrupt Flag.
Set to 1 by hardware when a byte of data has been received by UART0 (set at the
STOP bit sampling time). When the UART0 interrupt is enabled, setting this bit to 1
causes the CPU to vector to the UART0 interrupt service routine. This bit must be
cleared manually by software.
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SFR Definition 22.2. SBUF0: Serial (UART0) Port Data Buffer
Bit
7
6
5
4
3
Name
SBUF0[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x99
Bit
Name
7:0
0
2
1
0
0
0
0
Function
SBUF0[7:0] Serial Data Buffer Bits 7–0 (MSB–LSB).
This SFR accesses two registers; a transmit shift register and a receive latch register.
When data is written to SBUF0, it goes to the transmit shift register and is held for
serial transmission. Writing a byte to SBUF0 initiates the transmission. A read of
SBUF0 returns the contents of the receive latch.
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Table 22.1. Timer Settings for Standard Baud Rates
Using The Internal 24.5 MHz Oscillator
Internal Osc.
SYSCLK from
Frequency: 24.5 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error
230400
115200
57600
28800
14400
9600
2400
1200
–0.32%
–0.32%
0.15%
–0.32%
0.15%
–0.32%
–0.32%
0.15%
Oscillator Timer Clock
Divide
Source
Factor
106
212
426
848
1704
2544
10176
20448
SCA1–SCA0
(pre-scale
select)1
T1M1
Timer 1
Reload
Value (hex)
XX2
XX
XX
01
00
00
10
10
1
1
1
0
0
0
0
0
0xCB
0x96
0x2B
0x96
0xB9
0x96
0x96
0x2B
SCA1–SCA0
(pre-scale
select)1
T1M1
Timer 1
Reload
Value (hex)
XX2
XX
XX
00
00
00
10
10
11
11
11
11
11
11
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0xD0
0xA0
0x40
0xE0
0xC0
0xA0
0xA0
0x40
0xFA
0xF4
0xE8
0xD0
0xA0
0x70
SYSCLK
SYSCLK
SYSCLK
SYSCLK/4
SYSCLK/12
SYSCLK/12
SYSCLK/48
SYSCLK/48
Notes:
1. SCA1–SCA0 and T1M bit definitions can be found in Section 24.1.
2. X = Don’t care.
Table 22.2. Timer Settings for Standard Baud Rates
Using an External 22.1184 MHz Oscillator
SYSCLK from
External Osc.
SYSCLK from
Internal Osc.
Frequency: 22.1184 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error
230400
115200
57600
28800
14400
9600
2400
1200
230400
115200
57600
28800
14400
9600
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
Oscillator Timer Clock
Divide
Source
Factor
96
192
384
768
1536
2304
9216
18432
96
192
384
768
1536
2304
SYSCLK
SYSCLK
SYSCLK
SYSCLK / 12
SYSCLK / 12
SYSCLK / 12
SYSCLK / 48
SYSCLK / 48
EXTCLK / 8
EXTCLK / 8
EXTCLK / 8
EXTCLK / 8
EXTCLK / 8
EXTCLK / 8
Notes:
1. SCA1–SCA0 and T1M bit definitions can be found in Section 24.1.
2. X = Don’t care.
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23. Enhanced Serial Peripheral Interface (SPI0)
The Enhanced Serial Peripheral Interface (SPI0) provides access to a flexible, full-duplex synchronous
serial bus. SPI0 can operate as a master or slave device in both 3-wire or 4-wire modes, and supports multiple masters and slaves on a single SPI bus. The slave-select (NSS) signal can be configured as an input
to select SPI0 in slave mode, or to disable Master Mode operation in a multi-master environment, avoiding
contention on the SPI bus when more than one master attempts simultaneous data transfers. NSS can
also be configured as a chip-select output in master mode, or disabled for 3-wire operation. Additional general purpose port I/O pins can be used to select multiple slave devices in master mode.
SFR Bus
SYSCLK
SPI0CN
SPIF
WCOL
MODF
RXOVRN
NSSMD1
NSSMD0
TXBMT
SPIEN
SPI0CFG
SPIBSY
MSTEN
CKPHA
CKPOL
SLVSEL
NSSIN
SRMT
RXBMT
SCR7
SCR6
SCR5
SCR4
SCR3
SCR2
SCR1
SCR0
SPI0CKR
Clock Divide
Logic
SPI CONTROL LOGIC
Data Path
Control
SPI IRQ
Pin Interface
Control
MOSI
Tx Data
SPI0DAT
SCK
Transmit Data Buffer
Shift Register
Rx Data
7 6 5 4 3 2 1 0
Receive Data Buffer
Pin
Control
Logic
MISO
NSS
Read
SPI0DAT
Write
SPI0DAT
SFR Bus
Figure 23.1. SPI Block Diagram
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R
O
S
S
B
A
R
Port I/O
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23.1. Signal Descriptions
The four signals used by SPI0 (MOSI, MISO, SCK, NSS) are described below.
23.1.1. Master Out, Slave In (MOSI)
The master-out, slave-in (MOSI) signal is an output from a master device and an input to slave devices. It
is used to serially transfer data from the master to the slave. This signal is an output when SPI0 is operating as a master and an input when SPI0 is operating as a slave. Data is transferred most-significant bit
first. When configured as a master, MOSI is driven by the MSB of the shift register in both 3- and 4-wire
mode.
23.1.2. Master In, Slave Out (MISO)
The master-in, slave-out (MISO) signal is an output from a slave device and an input to the master device.
It is used to serially transfer data from the slave to the master. This signal is an input when SPI0 is operating as a master and an output when SPI0 is operating as a slave. Data is transferred most-significant bit
first. The MISO pin is placed in a high-impedance state when the SPI module is disabled and when the SPI
operates in 4-wire mode as a slave that is not selected. When acting as a slave in 3-wire mode, MISO is
always driven by the MSB of the shift register.
23.1.3. Serial Clock (SCK)
The serial clock (SCK) signal is an output from the master device and an input to slave devices. It is used
to synchronize the transfer of data between the master and slave on the MOSI and MISO lines. SPI0 generates this signal when operating as a master. The SCK signal is ignored by a SPI slave when the slave is
not selected (NSS = 1) in 4-wire slave mode.
23.1.4. Slave Select (NSS)
The function of the slave-select (NSS) signal is dependent on the setting of the NSSMD1 and NSSMD0
bits in the SPI0CN register. There are three possible modes that can be selected with these bits:
1. NSSMD[1:0] = 00: 3-Wire Master or 3-Wire Slave Mode: SPI0 operates in 3-wire mode, and NSS is
disabled. When operating as a slave device, SPI0 is always selected in 3-wire mode. Since no select
signal is present, SPI0 must be the only slave on the bus in 3-wire mode. This is intended for point-topoint communication between a master and one slave.
2. NSSMD[1:0] = 01: 4-Wire Slave or Multi-Master Mode: SPI0 operates in 4-wire mode, and NSS is
enabled as an input. When operating as a slave, NSS selects the SPI0 device. When operating as a
master, a 1-to-0 transition of the NSS signal disables the master function of SPI0 so that multiple
master devices can be used on the same SPI bus.
3. NSSMD[1:0] = 1x: 4-Wire Master Mode: SPI0 operates in 4-wire mode, and NSS is enabled as an
output. The setting of NSSMD0 determines what logic level the NSS pin will output. This configuration
should only be used when operating SPI0 as a master device.
See Figure 23.2, Figure 23.3, and Figure 23.4 for typical connection diagrams of the various operational
modes. Note that the setting of NSSMD bits affects the pinout of the device. When in 3-wire master or
3-wire slave mode, the NSS pin will not be mapped by the crossbar. In all other modes, the NSS signal will
be mapped to a pin on the device. See Section “20. Port Input/Output” on page 109 for general purpose
port I/O and crossbar information.
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23.2. SPI0 Master Mode Operation
A SPI master device initiates all data transfers on a SPI bus. SPI0 is placed in master mode by setting the
Master Enable flag (MSTEN, SPI0CN.6). Writing a byte of data to the SPI0 data register (SPI0DAT) when
in master mode writes to the transmit buffer. If the SPI shift register is empty, the byte in the transmit buffer
is moved to the shift register, and a data transfer begins. The SPI0 master immediately shifts out the data
serially on the MOSI line while providing the serial clock on SCK. The SPIF (SPI0CN.7) flag is set to logic
1 at the end of the transfer. If interrupts are enabled, an interrupt request is generated when the SPIF flag
is set. While the SPI0 master transfers data to a slave on the MOSI line, the addressed SPI slave device
simultaneously transfers the contents of its shift register to the SPI master on the MISO line in a full-duplex
operation. Therefore, the SPIF flag serves as both a transmit-complete and receive-data-ready flag. The
data byte received from the slave is transferred MSB-first into the master's shift register. When a byte is
fully shifted into the register, it is moved to the receive buffer where it can be read by the processor by
reading SPI0DAT.
When configured as a master, SPI0 can operate in one of three different modes: multi-master mode, 3-wire
single-master mode, and 4-wire single-master mode. The default, multi-master mode is active when
NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 1. In this mode, NSS is an input to the device, and
is used to disable the master SPI0 when another master is accessing the bus. When NSS is pulled low in
this mode, MSTEN (SPI0CN.6) and SPIEN (SPI0CN.0) are set to 0 to disable the SPI master device, and
a Mode Fault is generated (MODF, SPI0CN.5 = 1). Mode Fault will generate an interrupt if enabled. SPI0
must be manually re-enabled in software under these circumstances. In multi-master systems, devices will
typically default to being slave devices while they are not acting as the system master device. In multi-master mode, slave devices can be addressed individually (if needed) using general-purpose I/O pins.
Figure 23.2 shows a connection diagram between two master devices in multiple-master mode.
3-wire single-master mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. In this
mode, NSS is not used, and is not mapped to an external port pin through the crossbar. Any slave devices
that must be addressed in this mode should be selected using general-purpose I/O pins. Figure 23.3
shows a connection diagram between a master device in 3-wire master mode and a slave device.
4-wire single-master mode is active when NSSMD1 (SPI0CN.3) = 1. In this mode, NSS is configured as an
output pin, and can be used as a slave-select signal for a single SPI device. In this mode, the output value
of NSS is controlled (in software) with the bit NSSMD0 (SPI0CN.2). Additional slave devices can be
addressed using general-purpose I/O pins. Figure 23.4 shows a connection diagram for a master device in
4-wire master mode and two slave devices.
Master
Device 1
NSS
GPIO
MISO
MISO
MOSI
MOSI
SCK
SCK
GPIO
NSS
Master
Device 2
Figure 23.2. Multiple-Master Mode Connection Diagram
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Master
Device
MISO
MISO
MOSI
MOSI
SCK
SCK
Slave
Device
Figure 23.3. 3-Wire Single Master and 3-Wire Single Slave Mode Connection
Diagram
Master
Device
GPIO
MISO
MISO
MOSI
MOSI
SCK
SCK
NSS
NSS
MISO
MOSI
Slave
Device
Slave
Device
SCK
NSS
Figure 23.4. 4-Wire Single Master Mode and 4-Wire Slave Mode Connection
Diagram
23.3. SPI0 Slave Mode Operation
When SPI0 is enabled and not configured as a master, it will operate as a SPI slave. As a slave, bytes are
shifted in through the MOSI pin and out through the MISO pin by a master device controlling the SCK signal. A bit counter in the SPI0 logic counts SCK edges. When 8 bits have been shifted through the shift register, the SPIF flag is set to logic 1, and the byte is copied into the receive buffer. Data is read from the
receive buffer by reading SPI0DAT. A slave device cannot initiate transfers. Data to be transferred to the
master device is pre-loaded into the shift register by writing to SPI0DAT. Writes to SPI0DAT are doublebuffered, and are placed in the transmit buffer first. If the shift register is empty, the contents of the transmit
buffer will immediately be transferred into the shift register. When the shift register already contains data,
the SPI will load the shift register with the transmit buffer’s contents after the last SCK edge of the next (or
current) SPI transfer.
When configured as a slave, SPI0 can be configured for 4-wire or 3-wire operation. The default, 4-wire
slave mode, is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 1. In 4-wire mode, the
NSS signal is routed to a port pin and configured as a digital input. SPI0 is enabled when NSS is logic 0,
and disabled when NSS is logic 1. The bit counter is reset on a falling edge of NSS. Note that the NSS signal must be driven low at least 2 system clocks before the first active edge of SCK for each byte transfer.
Figure 23.4 shows a connection diagram between two slave devices in 4-wire slave mode and a master
device.
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3-wire slave mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. NSS is not
used in this mode, and is not mapped to an external port pin through the crossbar. Since there is no way of
uniquely addressing the device in 3-wire slave mode, SPI0 must be the only slave device present on the
bus. It is important to note that in 3-wire slave mode there is no external means of resetting the bit counter
that determines when a full byte has been received. The bit counter can only be reset by disabling and reenabling SPI0 with the SPIEN bit. Figure 23.3 shows a connection diagram between a slave device in 3wire slave mode and a master device.
23.4. SPI0 Interrupt Sources
When SPI0 interrupts are enabled, the following four flags will generate an interrupt when they are set to
logic 1:
All of the following bits must be cleared by software.

The SPI Interrupt Flag, SPIF (SPI0CN.7) is set to logic 1 at the end of each byte transfer. This flag can
occur in all SPI0 modes.
 The Write Collision Flag, WCOL (SPI0CN.6) is set to logic 1 if a write to SPI0DAT is attempted when
the transmit buffer has not been emptied to the SPI shift register. When this occurs, the write to
SPI0DAT will be ignored, and the transmit buffer will not be written.This flag can occur in all SPI0
modes.
 The Mode Fault Flag MODF (SPI0CN.5) is set to logic 1 when SPI0 is configured as a master, and for
multi-master mode and the NSS pin is pulled low. When a Mode Fault occurs, the MSTEN and SPIEN
bits in SPI0CN are set to logic 0 to disable SPI0 and allow another master device to access the bus.
 The Receive Overrun Flag RXOVRN (SPI0CN.4) is set to logic 1 when configured as a slave, and a
transfer is completed and the receive buffer still holds an unread byte from a previous transfer. The new
byte is not transferred to the receive buffer, allowing the previously received data byte to be read. The
data byte which caused the overrun is lost.
23.5. Serial Clock Phase and Polarity
Four combinations of serial clock phase and polarity can be selected using the clock control bits in the
SPI0 Configuration Register (SPI0CFG). The CKPHA bit (SPI0CFG.5) selects one of two clock phases
(edge used to latch the data). The CKPOL bit (SPI0CFG.4) selects between an active-high or active-low
clock. Both master and slave devices must be configured to use the same clock phase and polarity. SPI0
should be disabled (by clearing the SPIEN bit, SPI0CN.0) when changing the clock phase or polarity. The
clock and data line relationships for master mode are shown in Figure 23.5. For slave mode, the clock and
data relationships are shown in Figure 23.6 and Figure 23.7. Note that CKPHA should be set to 0 on both
the master and slave SPI when communicating between two Silicon Labs C8051 devices.
The SPI0 Clock Rate Register (SPI0CKR) as shown in SFR Definition 23.3 controls the master mode
serial clock frequency. This register is ignored when operating in slave mode. When the SPI is configured
as a master, the maximum data transfer rate (bits/sec) is one-half the system clock frequency or 12.5 MHz,
whichever is slower. When the SPI is configured as a slave, the maximum data transfer rate (bits/sec) for
full-duplex operation is 1/10 the system clock frequency, provided that the master issues SCK, NSS (in 4wire slave mode), and the serial input data synchronously with the slave’s system clock. If the master
issues SCK, NSS, and the serial input data asynchronously, the maximum data transfer rate (bits/sec)
must be less than 1/10 the system clock frequency. In the special case where the master only wants to
transmit data to the slave and does not need to receive data from the slave (i.e. half-duplex operation), the
SPI slave can receive data at a maximum data transfer rate (bits/sec) of 1/4 the system clock frequency.
This is provided that the master issues SCK, NSS, and the serial input data synchronously with the slave’s
system clock.
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SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=0)
SCK
(CKPOL=1, CKPHA=1)
MISO/MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (Must Remain High
in Multi-Master Mode)
Figure 23.5. Master Mode Data/Clock Timing
SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=1, CKPHA=0)
MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
MISO
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (4-Wire Mode)
Figure 23.6. Slave Mode Data/Clock Timing (CKPHA = 0)
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SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=1)
MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
MISO
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 0
NSS (4-Wire Mode)
Figure 23.7. Slave Mode Data/Clock Timing (CKPHA = 1)
23.6. SPI Special Function Registers
SPI0 is accessed and controlled through four special function registers in the system controller: SPI0CN
Control Register, SPI0DAT Data Register, SPI0CFG Configuration Register, and SPI0CKR Clock Rate
Register. The four special function registers related to the operation of the SPI0 Bus are described in the
following figures.
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SFR Definition 23.1. SPI0CFG: SPI0 Configuration
Bit
7
6
5
4
3
2
1
0
Name
SPIBSY
MSTEN
CKPHA
CKPOL
SLVSEL
NSSIN
SRMT
RXBMT
Type
R
R/W
R/W
R/W
R
R
R
R
Reset
0
0
0
0
0
1
1
1
SFR Address = 0xA1
Bit
Name
7
SPIBSY
Function
SPI Busy.
This bit is set to logic 1 when a SPI transfer is in progress (master or slave mode).
6
MSTEN
Master Mode Enable.
0: Disable master mode. Operate in slave mode.
1: Enable master mode. Operate as a master.
5
CKPHA
SPI0 Clock Phase.
0: Data centered on first edge of SCK period.*
1: Data centered on second edge of SCK period.*
4
CKPOL
SPI0 Clock Polarity.
0: SCK line low in idle state.
1: SCK line high in idle state.
3
SLVSEL
Slave Selected Flag.
This bit is set to logic 1 whenever the NSS pin is low indicating SPI0 is the selected
slave. It is cleared to logic 0 when NSS is high (slave not selected). This bit does
not indicate the instantaneous value at the NSS pin, but rather a de-glitched version of the pin input.
2
NSSIN
NSS Instantaneous Pin Input.
This bit mimics the instantaneous value that is present on the NSS port pin at the
time that the register is read. This input is not de-glitched.
1
SRMT
Shift Register Empty (valid in slave mode only).
This bit will be set to logic 1 when all data has been transferred in/out of the shift
register, and there is no new information available to read from the transmit buffer
or write to the receive buffer. It returns to logic 0 when a data byte is transferred to
the shift register from the transmit buffer or by a transition on SCK. SRMT = 1 when
in Master Mode.
0
RXBMT
Receive Buffer Empty (valid in slave mode only).
This bit will be set to logic 1 when the receive buffer has been read and contains no
new information. If there is new information available in the receive buffer that has
not been read, this bit will return to logic 0. RXBMT = 1 when in Master Mode.
Note: In slave mode, data on MOSI is sampled in the center of each data bit. In master mode, data on MISO is
sampled one SYSCLK before the end of each data bit, to provide maximum settling time for the slave device.
See Table 23.1 for timing parameters.
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SFR Definition 23.2. SPI0CN: SPI0 Control
Bit
7
6
5
4
Name
SPIF
WCOL
MODF
RXOVRN
Type
R/W
R/W
R/W
R/W
Reset
0
0
0
0
SFR Address = 0xF8; Bit-Addressable
Bit
Name
7
SPIF
3
2
1
0
NSSMD[1:0]
TXBMT
SPIEN
R/W
R
R/W
1
0
0
1
Function
SPI0 Interrupt Flag.
This bit is set to logic 1 by hardware at the end of a data transfer. If SPI interrupts
are enabled, an interrupt will be generated. This bit is not automatically cleared by
hardware, and must be cleared by software.
6
WCOL
Write Collision Flag.
This bit is set to logic 1 if a write to SPI0DAT is attempted when TXBMT is 0. When
this occurs, the write to SPI0DAT will be ignored, and the transmit buffer will not be
written. If SPI interrupts are enabled, an interrupt will be generated. This bit is not
automatically cleared by hardware, and must be cleared by software.
5
MODF
Mode Fault Flag.
This bit is set to logic 1 by hardware when a master mode collision is detected
(NSS is low, MSTEN = 1, and NSSMD[1:0] = 01). If SPI interrupts are enabled, an
interrupt will be generated. This bit is not automatically cleared by hardware, and
must be cleared by software.
4
RXOVRN
Receive Overrun Flag (valid in slave mode only).
This bit is set to logic 1 by hardware when the receive buffer still holds unread data
from a previous transfer and the last bit of the current transfer is shifted into the
SPI0 shift register. If SPI interrupts are enabled, an interrupt will be generated. This
bit is not automatically cleared by hardware, and must be cleared by software.
3:2
NSSMD[1:0]
Slave Select Mode.
Selects between the following NSS operation modes:
(See Section 23.2 and Section 23.3).
00: 3-Wire Slave or 3-Wire Master Mode. NSS signal is not routed to a port pin.
01: 4-Wire Slave or Multi-Master Mode (Default). NSS is an input to the device.
1x: 4-Wire Single-Master Mode. NSS signal is mapped as an output from the
device and will assume the value of NSSMD0.
1
TXBMT
Transmit Buffer Empty.
This bit will be set to logic 0 when new data has been written to the transmit buffer.
When data in the transmit buffer is transferred to the SPI shift register, this bit will
be set to logic 1, indicating that it is safe to write a new byte to the transmit buffer.
0
SPIEN
SPI0 Enable.
0: SPI disabled.
1: SPI enabled.
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SFR Definition 23.3. SPI0CKR: SPI0 Clock Rate
Bit
7
6
5
4
Name
SCR[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xA2
Bit
Name
7:0
SCR[7:0]
3
2
1
0
0
0
0
0
Function
SPI0 Clock Rate.
These bits determine the frequency of the SCK output when the SPI0 module is
configured for master mode operation. The SCK clock frequency is a divided version of the system clock, and is given in the following equation, where SYSCLK is
the system clock frequency and SPI0CKR is the 8-bit value held in the SPI0CKR
register.
SYSCLK
f SCK = ----------------------------------------------------------2   SPI0CKR[7:0] + 1 
for 0 <= SPI0CKR <= 255
Example: If SYSCLK = 2 MHz and SPI0CKR = 0x04,
2000000
f SCK = -------------------------2  4 + 1
f SCK = 200kHz
SFR Definition 23.4. SPI0DAT: SPI0 Data
Bit
7
6
5
4
3
Name
SPI0DAT[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xA3
Bit
Name
7:0
0
2
1
0
0
0
0
Function
SPI0DAT[7:0] SPI0 Transmit and Receive Data.
The SPI0DAT register is used to transmit and receive SPI0 data. Writing data to
SPI0DAT places the data into the transmit buffer and initiates a transfer when in
Master Mode. A read of SPI0DAT returns the contents of the receive buffer.
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SCK*
T
T
MCKH
MCKL
T
T
MIS
MIH
MISO
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 23.8. SPI Master Timing (CKPHA = 0)
SCK*
T
T
MCKH
MCKL
T
T
MIS
MIH
MISO
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 23.9. SPI Master Timing (CKPHA = 1)
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NSS
T
T
SE
T
CKL
SD
SCK*
T
CKH
T
SIS
T
SIH
MOSI
T
T
SEZ
T
SOH
SDZ
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 23.10. SPI Slave Timing (CKPHA = 0)
NSS
T
T
SE
T
CKL
SD
SCK*
T
CKH
T
SIS
T
SIH
MOSI
T
SEZ
T
T
SOH
SLH
T
SDZ
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 23.11. SPI Slave Timing (CKPHA = 1)
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Table 23.1. SPI Slave Timing Parameters
Parameter
Description
Min
Max
Units
Master Mode Timing (See Figure 23.8 and Figure 23.9)
TMCKH
SCK High Time
1 x TSYSCLK
—
ns
TMCKL
SCK Low Time
1 x TSYSCLK
—
ns
TMIS
MISO Valid to SCK Shift Edge
1 x TSYSCLK + 20
—
ns
TMIH
SCK Shift Edge to MISO Change
0
—
ns
Slave Mode Timing (See Figure 23.10 and Figure 23.11)
TSE
NSS Falling to First SCK Edge
2 x TSYSCLK
—
ns
TSD
Last SCK Edge to NSS Rising
2 x TSYSCLK
—
ns
TSEZ
NSS Falling to MISO Valid
—
4 x TSYSCLK
ns
TSDZ
NSS Rising to MISO High-Z
—
4 x TSYSCLK
ns
TCKH
SCK High Time
5 x TSYSCLK
—
ns
TCKL
SCK Low Time
5 x TSYSCLK
—
ns
TSIS
MOSI Valid to SCK Sample Edge
2 x TSYSCLK
—
ns
TSIH
SCK Sample Edge to MOSI Change
2 x TSYSCLK
—
ns
TSOH
SCK Shift Edge to MISO Change
—
4 x TSYSCLK
ns
TSLH
Last SCK Edge to MISO Change 
(CKPHA = 1 ONLY)
6 x TSYSCLK
8 x TSYSCLK
ns
Note: TSYSCLK is equal to one period of the device system clock (SYSCLK).
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24. Timers
Each MCU includes four counter/timers: two are 16-bit counter/timers compatible with those found in the
standard 8051, and two are 16-bit auto-reload timer for use with the ADC, SMBus, or for general purpose
use. These timers can be used to measure time intervals, count external events and generate periodic
interrupt requests. Timer 0 and Timer 1 are nearly identical and have four primary modes of operation.
Timer 2 and Timer 3 offer 16-bit and split 8-bit timer functionality with auto-reload. Additionally, Timer 3
offers the ability to be clocked from the external oscillator while the device is in Suspend mode, and can be
used as a wake-up source. This allows for implementation of a very low-power system, including RTC
capability.
Timer 0 and Timer 1 Modes:
13-bit counter/timer
16-bit counter/timer
8-bit counter/timer with
auto-reload
Two 8-bit counter/timers
(Timer 0 only)
Timer 2 Modes:
Timer 3 Modes:
16-bit timer with auto-reload
16-bit timer with auto-reload
Two 8-bit timers with auto-reload
Two 8-bit timers with auto-reload
Timers 0 and 1 may be clocked by one of five sources, determined by the Timer Mode Select bits (T1M–
T0M) and the Clock Scale bits (SCA1–SCA0). The Clock Scale bits define a pre-scaled clock from which
Timer 0 and/or Timer 1 may be clocked (See SFR Definition 24.1 for pre-scaled clock selection).
Timer 0/1 may then be configured to use this pre-scaled clock signal or the system clock. Timer 2 and
Timer 3 may be clocked by the system clock, the system clock divided by 12, or the external oscillator
clock source divided by 8.
Timer 0 and Timer 1 may also be operated as counters. When functioning as a counter, a counter/timer
register is incremented on each high-to-low transition at the selected input pin (T0 or T1). Events with a frequency of up to one-fourth the system clock frequency can be counted. The input signal need not be periodic, but it should be held at a given level for at least two full system clock cycles to ensure the level is
properly sampled.
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SFR Definition 24.1. CKCON: Clock Control
Bit
7
6
5
4
3
2
Name
T3MH
T3ML
T2MH
T2ML
T1M
T0M
SCA[1:0]
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
SFR Address = 0x8E
Bit
Name
7
T3MH
1
0
0
0
Function
Timer 3 High Byte Clock Select.
Selects the clock supplied to the Timer 3 high byte (split 8-bit timer mode only).
0: Timer 3 high byte uses the clock defined by the T3XCLK bit in TMR3CN.
1: Timer 3 high byte uses the system clock.
6
T3ML
Timer 3 Low Byte Clock Select.
Selects the clock supplied to Timer 3. Selects the clock supplied to the lower 8-bit timer
in split 8-bit timer mode.
0: Timer 3 low byte uses the clock defined by the T3XCLK bit in TMR3CN.
1: Timer 3 low byte uses the system clock.
5
T2MH
Timer 2 High Byte Clock Select.
Selects the clock supplied to the Timer 2 high byte (split 8-bit timer mode only).
0: Timer 2 high byte uses the clock defined by the T2XCLK bit in TMR2CN.
1: Timer 2 high byte uses the system clock.
4
T2ML
Timer 2 Low Byte Clock Select.
Selects the clock supplied to Timer 2. If Timer 2 is configured in split 8-bit timer mode,
this bit selects the clock supplied to the lower 8-bit timer.
0: Timer 2 low byte uses the clock defined by the T2XCLK bit in TMR2CN.
1: Timer 2 low byte uses the system clock.
3
T1
Timer 1 Clock Select.
Selects the clock source supplied to Timer 1. Ignored when C/T1 is set to 1.
0: Timer 1 uses the clock defined by the prescale bits SCA[1:0].
1: Timer 1 uses the system clock.
2
T0
Timer 0 Clock Select.
Selects the clock source supplied to Timer 0. Ignored when C/T0 is set to 1.
0: Counter/Timer 0 uses the clock defined by the prescale bits SCA[1:0].
1: Counter/Timer 0 uses the system clock.
1:0
SCA[1:0] Timer 0/1 Prescale Bits.
These bits control the Timer 0/1 Clock Prescaler:
00: System clock divided by 12
01: System clock divided by 4
10: System clock divided by 48
11: External clock divided by 8 (synchronized with the system clock)
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24.1. Timer 0 and Timer 1
Each timer is implemented as a 16-bit register accessed as two separate bytes: a low byte (TL0 or TL1)
and a high byte (TH0 or TH1). The Counter/Timer Control register (TCON) is used to enable Timer 0 and
Timer 1 as well as indicate status. Timer 0 interrupts can be enabled by setting the ET0 bit in the IE register (Section “15.2. Interrupt Register Descriptions” on page 82); Timer 1 interrupts can be enabled by setting the ET1 bit in the IE register (Section “15.2. Interrupt Register Descriptions” on page 82). Both
counter/timers operate in one of four primary modes selected by setting the Mode Select bits T1M1–T0M0
in the Counter/Timer Mode register (TMOD). Each timer can be configured independently. Each operating
mode is described below.
24.1.1. Mode 0: 13-bit Counter/Timer
Timer 0 and Timer 1 operate as 13-bit counter/timers in Mode 0. The following describes the configuration
and operation of Timer 0. However, both timers operate identically, and Timer 1 is configured in the same
manner as described for Timer 0.
The TH0 register holds the eight MSBs of the 13-bit counter/timer. TL0 holds the five LSBs in bit positions
TL0.4–TL0.0. The three upper bits of TL0 (TL0.7–TL0.5) are indeterminate and should be masked out or
ignored when reading. As the 13-bit timer register increments and overflows from 0x1FFF (all ones) to
0x0000, the timer overflow flag TF0 in TCON is set and an interrupt will occur if Timer 0 interrupts are
enabled.
The C/T0 bit in the TMOD register selects the counter/timer's clock source. When C/T0 is set to logic 1,
high-to-low transitions at the selected Timer 0 input pin (T0) increment the timer register (Refer to Section
“20.3. Priority Crossbar Decoder” on page 114 for information on selecting and configuring external I/O
pins). Clearing C/T selects the clock defined by the T0M bit in register CKCON. When T0M is set, Timer 0
is clocked by the system clock. When T0M is cleared, Timer 0 is clocked by the source selected by the
Clock Scale bits in CKCON (see SFR Definition 24.1).
Setting the TR0 bit (TCON.4) enables the timer when either GATE0 in the TMOD register is logic 0 or the
input signal INT0 is active as defined by bit IN0PL in register IT01CF (see SFR Definition 15.5). Setting
GATE0 to 1 allows the timer to be controlled by the external input signal INT0 (see Section “15.2. Interrupt
Register Descriptions” on page 82), facilitating pulse width measurements
TR0
GATE0
INT0
Counter/Timer
0
1
1
1
X
0
1
1
X
X
0
1
Disabled
Enabled
Disabled
Enabled
Note: X = Don't Care
Setting TR0 does not force the timer to reset. The timer registers should be loaded with the desired initial
value before the timer is enabled.
TL1 and TH1 form the 13-bit register for Timer 1 in the same manner as described above for TL0 and TH0.
Timer 1 is configured and controlled using the relevant TCON and TMOD bits just as with Timer 0. The
input signal INT0 is used with Timer 1; the /INT1 polarity is defined by bit IN1PL in register IT01CF (see
SFR Definition 15.5).
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TMOD
G
A
T
E
1
T0M
Pre-scaled Clock
C
/
T
1
T T
1 1
MM
1 0
G
A
T
E
0
C
/
T
0
IT01CF
T T
0 0
MM
1 0
I
N
1
P
L
I
N
1
S
L
2
I
N
1
S
L
1
I
N
1
S
L
0
I
N
0
P
L
I
N
0
S
L
2
I
N
0
S
L
1
I
N
0
S
L
0
0
0
SYSCLK
1
1
TCLK
TR0
TL0
(5 bits)
TH0
(8 bits)
GATE0
Crossbar
/INT0
IN0PL
TCON
T0
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Interrupt
XOR
Figure 24.1. T0 Mode 0 Block Diagram
24.1.2. Mode 1: 16-bit Counter/Timer
Mode 1 operation is the same as Mode 0, except that the counter/timer registers use all 16 bits. The counter/timers are enabled and configured in Mode 1 in the same manner as for Mode 0.
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24.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures Timer 0 and Timer 1 to operate as 8-bit counter/timers with automatic reload of the start
value. TL0 holds the count and TH0 holds the reload value. When the counter in TL0 overflows from all
ones to 0x00, the timer overflow flag TF0 in the TCON register is set and the counter in TL0 is reloaded
from TH0. If Timer 0 interrupts are enabled, an interrupt will occur when the TF0 flag is set. The reload
value in TH0 is not changed. TL0 must be initialized to the desired value before enabling the timer for the
first count to be correct. When in Mode 2, Timer 1 operates identically to Timer 0.
Both counter/timers are enabled and configured in Mode 2 in the same manner as Mode 0. Setting the
TR0 bit (TCON.4) enables the timer when either GATE0 in the TMOD register is logic 0 or when the input
signal INT0 is active as defined by bit IN0PL in register IT01CF (see Section “15.3. INT0 and INT1 External
Interrupts” on page 87 for details on the external input signals INT0 and INT1).
TMOD
G
A
T
E
1
T0M
Pre-scaled Clock
C
/
T
1
T T
1 1
MM
1 0
G
A
T
E
0
C
/
T
0
IT01CF
T T
0 0
MM
1 0
I
N
1
P
L
I
N
1
S
L
2
I
N
1
S
L
1
I
N
1
S
L
0
I
N
0
P
L
I
N
0
S
L
2
I
N
0
S
L
1
I
N
0
S
L
0
0
0
SYSCLK
1
1
T0
TL0
(8 bits)
TCON
TCLK
TR0
Crossbar
GATE0
TH0
(8 bits)
/INT0
IN0PL
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Interrupt
Reload
XOR
Figure 24.2. T0 Mode 2 Block Diagram
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24.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)
In Mode 3, Timer 0 is configured as two separate 8-bit counter/timers held in TL0 and TH0. The counter/timer in TL0 is controlled using the Timer 0 control/status bits in TCON and TMOD: TR0, C/T0, GATE0
and TF0. TL0 can use either the system clock or an external input signal as its timebase. The TH0 register
is restricted to a timer function sourced by the system clock or prescaled clock. TH0 is enabled using the
Timer 1 run control bit TR1. TH0 sets the Timer 1 overflow flag TF1 on overflow and thus controls the
Timer 1 interrupt.
Timer 1 is inactive in Mode 3. When Timer 0 is operating in Mode 3, Timer 1 can be operated in Modes 0,
1 or 2, but cannot be clocked by external signals nor set the TF1 flag and generate an interrupt. However,
the Timer 1 overflow can be used to generate baud rates for the SMBus and/or UART, and/or initiate ADC
conversions. While Timer 0 is operating in Mode 3, Timer 1 run control is handled through its mode settings. To run Timer 1 while Timer 0 is in Mode 3, set the Timer 1 Mode as 0, 1, or 2. To disable Timer 1,
configure it for Mode 3.
TMOD
G
A
T
E
1
T0M
Pre-scaled Clock
C
/
T
1
T T
1 1
MM
1 0
G
A
T
E
0
C
/
T
0
T T
0 0
MM
1 0
0
TR1
SYSCLK
TH0
(8 bits)
1
TCON
0
1
T0
TL0
(8 bits)
TR0
Crossbar
/INT0
GATE0
IN0PL
XOR
Figure 24.3. T0 Mode 3 Block Diagram
174
Rev. 1.0
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Interrupt
Interrupt
C8051T630/1/2/3/4/5
SFR Definition 24.2. TCON: Timer Control
Bit
7
6
5
4
3
2
1
0
Name
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0x88; Bit-Addressable
Bit
Name
7
TF1
Function
Timer 1 Overflow Flag.
Set to 1 by hardware when Timer 1 overflows. This flag can be cleared by software
but is automatically cleared when the CPU vectors to the Timer 1 interrupt service
routine.
6
TR1
Timer 1 Run Control.
Timer 1 is enabled by setting this bit to 1.
5
TF0
Timer 0 Overflow Flag.
Set to 1 by hardware when Timer 0 overflows. This flag can be cleared by software
but is automatically cleared when the CPU vectors to the Timer 0 interrupt service
routine.
4
TR0
Timer 0 Run Control.
Timer 0 is enabled by setting this bit to 1.
3
IE1
External Interrupt 1.
This flag is set by hardware when an edge/level of type defined by IT1 is detected. It
can be cleared by software but is automatically cleared when the CPU vectors to the
External Interrupt 1 service routine in edge-triggered mode.
2
IT1
Interrupt 1 Type Select.
This bit selects whether the configured /INT1 interrupt will be edge or level sensitive.
/INT1 is configured active low or high by the IN1PL bit in the IT01CF register (see
SFR Definition 15.5).
0: /INT1 is level triggered.
1: /INT1 is edge triggered.
1
IE0
External Interrupt 0.
This flag is set by hardware when an edge/level of type defined by IT1 is detected. It
can be cleared by software but is automatically cleared when the CPU vectors to the
External Interrupt 0 service routine in edge-triggered mode.
0
IT0
Interrupt 0 Type Select.
This bit selects whether the configured INT0 interrupt will be edge or level sensitive.
INT0 is configured active low or high by the IN0PL bit in register IT01CF (see SFR
Definition 15.5).
0: INT0 is level triggered.
1: INT0 is edge triggered.
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SFR Definition 24.3. TMOD: Timer Mode
Bit
7
6
Name
GATE1
C/T1
Type
R/W
R/W
Reset
0
0
5
4
3
2
T1M[1:0]
GATE0
C/T0
T0M[1:0]
R/W
R/W
R/W
R/W
0
0
0
0
SFR Address = 0x89
Bit
Name
7
GATE1
1
0
0
0
Function
Timer 1 Gate Control.
0: Timer 1 enabled when TR1 = 1 irrespective of INT1 logic level.
1: Timer 1 enabled only when TR1 = 1 AND INT1 is active as defined by bit IN1PL in
register IT01CF (see SFR Definition 15.5).
6
C/T1
Counter/Timer 1 Select.
0: Timer: Timer 1 incremented by clock defined by T1M bit in register CKCON.
1: Counter: Timer 1 incremented by high-to-low transitions on external pin (T1).
5:4
T1M[1:0]
Timer 1 Mode Select.
These bits select the Timer 1 operation mode.
00: Mode 0, 13-bit Counter/Timer
01: Mode 1, 16-bit Counter/Timer
10: Mode 2, 8-bit Counter/Timer with Auto-Reload
11: Mode 3, Timer 1 Inactive
3
GATE0
Timer 0 Gate Control.
0: Timer 0 enabled when TR0 = 1 irrespective of INT0 logic level.
1: Timer 0 enabled only when TR0 = 1 AND INT0 is active as defined by bit IN0PL in
register IT01CF (see SFR Definition 15.5).
2
C/T0
Counter/Timer 0 Select.
0: Timer: Timer 0 incremented by clock defined by T0M bit in register CKCON.
1: Counter: Timer 0 incremented by high-to-low transitions on external pin (T0).
1:0
T0M[1:0]
Timer 0 Mode Select.
These bits select the Timer 0 operation mode.
00: Mode 0, 13-bit Counter/Timer
01: Mode 1, 16-bit Counter/Timer
10: Mode 2, 8-bit Counter/Timer with Auto-Reload
11: Mode 3, Two 8-bit Counter/Timers
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SFR Definition 24.4. TL0: Timer 0 Low Byte
Bit
7
6
5
4
Name
TL0[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x8A
Bit
Name
7:0
TL0[7:0]
3
2
1
0
0
0
0
0
3
2
1
0
0
0
0
0
Function
Timer 0 Low Byte.
The TL0 register is the low byte of the 16-bit Timer 0.
SFR Definition 24.5. TL1: Timer 1 Low Byte
Bit
7
6
5
4
Name
TL1[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x8B
Bit
Name
7:0
TL1[7:0]
Function
Timer 1 Low Byte.
The TL1 register is the low byte of the 16-bit Timer 1.
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SFR Definition 24.6. TH0: Timer 0 High Byte
Bit
7
6
5
4
Name
TH0[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x8C
Bit
Name
7:0
TH0[7:0]
3
2
1
0
0
0
0
0
Function
Timer 0 High Byte.
The TH0 register is the high byte of the 16-bit Timer 0.
SFR Definition 24.7. TH1: Timer 1 High Byte
Bit
7
6
5
4
Name
TH1[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x8D
Bit
Name
7:0
TH1[7:0]
3
2
1
0
0
0
0
0
Function
Timer 1 High Byte.
The TH1 register is the high byte of the 16-bit Timer 1.
178
Rev. 1.0
C8051T630/1/2/3/4/5
24.2. Timer 2
Timer 2 is a 16-bit timer formed by two 8-bit SFRs: TMR2L (low byte) and TMR2H (high byte). Timer 2 may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T2SPLIT bit (TMR2CN.3) defines
the Timer 2 operation mode.
Timer 2 may be clocked by the system clock, the system clock divided by 12, or the external oscillator
source divided by 8. The external clock mode is ideal for real-time clock (RTC) functionality, where the
internal oscillator drives the system clock while Timer 2 (and/or the PCA) is clocked by an external precision oscillator. Note that the external oscillator source divided by 8 is synchronized with the system clock.
24.2.1. 16-bit Timer with Auto-Reload
When T2SPLIT (TMR2CN.3) is zero, Timer 2 operates as a 16-bit timer with auto-reload. Timer 2 can be
clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the
16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 2
reload registers (TMR2RLH and TMR2RLL) is loaded into the Timer 2 register as shown in Figure 24.4,
and the Timer 2 High Byte Overflow Flag (TMR2CN.7) is set. If Timer 2 interrupts are enabled (if IE.5 is
set), an interrupt will be generated on each Timer 2 overflow. Additionally, if Timer 2 interrupts are enabled
and the TF2LEN bit is set (TMR2CN.5), an interrupt will be generated each time the lower 8 bits (TMR2L)
overflow from 0xFF to 0x00.
CKCON
T2XCLK
SYSCLK / 12
T T T T T T S
3 3 2 2 1 0 C
MMMMMMA
H L H L
1
S
C
A
0
TL2
Overflow
0
SYSCLK
1
TCLK
TMR2L
TMR2H
TMR2CN
TR2
External Clock / 8
To ADC,
SMBus
To SMBus
0
1
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
Interrupt
T2XCLK
TMR2RLL TMR2RLH
Reload
Figure 24.4. Timer 2 16-Bit Mode Block Diagram
Rev. 1.0
179
C8051T630/1/2/3/4/5
24.2.2. 8-bit Timers with Auto-Reload
When T2SPLIT is set, Timer 2 operates as two 8-bit timers (TMR2H and TMR2L). Both 8-bit timers operate in auto-reload mode as shown in Figure 24.5. TMR2RLL holds the reload value for TMR2L; TMR2RLH
holds the reload value for TMR2H. The TR2 bit in TMR2CN handles the run control for TMR2H. TMR2L is
always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock
source divided by 8. The Timer 2 Clock Select bits (T2MH and T2ML in CKCON) select either SYSCLK or
the clock defined by the Timer 2 External Clock Select bit (T2XCLK in TMR2CN), as follows:
T2MH
T2XCLK
0
0
1
0
1
X
TMR2H Clock Source
SYSCLK / 12
External Clock / 8
SYSCLK
T2ML
T2XCLK
0
0
1
0
1
X
TMR2L Clock Source
SYSCLK / 12
External Clock / 8
SYSCLK
The TF2H bit is set when TMR2H overflows from 0xFF to 0x00; the TF2L bit is set when TMR2L overflows
from 0xFF to 0x00. When Timer 2 interrupts are enabled (IE.5), an interrupt is generated each time
TMR2H overflows. If Timer 2 interrupts are enabled and TF2LEN (TMR2CN.5) is set, an interrupt is generated each time either TMR2L or TMR2H overflows. When TF2LEN is enabled, software must check the
TF2H and TF2L flags to determine the source of the Timer 2 interrupt. The TF2H and TF2L interrupt flags
are not cleared by hardware and must be manually cleared by software.
CKCON
T T T T T T S
3 3 2 2 1 0 C
MMMMMMA
H L H L
1
T2XCLK
SYSCLK / 12
0
External Clock / 8
1
S
C
A
0
TMR2RLH
Reload
To SMBus
0
TCLK
TR2
TMR2H
TMR2RLL
SYSCLK
Reload
TMR2CN
1
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
T2XCLK
1
TCLK
TMR2L
To ADC,
SMBus
0
Figure 24.5. Timer 2 8-Bit Mode Block Diagram
180
Rev. 1.0
Interrupt
C8051T630/1/2/3/4/5
24.2.3. Low-Frequency Oscillator (LFO) Capture Mode
The Low-Frequency Oscillator Capture Mode allows the LFO clock to be measured against the system
clock or an external oscillator source. Timer 2 can be clocked from the system clock, the system clock
divided by 12, or the external oscillator divided by 8, depending on the T2ML (CKCON.4), and T2XCLK
settings.
Setting TF2CEN to 1 enables the LFO Capture Mode for Timer 2. In this mode, T2SPLIT should be set to
0, as the full 16-bit timer is used. Upon a falling edge of the low-frequency oscillator, the contents of Timer
2 (TMR2H:TMR2L) are loaded into the Timer 2 reload registers (TMR2RLH:TMR2RLL) and the TF2H flag
is set. By recording the difference between two successive timer capture values, the LFO clock frequency
can be determined with respect to the Timer 2 clock. The Timer 2 clock should be much faster than the
LFO to achieve an accurate reading.
CKCON
T2XCLK
SYSCLK / 12
TTTTTTSS
3 3 2 2 1 0CC
MMMMMM A A
HLHL
1 0
0
0
TR2
SYSCLK
Low-Frequency
Oscillator
TCLK
1
TMR2L
TMR2H
Capture
1
TF2CEN
TMR2RLL TMR2RLH
TMR2CN
External Clock / 8
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
Interrupt
T2XCLK
Figure 24.6. Timer 2 Low-Frequency Oscillation Capture Mode Block Diagram
Rev. 1.0
181
C8051T630/1/2/3/4/5
SFR Definition 24.8. TMR2CN: Timer 2 Control
Bit
7
6
5
4
3
2
Name
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
Type
R/W
R/W
R/W
R/W
R/W
R/W
R
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xC8; Bit-Addressable
Bit
Name
7
TF2H
1
0
T2XCLK
Function
Timer 2 High Byte Overflow Flag.
Set by hardware when the Timer 2 high byte overflows from 0xFF to 0x00. In 16 bit
mode, this will occur when Timer 2 overflows from 0xFFFF to 0x0000. When the
Timer 2 interrupt is enabled, setting this bit causes the CPU to vector to the Timer 2
interrupt service routine. This bit is not automatically cleared by hardware.
6
TF2L
Timer 2 Low Byte Overflow Flag.
Set by hardware when the Timer 2 low byte overflows from 0xFF to 0x00. TF2L will
be set when the low byte overflows regardless of the Timer 2 mode. This bit is not
automatically cleared by hardware.
5
TF2LEN
Timer 2 Low Byte Interrupt Enable.
When set to 1, this bit enables Timer 2 Low Byte interrupts. If Timer 2 interrupts are
also enabled, an interrupt will be generated when the low byte of Timer 2 overflows.
4
TF2CEN
Timer 2 Low-Frequency Oscillator Capture Enable.
When set to 1, this bit enables Timer 2 Low-Frequency Oscillator Capture Mode. If
TF2CEN is set and Timer 2 interrupts are enabled, an interrupt will be generated on
a falling edge of the low-frequency oscillator output, and the current 16-bit timer
value in TMR2H:TMR2L will be copied to TMR2RLH:TMR2RLL.
3
T2SPLIT
Timer 2 Split Mode Enable.
When this bit is set, Timer 2 operates as two 8-bit timers with auto-reload.
0: Timer 2 operates in 16-bit auto-reload mode.
1: Timer 2 operates as two 8-bit auto-reload timers.
2
TR2
Timer 2 Run Control.
Timer 2 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables
TMR2H only; TMR2L is always enabled in split mode.
1
0
Unused
T2XCLK
Unused. Read = 0b; Write = Don’t Care
Timer 2 External Clock Select.
This bit selects the external clock source for Timer 2. If Timer 2 is in 8-bit mode, this
bit selects the external oscillator clock source for both timer bytes. However, the
Timer 2 Clock Select bits (T2MH and T2ML in register CKCON) may still be used to
select between the external clock and the system clock for either timer.
0: Timer 2 clock is the system clock divided by 12.
1: Timer 2 clock is the external clock divided by 8 (synchronized with SYSCLK).
182
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 24.9. TMR2RLL: Timer 2 Reload Register Low Byte
Bit
7
6
5
4
3
Name
TMR2RLL[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0xCA
Bit
Name
7:0
2
1
0
0
0
0
2
1
0
0
0
0
2
1
0
0
0
0
Function
TMR2RLL[7:0] Timer 2 Reload Register Low Byte.
TMR2RLL holds the low byte of the reload value for Timer 2.
SFR Definition 24.10. TMR2RLH: Timer 2 Reload Register High Byte
Bit
7
6
5
4
3
Name
TMR2RLH[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0xCB
Bit
Name
Function
7:0 TMR2RLH[7:0] Timer 2 Reload Register High Byte.
TMR2RLH holds the high byte of the reload value for Timer 2.
SFR Definition 24.11. TMR2L: Timer 2 Low Byte
Bit
7
6
5
4
3
Name
TMR2L[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xCC
Bit
Name
7:0
0
Function
TMR2L[7:0] Timer 2 Low Byte.
In 16-bit mode, the TMR2L register contains the low byte of the 16-bit Timer 2. In 8bit mode, TMR2L contains the 8-bit low byte timer value.
Rev. 1.0
183
C8051T630/1/2/3/4/5
SFR Definition 24.12. TMR2H Timer 2 High Byte
Bit
7
6
5
4
3
Name
TMR2H[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0xCD
Bit
Name
7:0
0
2
1
0
0
0
0
Function
TMR2H[7:0] Timer 2 Low Byte.
In 16-bit mode, the TMR2H register contains the high byte of the 16-bit Timer 2. In 8bit mode, TMR2H contains the 8-bit high byte timer value.
184
Rev. 1.0
C8051T630/1/2/3/4/5
24.3. Timer 3
Timer 3 is a 16-bit timer formed by two 8-bit SFRs: TMR3L (low byte) and TMR3H (high byte). Timer 3 may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T3SPLIT bit (TMR3CN.3) defines
the Timer 3 operation mode.
Timer 3 may be clocked by the system clock, the system clock divided by 12, the external oscillator source
divided by 8, or the internal low-frequency oscillator divided by 8. The external clock mode is ideal for realtime clock (RTC) functionality, where the internal high-frequency oscillator drives the system clock while
Timer 3 is clocked by an external oscillator source. Note that the external oscillator source divided by 8 and
the LFO source divided by 8 are synchronized with the system clock when in all operating modes except
suspend. When the internal oscillator is placed in suspend mode, The external clock/8 signal or the LFO/8
output can directly drive the timer. This allows the use of an external clock or the LFO to wake up the
device from suspend mode. The timer will continue to run in suspend mode and count up. When the timer
overflow occurs, the device will wake from suspend mode, and begin executing code again. The timer
value may be set prior to entering suspend, to overflow in the desired amount of time (number of clocks) to
wake the device. If a wake-up source other than the timer wakes the device from suspend mode, it may
take up to three timer clocks before the timer registers can be read or written. During this time, the
STSYNC bit in register OSCICN will be set to 1, to indicate that it is not safe to read or write the timer registers.
Important Note: In internal LFO/8 mode, the divider for the internal LFO must be set to 1 for proper
functionality. The timer will not operate if the LFO divider is not set to 1.
24.3.1. 16-bit Timer with Auto-Reload
When T3SPLIT (TMR3CN.3) is zero, Timer 3 operates as a 16-bit timer with auto-reload. Timer 3 can be
clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the
16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 3
reload registers (TMR3RLH and TMR3RLL) is loaded into the Timer 3 register as shown in Figure 24.7,
and the Timer 3 High Byte Overflow Flag (TMR3CN.7) is set. If Timer 3 interrupts are enabled (if EIE1.7 is
set), an interrupt will be generated on each Timer 3 overflow. Additionally, if Timer 3 interrupts are enabled
and the TF3LEN bit is set (TMR3CN.5), an interrupt will be generated each time the lower 8 bits (TMR3L)
overflow from 0xFF to 0x00.
CKCON
T3XCLK[1:0]
SYSCLK / 12
T T T T T T S
3 3 2 2 1 0 C
MMMMMMA
H L H L
1
S
C
A
0
00
To ADC
01
Internal LFO / 8
11
0
TR3
TCLK
TMR3L
TMR3H
TMR3CN
External Clock / 8
1
SYSCLK
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
T3XCLK1
T3XCLK0
Interrupt
TMR3RLL TMR3RLH
Reload
Figure 24.7. Timer 3 16-Bit Mode Block Diagram
Rev. 1.0
185
C8051T630/1/2/3/4/5
24.3.2. 8-bit Timers with Auto-Reload
When T3SPLIT is set, Timer 3 operates as two 8-bit timers (TMR3H and TMR3L). Both 8-bit timers operate in auto-reload mode as shown in Figure 24.8. TMR3RLL holds the reload value for TMR3L; TMR3RLH
holds the reload value for TMR3H. The TR3 bit in TMR3CN handles the run control for TMR3H. TMR3L is
always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, the external oscillator clock
source divided by 8, or the internal Low-frequency Oscillator. The Timer 3 Clock Select bits (T3MH and
T3ML in CKCON) select either SYSCLK or the clock defined by the Timer 3 External Clock Select bits
(T3XCLK[1:0] in TMR3CN), as follows:
T3MH
T3XCLK[1:0] TMR3H Clock
Source
0
0
0
0
1
00
01
10
11
X
T3ML
SYSCLK / 12
External Clock / 8
Reserved
Internal LFO
SYSCLK
T3XCLK[1:0] TMR3L Clock
Source
0
0
0
0
1
00
01
10
11
X
SYSCLK / 12
External Clock / 8
Reserved
Internal LFO
SYSCLK
The TF3H bit is set when TMR3H overflows from 0xFF to 0x00; the TF3L bit is set when TMR3L overflows
from 0xFF to 0x00. When Timer 3 interrupts are enabled, an interrupt is generated each time TMR3H overflows. If Timer 3 interrupts are enabled and TF3LEN (TMR3CN.5) is set, an interrupt is generated each
time either TMR3L or TMR3H overflows. When TF3LEN is enabled, software must check the TF3H and
TF3L flags to determine the source of the Timer 3 interrupt. The TF3H and TF3L interrupt flags are not
cleared by hardware and must be manually cleared by software.
CKCON
TTTTTTSS
3 3 2 2 1 0 CC
MMMMMM A A
HLHL
1 0
T3XCLK[1:0]
SYSCLK / 12
00
External Clock / 8
01
TMR3RLH
Reload
0
TCLK
TR3
11
TMR3RLL
SYSCLK
Reload
TMR3CN
Internal LFO / 8
TMR3H
1
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
T3XCLK1
T3XCLK0
1
TCLK
TMR3L
To ADC
0
Figure 24.8. Timer 3 8-Bit Mode Block Diagram
186
Rev. 1.0
Interrupt
C8051T630/1/2/3/4/5
24.3.3. Low-Frequency Oscillator (LFO) Capture Mode
The Low-Frequency Oscillator Capture Mode allows the LFO clock to be measured against the system
clock or an external oscillator source. Timer 3 can be clocked from the system clock, the system clock
divided by 12, or the external oscillator divided by 8, depending on the T3ML (CKCON.6), and
T3XCLK[1:0] settings.
Setting TF3CEN to 1 enables the LFO Capture Mode for Timer 3. In this mode, T3SPLIT should be set to
0, as the full 16-bit timer is used. Upon a falling edge of the low-frequency oscillator, the contents of
Timer 3 (TMR3H:TMR3L) are loaded into the Timer 3 reload registers (TMR3RLH:TMR3RLL) and the
TF3H flag is set. By recording the difference between two successive timer capture values, the LFO clock
frequency can be determined with respect to the Timer 3 clock. The Timer 3 clock should be much faster
than the LFO to achieve an accurate reading. This means that the LFO/8 should not be selected as the
timer clock source in this mode.
CKCON
T3XCLK[1:0]
SYSCLK / 12
TTTTTTSS
3 3 2 2 1 0CC
MMMMMM A A
HLHL
1 0
00
0
TR3
SYSCLK
Low-Frequency
Oscillator
TCLK
01
TMR3L
TMR3H
Capture
1
TF3CEN
TMR3RLL TMR3RLH
TMR3CN
External Clock / 8
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
T3XCLK1
T3XCLK0
Interrupt
Figure 24.9. Timer 3 Low-Frequency Oscillation Capture Mode Block Diagram
Rev. 1.0
187
C8051T630/1/2/3/4/5
SFR Definition 24.13. TMR3CN: Timer 3 Control
Bit
7
6
5
4
3
2
Name
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
T3XCLK[1:0]
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
SFR Address = 0x91
Bit
Name
7
TF3H
1
0
0
0
Function
Timer 3 High Byte Overflow Flag.
Set by hardware when the Timer 3 high byte overflows from 0xFF to 0x00. In 16 bit
mode, this will occur when Timer 3 overflows from 0xFFFF to 0x0000. When the
Timer 3 interrupt is enabled, setting this bit causes the CPU to vector to the Timer 3
interrupt service routine. This bit is not automatically cleared by hardware.
6
TF3L
Timer 3 Low Byte Overflow Flag.
Set by hardware when the Timer 3 low byte overflows from 0xFF to 0x00. TF3L will
be set when the low byte overflows regardless of the Timer 3 mode. This bit is not
automatically cleared by hardware.
5
TF3LEN
Timer 3 Low Byte Interrupt Enable.
When set to 1, this bit enables Timer 3 Low Byte interrupts. If Timer 3 interrupts are
also enabled, an interrupt will be generated when the low byte of Timer 3 overflows.
4
TF3CEN
Timer 3 Low-Frequency Oscillator Capture Enable.
When set to 1, this bit enables Timer 3 Low-Frequency Oscillator Capture Mode. If
TF3CEN is set and Timer 3 interrupts are enabled, an interrupt will be generated on
a falling edge of the low-frequency oscillator output, and the current 16-bit timer
value in TMR3H:TMR3L will be copied to TMR3RLH:TMR3RLL.
3
T3SPLIT
Timer 3 Split Mode Enable.
When this bit is set, Timer 3 operates as two 8-bit timers with auto-reload.
0: Timer 3 operates in 16-bit auto-reload mode.
1: Timer 3 operates as two 8-bit auto-reload timers.
2
TR3
Timer 3 Run Control.
Timer 3 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables
TMR3H only; TMR3L is always enabled in split mode.
1:0
T3XCLK[1:0] Timer 3 External Clock Select.
This bit selects the “external” clock source for Timer 3. If Timer 3 is in 8-bit mode,
this bit selects the external oscillator clock source for both timer bytes. However, the
Timer 3 Clock Select bits (T3MH and T3ML in register CKCON) may still be used to
select between the external clock and the system clock for either timer.
00: System clock divided by 12.
01: External clock divided by 8 (synchronized with SYSCLK when not in suspend).
10: Reserved.
11: Internal LFO/8 (synchronized with SYSCLK when not in suspend).
188
Rev. 1.0
C8051T630/1/2/3/4/5
SFR Definition 24.14. TMR3RLL: Timer 3 Reload Register Low Byte
Bit
7
6
5
4
3
Name
TMR3RLL[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0x92
Bit
Name
7:0
2
1
0
0
0
0
2
1
0
0
0
0
2
1
0
0
0
0
Function
TMR3RLL[7:0] Timer 3 Reload Register Low Byte.
TMR3RLL holds the low byte of the reload value for Timer 3.
SFR Definition 24.15. TMR3RLH: Timer 3 Reload Register High Byte
Bit
7
6
5
4
3
Name
TMR3RLH[7:0]
Type
R/W
Reset
0
0
0
0
0
SFR Address = 0x93
Bit
Name
Function
7:0 TMR3RLH[7:0] Timer 3 Reload Register High Byte.
TMR3RLH holds the high byte of the reload value for Timer 3.
SFR Definition 24.16. TMR3L: Timer 3 Low Byte
Bit
7
6
5
4
3
Name
TMR3L[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x94
Bit
Name
7:0
TMR3L[7:0]
0
Function
Timer 3 Low Byte.
In 16-bit mode, the TMR3L register contains the low byte of the 16-bit Timer 3. In
8-bit mode, TMR3L contains the 8-bit low byte timer value.
Rev. 1.0
189
C8051T630/1/2/3/4/5
SFR Definition 24.17. TMR3H Timer 3 High Byte
Bit
7
6
5
4
3
Name
TMR3H[7:0]
Type
R/W
Reset
0
0
0
0
SFR Address = 0x95
Bit
Name
7:0
TMR3H[7:0]
0
2
1
0
0
0
0
Function
Timer 3 High Byte.
In 16-bit mode, the TMR3H register contains the high byte of the 16-bit Timer 3. In
8-bit mode, TMR3H contains the 8-bit high byte timer value.
190
Rev. 1.0
C8051T630/1/2/3/4/5
25. Programmable Counter Array
The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU
intervention than the standard 8051 counter/timers. The PCA consists of a dedicated 16-bit counter/timer
and three 16-bit capture/compare modules. Each capture/compare module has its own associated I/O line
(CEXn) which is routed through the Crossbar to Port I/O when enabled. The counter/timer is driven by a
programmable timebase that can select between six sources: system clock, system clock divided by four,
system clock divided by twelve, the external oscillator clock source divided by 8, Timer 0 overflows, or an
external clock signal on the ECI input pin. Each capture/compare module may be configured to operate
independently in one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Output, Frequency Output, 8 to 11-Bit PWM, or 16-Bit PWM (each mode is described in Section
“25.3. Capture/Compare Modules” on page 194). The external oscillator clock option is ideal for real-time
clock (RTC) functionality, allowing the PCA to be clocked by a precision external oscillator while the internal oscillator drives the system clock. The PCA is configured and controlled through the system controller's
Special Function Registers. The PCA block diagram is shown in Figure 25.1
Important Note: The PCA Module 2 may be used as a watchdog timer (WDT), and is enabled in this mode
following a system reset. Access to certain PCA registers is restricted while WDT mode is enabled.
See Section 25.4 for details.
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
PCA
CLOCK
MUX
16-Bit Counter/Timer
SYSCLK
External Clock/8
Capture/Compare
Module 0
Capture/Compare
Module 1
Capture/Compare
Module 2 / WDT
CEX2
CEX1
CEX0
ECI
Crossbar
Port I/O
Figure 25.1. PCA Block Diagram
Rev. 1.0
191
C8051T630/1/2/3/4/5
25.1. PCA Counter/Timer
The 16-bit PCA counter/timer consists of two 8-bit SFRs: PCA0L and PCA0H. PCA0H is the high byte
(MSB) of the 16-bit counter/timer and PCA0L is the low byte (LSB). Reading PCA0L automatically latches
the value of PCA0H into a “snapshot” register; the following PCA0H read accesses this “snapshot” register.
Reading the PCA0L Register first guarantees an accurate reading of the entire 16-bit PCA0 counter.
Reading PCA0H or PCA0L does not disturb the counter operation. The CPS2–CPS0 bits in the PCA0MD
register select the timebase for the counter/timer as shown in Table 25.1.
When the counter/timer overflows from 0xFFFF to 0x0000, the Counter Overflow Flag (CF) in PCA0MD is
set to logic 1 and an interrupt request is generated if CF interrupts are enabled. Setting the ECF bit in
PCA0MD to logic 1 enables the CF flag to generate an interrupt request. The CF bit is not automatically
cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. Clearing the CIDL bit in the PCA0MD register allows the PCA to continue normal operation while the
CPU is in Idle mode.
Table 25.1. PCA Timebase Input Options
CPS2
CPS1
CPS0
Timebase
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
System clock divided by 12
System clock divided by 4
Timer 0 overflow
High-to-low transitions on ECI (max rate = system clock divided
by 4)
System clock
1
1
0
1
1
x
External oscillator source divided by 8*
Reserved
*Note: External oscillator source divided by 8 is synchronized with the system clock.
IDLE
PCA0MD
CWW
I DD
DT L
L E C
K
CCCE
PPPC
SSSF
2 1 0
PCA0CN
CC
FR
CCC
CCC
FFF
2 1 0
To SFR Bus
PCA0L
read
Snapshot
Register
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
SYSCLK
External Clock/8
000
001
010
0
011
1
PCA0H
PCA0L
Overflow
CF
100
101
To PCA Modules
Figure 25.2. PCA Counter/Timer Block Diagram
192
To PCA Interrupt System
Rev. 1.0
C8051T630/1/2/3/4/5
25.2. PCA0 Interrupt Sources
Figure 25.3 shows a diagram of the PCA interrupt tree. There are five independent event flags that can be
used to generate a PCA0 interrupt. They are: the main PCA counter overflow flag (CF), which is set upon
a 16-bit overflow of the PCA0 counter, an intermediate overflow flag (COVF), which can be set on an overflow from the 8th, 9th, 10th, or 11th bit of the PCA0 counter, and the individual flags for each PCA channel
(CCF0, CCF1, and CCF2), which are set according to the operation mode of that module. These event
flags are always set when the trigger condition occurs. Each of these flags can be individually selected to
generate a PCA0 interrupt, using the corresponding interrupt enable flag (ECF for CF, ECOV for COVF,
and ECCFn for each CCFn). PCA0 interrupts must be globally enabled before any individual interrupt
sources are recognized by the processor. PCA0 interrupts are globally enabled by setting the EA bit and
the EPCA0 bit to logic 1.
(for n = 0 to 2)
PCA0CPMn
P ECCMT P E
WC A A AOWC
MOPP TGMC
1 MP N n n n F
6 n n n
n
n
PCA0CN
CC
FR
CCC
CCC
FFF
2 1 0
PCA0MD
C WW
I DD
DT L
LEC
K
PCA0PWM
A
R
S
E
L
CCCE
PPPC
SSSF
2 1 0
EC
CO
OV
VF
PCA Counter/Timer 8, 9,
10 or 11-bit Overflow
C
L
S
E
L
1
C
L
S
E
L
0
Set 8, 9, 10, or 11 bit Operation
0
PCA Counter/Timer 16bit Overflow
1
ECCF0
PCA Module 0
(CCF0)
0
1
EPCA0
EA
0
0
0
1
1
1
Interrupt
Priority
Decoder
ECCF1
0
PCA Module 1
(CCF1)
1
ECCF2
PCA Module 2
(CCF2)
0
1
Figure 25.3. PCA Interrupt Block Diagram
Rev. 1.0
193
C8051T630/1/2/3/4/5
25.3. Capture/Compare Modules
Each module can be configured to operate independently in one of six operation modes: edge-triggered
capture, software timer, high-speed output, frequency output, 8 to 11-bit pulse width modulator, or 16-bit
pulse width modulator. Each module has Special Function Registers (SFRs) associated with it in the CIP51 system controller. These registers are used to exchange data with a module and configure the module's
mode of operation. Table 25.2 summarizes the bit settings in the PCA0CPMn and PCA0PWM registers
used to select the PCA capture/compare module’s operating mode. Note that all modules set to use 8, 9,
10, or 11-bit PWM mode must use the same cycle length (8–11 bits). Setting the ECCFn bit in a
PCA0CPMn register enables the module's CCFn interrupt.
Table 25.2. PCA0CPM and PCA0PWM Bit Settings for PCA Capture/Compare
Modules
Operational Mode
PCA0CPMn
PCA0PWM
Bit Number 7 6 5 4 3 2 1 0 7 6 5
4–2
1–0
Capture triggered by positive edge on CEXn
X X 1 0 0 0 0 A 0 X B XXX
XX
Capture triggered by negative edge on CEXn
X X 0 1 0 0 0 A 0 X B XXX
XX
Capture triggered by any transition on CEXn
X X 1 1 0 0 0 A 0 X B XXX
XX
Software Timer
X C 0 0 1 0 0 A 0 X B XXX
XX
High Speed Output
X C 0 0 1 1 0 A 0 X B XXX
XX
Frequency Output
X C 0 0 0 1 1 A 0 X B XXX
XX
8-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A 0 X B XXX
00
9-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XXX
01
10-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XXX
10
11-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XXX
11
16-Bit Pulse Width Modulator
1 C 0 0 E 0 1 A 0 X B XXX
XX
Notes:
1. X = Don’t Care (no functional difference for individual module if 1 or 0).
2. A = Enable interrupts for this module (PCA interrupt triggered on CCFn set to 1).
3. B = Enable 8th, 9th, 10th or 11th bit overflow interrupt (Depends on setting of CLSEL[1:0]).
4. C = When set to 0, the digital comparator is off. For high speed and frequency output modes, the
associated pin will not toggle. In any of the PWM modes, this generates a 0% duty cycle (output = 0).
5. D = Selects whether the Capture/Compare register (0) or the Auto-Reload register (1) for the associated
channel is accessed via addresses PCA0CPHn and PCA0CPLn.
6. E = When set, a match event will cause the CCFn flag for the associated channel to be set.
7. All modules set to 8, 9, 10 or 11-bit PWM mode use the same cycle length setting.
194
Rev. 1.0
C8051T630/1/2/3/4/5
25.3.1. Edge-triggered Capture Mode
In this mode, a valid transition on the CEXn pin causes the PCA to capture the value of the PCA counter/timer and load it into the corresponding module's 16-bit capture/compare register (PCA0CPLn and
PCA0CPHn). The CAPPn and CAPNn bits in the PCA0CPMn register are used to select the type of transition that triggers the capture: low-to-high transition (positive edge), high-to-low transition (negative edge),
or either transition (positive or negative edge). When a capture occurs, the Capture/Compare Flag (CCFn)
in PCA0CN is set to logic 1. An interrupt request is generated if the CCFn interrupt for that module is
enabled. The CCFn bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. If both CAPPn and CAPNn bits are set to logic 1, then the
state of the Port pin associated with CEXn can be read directly to determine whether a rising-edge or falling-edge caused the capture.
PCA Interrupt
PCA0CPMn
P ECCMT P E
WC A A AOWC
MOPP TGMC
1 MP N n n n F
6 n n n
n
n
0 0 0 x
0
Port I/O
Crossbar
CEXn
CCC
CCC
FFF
2 1 0
(to CCFn)
x x
PCA0CN
CC
FR
1
PCA0CPLn
PCA0CPHn
Capture
0
1
PCA
Timebase
PCA0L
PCA0H
Figure 25.4. PCA Capture Mode Diagram
Note: The CEXn input signal must remain high or low for at least 2 system clock cycles to be recognized by the
hardware.
Rev. 1.0
195
C8051T630/1/2/3/4/5
25.3.2. Software Timer (Compare) Mode
In Software Timer mode, the PCA counter/timer value is compared to the module's 16-bit capture/compare
register (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in
PCA0CN is set to logic 1. An interrupt request is generated if the CCFn interrupt for that module is
enabled. The CCFn bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. Setting the ECOMn and MATn bits in the PCA0CPMn register enables Software Timer mode.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the
ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
Write to
PCA0CPLn
0
ENB
Reset
Write to
PCA0CPHn
PCA Interrupt
ENB
1
PCA0CPMn
P ECCMT P E
WC A A A OWC
MOPP TGMC
1 MP N n n n F
6 n n n
n
n
x
0 0
PCA0CN
PCA0CPLn
CC
FR
PCA0CPHn
0 0 x
Enable
16-bit Comparator
PCA
Timebase
PCA0L
Match
PCA0H
Figure 25.5. PCA Software Timer Mode Diagram
196
CCC
CCC
FFF
2 1 0
Rev. 1.0
0
1
C8051T630/1/2/3/4/5
25.3.3. High-Speed Output Mode
In High-Speed Output mode, a module’s associated CEXn pin is toggled each time a match occurs
between the PCA Counter and the module's 16-bit capture/compare register (PCA0CPHn and
PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic 1. An
interrupt request is generated if the CCFn interrupt for that module is enabled. The CCFn bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared
by software. Setting the TOGn, MATn, and ECOMn bits in the PCA0CPMn register enables the HighSpeed Output mode. If ECOMn is cleared, the associated pin will retain its state, and not toggle on the next
match event.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the
ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
Write to
PCA0CPLn
0
ENB
Reset
Write to
PCA0CPHn
PCA0CPMn
P ECCMT P E
WC A A AOWC
MOPP TGMC
1 MP N n n n F
6 n n n
n
n
ENB
1
x
0 0
0 x
PCA Interrupt
PCA0CN
PCA0CPLn
Enable
CC
FR
PCA0CPHn
16-bit Comparator
Match
CCC
CCC
FFF
2 1 0
0
1
TOGn
Toggle
PCA
Timebase
0 CEXn
1
PCA0L
Crossbar
Port I/O
PCA0H
Figure 25.6. PCA High-Speed Output Mode Diagram
Rev. 1.0
197
C8051T630/1/2/3/4/5
25.3.4. Frequency Output Mode
Frequency Output Mode produces a programmable-frequency square wave on the module’s associated
CEXn pin. The capture/compare module high byte holds the number of PCA clocks to count before the output is toggled. The frequency of the square wave is then defined by Equation 25.1.
F PCA
F CEXn = ----------------------------------------2  PCA0CPHn
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
Equation 25.1. Square Wave Frequency Output
Where FPCA is the frequency of the clock selected by the CPS2–0 bits in the PCA mode register,
PCA0MD. The lower byte of the capture/compare module is compared to the PCA counter low byte; on a
match, CEXn is toggled and the offset held in the high byte is added to the matched value in PCA0CPLn.
Frequency Output Mode is enabled by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn register. Note that the MATn bit should normally be set to 0 in this mode. If the MATn bit is set to 1, the CCFn
flag for the channel will be set when the 16-bit PCA0 counter and the 16-bit capture/compare register for
the channel are equal.
Write to
PCA0CPLn
0
ENB
Reset
PCA0CPMn
Write to
PCA0CPHn
ENB
1
P ECCMT P E
WC A A AOWC
MOPP TGMC
1 MP N n n n F
6 n n n
n
n
x
0 0 0
PCA0CPLn
8-bit Adder
PCA0CPHn
Adder
Enable
TOGn
Toggle
x
Enable
PCA Timebase
8-bit
Comparator
match
0 CEXn
1
Crossbar
Port I/O
PCA0L
Figure 25.7. PCA Frequency Output Mode
25.3.5. 8-bit, 9-bit, 10-bit and 11-bit Pulse Width Modulator Modes
Each module can be used independently to generate a pulse width modulated (PWM) output on its associated CEXn pin. The frequency of the output is dependent on the timebase for the PCA counter/timer, and
the setting of the PWM cycle length (8, 9, 10 or 11-bits). For backwards-compatibility with the 8-bit PWM
mode available on other devices, the 8-bit PWM mode operates slightly different than 9, 10 and 11-bit
PWM modes. It is important to note that all channels configured for 8/9/10/11-bit PWM mode will use
the same cycle length. It is not possible to configure one channel for 8-bit PWM mode and another for 11bit mode (for example). However, other PCA channels can be configured to Pin Capture, High-Speed Output, Software Timer, Frequency Output, or 16-bit PWM mode independently.
198
Rev. 1.0
C8051T630/1/2/3/4/5
25.3.5.1. 8-bit Pulse Width Modulator Mode
The duty cycle of the PWM output signal in 8-bit PWM mode is varied using the module's PCA0CPLn capture/compare register. When the value in the low byte of the PCA counter/timer (PCA0L) is equal to the
value in PCA0CPLn, the output on the CEXn pin will be set. When the count value in PCA0L overflows, the
CEXn output will be reset (see Figure 25.8). Also, when the counter/timer low byte (PCA0L) overflows from
0xFF to 0x00, PCA0CPLn is reloaded automatically with the value stored in the module’s capture/compare
high byte (PCA0CPHn) without software intervention. Setting the ECOMn and PWMn bits in the
PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM to 00b enables 8-Bit Pulse Width
Modulator mode. If the MATn bit is set to 1, the CCFn flag for the module will be set each time an 8-bit
comparator match (rising edge) occurs. The COVF flag in PCA0PWM can be used to detect the overflow
(falling edge), which will occur every 256 PCA clock cycles. The duty cycle for 8-Bit PWM Mode is given in
Equation 25.2.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the
ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
 256 – PCA0CPHn 
Duty Cycle = --------------------------------------------------256
Equation 25.2. 8-Bit PWM Duty Cycle
Using Equation 25.2, the largest duty cycle is 100% (PCA0CPHn = 0), and the smallest duty cycle is
0.39% (PCA0CPHn = 0xFF). A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to
PCA0CPLn
0
ENB
Reset
PCA0CPHn
Write to
PCA0CPHn
ENB
COVF
1
PCA0PWM
A
R
S
E
L
EC
CO
OV
VF
0 x
C
L
S
E
L
1
PCA0CPMn
C
L
S
E
L
0
0 0
P ECCMT P E
WC A A AOWC
MOPP TGMC
1 MP N n n n F
6 n n n
n
n
0
0 0 x 0
PCA0CPLn
x
Enable
8-bit
Comparator
match
S
R
PCA Timebase
SET
CLR
Q
CEXn
Crossbar
Port I/O
Q
PCA0L
Overflow
Figure 25.8. PCA 8-Bit PWM Mode Diagram
Rev. 1.0
199
C8051T630/1/2/3/4/5
25.3.5.2. 9/10/11-bit Pulse Width Modulator Mode
The duty cycle of the PWM output signal in 9/10/11-bit PWM mode should be varied by writing to an “AutoReload” Register, which is dual-mapped into the PCA0CPHn and PCA0CPLn register locations. The data
written to define the duty cycle should be right-justified in the registers. The auto-reload registers are
accessed (read or written) when the bit ARSEL in PCA0PWM is set to 1. The capture/compare registers
are accessed when ARSEL is set to 0.
When the least-significant N bits of the PCA0 counter match the value in the associated module’s capture/compare register (PCA0CPn), the output on CEXn is asserted high. When the counter overflows from
the Nth bit, CEXn is asserted low (see Figure 25.9). Upon an overflow from the Nth bit, the COVF flag is
set, and the value stored in the module’s auto-reload register is loaded into the capture/compare register.
The value of N is determined by the CLSEL bits in register PCA0PWM.
The 9, 10 or 11-bit PWM mode is selected by setting the ECOMn and PWMn bits in the PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM to the desired cycle length (other than 8-bits). If the
MATn bit is set to 1, the CCFn flag for the module will be set each time a comparator match (rising edge)
occurs. The COVF flag in PCA0PWM can be used to detect the overflow (falling edge), which will occur
every 512 (9-bit), 1024 (10-bit) or 2048 (11-bit) PCA clock cycles. The duty cycle for 9/10/11-Bit PWM
Mode is given in Equation 25.2, where N is the number of bits in the PWM cycle.
Important Note About PCA0CPHn and PCA0CPLn Registers: When writing a 16-bit value to the
PCA0CPn registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn
bit to 0; writing to PCA0CPHn sets ECOMn to 1.
 2 N – PCA0CPn Duty Cycle = ------------------------------------------2N
Equation 25.3. 9, 10, and 11-Bit PWM Duty Cycle
A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to
PCA0CPLn
0
R/W when
ARSEL = 1
ENB
Reset
Write to
PCA0CPHn
(Auto-Reload)
PCA0PWM
PCA0CPH:Ln
A
R
S
E
L
(right-justified)
ENB
1
C
L
S
E
L
1
EC
CO
OV
VF
PCA0CPMn
P ECCMT P E
WC A A AOWC
MOPP TGMC
1 MP N n n n F
6 n n n
n
n
0
0 0 x 0
R/W when
ARSEL = 0
C
L
S
E
L
0
x
(Capture/Compare)
Set “N” bits:
01 = 9 bits
10 = 10 bits
11 = 11 bits
PCA0CPH:Ln
(right-justified)
x
Enable
N-bit Comparator
match
S
R
PCA Timebase
SET
CLR
Q
CEXn
Crossbar
Q
PCA0H:L
Overflow of Nth Bit
Figure 25.9. PCA 9, 10 and 11-Bit PWM Mode Diagram
200
Rev. 1.0
Port I/O
C8051T630/1/2/3/4/5
25.3.6. 16-Bit Pulse Width Modulator Mode
A PCA module may also be operated in 16-Bit PWM mode. 16-bit PWM mode is independent of the other
(8/9/10/11-bit) PWM modes. In this mode, the 16-bit capture/compare module defines the number of PCA
clocks for the low time of the PWM signal. When the PCA counter matches the module contents, the output on CEXn is asserted high; when the 16-bit counter overflows, CEXn is asserted low. To output a varying duty cycle, new value writes should be synchronized with PCA CCFn match interrupts. 16-Bit PWM
Mode is enabled by setting the ECOMn, PWMn, and PWM16n bits in the PCA0CPMn register. For a varying duty cycle, match interrupts should be enabled (ECCFn = 1 AND MATn = 1) to help synchronize the
capture/compare register writes. If the MATn bit is set to 1, the CCFn flag for the module will be set each
time a 16-bit comparator match (rising edge) occurs. The CF flag in PCA0CN can be used to detect the
overflow (falling edge). The duty cycle for 16-Bit PWM Mode is given by Equation 25.4.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the
ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
 65536 – PCA0CPn 
Duty Cycle = ----------------------------------------------------65536
Equation 25.4. 16-Bit PWM Duty Cycle
Using Equation 25.4, the largest duty cycle is 100% (PCA0CPn = 0), and the smallest duty cycle is
0.0015% (PCA0CPn = 0xFFFF). A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to
PCA0CPLn
0
ENB
Reset
Write to
PCA0CPHn
ENB
1
PCA0CPMn
P ECCMT P E
WC A A AOWC
MOPP TGMC
1 MPN n n n F
6 n n n
n
n
1
0 0 x 0
PCA0CPHn
PCA0CPLn
x
Enable
16-bit Comparator
match
S
R
PCA Timebase
PCA0H
SET
CLR
Q
CEXn
Crossbar
Port I/O
Q
PCA0L
Overflow
Figure 25.10. PCA 16-Bit PWM Mode
Rev. 1.0
201
C8051T630/1/2/3/4/5
25.4. Watchdog Timer Mode
A programmable watchdog timer (WDT) function is available through the PCA Module 2. The WDT is used
to generate a reset if the time between writes to the WDT update register (PCA0CPH2) exceed a specified
limit. The WDT can be configured and enabled/disabled as needed by software.
With the WDTE bit set in the PCA0MD register, Module 2 operates as a watchdog timer (WDT). The Module 2 high byte is compared to the PCA counter high byte; the Module 2 low byte holds the offset to be
used when WDT updates are performed. The Watchdog Timer is enabled on reset. Writes to some
PCA registers are restricted while the Watchdog Timer is enabled. The WDT will generate a reset
shortly after code begins execution. To avoid this reset, the WDT should be explicitly disabled (and optionally re-configured and re-enabled if it is used in the system).
25.4.1. Watchdog Timer Operation
While the WDT is enabled:






PCA counter is forced on.
Writes to PCA0L and PCA0H are not allowed.
PCA clock source bits (CPS2–CPS0) are frozen.
PCA Idle control bit (CIDL) is frozen.
Module 2 is forced into software timer mode.
Writes to the Module 2 mode register (PCA0CPM2) are disabled.
While the WDT is enabled, writes to the CR bit will not change the PCA counter state; the counter will run
until the WDT is disabled. The PCA counter run control bit (CR) will read zero if the WDT is enabled but
user software has not enabled the PCA counter. If a match occurs between PCA0CPH2 and PCA0H while
the WDT is enabled, a reset will be generated. To prevent a WDT reset, the WDT may be updated with a
write of any value to PCA0CPH2. Upon a PCA0CPH2 write, PCA0H plus the offset held in PCA0CPL2 is
loaded into PCA0CPH2 (See Figure 25.11).
PCA0MD
CWW
I D D
D T L
L E C
K
CCCE
PPPC
SSSF
2 1 0
PCA0CPH2
Enable
PCA0CPL2
Write to
PCA0CPH2
8-bit Adder
8-bit
Comparator
PCA0H
Match
Reset
PCA0L Overflow
Adder
Enable
Figure 25.11. PCA Module 2 with Watchdog Timer Enabled
202
Rev. 1.0
C8051T630/1/2/3/4/5
The 8-bit offset held in PCA0CPH2 is compared to the upper byte of the 16-bit PCA counter. This offset
value is the number of PCA0L overflows before a reset. Up to 256 PCA clocks may pass before the first
PCA0L overflow occurs, depending on the value of the PCA0L when the update is performed. The total offset is then given (in PCA clocks) by Equation 25.5, where PCA0L is the value of the PCA0L register at the
time of the update.
Offset =  256  PCA0CPL2  +  256 – PCA0L 
Equation 25.5. Watchdog Timer Offset in PCA Clocks
The WDT reset is generated when PCA0L overflows while there is a match between PCA0CPH2 and
PCA0H. Software may force a WDT reset by writing a 1 to the CCF2 flag (PCA0CN.2) while the WDT is
enabled.
25.4.2. Watchdog Timer Usage
To configure the WDT, perform the following tasks:
1. Disable the WDT by writing a 0 to the WDTE bit.
2. Select the desired PCA clock source (with the CPS2–CPS0 bits).
3. Load PCA0CPL2 with the desired WDT update offset value.
4. Configure the PCA Idle mode (set CIDL if the WDT should be suspended while the CPU is in Idle
mode).
5. Enable the WDT by setting the WDTE bit to 1.
6. Reset the WDT timer by writing to PCA0CPH2.
The PCA clock source and Idle mode select cannot be changed while the WDT is enabled. The watchdog
timer is enabled by setting the WDTE or WDLCK bits in the PCA0MD register. When WDLCK is set, the
WDT cannot be disabled until the next system reset. If WDLCK is not set, the WDT is disabled by clearing
the WDTE bit.
The WDT is enabled following any reset. The PCA0 counter clock defaults to the system clock divided by
12, PCA0L defaults to 0x00, and PCA0CPL2 defaults to 0x00. Using Equation 25.5, this results in a WDT
timeout interval of 256 PCA clock cycles, or 3072 system clock cycles. Table 25.3 lists some example timeout intervals for typical system clocks.
Table 25.3. Watchdog Timer Timeout Intervals1
System Clock (Hz)
PCA0CPL2
Timeout Interval (ms)
24,500,000
24,500,000
24,500,000
255
128
32
32.1
16.2
4.1
3,062,5002
255
257
3,062,5002
128
129.5
3,062,5002
32
33.1
32,000
32,000
32,000
255
128
32
24576
12384
3168
Notes:
1. Assumes SYSCLK/12 as the PCA clock source, and a PCA0L value
of 0x00 at the update time.
2. Internal SYSCLK reset frequency = Internal Oscillator divided by 8.
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25.5. Register Descriptions for PCA0
Following are detailed descriptions of the special function registers related to the operation of the PCA.
SFR Definition 25.1. PCA0CN: PCA Control
Bit
7
6
5
4
Name
CF
CR
Type
R/W
R/W
R
R
Reset
0
0
0
0
SFR Address = 0xD8; Bit-Addressable
Bit
Name
7
CF
3
2
1
0
CCF2
CCF1
CCF0
R
R/W
R/W
R/W
0
0
0
0
Function
PCA Counter/Timer Overflow Flag.
Set by hardware when the PCA Counter/Timer overflows from 0xFFFF to 0x0000.
When the Counter/Timer Overflow (CF) interrupt is enabled, setting this bit causes the
CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared
by hardware and must be cleared by software.
6
CR
PCA Counter/Timer Run Control.
This bit enables/disables the PCA Counter/Timer.
0: PCA Counter/Timer disabled.
1: PCA Counter/Timer enabled.
5:3
2
Unused
CCF2
Unused. Read = 000b, Write = Don't care.
PCA Module 2 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF2 interrupt
is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and must be cleared by software.
1
CCF1
PCA Module 1 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF1 interrupt
is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and must be cleared by software.
0
CCF0
PCA Module 0 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF0 interrupt
is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and must be cleared by software.
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SFR Definition 25.2. PCA0MD: PCA Mode
Bit
7
6
5
Name
CIDL
WDTE
WDLCK
Type
R/W
R/W
R/W
Reset
0
1
0
4
3
2
1
0
CPS2
CPS1
CPS0
ECF
R
R/W
R/W
R/W
R/W
0
0
0
0
0
SFR Address = 0xD9
Bit
Name
7
CIDL
Function
PCA Counter/Timer Idle Control.
Specifies PCA behavior when CPU is in Idle Mode.
0: PCA continues to function normally while the system controller is in Idle Mode.
1: PCA operation is suspended while the system controller is in Idle Mode.
6
WDTE
Watchdog Timer Enable.
If this bit is set, PCA Module 2 is used as the watchdog timer.
0: Watchdog Timer disabled.
1: PCA Module 2 enabled as Watchdog Timer.
5
WDLCK
Watchdog Timer Lock.
This bit locks/unlocks the Watchdog Timer Enable. When WDLCK is set, the Watchdog
Timer may not be disabled until the next system reset.
0: Watchdog Timer Enable unlocked.
1: Watchdog Timer Enable locked.
4
3:1
Unused Unused. Read = 0b, Write = Don't care.
CPS[2:0] PCA Counter/Timer Pulse Select.
These bits select the timebase source for the PCA counter
000: System clock divided by 12
001: System clock divided by 4
010: Timer 0 overflow
011: High-to-low transitions on ECI (max rate = system clock divided by 4)
100: System clock
101: External clock divided by 8 (synchronized with the system clock)
11x: Reserved
0
ECF
PCA Counter/Timer Overflow Interrupt Enable.
This bit sets the masking of the PCA Counter/Timer Overflow (CF) interrupt.
0: Disable the CF interrupt.
1: Enable a PCA Counter/Timer Overflow interrupt request when CF (PCA0CN.7) is
set.
Note: When the WDTE bit is set to 1, the other bits in the PCA0MD register cannot be modified. To change the
contents of the PCA0MD register, the Watchdog Timer must first be disabled.
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SFR Definition 25.3. PCA0PWM: PCA PWM Configuration
Bit
7
6
5
4
Name
ARSEL
ECOV
COVF
Type
R/W
R/W
R/W
R
R
R
Reset
0
0
0
0
0
0
ARSEL
2
1
0
CLSEL[1:0]
SFR Address = 0xF7
Bit
Name
7
3
R/W
0
0
Function
Auto-Reload Register Select.
This bit selects whether to read and write the normal PCA capture/compare registers
(PCA0CPn), or the Auto-Reload registers at the same SFR addresses. This function
is used to define the reload value for 9, 10, and 11-bit PWM modes. In all other
modes, the Auto-Reload registers have no function.
0: Read/Write Capture/Compare Registers at PCA0CPHn and PCA0CPLn.
1: Read/Write Auto-Reload Registers at PCA0CPHn and PCA0CPLn.
6
ECOV
Cycle Overflow Interrupt Enable.
This bit sets the masking of the Cycle Overflow Flag (COVF) interrupt.
0: COVF will not generate PCA interrupts.
1: A PCA interrupt will be generated when COVF is set.
5
COVF
Cycle Overflow Flag.
This bit indicates an overflow of the 8th, 9th, 10th, or 11th bit of the main PCA counter
(PCA0). The specific bit used for this flag depends on the setting of the Cycle Length
Select bits. The bit can be set by hardware or software, but must be cleared by software.
0: No overflow has occurred since the last time this bit was cleared.
1: An overflow has occurred since the last time this bit was cleared.
4:2
Unused
Unused. Read = 000b; Write = Don’t care.
1:0 CLSEL[1:0] Cycle Length Select.
When 16-bit PWM mode is not selected, these bits select the length of the PWM
cycle, between 8, 9, 10, or 11 bits. This affects all channels configured for PWM which
are not using 16-bit PWM mode. These bits are ignored for individual channels configured to16-bit PWM mode.
00: 8 bits.
01: 9 bits.
10: 10 bits.
11: 11 bits.
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SFR Definition 25.4. PCA0CPMn: PCA Capture/Compare Mode
Bit
7
6
5
4
3
2
1
0
Name
PWM16n
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMn
ECCFn
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Addresses: PCA0CPM0 = 0xDA, PCA0CPM1 = 0xDB, PCA0CPM2 = 0xDC
Bit
Name
Function
7
PWM16n 16-bit Pulse Width Modulation Enable.
This bit enables 16-bit mode when Pulse Width Modulation mode is enabled.
0: 8 to 11-bit PWM selected.
1: 16-bit PWM selected.
6
ECOMn
Comparator Function Enable.
This bit enables the comparator function for PCA module n when set to 1.
5
CAPPn
Capture Positive Function Enable.
This bit enables the positive edge capture for PCA module n when set to 1.
4
CAPNn
Capture Negative Function Enable.
This bit enables the negative edge capture for PCA module n when set to 1.
3
MATn
Match Function Enable.
This bit enables the match function for PCA module n when set to 1. When enabled,
matches of the PCA counter with a module's capture/compare register cause the CCFn
bit in PCA0MD register to be set to logic 1.
2
TOGn
Toggle Function Enable.
This bit enables the toggle function for PCA module n when set to 1. When enabled,
matches of the PCA counter with a module's capture/compare register cause the logic
level on the CEXn pin to toggle. If the PWMn bit is also set to logic 1, the module operates in Frequency Output Mode.
1
PWMn
Pulse Width Modulation Mode Enable.
This bit enables the PWM function for PCA module n when set to 1. When enabled, a
pulse width modulated signal is output on the CEXn pin. 8 to 11-bit PWM is used if
PWM16n is cleared; 16-bit mode is used if PWM16n is set to logic 1. If the TOGn bit is
also set, the module operates in Frequency Output Mode.
0
ECCFn
Capture/Compare Flag Interrupt Enable.
This bit sets the masking of the Capture/Compare Flag (CCFn) interrupt.
0: Disable CCFn interrupts.
1: Enable a Capture/Compare Flag interrupt request when CCFn is set.
Note: When the WDTE bit is set to 1, the PCA0CPM2 register cannot be modified, and module 2 acts as the
watchdog timer. To change the contents of the PCA0CPM2 register or the function of module 2, the Watchdog
Timer must be disabled.
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SFR Definition 25.5. PCA0L: PCA Counter/Timer Low Byte
Bit
7
6
5
4
3
2
1
0
PCA0[7:0]
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xF9
Bit
Name
7:0
Function
PCA0[7:0] PCA Counter/Timer Low Byte.
The PCA0L register holds the low byte (LSB) of the 16-bit PCA Counter/Timer.
Note: When the WDTE bit is set to 1, the PCA0L register cannot be modified by software. To change the contents of
the PCA0L register, the Watchdog Timer must first be disabled.
SFR Definition 25.6. PCA0H: PCA Counter/Timer High Byte
Bit
7
6
5
4
3
2
1
0
PCA0[15:8]
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xFA
Bit
Name
7:0
Function
PCA0[15:8] PCA Counter/Timer High Byte.
The PCA0H register holds the high byte (MSB) of the 16-bit PCA Counter/Timer.
Reads of this register will read the contents of a “snapshot” register, whose contents
are updated only when the contents of PCA0L are read (see Section 25.1).
Note: When the WDTE bit is set to 1, the PCA0H register cannot be modified by software. To change the contents of
the PCA0H register, the Watchdog Timer must first be disabled.
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SFR Definition 25.7. PCA0CPLn: PCA Capture Module Low Byte
Bit
7
6
5
4
3
2
1
0
PCA0CPn[7:0]
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Addresses: PCA0CPL0 = 0xFB, PCA0CPL1 = 0xE9, PCA0CPL2 = 0xEB
Bit
Name
Function
7:0
PCA0CPn[7:0] PCA Capture Module Low Byte.
The PCA0CPLn register holds the low byte (LSB) of the 16-bit capture module n.
This register address also allows access to the low byte of the corresponding
PCA channel’s auto-reload value for 9, 10, or 11-bit PWM mode. The ARSEL bit
in register PCA0PWM controls which register is accessed.
Note: A write to this register will clear the module’s ECOMn bit to a 0.
SFR Definition 25.8. PCA0CPHn: PCA Capture Module High Byte
Bit
7
6
5
4
3
2
1
0
PCA0CPn[15:8]
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Addresses: PCA0CPH0 = 0xFC, PCA0CPH1 = 0xEA, PCA0CPH2 = 0xEC
Bit
Name
Function
7:0 PCA0CPn[15:8] PCA Capture Module High Byte.
The PCA0CPHn register holds the high byte (MSB) of the 16-bit capture module n.
This register address also allows access to the high byte of the corresponding
PCA channel’s auto-reload value for 9, 10, or 11-bit PWM mode. The ARSEL bit in
register PCA0PWM controls which register is accessed.
Note: A write to this register will set the module’s ECOMn bit to a 1.
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26. C2 Interface
C8051T630/1/2/3/4/5 devices include an on-chip Silicon Labs 2-Wire (C2) debug interface to allow
EPROM programming and in-system debugging with the production part installed in the end application.
The C2 interface operates using only two pins: a bi-directional data signal (C2D), and a clock input
(C2CK). See the C2 Interface Specification for details on the C2 protocol.
26.1. C2 Interface Registers
The following describes the C2 registers necessary to perform EPROM programming functions through the
C2 interface. All C2 registers are accessed through the C2 interface as described in the C2 Interface Specification.
C2 Register Definition 26.1. C2ADD: C2 Address
Bit
7
6
5
4
3
Name
C2ADD[7:0]
Type
R/W
Reset
Bit
0
0
0
0
Name
0
2
1
0
0
0
0
Function
7:0 C2ADD[7:0] Write: C2 Address.
Selects the target Data register for C2 Data Read and Data Write commands according to the following list.
Address
Name
Description
0x00
0x01
0x02
0xDF
0xBF
0xB7
0xAF
0xAE
0xA9
0xAA
0xAB
0xAC
DEVICEID
REVID
DEVCTL
EPCTL
EPDAT
EPSTAT
EPADDRH
EPADDRL
CRC0
CRC1
CRC2
CRC3
Selects the Device ID Register (read only)
Selects the Revision ID Register (read only)
Selects the C2 Device Control Register
Selects the C2 EPROM Programming Control Register
Selects the C2 EPROM Data Register
Selects the C2 EPROM Status Register
Selects the C2 EPROM Address High Byte Register
Selects the C2 EPROM Address Low Byte Register
Selects the CRC0 Register
Selects the CRC1 Register
Selects the CRC2 Register
Selects the CRC3 Register
Read: C2 Status
Returns status information on the current programming operation.
When the MSB (bit 7) is set to ‘1’, a read or write operation is in progress. All other
bits can be ignored by the programming tools.
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C2 Register Definition 26.2. DEVICEID: C2 Device ID
Bit
7
6
5
4
3
Name
DEVICEID[7:0]
Type
R/W
Reset
0
0
0
1
0
C2 Address: 0x00
Bit
Name
7:0
2
1
0
1
1
1
Function
DEVICEID[7:0] Device ID.
This read-only register returns the 8-bit device ID: 0x17 (C8051T630/1/2/3/4/5).
C2 Register Definition 26.3. REVID: C2 Revision ID
Bit
7
6
5
4
3
Name
REVID[7:0]
Type
R/W
Reset
Varies
Varies
Varies
Varies
C2 Address: 0x01
Bit
Name
7:0
Varies
2
1
0
Varies
Varies
Varies
Function
REVID[7:0] Revision ID.
This read-only register returns the 8-bit revision ID. For example: 0x00 = Revision A.
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C2 Register Definition 26.4. DEVCTL: C2 Device Control
Bit
7
6
5
4
3
Name
DEVCTL[7:0]
Type
R/W
Reset
0
0
0
0
0
C2 Address: 0x02
Bit
Name
2
1
0
0
0
0
Function
7:0 DEVCTL[7:0] Device Control Register.
This register is used to halt the device for EPROM operations via the C2 interface.
Refer to the EPROM chapter for more information.
C2 Register Definition 26.5. EPCTL: EPROM Programming Control Register
Bit
7
6
5
4
3
Name
EPCTL[7:0]
Type
R/W
Reset
0
0
0
0
C2 Address: 0xDF
Bit
Name
7:0
0
2
1
0
0
0
0
Function
EPCTL[7:0] EPROM Programming Control Register.
This register is used to enable EPROM programming via the C2 interface. Refer to
the EPROM chapter for more information.
212
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C2 Register Definition 26.6. EPDAT: C2 EPROM Data
Bit
7
6
5
4
3
Name
EPDAT[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
C2 Address: 0xBF
Bit
7:0
Name
Function
EPDAT[7:0] C2 EPROM Data Register.
This register is used to pass EPROM data during C2 EPROM operations.
C2 Register Definition 26.7. EPSTAT: C2 EPROM Status
Bit
7
Name WRLOCK
6
5
4
3
2
1
RDLOCK
0
ERROR
Type
R
R
R
R
R
R
R
R
Reset
0
0
0
0
0
0
0
0
C2 Address: 0xB7
Bit
Name
7
WRLOCK
Function
Write Lock Indicator.
Set to '1' if EPADDR currently points to a write-locked address.
6
RDLOCK
Read Lock Indicator.
Set to '1' if EPADDR currently points to a read-locked address.
5:1
0
Unused
ERROR
Unused. Read = 00000b; Write = don’t care.
Error Indicator.
Set to '1' if last EPROM read or write operation failed due to a security restriction.
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C2 Register Definition 26.8. EPADDRH: C2 EPROM Address High Byte
Bit
7
6
5
4
3
Name
EPADDR[15:8]
Type
R/W
Reset
0
0
0
0
0
C2 Address: 0xAF
Bit
Name
7:0
2
1
0
0
0
0
Function
EPADDR[15:8] C2 EPROM Address High Byte.
This register is used to set the EPROM address location during C2 EPROM operations.
C2 Register Definition 26.9. EPADDRL: C2 EPROM Address Low Byte
Bit
7
6
5
4
3
Name
EPADDR[7:0]
Type
R/W
Reset
0
0
0
0
C2 Address: 0xAE
Bit
Name
7:0
0
2
1
0
0
0
0
Function
EPADDR[15:8] C2 EPROM Address Low Byte.
This register is used to set the EPROM address location during C2 EPROM operations.
214
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C2 Register Definition 26.10. CRC0: CRC Byte 0
Bit
7
6
5
4
Name
CRC[7:0]
Type
R/W
Reset
0
0
0
0
C2 Address: 0xA9
Bit
Name
7:0
CRC[7:0]
3
2
1
0
0
0
0
0
Function
CRC Byte 0.
A write to this register initiates a 16-bit CRC of one 256-byte block of EPROM memory. The byte written to CRC0 is the upper byte of the 16-bit address where the CRC
will begin. The lower byte of the beginning address is always 0x00. When complete,
the 16-bit result will be available in CRC1 (MSB) and CRC0 (LSB). See Section
“16.3. Program Memory CRC” on page 91.
C2 Register Definition 26.11. CRC1: CRC Byte 1
Bit
7
6
5
4
Name
CRC[15:8]
Type
R/W
Reset
0
0
0
0
C2 Address: 0xAA
Bit
Name
7:0
CRC[15:8]
3
2
1
0
0
0
0
0
Function
CRC Byte 1.
A write to this register initiates a 32-bit CRC on the entire program memory space.
The CRC begins at address 0x0000. When complete, the 32-bit result is stored in
CRC3 (MSB), CRC2, CRC1, and CRC0 (LSB). See Section “16.3. Program Memory
CRC” on page 91.
Rev. 1.0
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C2 Register Definition 26.12. CRC2: CRC Byte 2
Bit
7
6
5
4
3
Name
CRC[23:16]
Type
R/W
Reset
0
0
0
0
0
C2 Address: 0xAB
Bit
Name
7:0
2
1
0
0
0
0
2
1
0
0
0
0
Function
CRC[23:16] CRC Byte 2.
See Section “16.3. Program Memory CRC” on page 91.
C2 Register Definition 26.13. CRC3: CRC Byte 3
Bit
7
6
5
4
3
Name
CRC[31:24]
Type
R/W
Reset
0
0
0
0
C2 Address: 0xAC
Bit
Name
7:0
0
Function
CRC[31:24] CRC Byte 3.
See Section “16.3. Program Memory CRC” on page 91.
216
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26.2. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and
EPROM programming functions may be performed. This is possible because C2 communication is typically performed when the device is in the halt state, where all on-chip peripherals and user software are
stalled. In this halted state, the C2 interface can safely ‘borrow’ the C2CK (normally RST) and C2D pins. In
most applications, external resistors are required to isolate C2 interface traffic from the user application
when performing debug functions. These external resistors are not necessary for production boards. A typical isolation configuration is shown in Figure 26.1.
/Reset (a)
C2CK
Input (b)
C2D
Output (c)
C2 Interface Master
Figure 26.1. Typical C2 Pin Sharing
The configuration in Figure 26.1 assumes the following:
1. The user input (b) cannot change state while the target device is halted.
2. The RST pin on the target device is used as an input only.
Additional resistors may be necessary depending on the specific application.
Rev. 1.0
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DOCUMENT CHANGE LIST
Revision 0.2 to Revision 1.0

Updated electrical specification tables based on test, characterization, and qualification data.
Updated figures and text to correct minor typographical errors throughout document.
 Updated package definitions to include all possible vendor information, and JEDEC-standard drawings.

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NOTES:
Rev. 1.0
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CONTACT INFORMATION
Silicon Laboratories Inc.
Silicon Laboratories Inc.
400 West Cesar Chavez
Austin, TX 78701
Tel: 1+(512) 416-8500
Fax: 1+(512) 416-9669
Toll Free: 1+(877) 444-3032
Email: [email protected]
Internet: www.silabs.com
The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without
notice. Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences
resulting from the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the functioning of undescribed features or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon
Laboratories makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose,
nor does Silicon Laboratories assume any liability arising out of the application or use of any product or circuit, and specifically
disclaims any and all liability, including without limitation consequential or incidental damages. Silicon Laboratories products are
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Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holders
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