Texas Instruments | NS16C2552/2752 Dual UART w/ 16-byte/64-byte FIFO's and up to 5 Mbit/s Data Rate (Rev. D) | Datasheet | Texas Instruments NS16C2552/2752 Dual UART w/ 16-byte/64-byte FIFO's and up to 5 Mbit/s Data Rate (Rev. D) Datasheet

Texas Instruments NS16C2552/2752 Dual UART w/ 16-byte/64-byte FIFO's and up to 5 Mbit/s Data Rate (Rev. D) Datasheet
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
NS16C2552/NS16C2752 Dual UART with 16-byte/64-byte FIFO's and up to 5 Mbit/s Data
Rate
Check for Samples: NS16C2552, NS16C2752
FEATURES
1
•
•
•
•
2
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Dual Independent UART
Up to 5 Mbits/s Data Transfer Rate
2.97 V to 5.50 V Operational Vcc
5 V Tolerant I/Os in the Entire Supply Voltage
Range
Industrial Temperature: -40°C to 85°C
Default Registers are Identical to the
PC16552D
NS16C2552/NS16C2752 is Pin-to-Pin
Compatible to TI PC16552D, EXAR ST16C2552,
XR16C2552, XR 16L2552, and Phillips
SC16C2552B
NS16C2752 is Compatible to EXAR
XR16L2752, and Register Compatible to
Phillips SC16C752
Auto Hardware Flow Control (Auto-CTS, AutoRTS)
Auto Software Flow Control (Xon, Xoff, and
Xon-any)
Fully Programmable Character Length (5, 6, 7,
or 8) with Even, Odd, or No Parity, Stop Bit
Adds or Deletes Standard Asynchronous
Communication Bits (Start, Stop, and Parity) to
or from the Serial Data
Independently Controlled and Prioritized
Transmit and Receive Interrupts
Complete Line Status Reporting Capabilities
Line Break Generation and Detection
Internal Diagnostic Capabilities
– Loopback Controls for Communications
Link Fault Isolation
– Break, Parity, Overrun, Framing Error
Detection
Programmable Baud Generators Divide any
Input Clock by 1 to (216 - 1) and Generate the
16 X clock
IrDA v1.0 Wireless Infrared Encoder/Decoder
DMA Operation (TXRDY/RXRDY)
Concurrent Write to DUART Internal Register
Channels 1 and 2
•
•
Multi-Function Output Allows More Package
Functions with Fewer I/O Pins
44-PLCC or 48-TQFP Package
DESCRIPTION
The NS16C2552 and NS16C2752 are dual channel
Universal
Asynchronous
Receiver/Transmitter
(DUART). The footprint and the functions are
compatible to the PC16552D, while new features are
added to the UART device. These features include
low voltage support, 5V tolerant inputs, enhanced
features, enhanced register set, and higher data rate.
The two serial channels are completely independent
of each other, except for a common CPU interface
and crystal input. On power-up both channels are
functionally identical to the PC16552D. Each channel
can operate with on-chip transmitter and receiver
FIFO’s (in FIFO mode).
In the FIFO mode each channel is capable of
buffering 16 bytes (for NS16C2552) or 64 bytes (for
NS16C2752) of data in both the transmitter and
receiver. The receiver FIFO also has additional 3 bits
of error data per location. All FIFO control logic is onchip to minimize system software overhead and
maximize system efficiency.
To improve the CPU processing bandwidth, the data
transfers between the DUART and the CPU can be
done using DMA controller. Signaling for DMA
transfers is done through two pins per channel
(TXRDY and RXRDY). The RXRDYfunction is
multiplexed on one pin with the OUT2 and BAUDOUT
functions. The configuration is through Alternate
Function Register.
The fundamental function of the UART is converting
between parallel and serial data. Serial-to-parallel
conversion is done on the UART receiver and
parallel-to-serial conversion is done on the
transmitter. The CPU can read the complete status of
each channel at any time. Status information reported
includes the type and condition of the transfer
operations being performed by the DUART, as well
as any error conditions (parity, overrun, framing, or
break interrupt).
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006–2013, Texas Instruments Incorporated
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
DESCRIPTION (CONTINUED)
The NS16C2552 and NS16C2752 include one programmable baud rate generator for each channel. Each baud
rate generator is capable of dividing the clock input by divisors of 1 to (216 - 1), and producing a 16X clock for
driving the internal transmitter logic and for receiver sampling circuitry. The NS16C2552 and NS16C2752 have
complete MODEM-control capability, and a processor-interrupt system. The interrupts can be programmed by the
user to minimize the processing required to handle the communications link.
System Block Diagram
Connection Diagrams
Figure 1. 44–PLCC
See Package Number FN0044A
2
Submit Documentation Feedback
Figure 2. 48–TQFP
See Package Number PFB0048A
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Pin Descriptions
The NS16C2552/NS16C2752 pins are classified into the following interface categories.
• Bus Interface
• Serial I/O Interface
• Clock and Reset
• Power supply and Ground pins
Serial channel number (1 or 2) is designated by a numerical suffix after each pin name. If a numerical suffix (1 or
2) is not associated with the pin name, the information applies to both channels.
The I/O types are as follows:
Type: I
Input
Type: O
Output
Type: IO_Z
TRI-STATE I/O
PARALLEL BUS INTERFACE
Signal
Name
Type
PLCC
Pin #
TQFP
Pin #
Description
D7
D6
D5
D4
D3
D2
D1
D0
IO_Z
9
8
7
6
5
4
3
2
3
2
1
48
47
46
45
44
Data Bus:
Data bus comprises eight TRI-STATE input/output lines. The bus provides bidirectional
communications between the UART and the CPU. Data, control words, and status information
are transferred via the D7-D0 Data Bus.
A2
A1
A0
I
15
14
10
10
9
4
Register Addresses:
Address signals connected to these 3 inputs select a DUART register for the CPU to read
from or write to during data transfer. Table 1 shows the registers and their addresses. Note
that the state of the Divisor Latch Access Bit (DLAB), which is the most significant bit of the
Line Control Register, affects the selection of certain DUART registers. The DLAB must be
set high by the system software to access the Baud Generator Divisor Latches and the
Alternate Function Register.
CS
I
18
13
Chip Select:
When CS is low, the chip is selected. This enables communication between the DUART and
the CPU. Valid chip select should stabilize according to the tAW parameter.
CHSL
I
16
11
Channel Select:
CHSL directs the address and data information to the selected serial channel. (Table 1)
1 = channel 1 is selected.
0 = channel 2 is selected.
RD
I
24
20
IO Read:
The register data is placed on the D0 - D7 on the falling edge of RD. The CPU can read
status information or data from the selected DUART register on the rising edge.
WR
I
20
15
IO Write:
On the falling edge of WR, data is placed on the D0 - D7. On the rising edge, the data is
latched into the selected DUART register.
RXRDY1
RXRDY2
O
N/A
31
8
UART Receive-ready: The receiver DMA signaling is available through this pin which is a
separate pin on the TQFP package, while on the PLCC package it is available through the MF
pins (19, 35). When operating in the FIFO mode, the CPU selects one of two types of DMA
transfer via FCR[3]. When operating in the 16450 Mode, only DMA mode 0 is available. Mode
0 supports single transfer DMA (and a transfer is usually made between CPU bus cycles).
Mode 1 supports multi-transfer DMA where multiple transfers are made continuously until the
Rx FIFO is empty. Details regarding the active and inactive states of this signal are described
in FIFO CONTROL REGISTER (FCR) and DMA OPERATION.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
3
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Signal
Name
Type
PLCC
Pin #
TQFP
Pin #
www.ti.com
Description
TXRDY1
TXRDY2
O
1
32
43
28
UART Transmit-ready:
Transmitter DMA signaling is available through this pin. When operating in the FIFO mode,
the CPU selects one of two types of DMA transfer via FCR[3]. When operating in the 16450
Mode, only DMA mode 0 is allowed. Mode 0 supports single transfer DMA (and a transfer is
usually made between CPU bus cycles). Mode 1 supports multi-transfer DMA where multiple
transfers are made continuously until the Tx FIFO is full. Details regarding the active and
inactive states of this signal are described in FIFO CONTROL REGISTER (FCR) and DMA
OPERATION.
INTR1
INTR2
O
34
17
30
12
Interrupt Output:
INTR goes high whenever any one of the following interrupt types has an active high
condition and is enabled via the IER: Receiver Error Flag; Received Data Available: time-out
(FIFO Mode only); Transmitter Holding Register Empty; MODEM Status; and hardware and
software flow control. The INTR signal is reset low upon the appropriate interrupt service or a
Master Reset operation.
SERIAL IO INTERFACE
Signal
Name
SOUT1
Type
PLCC
Pin #
TQFP
Pin #
O
38
35
UART Serial Data Out:
26
22
UART transmit data output or infrared data output. The SOUT signal is set to logic 1 upon reset or
idle in the UART mode when MCR[6]=0. The SOUT signal transitions to logic 0 (idle state of IrDA
mode) in the infrared mode when MCR[6]=1.
Note: SOUT1 and SOUT2 can not be reset to IrDA mode.
SOUT2
Description
SIN1
SIN2
I
39
25
36
21
UART Serial Data In:
UART receive data input or infrared data input. The SIN should be idling in logic 1 in the UART
mode. The SIN should be idling in logic 0 in the infrared mode. The SIN should be pulled high
through a 10K resistor if not used.
RTS1
RTS2
O
36
23
33
18
UART Request-to-send:
When low, RTS informs the remote link partner that it is ready to receive data. The RTS output
signal can be set to an active low by writing “1” to MCR[1]. The RTS output can also be configured
in auto hardware flow control based on FIFO trigger level. This pin stays logic 1 upon reset or idle
(i.e., between data transfers). Loop mode operation holds this signal in its inactive state.
DTR1
DTR2
O
37
27
34
23
UART Data-terminal-ready:
When low, DTR informs the remote link partner that the UART is ready to establish a
communications link. The DTR output signal can be set to an active low by writing “1” to MCR[0].
This pin stays at logic 1 upon reset or idle. Loop mode operation holds this signal to its inactive
state.
CTS1
CTS2
I
40
28
38
24
UART Clear-to-send:
When low, CTS indicates that the remote link partner is ready to receive data. The CTS signal is a
modem status input and can be read for the appropriate channel in MSR[4]. This bit reflects the
complement of the CTS signal. MSR[0] indicates whether the CTS input has changed state since
the previous read of the MSR. CTS can also be configured to perform auto hardware flow control.
Note: Whenever the CTS bit of the MSR changes state, an interrupt is generated if the MODEM
Status Interrupt is enabled.
DSR1
DSR2
I
41
29
39
25
UART Data-set-ready:
When low, DSR indicates that the remote link partner is ready to establish the communications
link. The DSR signal is a MODEM status input and can be read for the appropriate channel in
MSR[5]. This bit reflects the complement of the DSR signal. MSR[1] indicates whether the DSR
input has changed state since the previous read of the MODEM Status Register.
Note: Whenever the DSR bit of the MSR changes state, an interrupt is generated if the MODEM
Status Interrupt is enabled.
DCD1
DCD2
I
42
30
40
26
UART Data-carrier-detect:
When low, DCD indicates that the data carrier has been detected by the remote link partner. The
DCD signal is a MODEM status input and can be read for the appropriate channel in MSR[7]. This
bit reflects the complement of the DCD signal. MSR[3] indicates if the DCD input has changed
state since the previous reading of the MODEM Status Register. DCD has no effect on the
receiver.
Note: Whenever the DCD bit of the MSR changes state, an interrupt is generated if the MODEM
Status Interrupt is enabled.
4
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
Signal
Name
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Type
PLCC
Pin #
TQFP
Pin #
Description
RI1
RI2
I
43
31
41
27
UART Ring-detector:
When low, RI indicates that a telephone ringing is active. The RI signal is a MODEM status input
and can be read for the appropriate channel in MSR[6]. This bit reflects the complement of the RI
signal. MSR[2] indicates whether the RI input signal has changed state from low to high since the
previous reading of the MSR.
Note: Whenever the RI bit of the MSR changes from a high to a low state, an interrupt is
generated if the MODEM Status Interrupt is enabled.
MF1
MF2
O
35
19
32
14
UART Multi-function Pin:
MF can be programmed for any one of three signal functions OUT2, BAUDOUT or RXRDY. Bits 2
and 1 of the Alternate Function Register select which output signal will be present on this pin.
OUT2 is the default signal and it is selected immediately after master reset or power-up.
The OUT2 can be set active low by programming bit 3 (OUT2) of the MCR to a logic 1. A Master
Reset operation sets this signal to its inactive (high) state. Loop Mode holds this signal in its
inactive state.
The BAUDOUT signal is the 16X clock output that drives the transmitter and receiver logic of the
associated serial channel. This signal is the result of the XIN clock divided by the value in the
Divisor Latch Registers. The BAUDOUT signal for each channel is internally connected to provide
the receiver clock (formerly RCLK on the PC16550D).
The RXRDY signal can be used to request a DMA transfer of data from the RCVR FIFO. Details
regarding the active and inactive states of this signal are described in FIFO CONTROL
REGISTER (FCR) and DMA OPERATION.
CLOCK AND RESET
Signal
Name
Type
PLCC
Pin #
TQFP
Pin #
XIN
I
11
5
External Crystal Input:
XIN input is used in conjunction with XOUT to form a feedback circuit for the baud
rate generator's oscillator. If a clock signal is generated off-chip, then it should drive
the baud rate generator through this pin. Refer to CLOCK INPUT.
XOUT
O
13
7
External Crystal Output:
XOUT output is used in conjunction with XIN to form a feedback circuit for the baud
rate generator's oscillator. If the clock signal is generated off-chip, then this pin is
unused. Refer to CLOCK INPUT.
MR
I
21
16
Master Reset:
When MR input is high, it clears all the registers including Tx and Rx serial shift
registers (except the Receiver Buffer, Transmitter Holding, and Divisor Latches). The
output signals, such as OUT2, RTS, DTR, INTR, and SOUT are also affected by an
active MR input. (Refer to Table 26 and RESET).
Description
POWER AND GROUND
Signal
Name
Type
PLCC
Pin #
TQFP
Pin #
Description
VCC
I
33
44
29
42
VCC:
+2.97V to +5.5V supply.
GND
I
12
22
6
17
GND:
Device ground reference.
NC
I
N/A
19
37
No Connection:
These pins are only available on the TQFP package.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
5
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Register Set
There are two identical register sets, one for each channel, in the DUART. All register descriptions in this section
apply to the register sets in both channels.
To clarify the descriptions of transmission and receiving operations, the nomenclatures through out this
documentation are as follows:
• Frame - Refers to all the bits between Start and Stop.
• Character or word - The payload of a frame, between 5 to 8 bits.
• “!=” - Not equal to.
• Res - Reserved bit.
The address and control pins to register selection is summarized in Table 1.
Table 1. Basic Register Addresses
C
H
A
N
N
E
L
1
C
H
A
N
N
E
L
2
6
DLAB1
CHSL
A2
A1
A0
Register
0
1
0
0
0
Receive Buffer (Read), Transmitter Holding Register (Write)
0
1
0
0
1
Interrupt Enable
0
1
0
1
0
Interrupt Identification (Read)
0
1
0
1
0
FIFO Control (Write)
x
1
0
1
1
Line Control
x
1
1
0
0
Modem Control
x
1
1
0
1
Line Status (Read)
x
1
1
1
0
Modem Status (Read)
x
1
1
1
1
Scratchpad
1
1
0
0
0
Divisor Latch (Least Significant Byte)
1
1
0
0
1
Divisor Latch (Most Significant Byte)
1
1
0
1
0
Alternate Function
DLAB1
CHSL
A2
A1
A0
Register
0
0
0
0
0
Receive Buffer (Read), Transmitter Holding Register (Write)
0
0
0
0
1
Interrupt Enable
0
0
0
1
0
Interrupt Identification (Read)
0
0
0
1
0
FIFO Control (Write)
x
0
0
1
1
Line Control
x
0
1
0
0
Modem Control
x
0
1
0
1
Line Status (Read)
x
0
1
1
0
Modem Status (Read)
x
0
1
1
1
Scratchpad
1
0
0
0
0
Divisor Latch (Least Significant Byte)
1
0
0
0
1
Divisor Latch (Most Significant Byte)
1
0
0
1
0
Alternate Function
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Table 2. NS16C2552 Register Summary
Reg
Addr
A2-A0
RD/
WR
BIT 7
R/W
Data7
X
X
X
X
X
X
X
X
R/W
CTS Int
Ena
RTS Int
Ena
Xoff Int
Ena
Sleep Md
Ena
Modem
Stat Int
Ena
RX Line
Stat Int
Ena
Tx Empty
Int Ena
Rx Data
Int Ena
0
0
0
0
0
0
0
0
R
FIFOs
Ena
FIFOs
Ena
INT Src
Bit 5
INT Src
Bit 4
INT Src
Bit 3
INT Src
Bit 2
INT Src
Bit 1
INT Src
Bit 0
0
0
0
0
0
0
0
1
W
RX FIFO
Trigger
RX FIFO
Trigger
Tx FIFO
Trigger
(2752)
Tx FIFO
Trigger
(2752)
DMA Md
Ena
Tx FIFO
Reset
Rx FIFO
Reset
FIFOs Ena
0
0
0
0
0
0
0
0
R/W
Divisor
Ena
Set Tx
Break
Set
Parity
Even
Parity
Parity
Ena
Stop
Bits
Word
Length
Bit 1
Word
Length
Bit 0
0
0
0
0
0
0
0
0
R/W
Clk Div
Sel
IR Md
Ena
Xon
Any
Internal
Loopbk
Ena
OUT2
OUT1
RTS
Output
Control
DTR
Output
Control
0
0
0
0
0
0
0
0
R
Rx FIFO
Gbl Err
THR &
TSR
Empty
THR E
mpty
Rx
Break
Rx Frame
Error
Rx Parity
Error
Rx
Overrun
Error
Rx Data
Ready
0
1
1
0
0
0
0
0
DCD
Input
RI
Input
DSR
Input
CTS
Input
Delta
DCD
Delta
RI
Delta
DSR
Delta
CTS
DCD
RI
DSR
CTS
0
0
0
0
SCR
SCR
SCR
SCR
SCR
SCR
SCR
SCR
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Data1
Data0
Comment
UART 16C550 Compatible Registers (Default Values Upon Reset)
RBR
THR
0x0
Default
IER
0x1
Default
IIR
0x2
Default
FCR
0x2
Default
LCR
0x3
Default
MCR
0x4
Default
LSR
0x5
Default
MSR
0x6
R
Default
SCR
R/W
0x7
Default
Data6
Data5
Data4
Data3
Data2
LCR[7] = 0
LCR !=
0xBF
Baud Rate Generator Divisor
DLL
R/W
0x0
Default
DLM
R/W
0x1
Default
DLL
DLL
DLL
DLL
DLL
DLL
DLL
DLL
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
X
X
X
X
X
X
X
X
DLM
DLM
DLM
DLM
DLM
DLM
DLM
DLM
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
X
X
X
X
X
X
X
X
Rsrvd
Rsrvd
Rsrvd
Rsrvd
Rsrvd
RXRDY
BAUDOUT
Concurrent
0x2
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Sel
Sel
WR
Default
0
0
0
0
0
0
0
0
ID
Bit 7
ID
Bit 6
ID
Bit 5
ID
Bit 4
DREV
Bit 3
DREV
Bit 2
DREV
Bit 1
DREV
Bit 0
AFR
DREV
0x0
R/W
R
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
LCR[7] = 1
LCR !
0xBF
LCR[7] = 1
LCR !=
0xBF
DLL =
0x00
DLM =
0x00
Submit Documentation Feedback
7
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Table 2. NS16C2552 Register Summary (continued)
Reg
Addr
A2-A0
RD/
WR
BIT 7
BIT 6
BIT 5
BIT 4
Auto CTS
Ena
Auto RTS
Ena
Special
Char Sel
IER[7:4]
IIR[5:4]
FCR[5:4]
MCR[7:5]
0
0
0
XON1
XON1
Bit 7
Bit 6
0
BIT 3
BIT 2
BIT 1
BIT 0
SW Flow
Control Bit
3
SW Flow
Control Bit
2
SW Flow
Control Bit
1
SW Flow
Control Bit
0
0
0
0
0
0
XON1
XON1
XON1
XON1
XON1
XON1
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
XON2
XON2
XON2
XON2
XON2
XON2
XON2
XON2
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Comment
Enhanced Registers
EFR
0x2
R/W
Default
XON1
R/W
0x4
Default
XON2
R/W
0x5
Default
0
0
0
0
0
0
0
0
XOFF1
XOFF1
XOFF1
XOFF1
XOFF1
XOFF1
XOFF1
XOFF1
0x6
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Default
0
0
0
0
0
0
0
0
XOFF2
XOFF2
XOFF2
XOFF2
XOFF2
XOFF2
XOFF2
XOFF2
0x7
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Default
0
0
0
0
0
0
0
0
XOFF1
R/W
XOFF2
R/W
LCR =
0xBF
Legend:
• Bit Name
• Default Value
The Nomenclature of register descriptions:
• Register name, address, register bit, and value example:
– FCR 0x2.7:6 = 2’b11 - bits 6 and 7 of FCR are both 1.
– Alternative description: FCR[7:6] = 2’b11.
• ‘b - binary number.
• ‘h - hex number.
• 0xNN - hex number.
• n’bN - n is the number of bits; N is the bit value. Example 8’b01010111 = 8’h57 = 0x57.
RECEIVE BUFFER REGISTER (RBR)
The receiver section contains an 8-bit Receive Shift Register (RSR) and a 16 (or 64)-byte FIFO that can be
accessed through Receive Buffer Register (RBR).
Table 3. RBR (0x0)
8
Bit
Bit Name
R/W Def
7:0
RBR Data
R
0xXX
Submit Documentation Feedback
Description
Receive Buffer Register
Rx FIFO data.
Note: This register value does not change upon MR reset.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
TRANSMIT HOLDING REGISTER (THR)
This register holds the byte-wide transmit data (THR). This is a write-only register.
Table 4. THR (0x0)
Bit
Bit Name
R/W Def
7:0
THR Data
W
0xXX
Description
Transmit Holding Register
Tx FIFO data.
Note: This register value does not change upon MR reset.
INTERRUPT ENABLE REGISTER (IER)
This register enables eight types of interrupts for the corresponding serial channel. Each interrupt source can
individually activate the interrupt (INTR) output signal. Setting the bits of the IER to a logic 1 unmasks the
selected interrupt(s). Similarly, the interrupt can be masked off by resetting bits 0 through 7 of the Interrupt
Enable Register (IER). If not desired to be used, masking an interrupt source prevents it from going active in the
IIR and activating the INTR output signal. While interrupt sources are masked off, all system functions including
the Line Status and MODEM Status still operate in their normal manner. Table 5 shows the contents of the IER.
Table 5. IER (0x1)
Bit
7
Bit Name
R/W
Def
CTS Int Ena
R/W
0
Description
CTS Input Interrupt Enable
1 = Enable the CTS to generate interrupt at low to high transition. Requires EFR 0x2.4 = 1.
0 = Disable the CTS interrupt (default).
6
RTS Int Ena
R/W
0
RTS Output Interrupt Enable
1 = Enable the RTS to generate interrupt at low to high transition. Requires EFR 0x2.4 = 1.
0 = Disable the RTS interrupt (default).
5
Xoff Int Ena
R/W
0
Xoff Input Interrupt Enable
1 = Enable the software flow control character Xoff to generate interrupt. Requires EFR 0x2.4 = 1.
0 = Disable the Xoff interrupt (default).
4
Sleep Mode
Ena
R/W
Mdm Stat Int
Ena
R/W
Rx Line Stat Int
Ena
R/W
0
Sleep Mode Enable
1 = Enable the Sleep Mode for the respective channel. Requires EFR 0x2.4 = 1.
0 = Disable Sleep Mode (default).
3
0
Modem Status Interrupt Enable
1 = Enable the Modem Status Register interrupt.
0 = Disable the Modem Status Register interrupt (default).
2
0
Receive Line Status Interrupt Enable
An interrupt can be generated when any of the LSR bits 0x5.4:1=1. LSR 0x5.1 generates an interrupt as
soon as an overflow frame is received. LSR 0x5.4:2 generate an interrupt when there is read error from
FIFO.
1 = Enable the receive line status interrupt.
0 = Disable the receive line status interrupt (default).
1
Tx_Empty Int
Ena
R/W
Rx_DV Int Ena
R/W
0
Tx Holding Reg Empty Interrupt Enable
1 = Enable the interrupt when Tx Holding Register is empty.
0 = Disable the Tx Holding Register from generating interrupt (default).
0
0
Rx Data Available Interrupt Enable
1 = Enable the Received Data Available and FIFO mode time-out interrupt.
0 = Disable the Received Data Available interrupt (default).
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
9
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
INTERRUPT IDENTIFICATION REGISTER (IIR)
In order to provide minimum software overhead during data word transfers, each serial channel of the DUART
prioritizes interrupts into seven levels and records these levels in the Interrupt Identification Register. The seven
levels of interrupt conditions are listed in Table 7. When the CPU reads the IIR, the associated DUART serial
channel freezes all interrupts and indicates the highest priority pending interrupt to the CPU. While this CPU
access is occurring, the associated DUART serial channel records new interrupts, but does not change its
current indication until the access is complete. Table 6 shows the contents of the IIR.
Table 6. IIR (0x2)
Bit
Bit Name
7:6
FIFOs Ena
R/W
Def
Description
R
FIFO Enable Status (FCR 0x2.0)
00
2'b11 = Tx and Rx FIFOs enabled.
2'b00 = Tx and Rx FIFOs disabled (default).
5
INT Src 5
R
RTS/CTS Interrupt Status
0
1 = RTS or CTS changed state from low to high.
0 = No change on RTS or CTS from low to high (default).
4
INT Src 4
R
Xoff or Special Character Interrupt Status
0
1 = Receiver detected Xoff or special character.
0 = No Xoff character match (default).
3:1
INT Src 3:1
R
Interrupt Source Status
000
0
INT Src 0
These three bits indicates the source of a pending interrupt. Refer to Table 7 for interrupt
source and priority.
R
Interrupt Status
1
1 = No interrupt is pending (default).
0 = An interrupt is pending and the IIR content may be used as a pointer for the interrupt
service routine.
Table 7. Interrupt Source and Priority Level
IIR Register Status Bits
Priority
Level
5
4
3
2
1
0
1
0
0
0
1
1
0
LSR
2
0
0
1
1
0
0
RXRDY (Receive data time-out)
3
0
0
0
1
0
0
RXRDY (Receive data ready)
4
0
0
0
0
1
0
TXRDY (Transmit data ready)
5
0
0
0
0
0
0
MSR (Modem Status Register)
6
0
1
0
0
0
0
RXRDY (Received Xoff or special character)
7
1
0
0
0
0
0
CTS, RTS change state from low to high
-
0
0
0
0
0
1
None (default)
Interrupt Source
Table 8. Interrupt Sources and Clearing
Interrupt
Generation
Interrupt Sources
Interrupt Clearing
LSR
Any bit is set in LSR[4:1] (Break Interrupt, Framing, Rx
parity, or overrun error).
Read LSR register. (Interrupt flags and tags are not cleared until
the character(s) that generated the interrupt(s) has/have been
emptied or cleared.)
Rx Trigger
Rx FIFO reached trigger level.
Read FIFO data until FIFO pointer falls below the trigger level.
RXRDY Timer
Time-out in 4-word time plus 12-bit delay time.
Read RBR.
TXRDY
THR empty.
Read from IIR register or a write to THR.
MSR
Any state change in MSR[3:0].
Read from MSR register.
10
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Table 8. Interrupt Sources and Clearing (continued)
Interrupt
Generation
Interrupt Sources
Interrupt Clearing
Xoff or Special
character
Detection of Xoff or Special character.
Read from IIR register or reception of Xon character (or
reception of next character if interrupt is caused by Special
character).
CTS
Input pin toggles from logic 0 to 1 during CTS auto flow
control mode.
Read from IIR or MSR.
RTS
Output pin toggles from logic 0 to 1 during RTS auto
flow control mode.
Read from IIR or MSR.
FIFO CONTROL REGISTER (FCR)
This is a write only register at the same location as the IIR (the IIR is a read only register). This register is used
to enable the FIFOs, clear the FIFOs, set the FIFO trigger level, and select the DMA mode.
Mode 0: Mode 0 allows for single transfer in each DMA cycle. When in the 16450 Mode (FCR[0] = 0) or in the
FIFO Mode (FCR[0] = 1, FCR[3] = 0) and there is at least one character in the RCVR FIFO or RCVR Buffer
Register, the RXRDY pin will go active low. After going active, the RXRDY pin will be inactive when there is no
character in the FIFO or Buffer Register.
On The Tx side, TXRDY is active low when XMIT FIFO or XMIT Holding Register is empty. TXRDY returns to
high when XMIT FIFO or XMIT holding register is not empty.
Mode 1: Mode 1 allows for multiple transfer or multi-character burst transfer. In the FIFO Mode (FCR[0] = 1,
FCR[3] = 1) when the number of characters in the RCVR FIFO equals the trigger threshold level or timeout
occurs, the RXRDY goes active low to initiate DMA transfer request. The RXRDY returns high when RCVR FIFO
becomes empty.
In the FIFO Mode (FCR[0] = 1, FCR[3] = 1) when there is (1) no character in the XMIT FIFO for NS16C2552, or
(2) empty spaces exceed the threshold level for NS16C2752; the TXRDY pin will go active low. This pin will
become inactive when the XMIT FIFO is completely full.
Table 9. FCR (0x2)
Bit
Bit Name
R/W
Def
7:6
Rx FIFO
W
Rx FIFO Trigger Select
Trig
Select
00
FCR[6] and FCR[7] are used to designate the interrupt trigger level. When the number of characters in the
RCVR FIFO equals the designated interrupt trigger level, a Received Data Available Interrupt is activated.
This interrupt must be enabled by IER[0]=1.
Description
For NS16C2552 with 16-byte FIFO:
FCR[7]
FCR[6]
Rx FIFO Trigger Level
1
1
= 14
1
0
=8
0
1
=4
0
0
= 1 (Default)
For NS16C2752 with 64-byte FIFO:
FCR[7]
FCR[6]
Rx FIFO Trigger Level
1
1
= 60
1
0
= 56
0
1
= 16
0
0
= 8 (Default)
Refer to SOFTWARE XON/XOFF FLOW CONTROL and DMA OPERATION for software flow control using
FIFO trigger level.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
11
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Table 9. FCR (0x2) (continued)
Bit
Bit Name
5:4
Tx FIFO
Trig Level
Sel
R/W
Def
Description
W
Transmit FIFO Trigger Level Selection
00
The transmit FIFO trigger threshold selection is only available in NS16C2752. When enabled, a transmit
interrupt is generated and TXRDY is asserted when the number of empty spaces in the FIFO exceeds the
threshold level.
For NS16C2752 with 64-byte FIFO:
FCR[5]
FCR[4]
Tx FIFO Trigger Level
1
1
= 56
1
0
= 32
0
1
= 16
0
0
= 8 (Default)
Refer to TRANSMIT OPERATION and DMA OPERATION for transmit FIFO descriptions.
These two bits are reserved in NS16C2552 and have no impact when they are written to.
3
DMA
Mode
Select
W
DMA Mode Select
0
This bit controls the RXRDY and TXRDY initiated DMA transfer mode.
1 = DMA Mode 1. Allows block transfers. Requires FCR 0x2.0=1 (FIFO mode).
0 = DMA Mode 0 (default). Single transfers.
2
Tx FIFO
Reset
W
Transmit FIFO Reset
0
This bit is only active when FCR bit 0 = 1.
1 = Reset XMIT FIFO pointers and all bytes in the XMIT FIFO (the Tx shift register is not cleared and is
cleared by MR reset). This bit has the self-clearing capability.
0 = No impact (default).
Note: Reset pointer will cause the characters in Tx FIFO to be lost.
1
Rx FIFO
Reset
W
Receive FIFO Reset
0
This bit is only active when FCR bit 0 = 1.
1 = Reset RCVR FIFO pointers and all bytes in the RCVR FIFO (the Rx shift register is not cleared and is
cleared by MR reset). This bit has the self-clearing capability.
0 = No impact (default).
Note: Reset pointer will cause the characters in Rx FIFO to be lost.
0
Tx and Rx
FIFO
Enable
W
Transmit and Receive FIFO Enable
0
1 = Enable transmit and receive FIFO. This bit must be set before other FCR bits are written. Otherwise, the
FCR bits can not be programmed.
0 = Disable transmit and receive FIFO (default).
LINE CONTROL REGISTER (LCR)
The system programmer specifies the format of the asynchronous data communications exchange and sets the
Divisor Latch Access bit via the Line Control Register (LCR). This is a read and write register.
Table 10. LCR (0x3)
Bit
7
12
Bit Name
Default
R/W
Def
Divisor Latch
Ena
R/W
0
Description
Divisor Latch Access Bit (DLAB)
This bit must be set (logic 1) to access the Divisor Latches of the Baud Generator and the Alternate
Function Register during a read or write operation. It must be cleared (logic 0) to access any other
register.
1 = Enable access to the Divisor Latches of the Baud Generator and the AFR.
0 = Enable access to other registers (default).
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Table 10. LCR (0x3) (continued)
Bit
Bit Name
Default
R/W
Def
6
Tx Break Ena
R/W
0
Description
Set Tx Break Enable
This bit is the Break Control bit. It causes a break condition to be transmitted to the receiving UART.
The Break Control bit acts only on SOUT and has no effect on the transmitter logic.
1 = Serial output (SOUT) is forced to the Spacing State (break state, logic 0).
0 = The break transmission is disabled (default).
Note: This feature enables the CPU to alert a terminal in a computer communication system. If the
following sequence is followed, no erroneous or extraneous character will be transmitted because of
the break.
1. Load an all 0s, pad character, in response to THRE.
2. Set break after the next THRE.
3. Wait for the transmitter to be idle, (Transmitter Empty TEMT = 1), and clear break when normal
transmission has to be restored.
During the break, the transmitter can be used as a character timer to establish the break duration.
During the break state, any word left in THR will be shifted out of the register but blocked by SOUT
as forced to break state. This word will be lost.
5
4
Forced
Parity Sel
Even/Odd
Parity Sel
R/W
0
R/W
0
Tx and Rx Forced Parity Select
When parity is enabled, this bit selects the forced parity format.
LCR[5]
LCR[4]
LCR[3]
1
1
1
Force parity to space = 0
Parity Select
1
0
1
Force parity to mark = 1
0
1
1
Even parity
0
0
1
Odd parity
X
X
0
No parity
Tx and Rx Even/Odd Parity Select
This bit is only effective when LCR[3]=1. This bit selects even or odd parity format.
1 = Odd parity is transmitted or checked.
0 = Even parity is transmitted or checked (default).
3
Tx/Rx Parity
Ena
R/W
0
Tx and Rx Parity Enable
This bit enables parity generation.
1 = A parity is generated during the data transmission. The receiver checks for parity error of the
data received.
0 = No parity (default).
2
Tx/Rx Stop-bit
Length Sel
R/W
0
Tx and Rx Stop-bit Length Select
This bit specifies the number of Stop bits transmitted with each serial character.
LCR[2]
Word Length Sel
Stop-bit Length
1
6,7,8
=2
1
5
= 1.5
0
5,6,7,8
= 1(Default)
Stop-bit length is measured in bit time.
1:0
Tx/Rx Word
Length Sel
R/W
0
Tx and Rx Word Length Select
These two bits specify the word length to be transmitted or received.
LCR[1]
LCR[0]
1
1
Word Length
=8
1
0
=7
0
1
=6
0
0
= 5 (Default)
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
13
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
MODEM CONTROL REGISTER (MCR)
This register controls the interface with the MODEM or data set (or a peripheral device emulating a MODEM).
There is a clock divider for each channel. Each is capable of taking a common clock input from DC to 80 MHz
and dividing the clock frequency by 1 (default) or 4 depending on the MCR[7] value. The clock divider and the
internal clock division flow is shown in Figure 3.
Figure 3. Internal Clock Dividers
Table 11. MCR (0x4)
Bit
Bit Name
7
Clk Divider
Sel
R/W
Def
R/W
0
Description
Clock Divider Select
This bit selects the clock divider from crystal or oscillator input. The divider output connects to the Baud
Rate Generator.
1 = Divide XIN frequency by 4.
0 = Divide XIN frequency by 1 (default).
6
IR Mode Sel
R/W
0
Infrared Encoder/Decoder Select
This bit selects standard modem or IrDA interface.
1 = Infrared IrDA Tx/Rx. The data input and output levels complies to the IrDA infrared interface. The Tx
output is at logic 0 during the idle state.
0 = Standard modem Tx/Rx (default).
5
Xon-Any
Ena
R/W
0
Xon-Any Enable
This bit enables Xon-Any feature.
1 = Enable Xon-Any function. When Xon/Xoff flow control is enabled, the transmission resumes when
any character is received. The received character is loaded into the Rx FIFO except for Xon or Xoff
characters.
0 = Disable Xon-Any function (default).
4
Internal
Loopback
Ena
R/W
0
Internal Loopback Enable
This bit provides a local loopback feature for diagnostic testing of the associated serial channel. (Refer
to INTERNAL LOOPBACK MODE and Figure 15.)
1 = the transmitter Serial Output (SOUT) is set to the Marking (logic 1) state; the receiver Serial Input
(SIN) is disconnected; the output of the Transmitter Shift Register is looped back into the Receiver Shift
Register input; the four MODEM Control inputs (DSR, CTS, RI, and DCD) are disconnected; the four
MODEM Control outputs (DTR, RTS, OUT1 and OUT2) are internally connected to the four MODEM
Control inputs; and the MODEM Control output pins are forced to their inactive state (high). In this
diagnostic mode, data that is transmitted is immediately received. This feature allows the processor to
verify transmit and receive data paths of the DUART. In this diagnostic mode, the receiver and
transmitter interrupts are fully operational. Their sources are external to the part. The MODEM Control
Interrupts are also operational, but the interrupt sources are now the lower four bits of the MODEM
Control Register instead of the four MODEM Control inputs. The interrupts are still controlled by the
Interrupt Ena
0 = Normal Tx/Rx operation; loopback disabled (default).
14
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Table 11. MCR (0x4) (continued)
Bit
Bit Name
R/W
Def
3
OUT2
R/W
Description
Output2
0
This bit controls the Output 2 (OUT2) signal, which is an auxiliary user-designated output. Bit 3 affects
the OUT2 pin as described below. The function of this bit is multiplexed on a single output pin with two
other functions: BAUDOUT and RXDRY. The OUT2 function is the default function of the pin after a
master reset. See ALTERNATE FUNCTION REGISTER (AFR) for more information about selecting one
of these 3 pin functions.
1 = Force OUT2 to logic 0.
0 = Force OUT2 to logic 1 (default).
2
OUT1
R/W
Output1
0
In normal operation, OUT1 bit is not available as an output.
In internal Loopback Mode (MCR 0x4.4=1) this bit controls the state of the modem input RI in the MSR
bit 6.
1 = MSR 0x06.6 is at logic 1.
0 = MSR 0x06.6 is at logic 0.
1
RTS Output
R/W
RTS Output Control
0
This bit controls the RTS pin. If modem interface is not used, this output is used as a general purpose
output.
1 = Force RTS pin to logic 0.
0 = Force RTS pin to logic 1(default).
0
DTR Output
R/W
DTR Output Control
0
This bit controls the DTR pin. If modem interface is not used, this output is used as a general purpose
output.
1 = Force DTR pin to logic 0.
0 = Force DTR pin to logic 1(default).
LINE STATUS REGISTER (LSR)
This register provides status information to the CPU concerning the data transfer.
Bits 1 through 4 are the error conditions that produce a Receiver Line Status interrupt whenever any of the
corresponding conditions are detected and the interrupt is enabled.
Table 12. LSR (0x5)
Bit
Bit Name
R/W
Def
7
Rx FIFO Err
R
Rx FIFO Data Error
0
This bit is a global Rx FIFO error flag. In the 16450 Mode this bit is 0.
Description
1 = A sum of all error bits in the Rx FIFO. These errors include parity, framing, and break indication
in the FIFO data.
0 = No Rx FIFO error (default).
Note: The Line Status Register is intended for read operations only. Writing to this register is not
recommended as this operation is only used for factory testing.
6
THR & TSR
Empty
R
THR and TSR Empty
1
This bit is the Transmitter Empty (TEMT) flag.
1 = Whenever the Transmitter Holding Register (THR) (or the Tx FIFO in FIFO mode) and the
Transmitter Shift Register (TSR) are both empty (default).
0 = Whenever either the THR (or the Tx FIFO in FIFO mode) or the TSR contains a data word.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
15
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Table 12. LSR (0x5) (continued)
Bit
Bit Name
R/W
Def
5
THR Empty
R
THR Empty
1
This bit is the Transmitter Holding Register Empty (THRE) flag. In the 16450 mode bit 5 indicates
that the associated serial channel is ready to accept a new character for transmission. In addition,
this bit causes the DUART to issue an interrupt to the CPU when the Transmit Holding Register
Empty interrupt enable is set.
Description
1 = In 16450 mode, whenever a character is transferred from the Transmitter Holding Register into
the Transmitter Shift Register, or in FIFO mode when the Tx FIFO is empty (default).
0 = In 16450 mode, this bit is reset to logic 0 concurrently with the loading of the Transmitter Holding
Register by the CPU. In FIFO mode, it is cleared when at least 1 byte is written to the Tx FIFO.
4
Rx Break
Interrupt
R
Receive Break Interrupt Indicator
0
This bit is the Break Interrupt (BI) indicator.
1 = Whenever the received data input is held in the Spacing (logic 0) state for longer than a full
frame transmission time (that is, the total time of Start bit + data bits + Parity + Stop bits).
0 = No break condition (default).
This bit is reset to 0 whenever the CPU reads the contents of the Line Status Register or when the
next valid character is loaded into the Receiver Buffer Register.
In the FIFO Mode this condition is associated with the particular character in the FIFO it applies to. It
is revealed to the CPU when its associated character is at the top of the FIFO. When break occurs
only one zero character is loaded into the FIFO. The next character transfer is enabled after SIN
goes to the Marking (logic 1) state and receives the next valid start bit.
3
Rx Frame Error
R
Framing Error Indicator
0
This bit is the Framing Error (FE) indicator.
1= Received character did not have a valid Stop bit when the serial channel detects a logic 0 during
the first Stop bit time.
0 = No frame error (default).
The bit is reset to 0 whenever the CPU reads the contents of the Line Status Register or when the
next valid character is loaded into the Receiver Buffer Register. In the FIFO Mode this error is
associated with the particular character in the FIFO it applies to. This error is revealed to the CPU
when its associated character is at the top of the FIFO. The serial channel will try to resynchronize
after a framing error. This assumes that the framing error was due to the next start bit, so it samples
this start bit twice and then takes in the data.
2
Rx Parity Error
R
Parity Error Indicator
0
This bit is the Parity Error (PE) indicator.
1 = Received data word does not have the correct even or odd parity, as selected by the evenparity-select bit during the character Stop bit time when the character has a parity error.
0 = No parity error (default).
This bit is reset to a logic 0 whenever the CPU reads the contents of the Line Status Register or
when the next valid character is loaded into the Receiver Buffer Register. In the FIFO mode this
error is associated with the particular character in the FIFO it applies to. This error is revealed to the
host when its associated character is at the top of the FIFO.
1
Rx Overrun
Error
R
Overrun Error Indicator
0
This bit is the Overrun Error (OE) indicator.
This bit indicates that the next character received was transferred into the Receiver Buffer Register
before the CPU could read the previously received character. This transfer overwrites the previous
character. It is reset whenever the CPU reads the contents of the Line Status Register. If the FIFO
mode data continues to fill the FIFO beyond the trigger level, an overrun error will occur only after
the FIFO is full and the next character has been completely received in the shift register. OE is
indicated to the CPU as soon as it happens. The character in the shift register can be overwritten,
but it is not transferred to the FIFO.
1 = Set to a logic 1 during the character stop bit time when the overrun condition exists.
0 = No overrun error (default).
0
Rx Data Ready
R
Receiver Data Indicator
0
This bit is the receiver Data Ready (DR) indicator.
1 = Whenever a complete incoming character has been received and transferred into the Receiver
Buffer Register (RBR) or the FIFO. Bit 0 is reset by reading all of the data in the RBR or the FIFO.
0 = No receive data available (default).
16
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
MODEM STATUS REGISTER (MSR)
This register provides the current state of the control lines from the MODEM (or peripheral device) to the CPU. In
addition to this current-state information, four bits of the MODEM Status Register provide change information.
The latter bits are set to a logic 1 whenever a control input from the MODEM changes state. They are reset to
logic 0 whenever the CPU reads the MODEM Status Register.
Table 13. MSR (0x6)
Bit
Bit Name
R/W
Def
7
DCD Input
R
Status
DCD
6
RI Input
Status
Description
DCD Input Status
This bit is the complement of the Data Carrier Detect (DCD) input. In the loopback mode, this bit is
equivalent to the OUT2 of the MCR.
1 = DCD input is logic 0.
0 = DCD input is logic 1.
R
RI Input Status
RI
This bit is the complement of the Ring Indicator (RI) input. In the loopback mode, this bit is equivalent to
OUT1 of the MCR.
1 = RI input is logic 0.
0 = RI input is logic 1.
5
DSR Input
Status
R
DSR
DSR Input Status
This bit is the complement of the Data Set Ready (DSR) input. In the loopback mode, this bit is
equivalent to DTR in the MCR.
1 = DSR input is logic 0.
0 = DSR input is logic 1.
4
CTS Input
Status
R
CTS
CTS Input Status
This bit is the complement of the Clear to Send (CTS) input. In the loopback mode, this bit is equivalent
to RTS in the MCR.
1 = CTS input is logic 0.
0 = CTS input is logic 1.
3
DDCD Input
Status
R
Delta DCD Input Indicator
0
This bit is the Delta Data Carrier Detect (DDCD) indicator. Bit 3 indicates that the DCD input has changed
state since the last read by the host.
1 = DCD input has changed state.
0 = DCD input has no state change (default).
Note: Whenever bit 0, 1, 2, or 3 is set to logic 1, a MODEM Status Interrupt is generated.
2
Falling Edge
RI Indicator
R
Falling Edge RI Indicator
0
This bit is theFalling Edge of Ring Indicator (TERI) detector. Bit 2 indicates that the RI input pin has
changed from a logic 0 to 1 since the last read by the host.
1 = RI input has changed state from logic 0 to 1.
0 = RI input has no state change from 0 to 1 (default).
1
DDSR Input
Indicator
R
Delta DSR Input Indicator
0
This bit is the Delta Data Set Ready (DDSR) indicator. Bit 1 indicates that the DSR input pin has changed
state since the last read by the host.
1 = DSR input has changed state from logic 0 to 1.
0 = DSR input has no state change from 0 to 1 (default).
0
DCTS Input
Indicator
R
Delta CTS Input Indicator
0
This bit is the Delta Clear to Send (DCTS) indicator. Bit 0 indicates that the CTS input pin has changed
state since the last time it was read by the host.
1 = CTS input has changed state.
0 = CTS input has no state change (default).
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
17
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
SCRATCHPAD REGISTER (SCR)
This 8-bit Read/Write Register does not control the serial channel in any way. It is intended as a Scratchpad
Register to be used by the programmer to hold data temporarily.
Table 14. SCR (0x7)
Bit
Bit Name
7:0
SCR Data
R/W
Def
Description
R/W
0xFF
Scratchpad Register
This 8-bit register does not control the UART in any way. It is intended as a scratchpad register
to be used by the programmer to hold temporary data.
PROGRAMMABLE BAUD GENERATOR
The NS16C2552 contains two independently programmable Baud Generators. Each is capable of taking
prescaler input and dividing it by any divisor from 1 to 216 -1 (Figure 3). The highest input clock frequency
recommended with a divisor = 1 is 80MHz. The output frequency of the Baud Generator is 16 X the baud rate,
[divisor # = (frequency input) / (baud rate X 16)]. The output of each Baud Generator drives the transmitter and
receiver sections of the associated serial channel. Two 8-bit latches per channel store the divisor in a 16-bit
binary format. These Divisor Latches must be loaded during initialization to ensure proper operation of the Baud
Generator. Upon loading either of the Divisor Latches, a 16-bit Baud Counter is loaded.
Table 15. DLL (0x0, LCR[7] = 1, LCR != 0xBF)
Bit
Bit Name
7:0
DLL Data
R/W
Def
R/W
0xXX
Description
Divisor Latch LSB
This 8-bit register holds the least significant byte of the 16-bit baud rate generator divisor.
This register value does not change upon MR reset.
Table 16. DLM (0x1, LCR[7] = 1, LCR != 0xBF)
Bit
Bit Name
7:0
DLM Data
R/W
Def
R/W
0xXX
Description
Divisor Latch MSB
This 8-bit register holds the most significant byte of the 16-bit baud rate generator divisor.
This register value does not change upon MR reset.
Table 17 provides decimal divisors to use with crystal frequencies of 1.8432 MHz, 3.072 MHz and 18.432 MHz.
For baud rates of 38400 and below, the error obtained is minimal. The accuracy of the desired baud rate is
dependent on the crystal frequency chosen. Using a divisor of zero is not recommended.
Table 17. Baud Rate Generation Using 1.8432 MHz Clock with MCR[7]=0
18
Output Data
Baud Rate
Output 16x Clock
Divider (dec)
User 16x Clock
Divisor (hex)
DLM Program
Value (hex)
DLL Program
Value (hex)
Data Rate
Error (%)
50
2304
900
09
00
0
75
1536
600
06
00
0
150
768
300
03
00
0
300
384
180
01
80
0
600
192
C0
00
C0
0
1200
96
60
00
60
0
2400
48
30
00
30
0
4800
24
18
00
18
0
9600
12
0C
00
0C
0
19,200
6
06
00
06
0
38,400
3
03
00
03
0
115,200
1
01
00
01
0
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
NOTE
For baud rates of 250k, 300k, 375k, 500k, 750k and 1.5M using a 24MHz crystal causes
minimal error.
ALTERNATE FUNCTION REGISTER (AFR)
This is a read/write register used to select simultaneous write to both register sets and alter MF pin functions.
Table 18. AFR (0x2, LCR[7] = 1, LCR != 0xBF)
Bit
Bit Name
Default
7:3
Reserved
2:1
MF Output Sel
R/W
Def
Description
Reserved
These bits are set to a logic 0.
R/W
Multi-function Pin Output Select
0
0
Concurrent Write
Ena
These select the output signal that will be present on the multi-function pin, MF. These bits are
individually programmable for each channel, so that different signals can be selected on each
channel.
R/W
AFR[2]
AFR[1]
1
1
MF Function
= Reserved (MF output is forced logic 1)
1
0
= RXRDY
0
1
= BAUDOUT
0
0
= OUT2 (default)
Concurrent Write Enable
0
1 = CPU can write concurrently to the same register in both registers sets. This function is
intended to reduce the DUART initialization time. It can be used by a CPU when both channels
are initialized to the same state. The CPU can set or clear this bit by accessing either register set.
When this bit is set the channel select pin still selects the channel to be accessed during read
operations. Setting or clearing this bit has no effect on read operations.
The user should ensure that the DLAB bit LCR[7] of both channels are in the same state before
executing a concurrent write to register addresses 0, 1 and 2.
0 = No concurrent write (default). (No impact on read operations.)
DEVICE IDENTIFICATION REGISTER (ID)
The device ID for NS16C2552 is 0x03. DLL and DLM should be initialized to 0x00 before reading the ID register.
This is a read-only register.
Table 19. DREV (0x0, LCR[7]=1, LCR!=0xBF, DLL=DLM=0x00)
Bit
Bit Name
R/W
Def
7:4
Device ID
R
Device ID
Value = 0x3 for NS16C2552; 0x2 for NS16C2752
3:0
Device Rev
R
Device Revision
Value = 0x1.
Description
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
19
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
ENHANCED FEATURE REGISTER (EFR)
This register enables the enhanced features of the device.
Table 20. EFR (0x2, LCR = 0xBF)
Bit
7
Bit Name
Default
R/W
Def
Auto CTS
Flow Ctl
Ena
R/W
Auto RTS
Flow Ctl
Ena
R/W
0
Description
Automatic CTS Flow Control Enable
1 = Enable automatic CTS flow control. Data transmission stops when CTS input deasserts to logic 1. Data
transmission resumes when CTS returns to logic 0.
0 = Automatic CTS flow control is disabled (Default)
6
0
Automatic RTS Flow Control Enable
By setting EFR[6] to logic 1, RTS output can be used for hardware flow control. When Auto RTS is selected,
an interrupt is generated when the receive FIFO is filled to the programmed trigger level and RTS de-asserts
to a logic 1. The RTS output must be logic 0 before the auto RTS can take effect. RTS pin functions as a
general purpose output when hardware flow control is disabled.
1 = Enable automatic RTS flow control.
0 = Automatic RTS flow control is disabled (Default)
5
Special
Char Det
Ena
R/W
Enhanced
Fun Bit Ena
R/W
0
Special Character Detect Enable
1 = Special character detect enabled. The UART compares each incoming received character with data in
Xoff-2 register (0x4, LCR = 0xBF). If a match is found, the received data will be transferred to FIFO and
IIR[4] is set to indicate the detection of a special character if IER[5] = 1. Bit 0 corresponds with the LSB of
the received character. If flow control is set for comparing Xon1, Xoff1 (EFR[1:0] = 10) then flow control and
special character work normally; If flow control is set for comparing Xon2, Xoff2 (EFR[1:0]=01) then flow
control works normally, but Xoff2 will not go to the FIFO, and will generate an Xoff interrupt and a special
character interrupt if IER[5] is enabled. Special character interrupts are cleared automatically after the next
received character.
0 = Special character detect disabled. (Default)
4
0
Enhanced Function Bits Enable
This bit enables IER[7:4], FCR[5:4], and MCR [7:5] to be changed. After changing the enhanced bits, EFR[4]
can be cleared to logic 0 to latch in the updated values. EFR[4] allows compatibility with the legacy mode
software by disabling alteration of the enhanced functions.
1 = Enables writing to IER[7:4], FCR[5:4], and MCR [7:5].
0 = Disable writing to IER[7:4], FCR[5:4], MCR [7:5] and, latching in updated value. Upon reset, IER[7:4],
IIR[5:4], FCR[5:4], and MCR [7:5] are cleared to logic 0. (Default)
3:0
Software
Flow
Control Sel
R/W
0
Software Flow Control Select
Single character and dual sequential character software flow control is supported. Combinations of software
flow control can be selected by programming the bits.
EFR[3]
EFR[1]
EFR[0]
Rx Flow Control
1
1
1
Rx compares Xon1 & Xon2, Xoff1 & Xoff2
1
0
1
1
Rx compares Xon1 or Xon2, Xoff1 or Xoff2
0
1
1
1
Rx compares Xon1 or Xon2, Xoff1 or Xoff2
0
0
1
1
Rx compares Xon1 & Xon2, Xoff1 & Xoff2
X
X
1
0
Rx compares Xon1, Xoff1
X
X
0
1
Rx compares Xon2, Xoff2
X
X
0
0
No Rx flow control
0
0
0
0
No Tx & Rx flow control (default)
EFR[3]
20
EFR[2]
1
EFR[2]
EFR[1]
EFR[0]
Tx Flow Control
1
1
X
X
Tx Xon1 and Xon2, Xoff1 and Xoff2
1
0
X
X
Tx Xon1, Xoff1
0
1
X
X
Tx Xon2, Xoff2
0
0
X
X
No Tx flow control
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
SOFTWARE FLOW CONTROL REGISTERS (SFR)
The following four registers are used as programmable software flow control characters.
Table 21. Xon1 (0x4, LCR=0xBF)
Bit
Bit Name
7:0
Xon1 Data
R/W
Def
R/W
0
Description
Xon1 Data
Table 22. Xon2 (0x5, LCR=0xBF)
Bit
Bit Name
7:0
Xon2 Data
R/W
Def
R/W
0
Description
Xon2 Data
Table 23. Xoff1 (0x6, LCR=0xBF)
Bit
Bit Name
7:0
Xoff1 Data
R/W
Def
R/W
0
Description
Xoff1 Data
Table 24. Xoff2 (0x7, LCR=0xBF)
Bit
Bit Name
7:0
Xoff2 Data
R/W
Def
R/W
0
Description
Xoff2 Data
Operation and Configuration
CLOCK INPUT
The NS16C2552/2752 has an on-chip oscillator that accepts standard crystal with parallel resonant and
fundamental frequency. The generated clock is supplied to both UART channels with the capability range from
DC to 24 MHz. The frequency of the clock oscillator is divided by 16 internally, combined with an on-chip
programmable clock divider providing the baud rate for data transmission. The divisor is 16-bit with MSB byte in
DLM and LSB byte in DLL. The divisor calculation is shown in PROGRAMMABLE BAUD GENERATOR.
The external oscillator circuitry requires two load capacitors, a parallel resistor, and an optional damping resistor.
The oscillator circuitry is shown in Figure 4.
Figure 4. Crystal Oscillator Circuitry
The requirement of the crystal is listed in Table 25.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
21
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Table 25. Crystal Component Requirement
Parameter
Value
Crystal Frequency Range
<= 24 MHz
Crystal Type
Parallel resonant
Fundamental
C1 & C2, Load Capacitance
10 - 22 pF
ESR
20 - 120 Ω
Frequency Stability 0 to 70°C
100 ppm
The capacitors C1 and C2 are used to adjust the load capacitance on these pins. The total load capacitance (C1,
C2 and crystal) must be within a certain range for the NS16C2552/2752 to function properly. The parallel resistor
Rp and load resistor Rs are recommended by some crystal vendors. Refer to the vendor’s crystal datasheet for
details.
Since each channel has a separate programmable clock divider, each channel can have a different baud rate.
The oscillator provides clock to the internal data transmission circuitry, writing and reading from the parallel bus
is not affected by the oscillator frequency. For circuits not using the external crystal, the clock input is XIN
(Figure 5.)
Figure 5. Clock Input Circuitry
RESET
The NS16C2552/2752 has an on-chip power-on reset that can accommodate a slow risetime power supply. The
power-on reset has a circuit that holds the device in reset state for 223 XIN clock cycles. For example, if the
crystal frequency is 24MHz, the reset time will be 223 X 1/(24 X 106) = 349ms. An external active high reset can
also be applied. The default output state of the device is listed in Table 26.
Table 26. Output State After Reset
Output
Reset State
SOUT1, SOUT2
Logic 1
OUT2
Logic 1
RTS1, RTS2
Logic 1
DTR1, DTR2
Logic 1
INTR1, INTR2
Logic 0
TXRDY1, TXRDY2
Logic 0
22
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
RECEIVER OPERATION
Each serial channel consists of an 8-bit Receive Shift Register (RSR) and a 16 (or 64) -byte by 11-bit wide
Receive FIFO. The RSR contains a 8-bit Receive Buffer Register (RBR) that is part of the Receive FIFO. The 11bit wide FIFO contains an 8-bit data field and a 3-bit error flag field. The RSR uses 16X clock as timing source.
(Figure 6.)
Figure 6. Rx FIFO Mode
The RSR operation is described as follows:
1. At the falling edge of the start bit, an internal timer starts counting at 16X clock. At 8th 16X clock,
approximately the middle of the start bit, the logic level is sampled. If a logic 0 is detected the start bit is
validated.
2. The validation logic continues to detect the remaining data bits and stop bit to ensure the correct framing. If
an error is detected, it is reported in LSR[4:2].
3. The data frame is then loaded into the RBR and the Receive FIFO pointer is incremented. The error tags are
updated to reflect the status of the character data in RBR. The data ready bit (LSR[0]) is set as soon as a
character is transferred from the shift register to the Receive FIFO. It is reset when the Receive FIFO is
empty.
Receive in FIFO Mode
Interrupt Mode
In the FIFO mode, FCR[0]=1, RBR can be configured to generate an interrupt after the FIFO pointer reaches a
trigger threshold. The interrupt causes CPU host to fetch the Rx character in the FIFO in a burst mode and the
transfer number is set by the trigger level. The interrupt is cleared as soon as the number of bytes in the Rx FIFO
drops below the trigger level. The Rx FIFO continues to receive new characters, and the interrupt is re-asserted
when the character reaches the trigger threshold.
To ensure the data is delivered to the host, a receive data ready time-out interrupt IIR[3] is generated when RBR
data is not fetched by the host in 4-word length long (defined in LCR[1:0]) plus 12 bit-time. The RBR interrupt is
enabled through IER[0]. This is equivalent of 3.6 to 4.7 frame-time.
The maximum time between a received character and a time-out interrupt will be 147 ms at 300 baud with an 8bit receive word.
Character delay time is calculated by using the BAUDOUT signal as a clock signal. This makes the delay
proportional to the baud rate.
Time-out interrupt is cleared and the timer is reset when the CPU reads one character from the Receive FIFO.
When the time-out interrupt is inactive the time-out timer is reset after a new character is received or after the
CPU reads the Receive FIFO.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
23
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
After the first character is read by the host, the next character is loaded into the RBR and the error flags are
loaded into LSR[4:2].
DMA Mode
In the FIFO mode, the RXRDY asserts when the character in the Rx FIFO reaches the trigger threshold or
timeout occurs. The RXRDY initiates DMA transfer in a burst mode. The RXRDY deasserts when the Rx FIFO is
completely emptied and the DMA transfer stops (Figure 7.)
Figure 7. RXRDY in DMA Mode 1
Receive in non-FIFO Mode
Interrupt Mode
In the non-FIFO mode, FCR[0]=0, RBR can be configured to generate an IIR Receive Data Available interrupt
IIR[2] immediately after the first byte is received. Upon interrupt, the CPU host reads the RBR and clears the
interrupt. The interrupt is reasserted when the next character is received. (Figure 8.)
Figure 8. Rx Non-FIFO Mode
DMA Mode
In the non-FIFO mode, the presence of a received character in RBR causes the assertion of RXRDY at which
point DMA transfer can be initiated. Upon transfer completion RXRDY is deasserted. DMA transfer stops and
awaits for the next character. (Figure 9.)
24
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Figure 9. RXRDY in DMA Mode 0
Receive Hardware Flow Control
On the line side, RTS signal provides automatic flow control to prevent data overflow in the Receive FIFO. The
RTS is used to request remote unit to suspend or resume data transmission. This feature is enabled to suit
specific application. The RTS flow control can be enabled by the following steps:
• Enable auto-RTS flow control EFR[6]=1.
• The auto-RTS function is initiated by asserting RTS output pin, MCR[1]=1.
The auto-RTS assertion and deassertion timing is based upon the Rx FIFO trigger level (Table 27 and Table 28).
Receive Flow Control Interrupt
To enable auto RTS interrupt:
• Enable auto RTS flow control EFR[6]=1.
• Enable RTS interrupt IER[6]=1.
An interrupt is generated when RTS pin makes a transition from logic 0 to 1; IIR[5] is set to logic 1.
The receive data ready interrupt (IIR[2]) generation timing is based upon the Rx FIFO trigger level (Table 27 and
Table 28).
Table 27. Auto-RTS HW Flow Control on NS16C2552
Rx Trigger
Level
INTR Pin
Activation
RTS
Desertion
RTS
Assertion
1
1
2
0
4
4
8
1
8
8
14
4
14
14
14
8
Table 28. Auto-RTS HW flow Control on NS16C2752
Rx Trigger
Level
INTR Pin
Activation
RTS
Desertion
RTS
Assertion
8
8
16
0
16
16
56
8
56
56
60
16
60
60
60
56
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
25
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
TRANSMIT OPERATION
Each serial channel consists of an 8-bit Transmit Shift Register (TSR) and a 16-byte (or 64-byte) Transmit FIFO.
The Transmit FIFO includes a 8-bit Transmit Holding Register (THR). The TSR shifts data out at the 16X internal
clock. A bit time is 16 clock periods. The transmitter begins with a start-bit followed by data bits, asserts parity-bit
if enabled, and adds the stop-bit(s). The FIFO and TSR status is reported in the LSR[6:5].
The THR is an 8-bit register providing a data interface to the host processor. The host writes transmit data to the
THR. The THR is the Transmit FIFO input register in FIFO operation. The FIFO operation can be enabled by
FCR[0]=1. During the FIFO operation, the FIFO pointer is incremented pointing to the next FIFO location when a
data word is written into the THR.
Transmit in FIFO Mode
Interrupt mode
In the NS16C2752 FIFO mode (FCR[0]=1), when the Tx FIFO empty spaces exceed the threshold level the THR
empty flag is set (LSR[5]=1). The THR empty flag generates a TXRDY interrupt (IIR[1]=1) when the transmit
empty interrupt is enabled (IER[1]=1). Writing to THR or reading from IIR deasserts the interrupt.
There is a two-character hysteresis in interrupt generation. The host needs to service the interrupt by writing at
least two characters into the Tx FIFO before the next interrupt can be generated.
The NS16C2552 does not have the FIFO threshold level control. The interrrupt is generated when the FIFO is
completely empty.
Figure 10. Tx FIFO Mode
DMA mode
To fully take advantage of the FIFO buffer, the UART is best operating in DMA mode 1 (FCR[3]=1) when
characters are transferred in bursts. The NS16C2752 has a Tx FIFO threshold level control in register FCR[5:4].
The threshold level sets the number of empty spaces in the FIFO and determines when the TXRDY is asserted.
If the number of empty spaces in the FIFO exceeds the threshold, the TXRDY asserts initiating DMA transfers to
fill the Tx FIFO. When the empty spaces in the Tx FIFO becomes zero (i.e., FIFO is full), the TXRDY deasserts
and the DMA transfer stops. TXRDY reasserts when empty space exceeds the set threshold, starting a new
DMA transfer cycle. (Figure 11.)
The NS16C2552 does not have the FIFO threshold level control. The TXRDY is asserted when FIFO is empty
and deasserted when FIFO is full. It is equivalent of having trigger threshold set at 16 empty spaces.
26
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Figure 11. TXRDY in DMA Mode 1
Transmit in non-FIFO Mode
Interrupt Mode
The THR empty flag LSR[5] is set when a data word is transferred to the TSR. THR flag can generate a transmit
empty interrupt IIR[1] enabled by IER[1]. The TSR flag LSR[6] is set when TSR becomes empty. The host CPU
may write one character into the THR and wait for the next IIR[1] interrupt. (Figure 12.)
Figure 12. Tx Non-FIFO Mode
DMA mode
In the DMA single transfer (mode 0), TXRDY asserts when FIFO is empty initiating one DMA transfer and
deasserts when a character is written into the FIFO. (Figure 13.)
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
27
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Figure 13. TXRDY in DMA Mode 0
Transmit Hardware Flow Control
CTS is a flow control input used to prevent remote receiver FIFO data overflow. The CTS input is monitored to
suspend/resume the local transmitter. The automatic CTS flow control can be enabled to suit specific application.
• Enable auto CTS flow control EFR[7]=1.
Transmit Flow Control Interrupt
• Enable auto CTS flow control EFR[7]=1.
• Enable CTS interrupt IER[7]=1.
An interrupt is generated when CTS pin is de-asserted (logic 1). IIR[5] is set to logic 1. The transmitter suspends
transmission as soon as the stop bit is shifted out. Transmission is resumed after the CTS pin is asserted logic 0,
indicating remote receiver is ready to accept data word.
SOFTWARE XON/XOFF FLOW CONTROL
Software flow control uses programmed Xon or Xoff characters to enable the transmit/receive flow control. The
receiver compares one or two sequentially received data words. If the received character(s) match the
programmed values, the transmitter suspends operation as soon as the current transmitting frame is completed.
When a match occurs, the Xoff (if enabled via IER[5]) flag is set and an interrupt is generated. Following a
transmission suspension, the UART monitors the receive data stream for an Xon character. When a match is
found, the transmission resumes and the IIR[4] flag clears.
Upon reset, the Xon/Xoff characters are cleared to logic 0. The user may write any Xon/Xoff value desired for
software flow control. Different conditions can be set to detect Xon/Xoff characters and suspend/resume
transmissions. When double 8-bit Xon/Xoff characters are selected, the UART compares two consecutively
received characters with two software flow control 8-bit values (Xon1, Xon2, Xoff1, and Xoff2) and controls
transmission accordingly. Under the above described flow control mechanisms, flow control characters are not
placed in the user accessible Rx data buffer or FIFO.
During the flow control operation, when Receive FIFO pointer reaches the upper trigger level, the UART
automatically transmits Xoff1 and Xoff 2 messages via the serial TX line output to the remote modem. When
Receive FIFO pointer position matches the lower trigger level, the UART automatically transmits Xon1 and Xon2
characters.
Care should be taken when designing the software flow control section of the driver. In the case where a local
UART is transmitting and the remote UART initiates flow control, an Xoff character is sent by the remote UART.
Upon receipt the local UART ceases to transmit until such time as the remote UART FIFO has been drained
sufficiently and it signals that it can accept further data by sending an Xon character to the local UART.
28
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
There is a corner case in which the receipt of an Xoff by the local UART can occur just after it has sent the last
character of a data transfer and is ready to close the transmission. If in so doing the driver disables the local
UART, it may not receive the corresponding XON and thus can remain in a flow-controlled state. This will persist
even when the UART is re-enabled for a succeeding transmission creating a lock-up situation.
To resolve this lock-up issue, the driver should implement a delay before shutting down the local transmitter at
the end of a data transfer. This delay time should be equal to the transmission time of four characters PLUS the
latency required to drain the RX FIFO on the remote side of the connection. This will allow the remote modem to
send an Xon character and for it to be received before the local transmitter shuts down.
Table 29. Xon/Xoff SW Flow Control on NS16C2552
Rx Trigge
Level
INTR Pin
Activation
Xoff Char
Sent
Xon Char
Sent
1
1
1
0
4
4
4
1
8
8
8
4
14
14
14
8
Table 30. Xon/Xoff SW Flow Control on NS16C2752
Rx Trigger
Level
INTR Pin
Activation
Xoff Char
Sent
Xon Char
Sent
0
8
8
8
16
16
16
8
56
56
56
16
60
60
60
56
SPECIAL CHARACTER DETECT
UART can detect an 8-bit special character if EFR[5]=1. When special character detect mode is enabled, the
UART compares each received character with Xoff2. If a match is found, Xoff2 is loaded into the FIFO along with
the normal received data and IIR[4] is flagged to logic 1.
The Xon and Xoff word length is programmable between 5 and 8 bits depending on LCR[1:0] with the LSB bit
mapped to bit 0. The same word length is used for special character comparison.
SLEEP MODE
To reduce power consumption, NS16C2552/2752 has a per channel sleep mode when channel is not being
used. The sleep mode requires following conditions to be met:
• Sleep mode of the respective channel is enabled (IER[4]=1).
• No pending interrupt for the respective channel (IIR[0]=1).
• Divisor is a non-zero value (DLL or DLM != 0x00).
• Modem inputs are not toggling (MSR[3:0]=0).
• Receiver input is idling at logic 1.
The channel wakes up from sleep mode and returns to normal operation when one of the following conditions is
met:
• Start bit falling edge (logic 1 to 0) is detected on receiver.
• A character is loaded into the THR or Tx FIFO
• A state change on any of the modem interface inputs, DTS, DSR, DCD, and RI.
Following the awakening, the channel can fall back into the sleep mode when all interrupt conditions are serviced
and cleared. If channel is awakened by the modem line inputs, reading the MSR resets the line inputs.
Following the awakening, the interrupts from the respective channel has to be serviced and cleared before reentering into the sleep mode. The NS16C2552/2752 sleep mode can be disabled by IER[4]=0.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
29
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
INTERNAL LOOPBACK MODE
NS16C2552 incorporates internal loopback path for design validation and diagnostic trouble shooting. In the
loopback mode, the transmitted data is looped from the transmit shift register output to the receive shift register
input internally. The system receives its transmitted data. The loopback mode is enabled by MCR[4]=1
(Figure 15).
In the loopback mode, Tx pin is held at logic 1 or mark condition while RTS and DTR are de-asserted and CTS,
DRS, CD, and RI inputs are ignored. Note that Rx input must be held at logic 1 during the loopback test. This is
to prevent false start bit detection upon exiting the loopback mode. RTS and CTS are disabled during the test.
DMA OPERATION
LSR[6:5] provide status of the transmit FIFO and LSR[0] provides the receive FIFO status. User may read the
LSR status bits to initiate and stop data transfers.
More efficient direct memory access (DMA) transfers can be setup using the RXRDY and TXRDY signals. The
DMA transfers are asserted between the CPU cycles and saves CPU processing bandwidth. In mode 0,
(FCR[3]=0), each assertion of RXRDY and TXRDY will cause a single transfer. Note that the user should verify
the interface to make sure the signaling is compatible with the DMA controller.
With built-in transmit and receive FIFO buffers it allows data to be transferred in blocks (mode 1) and it is ideal
for more efficient DMA operation that further saves the CPU processing bandwidth.
To enable the DMA mode 1, FCR[3]=1. The DMA Rx FIFO reading is controlled by RXRDY. When FIFO data is
filled to the trigger level, RXRDY asserts and the DMA burst transfer begins removing characters from Rx FIFO.
The DMA transfer stops when Rx FIFO is empty and RXRDY deasserts.
The DMA transmit operation is controlled by TXRDY and is different between the NS16C2552 and NS16C2752.
On the NS16C2552, the DMA operation is initiated when transmit FIFO becomes empty and TXRDY is asserted.
The DMA controller fills the Tx FIFO and the filling stops when FIFO is full and TXRDY is deasserted.
On the NS16C2752, the DMA transfer starts when the Tx FIFO empty space exceeds the threshold set in
FCR[5:4] and TXRDY asserts. The transfer stops when Tx FIFO is full and TXRDY desserts. The threshold
setting gives CPU more time to arbitrate and relinquish bus control to DMA controller providing higher bus
efficiency.
INFRARED MODE
NS16C2552/2752 also integrates an IrDA version 1.0 compatible infrared encoder and decoder. The infrared
mode is enabled by MCR[6]=1.
In the infrared mode, the SOUT idles at logic 0. During data transmission, the encoder transmits a 3/16 bit wide
pulse for each logic 0. With shortened transmitter-on light pulse, power saving is achieved.
On the receiving end, each light pulse detected translates to a logic 0, active low (Figure 14.)
Figure 14. IrDA Data Transmission
30
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Figure 15. Internal Loopback Functional Diagram
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
31
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Design Notes
DEBUGGING HINTS
Although the UART device is fairly straight forward, there are cases that when device does not behave as
expected. The normal trouble shooting steps should include the following.
1. Check power supply voltage and make sure it is within the operating range.
2. Check device pin connections against the datasheet pin list.
3. Check an unpopulated printed circuit board (PCB) against the schematic diagram for any shorts.
4. Check the device clock input. For oscillator input, the scope probe can be attached to Xin to verify the clock
voltage swing and frequency. For crystal connection, attach the scope probe to Xout to check for the
oscillation frequency.
5. Reset should be active high and normally low.
6. Use internal loopback mode to test the CPU host interface. If loopback mode is not working, check the CPU
interface timing including read and write bus timing.
7. If loopback mode is getting the correct data, check serial data output and input. The transmit and receive
data may be looped back externally to verify the data path integrity.
CLOCK FREQUENCY ACCURACY
In the UART transmission, the transmitter clock and the receive clock are running in two different clock domains
(unlike in some communication interface that the received clock is a copy of the transmitter clock by sharing the
same clock or by performing clock-data-recovery). Not only the local oscillator frequency, but also the clock
divisor may introduce error in between the transmitter and receiver’s baud rate. The question is how much error
can be tolerated and does not cause data error?
The UART receiver has an internal sampling clock that is 16X the data rate. The sampling clock allows data to
be sampled at the 6/16 to 7/16 point of each bit. The following is an example of a 8-bit data packet with a start, a
parity, and one stop bit. (Figure 16)
Figure 16. Nominal Mid-bit Sampling
If a receiver baud rate generator deviates from the nominal baud rate by Δf, where 1/Δf = ΔT, the first sampling
point will deviate from the nominal sample point by 0.5ΔT. Consequently, the second sampling point will deviate
by 1.5ΔT, 3rd will deviate by 2.5ΔT, and the last bit of a packet with L length (in number of bits) will deviate by
(L − 0.5) x ΔT
In this example, L=11, so that the last bit will deviate by
(11 − 0.5) x ΔT = 10.5ΔT(Figure 17)
32
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Figure 17. Deviated Baud Rate Sampling
Giving some margin for sampling error due to metastability and jitter assuming that the bit period deviation can
not be more than 6/16 the bit time (i.e., the worst case), 0.375T. So that
(L − 0.5) x ΔT< 0.375T
for the receiver to correctly recover the transmitted data. Reform the equation
ΔT < 0.375T / (L − 0.5)
Using the same example of 11-bit packet (L = 11), at 9600 baud, f = 9600, the sampling clock rate is f (i.e., one
sample per period) and the bit period is
T=1/f
ΔT < 0.375T / (L − 0.5) = 0.375 / (f x (L − 0.5))
ΔT < 0.375 / (9600 x 10.5) = 3.7 x 10-6 (sec) or 3.7 µs.
The percentage of the deviation from nominal bit period has to be less than
ΔT / T = (0.375 / (f x (L − 0.5)) x f = 0.375 / L − 0.5)
ΔT / T =3.7 x 10-6 x 9600 = 3.6%
From the above example, the error percentage increases with longer packet length (i.e., larger L). The best case
is packet with word length 5, a start bit and a stop bit (L = 7) that is most tolerant to error.
ΔT / T = 0.375 / (L − 0.5) = 0.375 / 6.5 = 5.8%
The worst case is packet with word length 8, a start bit, a parity bit, and two stop bits (L = 12) that is least
tolerant to error.
ΔT / T = 0.375 / L − 0.5) = 0.375 / 11.5 = 3.2%
CRYSTAL REQUIREMENTS
The crystal used should meet the following requirements.
1. AT cut with parallel resonance.
2. Fundamental oscillation mode between 1 to 24 MHz.
3. Frequency tolerance and drift is well within the UART application requirements, and they are not a concern.
4. The load capacitance of the crystal should match the load capacitance of the oscillator circuitry seen by the
crystal. Under the AC conditions, the oscillator load capacitance is a lump sum of parasitic capacitance and
external capacitors. The capacitances connecting to oscillator input and output are in series seen by the
crystal. (Figure 18.) External capacitors, C1 and C2, are not required to be very accurate. The best practice
to follow crystal manufacturer’s recommendation for the load capacitance value.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
33
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Figure 18. Crystal Oscillator Circuit
It should be noted that the parasitic capacitance also include printed circuit board traces. The circuit board traces
connecting to the crystal should be kept as short as possible.
CONFIGURATION EXAMPLES
Set Baud Rate
Set divisor values to DIV_L and DIV_M.
• LCR 0x03.7 = 1
• DLL 0x00.7:0 = DIV_L
• DLM 0x01.7:0 = DIV_M
• LCR 0x03.7 = 0
Configure Prescaler Output
Set prescaler output to XIN divide by 4.
• Save LCR 0x03.7:0 in temp
• LCR 0x03.7:0 = 0xBF
• EFR 0x02.4 = 1
• LCR 0x03.7:0 = 0
• MCR 0x04.7 = 1
• LCR 0x03.7:0 = 0xBF
• EFR 0x02.4 = 0 (optional)
• LCR 0x03.7:0 = temp
Set prescaler output to XIN divide by 1.
• Save LCR 0x03.7:0 in temp
• LCR 0x03.7:0 = 0xBF
• EFR 0x02.4 = 1
• LCR 0x03.7:0 = 0
• MCR 0x04.7 = 0
• LCR 0x03.7:0 = 0xBF
• EFR 0x02.4 = 0 (optional)
• LCR 0x03.7:0 = temp
34
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Set Xon and Xoff flow control
Set Xon1, Xoff1 to VAL1 and VAL2.
• Save LCR 0x03.7:0 in temp
• LCR 0x03.7:0 = 0xBF
• Xon1 0x04.7:0 = VAL1
• Xoff1 0x06.7:0 = VAL2
• LCR 0x03.7:0 = temp
Set Xon2, Xoff2 to VAL1 and VAL2.
• Save LCR 0x03.7:0 in temp
• LCR 0x03.7:0 = 0xBF
• Xon2 0x05.7:0 = VAL1
• Xoff2 0x07.7:0 = VAL2
• LCR 0x03.7:0 = temp
Set Software Flow Control
Set software flow control mode to VAL.
• Save LCR 0x03.7:0 in temp
• LCR 0x03.7:0 = 0xBF
• EFR 0x02.3:0 = VAL
• LCR 0x03.7:0 = temp
Configure Tx/Rx FIFO Threshold
Set Tx (2752) and Rx FIFO thresholds to VAL.
• Save LCR 0x03.7:0 in temp
• LCR 0x03.7:0 = 0xBF
• EFR 0x02.4 = 1
• LCR 0x03.7:0 = 0
• FCR 0x02.7:0 = VAL
• LCR 0x03.7:0 = 0xBF
• EFR 0x02.4 = 0 (optional)
• LCR 0x03.7:0 = temp
Tx and Rx Hardware Flow Control
Configure auto RTS and CTS flow controls, enable RTS and CTS interrupts, and assert RTS.
• Save LCR 0x03.7:0 in temp
• LCR 0x03.7:0 = 0xBF
• EFR 0x02.7:6 = 2b’11
• EFR 0x02.4 = 1
• LCR 0x03.7:0 = 0
• IER 0x01.7:6 = 2b’11
• MCR 0x04.1 = 1
• LCR 0x03.7:0 = temp
Tx and Rx DMA Control
Configure Tx and Rx in FIFO mode DMA transfers using the threshold in FCR[7:4].
• Save LCR 0x03.7:0 in temp
• LCR 0x03.7:0 = 0
• FCR 0x02.0 = 1
• FCR 0x02.3 = 1
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
35
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
•
36
www.ti.com
LCR 0x03.7:0 = temp
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
DIFFERENCES BETWEEN THE PC16552D AND NS16C2552/2752
The following are differences between the versions of UART that helps user to identify the feature differences.
Table 31. Differences among the UART products
Features
Tx and Rx FIFO sizes
Supply voltage
Highest baud rate
PC16552D
NS16C2552
16-byte
16-byte
NS16C2752
64-byte
4.5V to 5.5V
2.97V to 5.5V
2.97V to 5.5V
5.0Mbps
1.5Mbps
5.0Mbps
Highest clock input frequency
24MHz
80MHz
80MHz
Operating temperature
0 - 70°C
-40 to 85°C
-40 to 85°C
Enhanced Register Set
No
Yes
Yes
Sleep mode IER[4]
No
Yes
Yes
Xon, Xoff, and Xon-Any software auto flow control
No
Yes
Yes
CTS and RTS hardware auto flow control
No
Yes
Yes
Interrupt source ID in IIR
3-bit
5-bit
5-bit
1 level
1 level
4 levels
IrDA v1.0 mode MCR[6]
No
Yes
Yes
Clock divisor 1 or 4 select MCR[7]
No
Yes
Yes
Tx FIFO trigger level select FCR[5:4]
NOTES ON TX FIFO OF NS16C2752
Notes on interrupt assertion and deassertion.
1. To avoid frequent interrupt request generation, there is a hysteresis of two characters. When the transmit
FIFO threshold is enabled and the number of empty spaces reaches the threshold, a THR empty interrupt is
generated requesting the CPU to fill the transmit FIFO. The host has to fill at least two characters in the Tx
FIFO before another THR empty interrupt can be generated.
– The DMA request TXRDY works differently. When the number of empty spaces exceeds the threshold,
TXRDY asserts initiating the DMA transfer. The TXRDY deasserts when the transmit FIFO is full.
2. When the number of empty spaces reaches the threshold level, an interrupt is generated. If the host does not
fill the FIFO, the interrupt will remain asserted until the host writes to the THR or reads from IIR.
3. When the number of empty spaces reaches the threshold level, an interrupt is generated. If the host reads
the IIR but does not fill the Tx FIFO, the INTR is deasserted. However, if the host still does not fill the Tx
FIFO, the FIFO becomes empty. The THR empty interrupt is not generated because the host has not written
to the Tx FIFO and the interrupt service is not complete.
4. When the number of empty spaces reaches the threshold level, a THR empty interrupt is generated. If the
host writes at least one character into the Tx FIFO, the interrupt is serviced and the THR empty flag is
deasserted. Subsequently, if the host fails to fill the FIFO before it reaches empty, a THR empty interrupt will
be asserted.
5. Reset Tx FIFO causes a THR empty interrupt.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
37
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS (1) (2)
−40°C to +85°C
Operating Temperature
−65°C to +150°C
Storage Temperature
−0.5V to +6.5V
All Input or Output Voltages with respect to Vss
Power Dissipation
250mW
ESD Rating HBM, 1.5K and 100 pF
8kV
ESD Rating Machine Model
(1)
(2)
400V
Maximum ratings indicate limits beyond which permanent damage may occur. Continuous operation at these limits is not intended and
should be limited to those conditions specified under DC electrical characteristics.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
DC SPECIFICATIONS
TA = -40°C to +85°C, VCC = +2.97V to 5.5V, VSS = 0V, unless otherwise specified.
Typical specifications are at TA=25°C, and represent most likely parametric norms at the time of product characterization.
The typical specifications are not ensured.
Symbol
Parameter
3.3V, 10%
Conditions
5.0V, 10%
Min
Max
Min
Max
Units
VILX
Clock Input Low Voltage
-0.3
0.6
-0.5
0.6
V
VIHX
Clock Input High Voltage
2.4
5.5
3.1
5.5
V
VIL
Input Low Voltage
-0.3
0.8
-0.5
0.8
V
VIH
Input High Voltage
2.0
5.5
2.2
5.5
V
VOL
Output Low Voltage
IOL = 6mA
0.4
V
VOH
Output High Voltage
IOH = -6mA
IOL = 4mA
0.4
IOH = -1mA
IIL
Input Low Leakage
IIH
Input High Leakage
IDD
Current Consumption
V
2.4
V
2.0
V
10
Static clock input
10
µA
10
10
µA
1.6
3.0
mA
CAPACITANCE
TA = 25°C, VDD = VSS = 0V
Symbol
CXIN
CXOUT
CIN
Parameter
Conditions
Min
Typ
Max
Units
Clock Input Capacitance
7
pF
Clock Output Capacitance
7
pF
Input Capacitance
fc = 1 MHz
Unmeasured Pins Returned to VSS
5
pF
COUT
Output Capacitance
6
pF
CI/O
Input/Output Capacitance
10
pF
AC SPECIFICATIONS
TA = -40°C to +85°C, VCC = +2.97V to 5.5V, VSS = 0V, unless otherwise specified.
Typical specifications are at TA=25°C, and represent most likely parametric norms at the time of product characterization.
The typical specifications are not ensured.
Symbol
Parameter
Condition
3.3V Limits
Min
fc
38
Crystal Frequency
tHILO
External Clock Low/High
fOSC
External Clock Frequency
Submit Documentation Feedback
5.0V Limits
Max
Min
24
6
Max
24
MHz
80
MHz
6
80
Units
ns
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
AC SPECIFICATIONS (continued)
TA = -40°C to +85°C, VCC = +2.97V to 5.5V, VSS = 0V, unless otherwise specified.
Typical specifications are at TA=25°C, and represent most likely parametric norms at the time of product characterization.
The typical specifications are not ensured.
Symbol
Parameter
Condition
3.3V Limits
Min
tRST
n
BCLK
Reset Pulse Width
5.0V Limits
Max
70
Baud Rate Divisor
1
Baud Clock
Min
Units
Max
70
16
2 -1
1
ns
16
2 -1
16 x of data rate
1/16 of a bit duration
Host Interface
tAR
Address Setup Time
10
10
ns
tRA
Address Hold Time
1
1
ns
tRD
RD Strobe Width
35
24
ns
35
tDY
Read Cycle Delay
tRDV
Data Access Time
24
tHZ
Data Disable Time
0
tWR
WR Strobe Width
35
24
ns
tDY
Write Cycle Delay
35
24
ns
tDS
Data Setup Time
12
12
ns
tDH
Data Hold Time
4
4
ns
35
18
0
ns
24
ns
18
ns
Modem Control
tMDO
Delay from WR to Output
20
15
ns
tSIM
Delay from Modem input to
Interrupt output
20
15
ns
tRIM
Delay to Reset interrupt from RD
falling edge
23
17
ns
tSINT
Delay from Stop to Interrupt Set
4
4
Bclk
tRINT
Delay from of RD to Reset
Interrupt
45
30
ns
tSTI
Delay from center of Start to INTR
Set
16
10
ns
tWST
Delay from WR to Transmit Start
16
Bclk
tHR
Delay from WR to interrupt clear
34
22
ns
Line Receive and Transmit
(1)
0
16
0
DMA Interface
(1)
tWXI
Delay from WR to TXRDY rising
edge
27
18
ns
tSXA
Delay from Center of Start to
TXRDY falling edge
8
8
Bclk
tSSR
Delay from Stop to RXRDY falling
edge
4
4
Bclk
tRXI
Delay from /RD to RXRDY rising
edge
27
18
ns
The BCLK period decreases with increasing reference clock input. At higher clock input frequency, the number of BCLK increases.
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
39
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
TIMING DIAGRAMS
Figure 19. External Clock Input
Figure 20. Modem Control Timing
Figure 21. Host Interface Read Timing
Figure 22. Host Interface Write Timing
40
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
Figure 23. Receiver Timing
Figure 24. Receiver Timing Non-FIFO Mode
Figure 25. Receiver Timing FIFO Mode
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
41
NS16C2552, NS16C2752
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
www.ti.com
Figure 26. Transmitter Timing
Figure 27. Transmitter Timing Non-FIFO Mode
Figure 28. Transmitter Timing FIFO Mode
42
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
NS16C2552, NS16C2752
www.ti.com
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
REVISION HISTORY
Changes from Revision C (April 2013) to Revision D
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 42
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: NS16C2552 NS16C2752
Submit Documentation Feedback
43
PACKAGE OPTION ADDENDUM
www.ti.com
8-Oct-2015
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
NS16C2552TVA/NOPB
ACTIVE
PLCC
FN
44
25
Green (RoHS
& no Sb/Br)
CU SN
Level-3-245C-168 HR
-40 to 85
NS16C2552TVA
NS16C2552TVS/NOPB
ACTIVE
TQFP
PFB
48
250
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
NS16C2
552TVS
NS16C2552TVSX/NOPB
ACTIVE
TQFP
PFB
48
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
NS16C2
552TVS
NS16C2752TVA/NOPB
ACTIVE
PLCC
FN
44
25
Green (RoHS
& no Sb/Br)
CU SN
Level-3-245C-168 HR
-40 to 85
NS16C2752TVA
>B
NS16C2752TVS/NOPB
ACTIVE
TQFP
PFB
48
250
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
NS16C2
752TVS
NS16C2752TVSX/NOPB
ACTIVE
TQFP
PFB
48
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
NS16C2
752TVS
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
8-Oct-2015
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
24-Apr-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
NS16C2552TVSX/NOPB
TQFP
PFB
48
1000
330.0
16.4
9.3
9.3
2.2
12.0
16.0
Q2
NS16C2752TVSX/NOPB
TQFP
PFB
48
1000
330.0
16.4
9.3
9.3
2.2
12.0
16.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
24-Apr-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
NS16C2552TVSX/NOPB
TQFP
PFB
48
1000
367.0
367.0
38.0
NS16C2752TVSX/NOPB
TQFP
PFB
48
1000
367.0
367.0
38.0
Pack Materials-Page 2
PACKAGE OUTLINE
FN0044A
PLCC - 4.57 mm max height
SCALE 0.800
PLASTIC CHIP CARRIER
B
.180 MAX
[4.57]
.650-.656
[16.51-16.66]
NOTE 3
A
6
1 44
(.008)
[0.2]
40
7
.020 MIN
[0.51]
39
PIN 1 ID
(OPTIONAL)
.650-.656
[16.51-16.66]
NOTE 3
.582-.638
[14.79-16.20]
17
29
18
28
.090-.120 TYP
[2.29-3.04]
44X .026-.032
[0.66-0.81]
C
SEATING PLANE
44X .013-.021
[0.33-0.53]
.007 [0.18]
C A B
40X .050
[1.27]
.004 [0.1] C
.685-.695
[17.40-17.65]
TYP
4215154/A 04/2017
NOTES:
1. All linear dimensions are in inches. Any dimensions in brackets are in millimeters. Any dimensions in parenthesis are for reference only.
Controlling dimensions are in inches. Dimensioning and tolerancing per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. Dimension does not include mold protrusion. Maximum allowable mold protrusion .01 in [0.25 mm] per side.
4. Reference JEDEC registration MS-018.
www.ti.com
EXAMPLE BOARD LAYOUT
FN0044A
PLCC - 4.57 mm max height
PLASTIC CHIP CARRIER
SYMM
44X (.093 )
[2.35]
1
6
44
40
7
39
44X (.030 )
[0.75]
SYMM
(.64 )
[16.2]
40X (.050 )
[1.27]
29
17
(R.002 ) TYP
[0.05]
18
28
(.64 )
[16.2]
LAND PATTERN EXAMPLE
EXPOSED METAL SHOWN
SCALE:4X
EXPOSED METAL
.002 MAX
[0.05]
ALL AROUND
METAL
SOLDER MASK
OPENING
.002 MIN
[0.05]
ALL AROUND
EXPOSED METAL
METAL UNDER
SOLDER MASK
SOLDER MASK
OPENING
NON SOLDER MASK
DEFINED
(PREFERRED)
SOLDER MASK
DEFINED
SOLDER MASK DETAILS
4215154/A 04/2017
NOTES: (continued)
5. Publication IPC-7351 may have alternate designs.
6. Solder mask tolerances between and around signal pads can vary based on board fabrication site.
www.ti.com
EXAMPLE STENCIL DESIGN
FN0044A
PLCC - 4.57 mm max height
PLASTIC CHIP CARRIER
SYMM
44X (.093 )
[2.35]
6
1
44
40
7
39
44X (.030 )
[0.75]
SYMM
(.64 )
[16.2]
40X (.050 )
[1.27]
29
17
(R.002 ) TYP
[0.05]
18
28
(.64 )
[16.2]
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
SCALE:4X
4215154/A 04/2017
NOTES: (continued)
7. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
8. Board assembly site may have different recommendations for stencil design.
www.ti.com
MECHANICAL DATA
MTQF019A – JANUARY 1995 – REVISED JANUARY 1998
PFB (S-PQFP-G48)
PLASTIC QUAD FLATPACK
0,27
0,17
0,50
36
0,08 M
25
37
24
48
13
0,13 NOM
1
12
5,50 TYP
7,20
SQ
6,80
9,20
SQ
8,80
Gage Plane
0,25
0,05 MIN
0°– 7°
1,05
0,95
Seating Plane
0,75
0,45
0,08
1,20 MAX
4073176 / B 10/96
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-026
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
IMPORTANT NOTICE
Texas Instruments Incorporated (TI) reserves the right to make corrections, enhancements, improvements and other changes to its
semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers
should obtain the latest relevant information before placing orders and should verify that such information is current and complete.
TI’s published terms of sale for semiconductor products (http://www.ti.com/sc/docs/stdterms.htm) apply to the sale of packaged integrated
circuit products that TI has qualified and released to market. Additional terms may apply to the use or sale of other types of TI products and
services.
Reproduction of significant portions of TI information in TI data sheets is permissible only if reproduction is without alteration and is
accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such reproduced
documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements
different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the
associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Buyers and others who are developing systems that incorporate TI products (collectively, “Designers”) understand and agree that Designers
remain responsible for using their independent analysis, evaluation and judgment in designing their applications and that Designers have
full and exclusive responsibility to assure the safety of Designers' applications and compliance of their applications (and of all TI products
used in or for Designers’ applications) with all applicable regulations, laws and other applicable requirements. Designer represents that, with
respect to their applications, Designer has all the necessary expertise to create and implement safeguards that (1) anticipate dangerous
consequences of failures, (2) monitor failures and their consequences, and (3) lessen the likelihood of failures that might cause harm and
take appropriate actions. Designer agrees that prior to using or distributing any applications that include TI products, Designer will
thoroughly test such applications and the functionality of such TI products as used in such applications.
TI’s provision of technical, application or other design advice, quality characterization, reliability data or other services or information,
including, but not limited to, reference designs and materials relating to evaluation modules, (collectively, “TI Resources”) are intended to
assist designers who are developing applications that incorporate TI products; by downloading, accessing or using TI Resources in any
way, Designer (individually or, if Designer is acting on behalf of a company, Designer’s company) agrees to use any particular TI Resource
solely for this purpose and subject to the terms of this Notice.
TI’s provision of TI Resources does not expand or otherwise alter TI’s applicable published warranties or warranty disclaimers for TI
products, and no additional obligations or liabilities arise from TI providing such TI Resources. TI reserves the right to make corrections,
enhancements, improvements and other changes to its TI Resources. TI has not conducted any testing other than that specifically
described in the published documentation for a particular TI Resource.
Designer is authorized to use, copy and modify any individual TI Resource only in connection with the development of applications that
include the TI product(s) identified in such TI Resource. NO OTHER LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE
TO ANY OTHER TI INTELLECTUAL PROPERTY RIGHT, AND NO LICENSE TO ANY TECHNOLOGY OR INTELLECTUAL PROPERTY
RIGHT OF TI OR ANY THIRD PARTY IS GRANTED HEREIN, including but not limited to any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
regarding or referencing third-party products or services does not constitute a license to use such products or services, or a warranty or
endorsement thereof. Use of TI Resources may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
TI RESOURCES ARE PROVIDED “AS IS” AND WITH ALL FAULTS. TI DISCLAIMS ALL OTHER WARRANTIES OR
REPRESENTATIONS, EXPRESS OR IMPLIED, REGARDING RESOURCES OR USE THEREOF, INCLUDING BUT NOT LIMITED TO
ACCURACY OR COMPLETENESS, TITLE, ANY EPIDEMIC FAILURE WARRANTY AND ANY IMPLIED WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL
PROPERTY RIGHTS. TI SHALL NOT BE LIABLE FOR AND SHALL NOT DEFEND OR INDEMNIFY DESIGNER AGAINST ANY CLAIM,
INCLUDING BUT NOT LIMITED TO ANY INFRINGEMENT CLAIM THAT RELATES TO OR IS BASED ON ANY COMBINATION OF
PRODUCTS EVEN IF DESCRIBED IN TI RESOURCES OR OTHERWISE. IN NO EVENT SHALL TI BE LIABLE FOR ANY ACTUAL,
DIRECT, SPECIAL, COLLATERAL, INDIRECT, PUNITIVE, INCIDENTAL, CONSEQUENTIAL OR EXEMPLARY DAMAGES IN
CONNECTION WITH OR ARISING OUT OF TI RESOURCES OR USE THEREOF, AND REGARDLESS OF WHETHER TI HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
Unless TI has explicitly designated an individual product as meeting the requirements of a particular industry standard (e.g., ISO/TS 16949
and ISO 26262), TI is not responsible for any failure to meet such industry standard requirements.
Where TI specifically promotes products as facilitating functional safety or as compliant with industry functional safety standards, such
products are intended to help enable customers to design and create their own applications that meet applicable functional safety standards
and requirements. Using products in an application does not by itself establish any safety features in the application. Designers must
ensure compliance with safety-related requirements and standards applicable to their applications. Designer may not use any TI products in
life-critical medical equipment unless authorized officers of the parties have executed a special contract specifically governing such use.
Life-critical medical equipment is medical equipment where failure of such equipment would cause serious bodily injury or death (e.g., life
support, pacemakers, defibrillators, heart pumps, neurostimulators, and implantables). Such equipment includes, without limitation, all
medical devices identified by the U.S. Food and Drug Administration as Class III devices and equivalent classifications outside the U.S.
TI may expressly designate certain products as completing a particular qualification (e.g., Q100, Military Grade, or Enhanced Product).
Designers agree that it has the necessary expertise to select the product with the appropriate qualification designation for their applications
and that proper product selection is at Designers’ own risk. Designers are solely responsible for compliance with all legal and regulatory
requirements in connection with such selection.
Designer will fully indemnify TI and its representatives against any damages, costs, losses, and/or liabilities arising out of Designer’s noncompliance with the terms and provisions of this Notice.
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2017, Texas Instruments Incorporated
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising