935279069128 [NXP]
4 CHANNEL(S), 5Mbps, SERIAL COMM CONTROLLER, PQFP64, 7 X 7 MM, 1.40 MM HEIGHT, PLASTIC, MS-026, SOT414-1, LQFP-64;
| 型号： | 935279069128 |
| 厂家： | 
NXP |
| 描述： | 4 CHANNEL(S), 5Mbps, SERIAL COMM CONTROLLER, PQFP64, 7 X 7 MM, 1.40 MM HEIGHT, PLASTIC, MS-026, SOT414-1, LQFP-64 通信 时钟 数据传输 外围集成电路 |
| 文件： | 总51页 (文件大小：253K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SC16C754B
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte
FIFOs
Rev. 04 — 6 October 2008
Product data sheet
1. General description
The SC16C754B is a quad Universal Asynchronous Receiver/Transmitter (UART) with
64-byte FIFOs, automatic hardware/software flow control, and data rates up to 5 Mbit/s
(3.3 V and 5 V). The SC16C754B offers enhanced features. It has a Transmission Control
Register (TCR) that stores receiver FIFO threshold levels to start/stop transmission during
hardware and software flow control. With the FIFO Ready (FIFO Rdy) register, the
software gets the status of TXRDY/RXRDY for all four ports in one access. On-chip status
registers provide the user with error indications, operational status, and modem interface
control. System interrupts may be tailored to meet user requirements. An internal
loopback capability allows on-board diagnostics.
The UART transmits data, sent to it over the peripheral 8-bit bus, on the TX signal and
receives characters on the RX signal. Characters can be programmed to be 5, 6, 7, or
8 bits. The UART has a 64-byte receive FIFO and transmit FIFO and can be programmed
to interrupt at different trigger levels. The UART generates its own desired baud rate
based upon a programmable divisor and its input clock. It can transmit even, odd, or no
parity and 1, 1.5, or 2 stop bits. The receiver can detect break, idle, or framing errors,
FIFO overflow, and parity errors. The transmitter can detect FIFO underflow. The UART
also contains a software interface for modem control operations, and has software flow
control and hardware flow control capabilities.
The SC16C754B is available in plastic LQFP64, LQFP80 and PLCC68 packages.
2. Features
I 4 channel UART
I 5 V, 3.3 V and 2.5 V operation
I Pin compatible with SC16C654IA68, TL16C754, and SC16C554IA68 with additional
enhancements, and software compatible with TL16C754
I Up to 5 Mbit/s data rate (at 3.3 V and 5 V; at 2.5 V maximum data rate is 3 Mbit/s)
I 5 V tolerant on input only pins1
I 64-byte transmit FIFO
I 64-byte receive FIFO with error flags
I Industrial temperature range (−40 °C to +85 °C)
I Programmable and selectable transmit and receive FIFO trigger levels for DMA and
interrupt generation
1. For data bus pins D7 to D0, see Table 24 “Limiting values”.
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
I Software (Xon/Xoff)/hardware (RTS/CTS) flow control
N Programmable Xon/Xoff characters
N Programmable auto-RTS and auto-CTS
I Optional data flow resume by Xon any character
I DMA signalling capability for both received and transmitted data
I Supports 5 V, 3.3 V and 2.5 V operation
I Software selectable baud rate generator
I Prescaler provides additional divide-by-4 function
I Fast data bus access time
I Programmable Sleep mode
I Programmable serial interface characteristics
N 5, 6, 7, or 8-bit characters
N Even, odd, or no-parity bit generation and detection
N 1, 1.5, or 2 stop bit generation
I False start bit detection
I Complete status reporting capabilities in both normal and Sleep mode
I Line break generation and detection
I Internal test and loopback capabilities
I Fully prioritized interrupt system controls
I Modem control functions (CTS, RTS, DSR, DTR, RI, and CD)
I Sleep mode
3. Ordering information
Table 1.
Ordering information
Type number
Package
Name
Description
Version
SC16C754BIBM
SC16C754BIB80
SC16C754BIA68
LQFP64
LQFP80
PLCC68
plastic low profile quad flat package; 64 leads; body 7 × 7 × 1.4 mm
plastic low profile quad flat package; 80 leads; body 12 × 12 × 1.4 mm
plastic leaded chip carrier; 68 leads
SOT414-1
SOT315-1
SOT188-2
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
2 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
4. Block diagram
SC16C754B
TRANSMIT
FIFO
TRANSMIT
SHIFT
TXA to TXD
REGISTERS
REGISTER
D0 to D7
IOR
DATA BUS
AND
IOW
RESET
CONTROL
LOGIC
FLOW
CONTROL
LOGIC
RECEIVE
FIFO
RECEIVE
SHIFT
RXA to RXD
REGISTERS
REGISTER
FLOW
CONTROL
LOGIC
REGISTER
SELECT
LOGIC
A0 to A2
CSA to CSD
DTRA to DTRD
RTSA to RTSD
MODEM
CONTROL
LOGIC
INTA to INTD
TXRDY
CTSA to CTSD
RIA to RID
CDA to CDD
DSRA to DSRD
RXRDY
INTERRUPT
CONTROL
LOGIC
CLOCK AND
BAUD RATE
GENERATOR
INTSEL
002aaa866
XTAL1 XTAL2
CLKSEL
Fig 1. Block diagram of SC16C754B
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
3 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
5. Pinning information
5.1 Pinning
1
2
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
DSRA
CTSA
DTRA
DSRD
CTSD
DTRD
GND
RTSD
INTD
CSD
3
4
V
CC
5
RTSA
INTA
CSA
6
7
8
TXA
TXD
SC16C754BIBM
9
IOW
IOR
10
11
12
13
14
15
16
TXB
TXC
CSB
CSC
INTB
RTSB
GND
DTRB
CTSB
INTC
RTSC
V
CC
DTRC
CTSC
002aab564
Fig 2. Pin configuration for LQFP64
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
4 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
1
2
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
n.c.
n.c.
n.c.
DSRD
CTSD
DTRD
GND
RTSD
INTD
CSD
TXD
3
DSRA
CTSA
DTRA
4
5
6
V
CC
7
RTSA
INTA
CSA
8
9
10
11
12
13
14
15
16
17
18
19
20
TXA
IOR
SC16C754BIB80
IOW
TXC
TXB
CSC
INTC
RTSC
CSB
INTB
RTSB
GND
DTRB
CTSB
DSRB
n.c.
V
CC
DTRC
CTSC
DSRC
n.c.
n.c.
002aaa867
Fig 3. Pin configuration for LQFP80
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
5 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
DSRA
CTSA
DTRA
DSRD
CTSD
DTRD
GND
RTSD
INTD
CSD
V
CC
RTSA
INTA
CSA
TXA
TXD
IOW
SC16C754BIA68
IOR
TXB
TXC
CSB
CSC
INTB
RTSB
GND
DTRB
CTSB
DSRB
INTC
RTSC
V
CC
DTRC
CTSC
DSRC
002aaa868
Fig 4. Pin configuration for PLCC68
5.2 Pin description
Table 2.
Pin description
Symbol Pin
Type Description
LQFP64 LQFP80 PLCC68
A0
24
23
22
64
18
31
49
-
30
29
28
79
23
39
63
26
34
33
32
9
I
I
I
I
Address 0 select bit. Internal registers address selection.
Address 1 select bit. Internal registers address selection.
Address 2 select bit. Internal registers address selection.
A1
A2
CDA
CDB
CDC
CDD
CLKSEL
Carrier Detect (active LOW). These inputs are associated with
individual UART channels A through D. A logic LOW on these pins
indicates that a carrier has been detected by the modem for that channel.
The state of these inputs is reflected in the Modem Status Register
(MSR).
27
43
61
30
I
Clock Select. CLKSEL selects the divide-by-1 or divide-by-4 prescalable
clock. During the reset, a logic 1 (VCC) on CLKSEL selects the
divide-by-1 prescaler. A logic 0 (GND) on CLKSEL selects the divide-by-4
prescaler. The value of CLKSEL is latched into MCR[7] at the trailing
edge of RESET. A logic 1 (VCC) on CLKSEL will latch a logic 0 into
MCR[7]. A logic 0 (GND) on CLKSEL will latch a logic 1 into MCR[7].
MCR[7] can be changed after RESET to alter the prescaler value. This
pin is associated with LQFP80 and PLCC68 packages only. This pin is
connected to VCC internally on LQFP64 package.
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
6 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Table 2.
Pin description …continued
Symbol Pin
Type Description
LQFP64 LQFP80 PLCC68
CSA
7
9
16
20
50
54
11
25
45
59
I
Chip Select (active LOW). These pins enable data transfers between
the user CPU and the SC16C754B for the channel(s) addressed.
Individual UART sections (A, B, C, D) are addressed by providing a logic
LOW on the respective CSA through CSD pins.
CSB
11
38
42
2
13
49
53
4
CSC
CSD
CTSA
CTSB
CTSC
CTSD
I
Clear to Send (active LOW). These inputs are associated with individual
UART channels A through D. A logic 0 (LOW) on the CTS pins indicates
the modem or data set is ready to accept transmit data from the
SC16C754B. Status can be tested by reading MSR[4]. These pins only
affect the transmit and receive operations when auto-CTS function is
enabled via the Enhanced Feature Register EFR[7] for hardware flow
control operation.
16
33
47
18
44
58
D0 to D7 53, 54, 68, 69, 66, 67, I/O
55, 56, 70, 71, 68, 1, 2,
Data bus (bidirectional). These pins are the 8-bit, 3-state data bus for
transferring information to or from the controlling CPU. D0 is the least
significant bit and the first data bit in a transmit or receive serial data
stream.
57, 58, 72, 73, 3, 4, 5
59, 60
74, 75
DSRA
DSRB
DSRC
DSRD
DTRA
DTRB
DTRC
DTRD
1
3
10
26
44
60
12
24
46
58
I
Data Set Ready (active LOW). These inputs are associated with
individual UART channels A through D. A logic 0 (LOW) on these pins
indicates the modem or data set is powered-on and is ready for data
exchange with the UART. The state of these inputs is reflected in the
Modem Status Register (MSR).
17
32
48
3
19
43
59
5
O
Data Terminal Ready (active LOW). These outputs are associated with
individual UART channels A through D. A logic 0 (LOW) on these pins
indicates that the SC16C754B is powered-on and ready. These pins can
be controlled via the Modem Control Register (MCR). Writing a logic 1 to
MCR[0] will set the DTR output to logic 0 (LOW), enabling the modem.
The output of these pins will be a logic 1 after writing a logic 0 to MCR[0],
or after a reset.
15
34
46
17
45
57
GND
14, 28, 16, 36, 6, 23,
I
Signal and power ground.
45, 61
56, 76
40, 57
INTA
INTB
INTC
INTD
6
8
15
O
Interrupt A, B, C, and D (active HIGH). These pins provide individual
channel interrupts INTA through INTD. INTA through INTD are enabled
when MCR[3] is set to a logic 1, interrupt sources are enabled in the
Interrupt Enable Register (IER). Interrupt conditions include: receiver
errors, available receiver buffer data, available transmit buffer space, or
when a modem status flag is detected. INTA to INTD are in the
high-impedance state after reset.
12
14
21
37
48
49
43
54
55
INTSEL
-
67
65
I
Interrupt Select (active HIGH with internal pull-down). INTSEL can be
used in conjunction with MCR[3] to enable or disable the 3-state
interrupts INTA to INTD or override MCR[3] and force continuous
interrupts. Interrupt outputs are enabled continuously by making this pin a
logic 1. Driving this pin LOW allows MCR[3] to control the 3-state
interrupt output. In this mode, MCR[3] is set to a logic 1 to enable the
3-state outputs. This pin is associated with LQFP80 and PLCC68
packages only. This pin is connected to GND internally on the LQFP64
package.
IOR
40
51
52
I
Input/Output Read strobe (active LOW). A HIGH-to-LOW transition on
IOR will load the contents of an internal register defined by address bits
A[2:0] onto the SC16C754B data bus (D[7:0]) for access by external
CPU.
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
7 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Table 2.
Pin description …continued
Symbol Pin
Type Description
LQFP64 LQFP80 PLCC68
IOW
n.c.
9
-
11
18
I
Input/Output Write strobe (active LOW). A LOW-to-HIGH transition on
IOW will transfer the contents of the data bus (D[7:0]) from the external
CPU to an internal register that is defined by address bits A[2:0] and CSA
and CSD.
1, 2, 20, 31
21, 22,
-
not connected
27, 40,
41, 42,
60, 61,
62, 80
RESET
27
33
37
I
I
Reset. This pin will reset the internal registers and all the outputs. The
UART transmitter output and the receiver input will be disabled during
reset time. RESET is an active HIGH input.
RIA
RIB
RIC
RID
63
19
30
50
78
24
38
64
8
Ring Indicator (active LOW). These inputs are associated with
individual UART channels, A through D. A logic 0 on these pins indicates
the modem has received a ringing signal from the telephone line. A
LOW-to-HIGH transition on these input pins generates a modem status
interrupt, if enabled. The state of these inputs is reflected in the Modem
Status Register (MSR).
28
42
62
RTSA
RTSB
RTSC
RTSD
5
7
14
22
48
56
O
Request to Send (active LOW). These outputs are associated with
individual UART channels, A through D. A logic 0 on the RTS pin
indicates the transmitter has data ready and waiting to send. Writing a
logic 1 in the Modem Control Register MCR[1] will set this pin to a logic 0,
indicating data is available. After a reset these pins are set to a logic 1.
These pins only affect the transmit and receive operations when
auto-RTS function is enabled via the Enhanced Feature Register
(EFR[6]) for hardware flow control operation.
13
36
44
15
47
55
RXA
62
20
29
51
-
77
25
37
65
34
7
I
Receive data input. These inputs are associated with individual serial
channel data to the SC16C754B. During the local loopback mode, these
RX input pins are disabled and TX data is connected to the UART RX
input internally.
RXB
29
41
63
38
RXC
RXD
RXRDY
O
O
O
Receive Ready (active LOW). RXRDY contains the wire-ORed status of
all four receive channel FIFOs, RXRDY A to RXRDY D. It goes LOW
when the trigger level has been reached or a time-out interrupt occurs. It
goes HIGH when all RX FIFOs are empty and there is an error in RX
FIFO. This pin is associated with LQFP80 and PLCC68 packages only.
TXA
8
10
12
50
52
35
17
19
51
53
39
Transmit data. These outputs are associated with individual serial
transmit channel data from the SC16C754B. During the local loopback
mode, the TX output pin is disabled and TX data is internally connected
to the UART RX input.
TXB
10
39
41
-
TXC
TXD
TXRDY
Transmit Ready (active LOW). TXRDY contains the wire-ORed status of
all four transmit channel FIFOs, TXRDY A to TXRDY D. It goes LOW
when there are a trigger level number of spaces available. It goes HIGH
when all four TX buffers are full. This pin is associated with LQFP80 and
PLCC68 packages only.
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
8 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Table 2.
Pin description …continued
Symbol Pin
Type Description
LQFP64 LQFP80 PLCC68
VCC
4, 21,
35, 52
6, 46, 66 13, 47,
64
I
I
Power supply input.
XTAL1
25
31
35
Crystal or external clock input. Functions as a crystal input or as an
external clock input. A crystal can be connected between XTAL1 and
XTAL2 to form an internal oscillator circuit (see Figure 14). Alternatively,
an external clock can be connected to this pin to provide custom data
rates.
XTAL2
26
32
36
O
Output of the crystal oscillator or buffered clock (see also XTAL1).
XTAL2 is used as a crystal oscillator output or a buffered clock output.
6. Functional description
The SC16C754B UART is pin-compatible with the SC16C554 and SC16C654 UARTs. It
provides more enhanced features. All additional features are provided through a special
enhanced feature register.
The UART will perform serial-to-parallel conversion on data characters received from
peripheral devices or modems, and parallel-to-parallel conversion on data characters
transmitted by the processor. The complete status of each channel of the SC16C754B
UART can be read at any time during functional operation by the processor.
The SC16C754B can be placed in an alternate mode (FIFO mode) relieving the processor
of excessive software overhead by buffering received/transmitted characters. Both the
receiver and transmitter FIFOs can store up to 64 bytes (including three additional bits of
error status per byte for the receiver FIFO) and have selectable or programmable trigger
levels. Primary outputs RXRDY and TXRDY allow signalling of DMA transfers.
The SC16C754B has selectable hardware flow control and software flow control.
Hardware flow control significantly reduces software overhead and increases system
efficiency by automatically controlling serial data flow using the RTS output and CTS input
signals. Software flow control automatically controls data flow by using programmable
Xon/Xoff characters.
The UART includes a programmable baud rate generator that can divide the timing
reference clock input by a divisor between 1 and (216 − 1).
6.1 Trigger levels
The SC16C754B provides independent selectable and programmable trigger levels for
both receiver and transmitter DMA and interrupt generation. After reset, both transmitter
and receiver FIFOs are disabled and so, in effect, the trigger level is the default value of
one byte. The selectable trigger levels are available via the FIFO Control Register (FCR).
The programmable trigger levels are available via the Trigger Level Register (TLR).
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
9 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
6.2 Hardware flow control
Hardware flow control is comprised of auto-CTS and auto-RTS. Auto-CTS and auto-RTS
can be enabled/disabled independently by programming EFR[7:6].
With auto-CTS, CTS must be active before the UART can transmit data.
Auto-RTS only activates the RTS output when there is enough room in the FIFO to receive
data and de-activates the RTS output when the RX FIFO is sufficiently full. The halt and
resume trigger levels in the TCR determine the levels at which RTS is
activated/deactivated.
If both auto-CTS and auto-RTS are enabled, when RTS is connected to CTS, data
transmission does not occur unless the receiver FIFO has empty space. Thus, overrun
errors are eliminated during hardware flow control. If not enabled, overrun errors occur if
the transmit data rate exceeds the receive FIFO servicing latency.
UART 1
UART 2
SERIAL TO
PARALLEL
RX
TX
PARALLEL
TO SERIAL
RX
TX
FIFO
FIFO
RTS
CTS
FLOW
FLOW
CONTROL
CONTROL
D7 to D0
D7 to D0
PARALLEL
TO SERIAL
SERIAL TO
PARALLEL
TX
RX
TX
RX
FIFO
FIFO
CTS
RTS
FLOW
FLOW
CONTROL
CONTROL
002aaa228
Fig 5. Autoflow control (auto-RTS and auto-CTS) example
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
10 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
6.2.1 Auto-RTS
Auto-RTS data flow control originates in the receiver block (see Figure 1 “Block diagram of
SC16C754B”). Figure 6 shows RTS functional timing. The receiver FIFO trigger levels
used in auto-RTS are stored in the TCR. RTS is active if the RX FIFO level is below the
halt trigger level in TCR[3:0]. When the receiver FIFO halt trigger level is reached, RTS is
de-asserted. The sending device (for example, another UART) may send an additional
byte after the trigger level is reached (assuming the sending UART has another byte to
send) because it may not recognize the de-assertion of RTS until it has begun sending the
additional byte. RTS is automatically reasserted once the receiver FIFO reaches the
resume trigger level programmed via TCR[7:4]. This re-assertion allows the sending
device to resume transmission.
RX
Start
byte N
Stop
Start
byte N + 1
Stop
Start
RTS
1
2
N
N+1
IOR
002aaa226
N = receiver FIFO trigger level.
The two blocks in dashed lines cover the case where an additional byte is sent, as described in Section 6.2.1.
Fig 6. RTS functional timing
6.2.2 Auto-CTS
The transmitter circuitry checks CTS before sending the next data byte. When CTS is
active, the transmitter sends the next byte. To stop the transmitter from sending the
following byte, CTS must be de-asserted before the middle of the last stop bit that is
currently being sent. The auto-CTS function reduces interrupts to the host system. When
flow control is enabled, CTS level changes do not trigger host interrupts because the
device automatically controls its own transmitter. Without auto-CTS, the transmitter sends
any data present in the transmit FIFO and a receiver overrun error may result.
Start
byte 0 to 7
Stop
TX
Start
byte 0 to 7
Stop
CTS
002aaa227
When CTS is LOW, the transmitter keeps sending serial data out.
When CTS goes HIGH before the middle of the last stop bit of the current byte, the transmitter
finishes sending the current byte, but it does not send the next byte.
When CTS goes from HIGH to LOW, the transmitter begins sending data again.
Fig 7. CTS functional timing
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
11 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
6.3 Software flow control
Software flow control is enabled through the enhanced feature register and the modem
control register. Different combinations of software flow control can be enabled by setting
different combinations of EFR[3:0]. Table 3 shows software flow control options.
Table 3.
Software flow control options (EFR[3:0])
EFR[3]
EFR[2]
EFR[1]
EFR[0]
TX, RX software flow controls
no transmit flow control
0
1
0
1
X
X
X
1
0
0
1
1
X
X
X
0
X
X
X
X
0
1
0
1
X
X
X
X
0
0
1
1
transmit Xon1, Xoff1
transmit Xon2, Xoff2
transmit Xon1, Xon2, Xoff1, Xoff2
no receive flow control
receiver compares Xon1, Xoff1
receiver compares Xon2, Xoff2
transmit Xon1, Xoff1
receiver compares Xon1 or Xon2, Xoff1 or Xoff2
transmit Xon2, Xoff2
0
1
0
1
1
0
1
1
1
1
1
1
receiver compares Xon1 or Xon2, Xoff1 or Xoff2
transmit Xon1, Xon2, Xoff1, Xoff2
receiver compares Xon1 and Xon2, Xoff1 and Xoff2
no transmit flow control
receiver compares Xon1 and Xon2, Xoff1 and Xoff2
Remark: When using software flow control, the Xon/Xoff characters cannot be used for
data characters.
There are two other enhanced features relating to software flow control:
• ‘Xon Any’ function (MCR[5]): Operation will resume after receiving any character
after recognizing the Xoff character. It is possible that an Xon1 character is
recognized as an ‘Xon Any’ character, which could cause an Xon2 character to be
written to the RX FIFO.
• Special character (EFR[5]): Incoming data is compared to Xoff2. Detection of the
special character sets the Xoff interrupt (IIR[4]) but does not halt transmission. The
Xoff interrupt is cleared by a read of the IIR. The special character is transferred to the
RX FIFO.
6.3.1 RX
When software flow control operation is enabled, the SC16C754B will compare incoming
data with Xoff1/Xoff2 programmed characters (in certain cases, Xoff1 and Xoff2 must be
received sequentially). When the correct Xoff character is received, transmission is halted
after completing transmission of the current character. Xoff detection also sets IIR[4] (if
enabled via IER[5]) and causes INT to go HIGH.
To resume transmission, an Xon1/Xon2 character must be received (in certain cases
Xon1 and Xon2 must be received sequentially). When the correct Xon characters are
received, IIR[4] is cleared, and the Xoff interrupt disappears.
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6.3.2 TX
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Xoff1/Xoff2 character is transmitted when the RX FIFO has passed the halt trigger level
programmed in TCR[3:0].
Xon1/Xon2 character is transmitted when the RX FIFO reaches the resume trigger level
programmed in TCR[7:4].
The transmission of Xoff/Xon(s) follows the exact same protocol as transmission of an
ordinary byte from the FIFO. This means that even if the word length is set to be 5, 6, or 7
characters, then the 5, 6, or 7 least significant bits of Xoff1/Xoff2 and Xon1/Xon2 will be
transmitted. (Note that the transmission of 5, 6, or 7 bits of a character is seldom done, but
this functionality is included to maintain compatibility with earlier designs.)
It is assumed that software flow control and hardware flow control will never be enabled
simultaneously. Figure 8 shows an example of software flow control.
6.3.3 Software flow control example
UART1
UART2
TRANSMIT FIFO
RECEIVE FIFO
data
PARALLEL-TO-SERIAL
SERIAL-TO-PARALLEL
Xon1 WORD
SERIAL-TO-PARALLEL
PARALLEL-TO-SERIAL
Xon1 WORD
Xoff–Xon–Xoff
Xon2 WORD
Xon2 WORD
Xoff1 WORD
Xoff1 WORD
compare
programmed
Xon-Xoff
Xoff2 WORD
Xoff2 WORD
characters
002aaa229
Fig 8. Software flow control example
6.3.3.1 Assumptions
UART1 is transmitting a large text file to UART2. Both UARTs are using software flow
control with single character Xoff (0Fh) and Xon (0Dh) tokens. Both have Xoff threshold
(TCR[3:0] = F) set to 60, and Xon threshold (TCR[7:4] = 8) set to 32. Both have the
interrupt receive threshold (TLR[7:4] = D) set to 52.
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NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
UART1 begins transmission and sends 52 characters, at which point UART2 will generate
an interrupt to its processor to service the RX FIFO, but assumes the interrupt latency is
fairly long. UART1 will continue sending characters until a total of 60 characters have
been sent. At this time, UART2 will transmit a 0Fh to UART1, informing UART1 to halt
transmission. UART1 will likely send the 61st character while UART2 is sending the Xoff
character. Now UART2 is serviced and the processor reads enough data out of the RX
FIFO that the level drops to 32. UART2 will now send a 0Dh to UART1, informing UART1
to resume transmission.
6.4 Reset
Table 4 summarizes the state of register after reset.
Table 4.
Register reset functions
Register
Reset control
RESET
RESET
RESET
RESET
RESET
RESET
RESET
RESET
RESET
RESET
RESET
RESET
Reset state
Interrupt enable register
Interrupt identification register
FIFO control register
all bits cleared
bit 0 is set; all other bits cleared
all bits cleared
Line control register
reset to 0001 1101 (1Dh)
all bits cleared
Modem control register
Line status register
bit 5 and bit 6 set; all other bits cleared
bits 3:0 cleared; bits 7:4 input signals
all bits cleared
Modem status register
Enhanced feature register
Receiver holding register
Transmitter holding register
Transmission control register
Trigger level register
pointer logic cleared
pointer logic cleared
all bits cleared
all bits cleared
Remark: Registers DLL, DLM, SPR, Xon1, Xon2, Xoff1, Xoff2 are not reset by the
top-level reset signal RESET, that is, they hold their initialization values during reset.
Table 5 summarizes the state of registers after reset.
Table 5.
Signal
TX
Signal RESET functions
Reset control
Reset state
HIGH
RESET
RESET
RESET
RESET
RESET
RTS
HIGH
DTR
HIGH
RXRDY
TXRDY
HIGH
LOW
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
6.5 Interrupts
The SC16C754B has interrupt generation and prioritization (six prioritized levels of
interrupts) capability. The Interrupt Enable Register (IER) enables each of the six types of
interrupts and the INT signal in response to an interrupt generation. The IER can also
disable the interrupt system by clearing bits 7:5 and 3:0. When an interrupt is generated,
the IIR indicates that an interrupt is pending and provides the type of interrupt through
IIR[5:0]. Table 6 summarizes the interrupt control functions.
Table 6.
IIR[5:0]
Interrupt control functions
Priority
level
Interrupt type
Interrupt source
Interrupt reset method
00 0001
00 0110
None
1
none
none
none
receiver line status
OE, FE, PE, or BI errors occur in
characters in the RX FIFO
FE, PE, BI: all erroneous
characters are read from the
RX FIFO.
OE: read LSR
read RHR
00 1100
00 0100
2
2
RX time-out
stale data in RX FIFO
DRDY (data ready)
(FIFO disable)
RHR interrupt
read RHR
RX FIFO above trigger level
(FIFO enable)
00 0010
3
THR interrupt
TFE (THR empty)
(FIFO disable)
read IIR or a write to the THR
TX FIFO passes above trigger level
(FIFO enable)
00 0000
01 0000
4
5
modem status
Xoff interrupt
MSR[3:0] = 0
read MSR
receive Xoff character(s)/special
character
receive Xon character(s)/Read of
IIR
10 0000
6
CTS, RTS
RTS pin or CTS pin change state from read IIR
active (LOW) to inactive (HIGH)
It is important to note that for the framing error, parity error, and break conditions, LSR[7]
generates the interrupt. LSR[7] is set when there is an error anywhere in the RX FIFO,
and is cleared only when there are no more errors remaining in the FIFO. LSR[4:2] always
represent the error status for the received character at the top of the RX FIFO. Reading
the RX FIFO updates LSR[4:2] to the appropriate status for the new character at the top of
the FIFO. If the RX FIFO is empty, then LSR[4:2] are all zeros.
For the Xoff interrupt, if an Xoff flow character detection caused the interrupt, the interrupt
is cleared by an Xon flow character detection. If a special character detection caused the
interrupt, the interrupt is cleared by a read of the IIR.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
6.5.1 Interrupt mode operation
In interrupt mode (if any bit of IER[3:0] is ‘1’) the processor is informed of the status of the
receiver and transmitter by an interrupt signal, INT. Therefore, it is not necessary to
continuously poll the Line Status Register (LSR) to see if any interrupt needs to be
serviced. Figure 9 shows interrupt mode operation.
IIR
IOW / IOR
INT
PROCESSOR
IER
1
1
1
1
THR
RHR
002aaa230
Fig 9. Interrupt mode operation
6.5.2 Polled mode operation
In polled mode (IER[3:0] = 0000) the status of the receiver and transmitter can be
checked by polling the Line Status Register (LSR). This mode is an alternative to the FIFO
interrupt mode of operation where the status of the receiver and transmitter is
automatically known by means of interrupts sent to the CPU. Figure 10 shows FIFO polled
mode operation.
LSR
IOW / IOR
PROCESSOR
IER
0
0
0
0
THR
RHR
002aaa231
Fig 10. FIFO polled mode operation
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
6.6 DMA operation
There are two modes of DMA operation, DMA mode 0 or DMA mode 1, selected by
FCR[3].
In DMA mode 0 or FIFO disable (FCR[0] = 0) DMA occurs in single character transfers. In
DMA mode 1, multi-character (or block) DMA transfers are managed to relieve the
processor for longer periods of time.
6.6.1 Single DMA transfers (DMA mode 0/FIFO disable)
Figure 11 shows TXRDY and RXRDY in DMA mode 0/FIFO disable.
TX
RX
TXRDY
RXRDY
at least one
at least one
wrptr
rdptr
location filled
location filled
TXRDY
RXRDY
FIFO EMPTY
FIFO EMPTY
wrptr
rdptr
002aaa232
Fig 11. TXRDY and RXRDY in DMA mode 0/FIFO disable
6.6.1.1 Transmitter
When empty, the TXRDY signal becomes active. TXRDY will go inactive after one
character has been loaded into it.
6.6.1.2 Receiver
RXRDY is active when there is at least one character in the FIFO. It becomes inactive
when the receiver is empty.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
6.6.2 Block DMA transfers (DMA mode 1)
Figure 12 shows TXRDY and RXRDY in DMA mode 1.
TX
RX
wrptr
trigger
level
TXRDY
rdptr
RXRDY
FIFO full
trigger
level
TXRDY
wrptr
RXRDY
FIFO EMPTY
rdptr
002aaa869
Fig 12. TXRDY and RXRDY in DMA mode 1
6.6.2.1 Transmitter
TXRDY is active when there is a trigger level number of spaces available. It becomes
inactive when the FIFO is full.
6.6.2.2 Receiver
RXRDY becomes active when the trigger level has been reached, or when a time-out
interrupt occurs. It will go inactive when the FIFO is empty or an error in the RX FIFO is
flagged by LSR[7].
6.7 Sleep mode
Sleep mode is an enhanced feature of the SC16C754B UART. It is enabled when EFR[4],
the enhanced functions bit, is set and when IER[4] is set. Sleep mode is entered when:
• The serial data input line, RX, is idle (see Section 6.8 “Break and time-out
conditions”).
• The TX FIFO and TX shift register are empty.
• There are no interrupts pending except THR and time-out interrupts.
Remark: Sleep mode will not be entered if there is data in the RX FIFO.
In Sleep mode, the UART clock and baud rate clock are stopped. Since most registers are
clocked using these clocks, the power consumption is greatly reduced. The UART will
wake up when any change is detected on the RX line, when there is any change in the
state of the modem input pins, or if data is written to the TX FIFO.
Remark: Writing to the divisor latches, DLL and DLM, to set the baud clock, must not be
done during Sleep mode. Therefore, it is advisable to disable Sleep mode using IER[4]
before writing to DLL or DLM.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
6.8 Break and time-out conditions
An RX idle condition is detected when the receiver line, RX, has been HIGH for
4 character time. The receiver line is sampled midway through each bit.
When a break condition occurs, the TX line is pulled LOW. A break condition is activated
by setting LCR[6].
6.9 Programmable baud rate generator
The SC16C754B UART contains a programmable baud generator that takes any clock
input and divides it by a divisor in the range between 1 and (216 − 1). An additional
divide-by-4 prescaler is also available and can be selected by MCR[7], as shown in
Figure 13. The output frequency of the baud rate generator is 16 × the baud rate. The
formula for the divisor is given in Equation 1:
XTAL1 crystal input frequency
------------------------------------------------------------------------------------
prescaler
divisor =
(1)
------------------------------------------------------------------------------------------
(desired baud rate × 16)
Where:
prescaler = 1, when MCR[7] is set to 0 after reset (divide-by-1 clock selected)
prescaler = 4, when MCR[7] is set to 1 after reset (divide-by-4 clock selected).
Remark: The default value of prescaler after reset is divide-by-1.
Figure 13 shows the internal prescaler and baud rate generator circuitry.
PRESCALER
MCR[7] = 0
LOGIC
(DIVIDE-BY-1)
internal
XTAL1
XTAL2
INTERNAL
OSCILLATOR
LOGIC
BAUD RATE
GENERATOR
LOGIC
baud rate
clock for
transmitter
and receiver
input clock
reference
clock
PRESCALER
LOGIC
(DIVIDE-BY-4)
MCR[7] = 1
002aaa233
Fig 13. Prescaler and baud rate generator block diagram
DLL and DLM must be written to in order to program the baud rate. DLL and DLM are the
least significant and most significant byte of the baud rate divisor. If DLL and DLM are
both zero, the UART is effectively disabled, as no baud clock will be generated.
Remark: The programmable baud rate generator is provided to select both the transmit
and receive clock rates.
Table 7 and Table 8 show the baud rate and divisor correlation for crystal with frequency
1.8432 MHz and 3.072 MHz, respectively.
Figure 14 shows the crystal clock circuit reference.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Table 7.
Baud rates using a 1.8432 MHz crystal
Desired baud rate
Divisor used to generate
Percent error difference
16× clock
between desired and actual
50
2304
1536
1047
857
768
384
192
96
75
110
0.026
0.058
134.5
150
300
600
1200
1800
2000
2400
3600
4800
7200
9600
19200
38400
56000
64
58
0.69
48
32
24
16
12
6
3
2
2.86
Table 8.
Baud rates using a 3.072 MHz crystal
Desired baud rate
Divisor used to generate
Percent error difference
16× clock
between desired and actual
50
3840
2560
1745
1428
1280
640
320
160
107
96
75
110
0.026
0.034
134.5
150
300
600
1200
1800
2000
2400
3600
4800
7200
9600
19200
38400
0.312
80
53
0.628
1.23
40
27
20
10
5
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NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
XTAL1
XTAL2
XTAL1
XTAL2
1.5 kΩ
X1
X1
1.8432 MHz
1.8432 MHz
C1
22 pF
C2
33 pF
C1
22 pF
C2
47 pF
002aaa870
Fig 14. Crystal oscillator connection
7. Register descriptions
Each register is selected using address lines A0, A1, A2, and in some cases, bits from
other registers. The programming combinations for register selection are shown in
Table 9.
Table 9.
Register map - read/write properties
A2 A1 A0 Read mode
Write mode
0
0
0
0
1
1
1
1
0
0
0
1
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
0
0
1
1
1
0
1
0
1
0
1
0
1
0
1
0
0
1
0
1
0
Receive Holding Register (RHR)
Interrupt Enable Register (IER)
Interrupt Identification Register (IIR)
Line Control Register (LCR)
Modem Control Register (MCR)[1]
Line Status Register (LSR)
Transmit Holding Register (THR)
Interrupt Enable Register (IER)
FIFO Control Register (FCR)
Line Control Register (LCR)
Modem Control Register (MCR)[1]
not applicable
Modem Status Register (MSR)
not applicable
ScratchPad Register (SPR)
ScratchPad Register (SPR)
Divisor Latch LSB (DLL)[2][3]
Divisor Latch MSB (DLM)[2][3]
Divisor Latch LSB (DLL)[2][3]
Divisor Latch MSB (DLM)[2][3]
Enhanced Feature Register (EFR)[2][4] Enhanced Feature Register (EFR)[2][4]
Xon1 word[2][4]
Xon2 word[2][4]
Xoff1 word[2][4]
Xoff2 word[2][4]
Xon1 word[2][4]
Xon2 word[2][4]
Xoff1 word[2][4]
Xoff2 word[2][4]
Transmission Control Register
(TCR)[2][5]
Transmission Control Register
(TCR)[2][5]
1
1
1
1
1
1
Trigger Level Register (TLR)[2][5]
FIFO ready register[2][6]
Trigger Level Register (TLR)[2][5]
[1] MCR[7] can only be modified when EFR[4] is set.
[2] Accessed by a combination of address pins and register bits.
[3] Accessible only when LCR[7] is logic 1.
[4] Accessible only when LCR is set to 1011 1111 (BFh).
[5] Accessible only when EFR[4] = 1 and MCR[6] = 1, that is, EFR[4] and MCR[6] are read/write enables.
[6] Accessible only when CSA to CSD = 0, MCR[2] = 1, and loopback is disabled (MCR[4] = 0).
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Table 10 lists and describes the SC16C754B internal registers.
Table 10. SC16C754B internal registers
Read/
Write
A2 A1 A0 Register Bit 7
General register set[1]
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
1
RHR
THR
IER
bit 7
bit 6
bit 5
bit 4
bit 4
bit 3
bit 3
bit 2
bit 2
bit 1
bit 1
THR
bit 0
bit 0
R
bit 7
bit 6
bit 5
0/Xoff[2]
W
0/CTS
interrupt interrupt
enable[2] enable[2]
0/RTS
0/X Sleep modem receive
mode[2]
RX data R/W
available
status
interrupt interrupt
line status empty
interrupt interrupt
RX FIFO FIFO
reset enable
0
1
0
FCR
RX
trigger
level
RX trigger 0/TX
level (LSB) trigger
level
0/TX
DMA
mode
select
TX FIFO
reset
W
trigger
level
(LSB)[2]
(MSB)
(MSB)[2]
0
0
1
1
1
1
0
0
0
1
0
1
IIR
FCR[0]
FCR[0]
0/CTS,
RTS
0/Xoff
interrupt interrupt
interrupt interrupt
R
priority
bit 2
priority
bit 1
priority
bit 0
status
LCR
MCR
LSR
DLAB
break
control bit
set parity paritytype parity
select enable
number of word
stop bits
word
length
bit 0
R/W
R/W
R
length
bit 1
1× or
1× / 4
clock[2]
TCR and
TLR
enable[2]
0/Xon Any 0/enable IRQ
[2]
FIFO
RTS
DTR
loopback enable
ready
enable
OP
0/error in THR and
THR
break
framing parity error overrun data in
RX FIFO TSR empty empty
interrupt
error
∆CD
bit 3
bit 3
bit 3
error
∆DSR
bit 1
receiver
∆CTS
bit 0
1
1
1
1
1
1
1
1
1
1
0
1
0
1
1
MSR
SPR
TCR
TLR
CD
RI
DSR
bit 5
bit 5
bit 5
CTS
bit 4
bit 4
bit 4
∆RI
R
bit 7
bit 7
bit 7
bit 6
bit 6
bit 6
bit 2
bit 2
bit 2
R/W
R/W
R/W
R
bit 1
bit 0
bit 1
bit 0
FIFO
Rdy
RX FIFO RX FIFO
D status C status
RX FIFO RX FIFO TXFIFO TX FIFO
TX FIFO TX FIFO
B status A status
B status
A status
D status C status
Special register set[3]
0
0
0
DLL
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 9
bit 0
bit 8
R/W
R/W
0
0
1
DLM
bit 15
bit 14
bit 13
bit 12
bit 11
bit 10
Enhanced register set[4]
0
1
0
EFR
auto-CTS auto-RTS special
enable
software software
software software R/W
character enhanced flow
flow
flow
flow
detect
functions control
control
bit 2
control
bit 1
control
bit 0
[2]
bit 3
1
1
1
1
0
0
1
1
0
1
0
1
Xon1
Xon2
Xoff1
Xoff2
bit 7
bit 7
bit 7
bit 7
bit 6
bit 6
bit 6
bit 6
bit 5
bit 5
bit 5
bit 5
bit 4
bit 4
bit 4
bit 4
bit 3
bit 3
bit 3
bit 3
bit 2
bit 2
bit 2
bit 2
bit 1
bit 1
bit 1
bit 1
bit 0
bit 0
bit 0
bit 0
R/W
R/W
R/W
R/W
[1] These registers are accessible only when LCR[7] = 0.
[2] This bit can only be modified if register bit EFR[4] is enabled, that is, if enhanced functions are enabled.
[3] The Special register set is accessible only when LCR[7] is set to a logic 1.
[4] Enhanced feature register; Xon1/Xon2 and Xoff1/Xoff2 are accessible only when LCR is set to BFh.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Remark: Refer to the notes under Table 9 for more register access information.
7.1 Receiver Holding Register (RHR)
The receiver section consists of the Receiver Holding Register (RHR) and the Receiver
Shift Register (RSR). The RHR is actually a 64-byte FIFO. The RSR receives serial data
from the RX terminal. The data is converted to parallel data and moved to the RHR. The
receiver section is controlled by the Line Control Register (LCR). If the FIFO is disabled,
location zero of the FIFO is used to store the characters.
Remark: In this case, characters are overwritten if overflow occurs.
If overflow occurs, characters are lost. The RHR also stores the error status bits
associated with each character.
7.2 Transmit Holding Register (THR)
The transmitter section consists of the Transmit Holding Register (THR) and the Transmit
Shift Register (TSR). The THR is actually a 64-byte FIFO. The THR receives data and
shifts it into the TSR, where it is converted to serial data and moved out on the TX
terminal. If the FIFO is disabled, the FIFO is still used to store the byte. Characters are
lost if overflow occurs.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
7.3 FIFO Control Register (FCR)
This is a write-only register that is used for enabling the FIFOs, clearing the FIFOs, setting
transmitter and receiver trigger levels, and selecting the type of DMA signalling. Table 11
shows FIFO control register bit settings.
Table 11. FIFO control register bits description
Bit
Symbol
Description
7:6
FCR[7] (MSB), RX trigger. Sets the trigger level for the RX FIFO.
FCR[6] (LSB)
00 — 8 characters
01 — 16 characters
10 — 56 characters
11 — 60 characters
5:4
FCR[5] (MSB), TX trigger. Sets the trigger level for the TX FIFO.
FCR[4] (LSB)
00 — 8 spaces
01 — 16 spaces
10 — 32 spaces
11 — 56 spaces
FCR[5:4] can only be modified and enabled when EFR[4] is set. This is
because the transmit trigger level is regarded as an enhanced function.
3
2
FCR[3]
FCR[2]
DMA mode select.
logic 0 = set DMA mode 0
logic 1 = set DMA mode 1
Reset TX FIFO.
logic 0 = no FIFO transmit reset (normal default condition)
logic 1 = clears the contents of the transmit FIFO and resets the FIFO
counter logic (the transmit shift register is not cleared or altered). This
bit will return to a logic 0 after clearing the FIFO.
1
0
FCR[1]
FCR[0]
Reset RX FIFO.
logic 0 = no FIFO receive reset (normal default condition)
logic 1 = clears the contents of the receive FIFO and resets the FIFO
counter logic (the receive shift register is not cleared or altered). This
bit will return to a logic 0 after clearing the FIFO.
FIFO enable.
logic 0 = disable the transmit and receive FIFO (normal default
condition)
logic 1 = enable the transmit and receive FIFO
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7.4 Line Control Register (LCR)
This register controls the data communication format. The word length, number of stop
bits, and parity type are selected by writing the appropriate bits to the LCR. Table 12
shows the line control register bit settings.
Table 12. Line control register bits description
Bit
Symbol
Description
7
LCR[7]
Divisor latch enable.
logic 0 = divisor latch disabled (normal default condition)
logic 1 = divisor latch enabled
6
5
LCR[6]
LCR[5]
Break control bit. When enabled, the Break control bit causes a break
condition to be transmitted (the TX output is forced to a logic 0 state). This
condition exists until disabled by setting LCR[6] to a logic 0.
logic 0 = no TX break condition (normal default condition)
logic 1 = forces the transmitter output (TX) to a logic 0 to alert the
communication terminal to a line break condition
Set parity. LCR[5] selects the forced parity format (if LCR[3] = 1).
logic 0 = parity is not forced (normal default condition)
LCR[5] = logic 1 and LCR[4] = logic 0: parity bit is forced to a logic 1 for
the transmit and receive data
LCR[5] = logic 1 and LCR[4] = logic 1: parity bit is forced to a logic 0 for
the transmit and receive data
4
3
LCR[4]
LCR[3]
Parity type select.
logic 0 = odd parity is generated (if LCR[3] = 1)
logic 1 = even parity is generated (if LCR[3] = 1)
Parity enable.
logic 0 = no parity (normal default condition)
logic 1 = a parity bit is generated during transmission and the receiver
checks for received parity
2
LCR[2]
Number of stop bits. Specifies the number of stop bits.
0 = 1 stop bit (word length = 5, 6, 7, 8)
1 = 1.5 stop bits (word length = 5)
1 = 2 stop bits (word length = 6, 7, 8)
1:0
LCR[1:0]
Word length bits 1, 0. These two bits specify the word length to be
transmitted or received.
00 — 5 bits
01 — 6 bits
10 — 7 bits
11 — 8 bits
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7.5 Line Status Register (LSR)
Table 13 shows the line status register bit settings.
Table 13. Line status register bits description
Bit
Symbol
Description
7
LSR[7]
FIFO data error.
logic 0 = no error (normal default condition)
logic 1 = at least one parity error, framing error, or break indication is in the
receiver FIFO. This bit is cleared when no more errors are present in the
FIFO.
6
5
LSR[6]
LSR[5]
THR and TSR empty. This bit is the Transmit Empty indicator.
logic 0 = transmitter hold and shift registers are not empty
logic 1 = transmitter hold and shift registers are empty
THR empty. This bit is the Transmit Holding Register Empty indicator.
logic 0 = Transmit Hold Register is not empty
logic 1 = Transmit Hold Register is empty. The processor can now load up
to 64 bytes of data into the THR if the TX FIFO is enabled.
4
3
LSR[4]
LSR[3]
Break interrupt.
logic 0 = no break condition (normal default condition)
logic 1 = a break condition occurred and associated byte is 00, that is,
RX was LOW for one character time frame
Framing error.
logic 0 = no framing error in data being read from RX FIFO (normal default
condition)
logic 1 = framing error occurred in data being read from RX FIFO, that is,
received data did not have a valid stop bit
2
1
0
LSR[2]
LSR[1]
LSR[0]
Parity error.
logic 0 = no parity error (normal default condition)
logic 1 = parity error in data being read from RX FIFO
Overrun error.
logic 0 = no overrun error (normal default condition)
logic 1 = overrun error has occurred
Data in receiver.
logic 0 = no data in receive FIFO (normal default condition)
logic 1 = at least one character in the RX FIFO
When the LSR is read, LSR[4:2] reflect the error bits (BI, FE, PE) of the character at the
top of the RX FIFO (next character to be read). The LSR[4:2] registers do not physically
exist, as the data read from the RX FIFO is output directly onto the output data bus,
DI[4:2], when the LSR is read. Therefore, errors in a character are identified by reading
the LSR and then reading the RHR.
LSR[7] is set when there is an error anywhere in the RX FIFO, and is cleared only when
there are no more errors remaining in the FIFO.
Reading the LSR does not cause an increment of the RX FIFO read pointer. The RX FIFO
read pointer is incremented by reading the RHR.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
7.6 Modem Control Register (MCR)
The MCR controls the interface with the modem, data set, or peripheral device that is
emulating the modem. Table 14 shows modem control register bit settings.
Table 14. Modem control register bits description
Bit
Symbol
Description
7
MCR[7][1]
Clock select.
logic 0 = divide-by-1 clock input
logic 1 = divide-by-4 clock input
TCR and TLR enable.
6
5
4
MCR[6][1]
MCR[5][1]
MCR[4]
logic 0 = no action
logic 1 = enable access to the TCR and TLR registers
Xon Any.
logic 0 = disable Xon Any function
logic 1 = enable Xon Any function
Enable loopback.
logic 0 = normal operating mode
logic 1 = enable local loopback mode (internal). In this mode the
MCR[3:0] signals are looped back into MSR[7:4] and the TX output is
looped back to the RX input internally.
3
MCR[3]
IRQ enable OP.
logic 0 = forces INTA to INTD outputs to the 3-state mode and OP
output to HIGH state
logic 1 = forces the INTA to INTD outputs to the active state and OP
output to LOW state. In loopback mode, controls MSR[7].
2
1
MCR[2]
MCR[1]
FIFO Ready enable.
logic 0 = disable the FIFO Rdy register
logic 1 = enable the FIFO Rdy register. In loopback mode, controls
MSR[6].
RTS
logic 0 = force RTS output to inactive (HIGH)
logic 1 = force RTS output to active (LOW). In loopback mode, controls
MSR[4]. If auto-RTS is enabled, the RTS output is controlled by
hardware flow control.
0
MCR[0]
DTR
logic 0 = force DTR output to inactive (HIGH)
logic 1 = force DTR output to active (LOW). In loopback mode, controls
MSR[5].
[1] MCR[7:5] can only be modified when EFR[4] is set, that is, EFR[4] is a write enable.
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7.7 Modem Status Register (MSR)
This 8-bit register provides information about the current state of the control lines from the
modem, data set, or peripheral device to the processor. It also indicates when a control
input from the modem changes state. Table 15 shows modem status register bit settings
per channel.
Table 15. Modem status register bits description
Bit
Symbol
Description
7
MSR[7][1]
CD (active HIGH, logic 1). This bit is the complement of the CD input during
normal mode. During internal loopback mode, it is equivalent to MCR[3].
6
5
4
MSR[6][1]
MSR[5][1]
MSR[4][1]
RI (active HIGH, logic 1). This bit is the complement of the RI input during
normal mode. During internal loopback mode, it is equivalent to MCR[2].
DSR (active HIGH, logic 1). This bit is the complement of the DSR input
during normal mode. During internal loopback mode, it is equivalent MCR[0].
CTS (active HIGH, logic 1). This bit is the complement of the CTS input
during normal mode. During internal loopback mode, it is equivalent to
MCR[1].
3
2
1
0
MSR[3]
MSR[2]
MSR[1]
MSR[0]
∆CD. Indicates that CD input (or MCR[3] in loopback mode) has changed
state. Cleared on a read.
∆RI. Indicates that RI input (or MCR[2] in loopback mode) has changed state
from LOW to HIGH. Cleared on a read.
∆DSR. Indicates that DSR input (or MCR[0] in loopback mode) has changed
state. Cleared on a read.
∆CTS. Indicates that CTS input (or MCR[1] in loopback mode) has changed
state. Cleared on a read.
[1] The primary inputs RI, CD, CTS, DSR are all active LOW, but their registered equivalents in the MSR and
MCR (in loopback) registers are active HIGH.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
7.8 Interrupt Enable Register (IER)
The Interrupt Enable Register (IER) enables each of the six types of interrupt, receiver
error, RHR interrupt, THR interrupt, Xoff received, or CTS/RTS change of state from LOW
to HIGH. The INT output signal is activated in response to interrupt generation. Table 16
shows the interrupt enable register bit settings.
Table 16. Interrupt enable register bits description
Bit
Symbol
Description
7
IER[7][1]
CTS interrupt enable.
logic 0 = disable the CTS interrupt (normal default condition)
logic 1 = enable the CTS interrupt
RTS interrupt enable.
6
5
4
3
IER[6][1]
IER[5][1]
IER[4][1]
IER[3]
logic 0 = disable the RTS interrupt (normal default condition)
logic 1 = enable the RTS interrupt
Xoff interrupt.
logic 0 = disable the Xoff interrupt (normal default condition)
logic 1 = enable the Xoff interrupt
Sleep mode.
logic 0 = disable Sleep mode (normal default condition)
logic 1 = enable Sleep mode. See Section 6.7 “Sleep mode” for details.
Modem status interrupt.
logic 0 = disable the modem status register interrupt (normal default
condition)
logic 1 = enable the modem status register interrupt
Receive line status interrupt.
2
1
0
IER[2]
IER[1]
IER[0]
logic 0 = disable the receiver line status interrupt (normal default condition)
logic 1 = enable the receiver line status interrupt
Transmit holding register interrupt.
logic 0 = disable the THR interrupt (normal default condition)
logic 1 = enable the THR interrupt
Receive holding register interrupt.
logic 0 = disable the RHR interrupt (normal default condition)
logic 1 = enable the RHR interrupt
[1] IER[7:4] can only be modified if EFR[4] is set, that is, EFR[4] is a write enable. Re-enabling IER[1] will
cause a new interrupt if the THR is below the threshold.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
7.9 Interrupt Identification Register (IIR)
The IIR is a read-only 8-bit register which provides the source of the interrupt in a
prioritized manner. Table 17 shows interrupt identification register bit settings.
Table 17. Interrupt identification register bits description
Bit
7:6
5
Symbol
IIR[7:6]
IIR[5]
Description
Mirror the contents of FCR[0].
RTS/CTS LOW-to-HIGH change of state.
1 = Xoff/special character has been detected.
3-bit encoded interrupt. See Table 18.
Interrupt status.
4
IIR[4]
3:1
0
IIR[3:1]
IIR[0]
logic 0 = an interrupt is pending
logic 1 = no interrupt is pending
The interrupt priority list is shown in Table 18.
Table 18. Interrupt priority list
Priority IIR[5]
level
IIR[4]
IIR[3]
IIR[2]
IIR[1]
IIR[0]
Source of the interrupt
1
2
2
3
4
5
0
0
0
0
0
0
0
0
0
0
0
1
0
1
0
0
0
0
1
1
1
0
0
0
1
0
0
1
0
0
0
0
0
0
0
0
Receiver line status error
Receiver time-out interrupt
RHR interrupt
THR interrupt
Modem interrupt
Received Xoff signal/
special character
6
1
0
0
0
0
0
CTS, RTS change of state from
active (LOW) to inactive (HIGH)
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7.10 Enhanced Feature Register (EFR)
This 8-bit register enables or disables the enhanced features of the UART. Table 19 shows
the enhanced feature register bit settings.
Table 19. Enhanced feature register bits description
Bit
Symbol
Description
7
EFR[7]
CTS flow control enable.
logic 0 = CTS flow control is disabled (normal default condition)
logic 1 = CTS flow control is enabled. Transmission will stop when a HIGH
signal is detected on the CTS pin.
6
EFR[6]
EFR[5]
EFR[4]
RTS flow control enable.
logic 0 = RTS flow control is disabled (normal default condition)
logic 1 = RTS flow control is enabled. The RTS pin goes HIGH when the
receiver FIFO HALT trigger level TCR[3:0] is reached, and goes LOW when
the receiver FIFO RESUME transmission trigger level TCR[7:4] is reached.
5
Special character detect.
logic 0 = special character detect disabled (normal default condition)
logic 1 = special character detect enabled. Received data is compared with
Xoff2 data. If a match occurs, the received data is transferred to FIFO and
IIR[4] is set to a logic 1 to indicate a special character has been detected.
4
Enhanced functions enable bit.
logic 0 = disables enhanced functions and writing to IER[7:4], FCR[5:4],
MCR[7:5].
logic 1 = enables the enhanced function IER[7:4], FCR[5:4], and MCR[7:5]
can be modified, that is, this bit is therefore a write enable.
3:0
EFR[3:0] Combinations of software flow control can be selected by programming these
bits. See Table 3 “Software flow control options (EFR[3:0])”.
7.11 Divisor latches (DLL, DLM)
These are two 8-bit registers which store the 16-bit divisor for generation of the baud clock
in the baud rate generator. DLM stores the most significant part of the divisor. DLL stores
the least significant part of the divisor.
Note that DLL and DLM can only be written to before Sleep mode is enabled, that is,
before IER[4] is set.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
7.12 Transmission Control Register (TCR)
This 8-bit register is used to store the RX FIFO threshold levels to stop/start transmission
during hardware/software flow control. Table 20 shows transmission control register bit
settings.
Table 20. Transmission control register bits description
Bit
7:4
3:0
Symbol
Description
TCR[7:4] RX FIFO trigger level to resume transmission [(0 to 60) bytes].
TCR[3:0] RX FIFO trigger level to halt transmission [(0 to 60) bytes].
TCR trigger levels are available from 0 to 60 bytes with a granularity of four.
Remark: TCR can only be written to when EFR[4] = 1 and MCR[6] = 1. The programmer
must program the TCR such that TCR[3:0] > TCR[7:4]. There is no built-in hardware
check to make sure this condition is met. Also, the TCR must be programmed with this
condition before auto-RTS or software flow control is enabled to avoid spurious operation
of the device.
7.13 Trigger Level Register (TLR)
This 8-bit register is used to store the transmit and received FIFO trigger levels used for
DMA and interrupt generation. Trigger levels from 4 to 60 can be programmed with a
granularity of 4. Table 21 shows trigger level register bit settings.
Table 21. Trigger level register bits description
Bit
7:4
3:0
Symbol
TLR[7:4]
TLR[3:0]
Description
RX FIFO trigger levels (4 to 60), number of characters available.
TX FIFO trigger levels (4 to 60), number of spaces available.
Remark: TLR can only be written to when EFR[4] = 1 and MCR[6] = 1. If TLR[3:0] or
TLR[7:4] are logic 0, the selectable trigger levels via the FIFO Control Register (FCR) are
used for the transmit and receive FIFO trigger levels. Trigger levels from 4 to 60 bytes are
available with a granularity of four. The TLR should be programmed for N⁄4, where N is the
desired trigger level.
7.14 FIFO Ready register (FIFO Rdy)
The FIFO Rdy register provides real-time status of the transmit and receive FIFOs of both
channels.
Table 22. FIFO ready register bits description
Bit
Symbol
Description
7:4
FIFO Rdy[7:4] 0 = there are less than a RX trigger level number of characters in the
RX FIFO
1 = the RX FIFO has more than a RX trigger level number of characters
available for reading or a time-out condition has occurred
3:0
FIFO Rdy[3:0] 0 = there are less than a TX trigger level number of spaces available in
the TX FIFO
1 = there are at least a TX trigger level number of spaces available in the
TX FIFO
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
The FIFO ready register is a read-only register that can be accessed when any of the four
UARTs is selected CSA to CSD = 0, MCR[2] (FIFO Rdy Enable) is a logic 1, and loopback
is disabled. The address is 111.
8. Programmer’s guide
The base set of registers that is used during high-speed data transfer have a
straightforward access method. The extended function registers require special access
bits to be decoded along with the address lines. The following guide will help with
programming these registers. Note that the descriptions below are for individual register
access. Some streamlining through interleaving can be obtained when programming all
the registers.
Table 23. Register programming guide
Command
Actions
read LCR (03h), save in temp
set baud rate to VALUE1, VALUE2
set LCR (03h) to 80h
set DLL (00h) to VALUE1
set DLM (01h) to VALUE2
set LCR (03h) to temp
set Xoff1, Xon1 to VALUE1, VALUE2
set Xoff2, Xon2 to VALUE1, VALUE2
read LCR (03h), save in temp
set LCR (03h) to BFh
set Xoff1 (06h) to VALUE1
set Xon1 (04h) to VALUE2
set LCR (03h) to temp
read LCR (03h), save in temp
set LCR (03h) to BFh
set Xoff2 (07h) to VALUE1
set Xon2 (05h) to VALUE2
set LCR (03h) to temp
set software flow control mode to VALUE
set flow control threshold to VALUE
read LCR (03h), save in temp
set LCR (03h) to BFh
set EFR (02h) to VALUE
set LCR (03h) to temp
read LCR (03h), save in temp1
set LCR (03h) to BFh
read EFR (02h), save in temp2
set EFR (02h) to 10h + temp2
set LCR (03h) to 00h
read MCR (04h), save in temp3
set MCR (04h) to 40h + temp3
set TCR (06h) to VALUE
set MCR (04h) to temp3
set LCR (03h) to BFh
set EFR (02h) to temp2
set LCR (03h) to temp1
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Table 23. Register programming guide …continued
Command Actions
read LCR (03h), save in temp1
set TX FIFO and RX FIFO thresholds
to VALUE
set LCR (03h) to BFh
read EFR (02h), save in temp2
set EFR (02h) to 10h + temp2
set LCR (03h) to 00h
read MCR (04h), save in temp3
set MCR (04h) to 40h + temp3
set TLR (07h) to VALUE
set MCR (04h) to temp3
set LCR (03h) to BFh
set EFR (02h) to temp2
set LCR (03h) to temp1
read FIFO Rdy register
read MCR (04h), save in temp1
set temp2 = temp1 × EFh [1]
set MCR (04h) = 40h + temp2
read FFR (07h), save in temp2
pass temp2 back to host
set MCR (04h) to temp1
read LCR (03h), save in temp1
set LCR (03h) to BFh
set prescaler value to divide-by-1
read EFR (02h), save in temp2
set EFR (02h) to 10h + temp2
set LCR (03h) to 00h
read MCR (04h), save in temp3
set MCR (04h) to temp3 × 7Fh [1]
set LCR (03h) to BFh
set EFR (02h) to temp2
set LCR (03h) to temp1
set prescaler value to divide-by-4
read LCR (03h), save in temp1
set LCR (03h) to BF
read EFR (02h), save in temp2
set EFR (02h) to 10h + temp2
set LCR (03h) to 00h
read MCR (04)h, save in temp3
set MCR (04h) to temp3 + 80h
set LCR (03)h to BFh
set EFR (02h) to temp2
set LCR (03h) to temp1
[1] × sign here means bit-AND.
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
9. Limiting values
Table 24. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol Parameter
Conditions
Min
Max
Unit
V
VCC
Vn
supply voltage
voltage on any other pin at D7 to D0
at any input only pin
operating in free-air
-
7
GND − 0.3 VCC + 0.3
GND − 0.3 5.3
V
V
Tamb
Tstg
ambient temperature
storage temperature
−40
−65
+85
°C
°C
+150
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5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
10. Static characteristics
Table 25. Static characteristics
Tolerance of VCC ± 10 %, unless otherwise specified.
Symbol Parameter
Conditions
VCC = 2.5 V
Typ
VCC = 3.3 V and 5 V
Min Typ Max
Unit
Min
Max
VCC
VI
supply voltage
input voltage
VCC − 10 % VCC VCC + 10 % VCC − 10 % VCC VCC + 10 % V
0
-
-
VCC
VCC
0
-
-
VCC
VCC
V
V
[1]
[1]
VIH
HIGH-level input
voltage
1.6
2.0
VIL
LOW-level input
voltage
-
-
0.65
-
-
0.8
V
[2]
[3]
[4]
[3]
[4]
[3]
[4]
[3]
[4]
VO
output voltage
0
-
VCC
0
-
VCC
V
VOH
HIGH-level
output voltage
IOH = −8 mA
IOH = −4 mA
IOH = −800 µA
IOH = −400 µA
-
-
-
-
2.0
-
-
-
V
-
-
2.0
-
V
1.85
-
-
-
-
-
V
1.85
-
-
-
-
-
V
VOL
LOW-level output IOL = 8 mA
voltage[5]
-
-
-
-
-
0.4
0.4
-
V
IOL = 4 mA
-
-
-
-
-
V
IOL = 2 mA
IOL = 1.6 mA
-
-
0.4
0.4
18
+85
-
-
V
-
-
-
-
-
-
-
-
-
V
Ci
input capacitance
18
+85
pF
°C
Tamb
ambient
temperature
operating in
free air
−40
+25
−40
+25
[6]
[7]
Tj
junction
temperature
0
-
25
-
125
50
0
-
25
-
125
80
°C
f(i)XTAL1 crystal input
frequency
MHz
δ
clock duty cycle
supply current
-
-
-
50
-
-
4.5
-
-
-
-
50
-
-
6
-
%
[8]
[9]
ICC
f = 5 MHz
mA
µA
ICC(sleep) sleep mode
supply current
200
200
[1] Meets TTL levels, Vio(min) = 2 V and VIH(max) = 0.8 V on non-hysteresis inputs.
[2] Applies for external output buffers.
[3] These parameters apply for D7 to D0.
[4] These parameters apply for DTRA, DTRB, INIA, INTB, RTSA, RTSB, RXRDYA, RXRDYB, TXRDYA, TXRDYB, TXA, TXB.
[5] Except XTAL2, VOL = 1 V typical.
[6] These junction temperatures reflect simulated conditions. Absolute maximum junction temperature is 150 °C. The customer is
responsible for verifying junction temperature.
[7] Applies to external clock; crystal oscillator max. 24 MHz.
[8] Measurement condition, normal operation other than Sleep mode:
VCC = 3.3 V; Tamb = 25 °C. Full duplex serial activity on all two serial (UART) channels at the clock frequency specified in the
recommended operating conditions with divisor of 1.
[9] When using crystal oscillator. The use of an external clock will increase the sleep current.
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Product data sheet
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NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
11. Dynamic characteristics
Table 26. Dynamic characteristics
Tamb = −40 °C to +85 °C; tolerance of VCC ± 10 %, unless otherwise specified.
Symbol Parameter
Conditions
VCC = 2.5 V
VCC = 3.3 V
VCC = 5.0 V
Unit
Min
Max
Min
Max
Min
Max
tWL
tWH
fXTAL
t6s
pulse width LOW
10
10
-
-
6
6
-
-
6
6
-
-
ns
ns
MHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
pulse width HIGH
-
[1][2]
oscillator/clock frequency
address set-up time
address hold time
48
-
80
-
80
-
0
-
0
0
0
t6h
0
-
0
-
-
t7d
IOR delay from chip select
IOR strobe width
10
90
0
-
10
26
0
-
10
23
0
-
t7w
25 pF load
-
-
-
t7h
chip select hold time from IOR
read cycle delay
-
-
-
t9d
25 pF load
25 pF load
25 pF load
20
-
-
20
-
-
20
-
-
t12d
t12h
t13d
t13w
t13h
t15d
t16s
t16h
t17d
t18d
delay from IOR to data
data disable time
90
26
15
-
23
15
-
-
15
-
-
IOW delay from chip select
IOW strobe width
10
20
0
-
10
20
0
10
15
0
-
-
-
chip select hold time from IOW
write cycle delay
-
-
-
25
20
15
-
-
-
25
15
5
-
20
15
5
-
data set-up time
-
-
data hold time
-
-
-
delay from IOW to output
25 pF load
25 pF load
100
100
-
33
24
-
29
23
delay to set interrupt from
Modem input
-
-
-
t19d
t20d
t21d
delay to reset interrupt from
IOR
25 pF load
-
-
-
-
100
-
-
-
-
24
-
-
-
-
23
ns
delay from stop to set interrupt
1TRCLK
1TRCLK
1TRCLK ns
[3]
[3]
[3]
delay from IOR to reset
interrupt
25 pF load
100
100
29
45
28
40
ns
ns
t22d
t23d
delay from start to set interrupt
delay from IOW to transmit start
8TRCLK 24TRCLK 8TRCLK 24TRCLK 8TRCLK 24TRCLK ns
[3]
[3]
[3]
[3]
[3]
[3]
t24d
t25d
delay from IOW to reset
interrupt
-
100
-
45
-
40
ns
delay from stop to set RXRDY
-
1TRCLK
-
1TRCLK
-
1TRCLK ns
[3]
[3]
[3]
t26d
t27d
t28d
delay from IOR to reset RXRDY
delay from IOW to set TXRDY
delay from start to reset TXRDY
-
-
-
100
100
-
-
-
45
45
-
-
-
40
40
ns
ns
8TRCLK
8TRCLK
8TRCLK ns
[3]
[3]
[3]
[4]
tRESET
N
RESET pulse width
baud rate divisor
200
1
-
200
1
-
200
1
-
ns
(216 − 1)
(216 − 1)
(216 − 1)
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NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
[1] Applies to external clock, crystal oscillator max 24 MHz.
1
[2] Maximum frequency =
--------------
tw(clk)
[3] RCLK is an internal signal derived from Divisor Latch LSB (DLL) and Divisor Latch MSB (DLM) divisor latches.
[4] RESET pulse must happen when CS, IOW, IOR signals are inactive.
11.1 Timing diagrams
t
6h
valid
address
A0 to A2
t
t
13h
6s
active
CSx
t
t
13d
15d
t
13w
IOW
active
t
16h
t
16s
D0 to D7
data
002aaa109
Fig 15. General write timing
t
t
6h
7h
valid
address
A0 to A2
t
6s
active
CSx
IOR
t
t
7d
9d
t
7w
active
t
t
12h
12d
D0 to D7
data
002aaa110
Fig 16. General read timing
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Product data sheet
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SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
active
IOW
RTS
t
17d
change of state
change of state
DTR
CD
CTS
DSR
change of state
change of state
t
t
18d
18d
INT
active
active
active
active
active
t
19d
active
IOR
t
18d
change of state
RI
002aaa352
Fig 17. Modem input/output timing
t
t
WH
WL
external clock
t
w(clk)
002aac357
1
f XTAL
=
--------------
tw(clk)
Fig 18. External clock timing
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Product data sheet
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SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
next
data
start
bit
parity stop start
bit
bit
bit
data bits (0 to 7)
D3 D4
RX
D0
D1
D2
D5
D6
D7
5 data bits
6 data bits
7 data bits
t
20d
active
INT
t
21d
active
IOR
16 baud rate clock
002aaa113
Fig 19. Receive timing
next
data
start
bit
parity stop start
bit bit
bit
data bits (0 to 7)
D3 D4
D0
D1
D2
D5
D6
D7
RX
t
25d
active data
ready
RXRDY
IOR
t
26d
active
002aab063
Fig 20. Receive ready timing in non-FIFO mode
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Product data sheet
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40 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
start
bit
parity stop
bit
bit
data bits (0 to 7)
D3 D4
D0
D1
D2
D5
D6
D7
RX
first byte that
reaches the
trigger level
t
25d
active data
ready
RXRDY
IOR
t
26d
active
002aab064
Fig 21. Receive ready timing in FIFO mode
next
data
start
bit
parity stop start
bit bit
bit
data bits (0 to 7)
TX
D0
D1
D2
D3
D4
D5
D6
D7
5 data bits
6 data bits
7 data bits
active
INT
transmitter ready
t
22d
t
24d
t
23d
active
active
IOW
16 baud rate clock
002aaa116
Fig 22. Transmit timing
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Product data sheet
Rev. 04 — 6 October 2008
41 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
next
data
start
bit
parity stop start
bit
bit
bit
data bits (0 to 7)
D3 D4
D0
D1
D2
D5
D6
D7
TX
IOW
active
t
28d
D0 to D7
byte #1
t
27d
active transmitter
ready
TXRDY
transmitter
not ready
002aab062
Fig 23. Transmit ready timing in non-FIFO mode
start
bit
parity stop
bit bit
data bits (0 to 7)
D3 D4
D0
D1
D2
D5
D6
D7
TX
5 data bits
6 data bits
7 data bits
IOW
active
t
28d
D0 to D7
byte #32
t
27d
TXRDY
FIFO full
002aab065
Fig 24. Transmit ready timing in FIFO mode (DMA mode 1)
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Product data sheet
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42 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
12. Package outline
LQFP64: plastic low profile quad flat package; 64 leads; body 7 x 7 x 1.4 mm
SOT414-1
y
X
A
48
33
49
32
Z
E
e
A
2
A
H
E
E
(A )
3
A
1
w M
p
θ
b
pin 1 index
L
p
L
64
17
detail X
1
16
Z
v M
A
D
e
w M
b
p
D
B
H
v M
B
D
0
2.5
scale
5 mm
DIMENSIONS (mm are the original dimensions)
A
(1)
(1)
(1)
(1)
UNIT
A
A
A
b
c
D
E
e
H
D
H
L
L
v
w
y
Z
Z
θ
1
2
3
p
E
p
D
E
max.
7o
0o
0.15 1.45
0.05 1.35
0.23 0.20 7.1
0.13 0.09 6.9
7.1
6.9
9.15 9.15
8.85 8.85
0.75
0.45
0.64 0.64
0.36 0.36
1.6
mm
0.25
0.4
1
0.2 0.08 0.08
Note
1. Plastic or metal protrusions of 0.25 mm maximum per side are not included.
REFERENCES
OUTLINE
EUROPEAN
PROJECTION
ISSUE DATE
VERSION
IEC
JEDEC
JEITA
00-01-19
03-02-20
SOT414-1
136E06
MS-026
Fig 25. Package outline SOT414-1 (LQFP64)
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Product data sheet
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43 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
LQFP80: plastic low profile quad flat package; 80 leads; body 12 x 12 x 1.4 mm
SOT315-1
y
X
A
60
41
Z
61
40
E
e
H
A
E
2
E
A
(A )
3
A
1
w M
p
θ
b
L
p
L
pin 1 index
80
21
detail X
1
20
Z
D
v
M
A
e
w M
b
p
D
B
H
v
M
B
D
0
5
10 mm
scale
DIMENSIONS (mm are the original dimensions)
A
(1)
(1)
(1)
(1)
UNIT
A
A
A
b
c
D
E
e
H
H
L
L
v
w
y
Z
Z
θ
1
2
3
p
D
E
p
D
E
max.
7o
0o
0.16 1.5
0.04 1.3
0.27 0.18 12.1 12.1
0.13 0.12 11.9 11.9
14.15 14.15
13.85 13.85
0.75
0.30
1.45 1.45
1.05 1.05
mm
1.6
0.25
0.5
1
0.2 0.15 0.1
Note
1. Plastic or metal protrusions of 0.25 mm maximum per side are not included.
REFERENCES
OUTLINE
EUROPEAN
PROJECTION
ISSUE DATE
VERSION
IEC
JEDEC
JEITA
00-01-19
03-02-25
SOT315-1
136E15
MS-026
Fig 26. Package outline SOT315-1 (LQFP80)
SC16C754B_4
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Product data sheet
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44 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
PLCC68: plastic leaded chip carrier; 68 leads
SOT188-2
e
e
E
D
y
X
A
60
44
Z
E
43
61
b
p
b
1
w
M
68
1
H
E
E
pin 1 index
A
e
A
1
A
4
(A )
3
L
p
9
k
27
β
detail X
10
26
v
M
A
e
Z
D
D
B
H
v
M
B
D
0
5
10 mm
scale
DIMENSIONS (mm dimensions are derived from the original inch dimensions)
(1)
(1)
A
A
Z
Z
E
4
1
(1)
(1)
D
UNIT
mm
A
A
b
D
E
e
e
e
H
H
k
L
p
v
w
y
β
b
3
1
D
E
D
E
p
max.
min.
max. max.
4.57
4.19
0.81 24.33 24.33
0.66 24.13 24.13
23.62 23.62 25.27 25.27 1.22 1.44
22.61 22.61 25.02 25.02 1.07 1.02
0.53
0.33
0.51 0.25
3.3
1.27
0.05
0.18 0.18
0.1
2.16 2.16
o
45
0.180
0.165
0.032 0.958 0.958
0.026 0.950 0.950
0.93 0.93 0.995 0.995 0.048 0.057
0.89 0.89 0.985 0.985 0.042 0.040
0.021
0.013
inches
0.02 0.01 0.13
0.007 0.007 0.004 0.085 0.085
Note
1. Plastic or metal protrusions of 0.25 mm (0.01 inch) maximum per side are not included.
REFERENCES
OUTLINE
EUROPEAN
PROJECTION
ISSUE DATE
99-12-27
VERSION
IEC
JEDEC
JEITA
SOT188-2
112E10
MS-018
EDR-7319
01-11-14
Fig 27. Package outline SOT188-2 (PLCC68)
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SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
13. Soldering of SMD packages
This text provides a very brief insight into a complex technology. A more in-depth account
of soldering ICs can be found in Application Note AN10365 “Surface mount reflow
soldering description”.
13.1 Introduction to soldering
Soldering is one of the most common methods through which packages are attached to
Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both
the mechanical and the electrical connection. There is no single soldering method that is
ideal for all IC packages. Wave soldering is often preferred when through-hole and
Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not
suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high
densities that come with increased miniaturization.
13.2 Wave and reflow soldering
Wave soldering is a joining technology in which the joints are made by solder coming from
a standing wave of liquid solder. The wave soldering process is suitable for the following:
• Through-hole components
• Leaded or leadless SMDs, which are glued to the surface of the printed circuit board
Not all SMDs can be wave soldered. Packages with solder balls, and some leadless
packages which have solder lands underneath the body, cannot be wave soldered. Also,
leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered,
due to an increased probability of bridging.
The reflow soldering process involves applying solder paste to a board, followed by
component placement and exposure to a temperature profile. Leaded packages,
packages with solder balls, and leadless packages are all reflow solderable.
Key characteristics in both wave and reflow soldering are:
• Board specifications, including the board finish, solder masks and vias
• Package footprints, including solder thieves and orientation
• The moisture sensitivity level of the packages
• Package placement
• Inspection and repair
• Lead-free soldering versus SnPb soldering
13.3 Wave soldering
Key characteristics in wave soldering are:
• Process issues, such as application of adhesive and flux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are
exposed to the wave
• Solder bath specifications, including temperature and impurities
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Product data sheet
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SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
13.4 Reflow soldering
Key characteristics in reflow soldering are:
• Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to
higher minimum peak temperatures (see Figure 28) than a SnPb process, thus
reducing the process window
• Solder paste printing issues including smearing, release, and adjusting the process
window for a mix of large and small components on one board
• Reflow temperature profile; this profile includes preheat, reflow (in which the board is
heated to the peak temperature) and cooling down. It is imperative that the peak
temperature is high enough for the solder to make reliable solder joints (a solder paste
characteristic). In addition, the peak temperature must be low enough that the
packages and/or boards are not damaged. The peak temperature of the package
depends on package thickness and volume and is classified in accordance with
Table 27 and 28
Table 27. SnPb eutectic process (from J-STD-020C)
Package thickness (mm) Package reflow temperature (°C)
Volume (mm3)
< 350
235
≥ 350
220
< 2.5
≥ 2.5
220
220
Table 28. Lead-free process (from J-STD-020C)
Package thickness (mm) Package reflow temperature (°C)
Volume (mm3)
< 350
260
350 to 2000
> 2000
260
< 1.6
260
250
245
1.6 to 2.5
> 2.5
260
245
250
245
Moisture sensitivity precautions, as indicated on the packing, must be respected at all
times.
Studies have shown that small packages reach higher temperatures during reflow
soldering, see Figure 28.
SC16C754B_4
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Product data sheet
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SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
maximum peak temperature
= MSL limit, damage level
temperature
minimum peak temperature
= minimum soldering temperature
peak
temperature
time
001aac844
MSL: Moisture Sensitivity Level
Fig 28. Temperature profiles for large and small components
For further information on temperature profiles, refer to Application Note AN10365
“Surface mount reflow soldering description”.
14. Abbreviations
Table 29. Abbreviations
Acronym
CPU
Description
Central Processing Unit
Divisor Latch LSB
DLL
DLM
Divisor Latch MSB
DMA
FIFO
LSB
Direct Memory Access
First In, First Out
Least Significant Bit
MSB
TTL
Most Significant Bit
Transistor-Transistor Logic
Universal Asynchronous Receiver/Transmitter
UART
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Product data sheet
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SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
15. Revision history
Table 30. Revision history
Document ID
SC16C754B_4
Modifications:
Release date
Data sheet status
Change notice
Supersedes
20081006
Product data sheet
-
SC16C754B_3
• Section 2 “Features”, 5th bullet item re-written; added Footnote 1 on page 1
• Table 24 “Limiting values”:
–
–
–
deleted symbol VI
deleted symbol VO
added symbol Vn
• Section 7.14 “FIFO Ready register (FIFO Rdy)”, last paragraph: changed from “when any of the
two UARTs is selected...” to “when any of the four UARTS is selected...”
• Table 26 “Dynamic characteristics”: added Table note [4] and its reference at tRESET
.
SC16C754B_3
20080516
Product data sheet
-
SC16C754B_2
SC16C754B_2
20050613
Product data sheet
-
SC16C754B_1
(9397 750 14668)
SC16C754B_1
20050127
Product data sheet
-
-
(9397 750 13114)
SC16C754B_4
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Product data sheet
Rev. 04 — 6 October 2008
49 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
16. Legal information
16.1 Data sheet status
Document status[1][2]
Product status[3]
Development
Definition
Objective [short] data sheet
This document contains data from the objective specification for product development.
This document contains data from the preliminary specification.
This document contains the product specification.
Preliminary [short] data sheet Qualification
Product [short] data sheet Production
[1]
[2]
[3]
Please consult the most recently issued document before initiating or completing a design.
The term ‘short data sheet’ is explained in section “Definitions”.
The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status
information is available on the Internet at URL http://www.nxp.com.
malfunction of an NXP Semiconductors product can reasonably be expected
16.2 Definitions
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors accepts no liability for inclusion and/or use of
NXP Semiconductors products in such equipment or applications and
therefore such inclusion and/or use is at the customer’s own risk.
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Short data sheet — A short data sheet is an extract from a full data sheet
with the same product type number(s) and title. A short data sheet is intended
for quick reference only and should not be relied upon to contain detailed and
full information. For detailed and full information see the relevant full data
sheet, which is available on request via the local NXP Semiconductors sales
office. In case of any inconsistency or conflict with the short data sheet, the
full data sheet shall prevail.
Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) may cause permanent
damage to the device. Limiting values are stress ratings only and operation of
the device at these or any other conditions above those given in the
Characteristics sections of this document is not implied. Exposure to limiting
values for extended periods may affect device reliability.
Terms and conditions of sale — NXP Semiconductors products are sold
subject to the general terms and conditions of commercial sale, as published
at http://www.nxp.com/profile/terms, including those pertaining to warranty,
intellectual property rights infringement and limitation of liability, unless
explicitly otherwise agreed to in writing by NXP Semiconductors. In case of
any inconsistency or conflict between information in this document and such
terms and conditions, the latter will prevail.
16.3 Disclaimers
General — Information in this document is believed to be accurate and
reliable. However, NXP Semiconductors does not give any representations or
warranties, expressed or implied, as to the accuracy or completeness of such
information and shall have no liability for the consequences of use of such
information.
No offer to sell or license — Nothing in this document may be interpreted
or construed as an offer to sell products that is open for acceptance or the
grant, conveyance or implication of any license under any copyrights, patents
or other industrial or intellectual property rights.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
16.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in medical, military, aircraft,
space or life support equipment, nor in applications where failure or
17. Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: salesaddresses@nxp.com
SC16C754B_4
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 04 — 6 October 2008
50 of 51
SC16C754B
NXP Semiconductors
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
18. Contents
1
2
3
4
General description . . . . . . . . . . . . . . . . . . . . . . 1
8
Programmer’s guide . . . . . . . . . . . . . . . . . . . . 33
Limiting values . . . . . . . . . . . . . . . . . . . . . . . . 35
Static characteristics . . . . . . . . . . . . . . . . . . . 36
Dynamic characteristics. . . . . . . . . . . . . . . . . 37
Timing diagrams. . . . . . . . . . . . . . . . . . . . . . . 38
Package outline . . . . . . . . . . . . . . . . . . . . . . . . 43
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Ordering information. . . . . . . . . . . . . . . . . . . . . 2
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3
9
10
11
11.1
12
5
5.1
5.2
Pinning information. . . . . . . . . . . . . . . . . . . . . . 4
Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 6
13
Soldering of SMD packages . . . . . . . . . . . . . . 46
Introduction to soldering. . . . . . . . . . . . . . . . . 46
Wave and reflow soldering . . . . . . . . . . . . . . . 46
Wave soldering. . . . . . . . . . . . . . . . . . . . . . . . 46
Reflow soldering. . . . . . . . . . . . . . . . . . . . . . . 47
6
6.1
6.2
Functional description . . . . . . . . . . . . . . . . . . . 9
Trigger levels. . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Hardware flow control. . . . . . . . . . . . . . . . . . . 10
Auto-RTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Auto-CTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Software flow control . . . . . . . . . . . . . . . . . . . 12
RX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
TX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Software flow control example . . . . . . . . . . . . 13
Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Interrupt mode operation . . . . . . . . . . . . . . . . 16
Polled mode operation . . . . . . . . . . . . . . . . . . 16
DMA operation . . . . . . . . . . . . . . . . . . . . . . . . 17
Single DMA transfers (DMA mode 0/FIFO
13.1
13.2
13.3
13.4
6.2.1
6.2.2
6.3
6.3.1
6.3.2
6.3.3
6.3.3.1
6.4
14
15
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . 48
Revision history . . . . . . . . . . . . . . . . . . . . . . . 49
16
Legal information . . . . . . . . . . . . . . . . . . . . . . 50
Data sheet status . . . . . . . . . . . . . . . . . . . . . . 50
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Disclaimers. . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . 50
16.1
16.2
16.3
16.4
6.5
17
18
Contact information . . . . . . . . . . . . . . . . . . . . 50
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
6.5.1
6.5.2
6.6
6.6.1
disable) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Block DMA transfers (DMA mode 1). . . . . . . . 18
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Sleep mode. . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Break and time-out conditions . . . . . . . . . . . . 19
Programmable baud rate generator . . . . . . . . 19
6.6.1.1
6.6.1.2
6.6.2
6.6.2.1
6.6.2.2
6.7
6.8
6.9
7
Register descriptions . . . . . . . . . . . . . . . . . . . 21
Receiver Holding Register (RHR). . . . . . . . . . 23
Transmit Holding Register (THR) . . . . . . . . . . 23
FIFO Control Register (FCR) . . . . . . . . . . . . . 24
Line Control Register (LCR) . . . . . . . . . . . . . . 25
Line Status Register (LSR). . . . . . . . . . . . . . . 26
Modem Control Register (MCR) . . . . . . . . . . . 27
Modem Status Register (MSR). . . . . . . . . . . . 28
Interrupt Enable Register (IER) . . . . . . . . . . . 29
Interrupt Identification Register (IIR). . . . . . . . 30
Enhanced Feature Register (EFR) . . . . . . . . . 31
Divisor latches (DLL, DLM). . . . . . . . . . . . . . . 31
Transmission Control Register (TCR). . . . . . . 32
Trigger Level Register (TLR). . . . . . . . . . . . . . 32
FIFO Ready register (FIFO Rdy) . . . . . . . . . . 32
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11
7.12
7.13
7.14
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP B.V. 2008.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: salesaddresses@nxp.com
Date of release: 6 October 2008
Document identifier: SC16C754B_4
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