UM10850
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User manual
Rev. 2.4 — 13 September 2016
260 of 464
NXP Semiconductors
UM10850
Chapter 21: LPC5410x USARTs (USART0/1/2/3)
21.4 Pin description
The USART receive, transmit, and control signals are movable functions and are
assigned to external pins through via IOCON.
See the IOCON description (
) to assign the USART functions to pins on the
device package. Recommended IOCON settings are shown in
.
Table 304. USART pin description
Function
Direction
Description
U0_TXD
O
Transmitter output for USART0. Serial transmit data.
U0_RXD
I
Receiver input for USART0. Serial receive data.
U0_RTS
O
Request To Send output for USART0. This signal supports inter-processor communication through
the use of hardware flow control. This signal can also be configured to act as an output enable for
an external RS-485 transceiver. RTS is active when the USART RTS signal is configured to appear
on a device pin.
U0_CTS
I
Clear To Send input for USART0. Active low signal indicates that the external device that is in
communication with the USART is ready to accept data. This feature is active when enabled by the
CTSEn bit in CFG register and when configured to appear on a device pin. When deasserted
(high) by the external device, the USART will complete transmitting any character already in
progress, then stop until CTS is again asserted (low).
U0_SCLK
I/O
Serial clock input/output for USART0 in synchronous mode. Clock input or output in synchronous
mode.
U1_TXD
O
Transmitter output for USART1. Serial transmit data.
U1_RXD
I
Receiver input for USART1.
U1_RTS
O
Request To Send output for USART1.
U1_CTS
I
Clear To Send input for USART1.
U1_SCLK
I/O
Serial clock input/output for USART1 in synchronous mode.
U2_TXD
O
Transmitter output for USART2. Serial transmit data.
U2_RXD
I
Receiver input for USART2.
U2_RTS
O
Request To Send output for USART2.
U2_CTS
I
Clear To Send input for USART2.
U2_SCLK
I/O
Serial clock input/output for USART2 in synchronous mode.
U3_TXD
O
Transmitter output for USART3. Serial transmit data.
U3_RXD
I
Receiver input for USART3.
U3_SCLK
I/O
Serial clock input/output for USART3 in synchronous mode.
Table 305: Suggested USART pin settings
IOCON
bit(s)
Type D pin
Type A pin
Type I pin
10
OD: Set to 0 unless open-drain output is desired.
Same as type D.
I2CFILTER: Set to 1.
9
SLEW: Generally set to 0.
Not used, set to 0.
I2CDRIVE: Set to 0.
8
FILTEROFF: Generally set to 1.
Same as type D.
Same as type D.
7
DIGIMODE: Set to 1.
Same as type D.
Same as type D.
6
INVERT: Set to 0.
Same as type D.
Same as type D.
5
Not used, set to 0.
Not used, set to 0.
I2CSLEW: Set to 1.