USART Pin description

The USART receive, transmit, and control signals are movable functions and are assigned to external pins through the switch matrix.

See SWM Connect an internal signal to a package pin to assign the USART functions to pins on the LPC81x package.

Table 1. USART USART pin description
Function Direction Pin Description SWM register Reference
U0_TXD O any

Transmitter output for USART0. Serial transmit data.

PINASSIGN0 SWM registerName = PINASSIGN0 addressOffset = 0x000
U0_RXD I any

Receiver input for USART0. Serial receive data.

PINASSIGN0 SWM registerName = PINASSIGN0 addressOffset = 0x000
U0_RTS O any

Request To Send output for USART0. Active low signal indicates that the USART0 is ready to receive data. This signal supports inter-processor communication through the use of hardware flow control. This feature is active when the USART RTS signal is configured to appear on a device pin.

PINASSIGN0 SWM registerName = PINASSIGN0 addressOffset = 0x000
U0_CTS I any

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).

PINASSIGN0 SWM registerName = PINASSIGN0 addressOffset = 0x000
U0_SCLK I/O any

Serial clock input/output for USART0 in synchronous mode. Clock input or output in synchronous mode.

PINASSIGN1 SWM registerName = PINASSIGN1 addressOffset = 0x004
U1_TXD O any

Transmitter output for USART1. Serial transmit data.

PINASSIGN1 SWM registerName = PINASSIGN1 addressOffset = 0x004
U1_RXD I any

Receiver input for USART1.

PINASSIGN1 SWM registerName = PINASSIGN1 addressOffset = 0x004
U1_RTS O any Request To Send output for USART1. PINASSIGN1 SWM registerName = PINASSIGN1 addressOffset = 0x004
U1_CTS I any Clear To Send input for USART1. PINASSIGN2 SWM registerName = PINASSIGN2 addressOffset = 0x008
U1_SCLK I/O any Serial clock input/output for USART1 in synchronous mode. PINASSIGN2 SWM registerName = PINASSIGN2 addressOffset = 0x008
U2_TXD O any

Transmitter output for USART2. Serial transmit data.

PINASSIGN2 SWM registerName = PINASSIGN2 addressOffset = 0x008
U2_RXD I any

Receiver input for USART2.

PINASSIGN2 SWM registerName = PINASSIGN2 addressOffset = 0x008
U2_RTS O any Request To Send output for USART2. PINASSIGN3 SWM registerName = PINASSIGN3 addressOffset = 0x00C
U2_CTS I any Clear To Send input for USART2. PINASSIGN3 SWM registerName = PINASSIGN3 addressOffset = 0x00C
U2_SCLK I/O any Serial clock input/output for USART2 in synchronous mode. PINASSIGN3 SWM registerName = PINASSIGN3 addressOffset = 0x00C

-->