Product Specs

Table Of Contents
50 UART Universal asynchronous receiver/
transmitter
Page
532
STARTRX
STARTTX
STOPRX
RXD
(signal)
STOPTX
TXD
(signal)
RXTO
RXDRDY
TXDRDY
TXD
50 UART Universal asynchronous receiver/
transmitter
PSELRXD
PSELCTS
PSELRTS
PSELTXD
RXD-5
RXD-4
RXD-3
RXD-2
RXD-1
RXD
Figure 160: UART configuration
50.1 Functional description
Listed here are the main features of UART.
The UART implements support for the following features:
Full-duplex operation
Automatic flow control
Parity checking and generation for the 9
th
data bit
As illustrated in Figure 160: UART configuration on page 532, the UART uses the TXD and RXD registers
directly to transmit and receive data. The UART uses one stop bit.
50.2 Pin configuration
The different signals RXD, CTS (Clear To Send, active low), RTS (Request To Send, active low), and
TXD associated with the UART are mapped to physical pins according to the configuration specified in the
PSELRXD, PSELCTS, PSELRTS, and PSELTXD registers respectively.
If a value of 0xFFFFFFFF is specified in any of these registers, the associated UART signal will not be
connected to any physical pin. The PSELRXD, PSELCTS, PSELRTS, and PSELTXD registers and their
configurations are only used as long as the UART is enabled, and retained only for the duration the device
is in ON mode. PSELRXD, PSELCTS, PSELRTS and PSELTXD must only be configured when the UART is
disabled.
To secure correct signal levels on the pins by the UART when the system is in OFF mode, the pins must be
configured in the GPIO peripheral as described in Pin configuration on page 532.
Only one peripheral can be assigned to drive a particular GPIO pin at a time. Failing to do so may result in
unpredictable behavior.
Table 127: GPIO configuration
UART pin
Direction
Output value
RXD
Input
Not applicable
CTS
Input
Not applicable
RTS
Output
1
TXD
Output
1