This section describes the
UART/RS-485/IrDA/CIR external connections (environment).
Table 12-69 lists the UART interface input/output (I/O) signals.
Table 12-69 UART I/O Signals
Module Pin Name |
I/O(1) |
Description |
RX |
I |
Serial data input |
TX |
O |
Serial data output(2) |
CTS |
I |
Clear to send(3) |
RTS |
O |
Request to send(4) |
DCD |
I |
Data Carrier Detect(5) |
DSR |
I |
Data Set Ready(6) |
DTR |
O |
Data Terminal Ready(7) |
RIN |
I |
Ring Indicator(8) |
(1) I = Input; O = Output
(2) Because this pin is active high in IrDA mode and
the output is muxed, this pin is set to low on reset (when the
UART_MDR1[2-0] bit field is set to 0x7) and takes the defined inactive level
of that signal corresponding to when and how the UART_MDR1 register is
programmed; that is, the output is 1 (inactive for UART modem modes) and 0
(inactive for IrDA modes).
(3) Active-low modem status signal. Reading the
UART_MSR[4] NCTS_STS bit checks the condition of CTS. Reading the
UART_MSR[0] CTS_STS bit checks a change of state of CTS since the last read
of the modem status register. The auto-CTS mode uses CTS to control the
transmitter.
(4) When active (low), the module is ready to receive
data. Setting the UART_MCR[1] RTS bit activates RTS signal, which becomes
inactive as the result of a module reset, loopback mode, or clearing the
UART_MCR[1] RTS bit. In auto-RTS mode, RTS signal becomes inactive as a
result of the receiver threshold logic.
(5) Active-low modem status signal. The condition of
DCD can be checked by reading the UART_MSR[7] NCD_STS bit. Any change in its
state can be detected by reading the UART_MSR[3] DCD_STS bit.
(6) Active-low modem status signal. Reading the
UART_MSR[5] NDSR_STS bit checks the condition of DSR. Reading the
UART_MSR[1] DSR_STS bit checks a change of state of DSR since the last read
of the UART_MSR register.
(7) When active (low), this signal informs the modem
that the module is ready to communicate. It is activated by setting the
UART_MCR[0] DTR bit.
(8) Active-low modem status signal. The condition of
RIN can be checked by reading the UART_MSR[6] NRI_STS bit. Any change in its
state can be detected by reading the UART_MSR[2] RI_STS bit.
Table 12-70 lists the RS-485 interface input/output (I/O) signals.
Table 12-70 UART I/O Signals (RS-485
Mode)
Module Pin |
I/O(1) |
Description |
RX |
I |
Serial data input |
TX |
O |
Serial data output |
DIR |
O |
RS-485 Direction |
(1) I = Input; O = Output
Table 12-71 lists the IrDA interface I/O signals.
Table 12-71 UART I/O Signals (IrDA
Mode)
Module Pin |
I/O(1) |
Description |
RX |
I |
Serial data input |
TX |
O |
Serial data output in CIR and IrDA modes (SIR,
MIR, and FIR).(2) |
SD |
O |
SD mode is used to configure the
transceivers.(3) |
(1) I = Input; O = Output
(2) In other modes, this pin is set to the reset value
(inactive state).
(3) The SD pinout (see UART_ACREG[6] SD_MOD bit).