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Table 62. I/O Description
Signal
I/O
Description
RX
I
Serial data input.
TX
O
Serial data output.
CTS
I
Clear to send.
Active-low modem status signal. Reading bit 4 of the modem status
register checks the condition of CTS. Reading bit 0 of that register
checks a change of state of CTS since the last read of the modem
status register. CTS is used in auto-CTS mode to control the
transmitter.
RTS
O
Request to send.
When active (low), the module is ready to receive data. Setting modem
control register bit 1 activates RTS. It becomes inactive as a result of a
module reset, loopback mode, or by clearing the MCR[1]. In auto-RTS
mode, it becomes inactive as a result of the receiver threshold logic.
DSR
I
Data set ready.
Active-low modem status signal. Reading bit 5 of the modem status
register checks the condition of DSR. Reading bit 1 of that register
checks a change of state of DSR since the last read of the modem
status register.
DTR
O
Data terminal ready.
Active-low modem control signal. Reading bit 0 of the modem control
register checks the condition of DTR.
DCD
I
Data carrier detect.
Active-low modem status signal. The condition of DCD is checked by
reading bit 7 of the modem status register, and any change in its state
can be detected by reading bit 3 of that register.
RI
I
Reading indicator.
Active-low modem status signal. The condition of RI is checked by
reading bit 6 of the modem status register, and any change in its state
is detected by reading bit 2 of that register.
SPRU760B
UART/MODEM Signals (UART 1,2,3)
UARTs
Reset
Unknown
1
Unknown
1
Unknown
1
Unknown
Unknown
Serial Interfaces
145
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