Freescale Semiconductor, Inc.
2.13 SERIAL MODULE SIGNALS
The following signals are used by the serial module for data and clock signals. See
Section 7 Serial Module for more information on these signals.
2.13.1 Serial Crystal Oscillator (X2, X1)
These pins furnish the connection to a crystal or external clock, which must be supplied
when using the baud rate generator. An external clock is connected to the X1 pin; X2 is
left floating.
2.13.2 Serial External Clock Input (SCLK)
This input can be used as the external clock input for channel A or channel B, bypassing
the baud rate generator.
2.13.3 Receive Data (RxDA, RxDB)
These signals are the receiver serial data input for each channel. Data received on this
signal is sampled on the rising edge of the clock source, with the least significant bit
received first.
2.13.4 Transmit Data (TxDA, TxDB)
These signals are the transmitter serial data output for each channel. The output is held
high ('mark' condition) when the transmitter is disabled, idle, or operating in the local
loopback mode. Data is shifted out on this signal at the falling edge of the clock source,
with the least significant bit transmitted first.
2.13.5 Clear to Send (CTSA, CTSB)
These active-low signals can be programmed as the clear-to-send inputs for each
channel.
2.13.6 Request to Send (RTSA, RTSB)
These active-low signals can be programmed as request-to-send outputs or used as
discrete outputs.
RTSB, RTSA
When used for this function, these signals function as the request-to-send outputs.
OP1, OP0
When used for this function, these outputs are controlled by the value of bit 1 and bit 0,
respectively, in the output port data registers.
2.13.7 Transmitter Ready (T≈RDYA)
This active-low output can be programmed as the channel A transmitter ready status
indicator or used as a discrete output.
MOTOROLA
MC68340 USER’S MANUAL
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