Typewriter User Manual

7- 6 MC68340 USER’S MANUAL MOTOROLA
7.2.3 External Input (SCLK)
This input can be used as the clock input for channel A and/or channel B and is
programmable in the clock-select registers (CSR). When used as the receiver clock,
received data is sampled on the rising edge of the clock. When used as the transmitter
clock, data is output on the falling edge of the clock. If this input is not used, it must be
connected to V
CC
or GND.
7.2.4 Channel A Transmitter Serial Data Output (TxDA)
This signal is the transmitter serial data output for channel A. 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 on the falling edge of the clock source, with the
least significant bit transmitted first.
7.2.5 Channel A Receiver Serial Data Input (RxDA)
This signal is the receiver serial data input for channel A. Data received on this signal is
sampled on the rising edge of the clock source, with the least significant bit received first.
7.2.6 Channel B Transmitter Serial Data Output (TxDB)
This signal is the transmitter serial data output for channel B. 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.
7.2.7 Channel B Receiver Serial Data Input (RxDB)
This signal is the receiver serial data input for channel B. Data on this signal is sampled
on the rising edge of the clock source, with the least significant bit received first.
7.2.8 Channel A Request-To-Send (RTSA)
This active-low output signal is programmable as the channel A request-to-send or as a
dedicated parallel output.
7.2.8.1
RTSA. When used for this function, this signal can be programmed to be
automatically negated and asserted by either the receiver or transmitter. When connected
to the clear-to-send (
CTS≈) input of a transmitter, this signal can be used to control serial
data flow.
7.2.8.2 OP0. When used for this function, this output is controlled by bit 0 in the output
port data register (OP).
7.2.9 Channel B Request-To-Send (RTSB)
This active-low output signal is programmable as the channel B request-to-send or as a
dedicated parallel output.
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc...