Channel A Receiver Serial Data Input (Rxda); Channel B Transmitter Serial Data Output (Txdb); Figure 6-2. External And Internal Interface Signals - Motorola MC68306 User Manual

ADDRESS BUS
CONTROL
INTERFACE
TO CPU
DATA
D7–D0
TIRQ
IRQ

Figure 6-2. External and Internal Interface Signals

6.2.4 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.

6.2.5 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.
MOTOROLA
INTERNAL
CONTROL
LOGIC
S
E
R
I
A
L
M
O
D
U
L
E
I
N
T
E
R
N
A
L
B
U
S
MC68306 USER'S MANUAL
X1/CLK
BAUD RATE
GENERATOR
X2
LOGIC
CHANNEL A
FOUR-CHARACTER RxDA
RECEIVE BUFFER
TWO-CHARACTER
TxDA
TRANSMIT BUFFER
16-BIT
COUNTER/TIMER
. . .
INPUT PORT
OUTPUT PORT
CHANNEL B
FOUR-CHARACTER RxDB
RECEIVE BUFFER
TWO-CHARACTER TxDB
TRANSMIT BUFFER
6-5