The major elements used in full-duplex operation
are shown in Figure 21-2 and include:
- A transmitter (TX) and the
major registers (upper half of Figure 21-2):
- SCITXBUF —
transmitter data buffer register. Contains data (loaded by the CPU)
to be transmitted
- TXSHF register —
transmitter shift register. Accepts data from register SCITXBUF and
shifts data onto the SCITXD pin, one bit at a time
- A receiver (RX) and the major
registers (lower half of Figure 21-2):
- RXSHF register —
receiver shift register. Shifts data in from SCIRXD pin, one bit at
a time
- SCIRXBUF — receiver
data buffer register. Contains data to be read by the CPU. Data from
a remote processor is loaded into register RXSHF and then into
registers SCIRXBUF and SCIRXEMU
- A programmable baud
generator
- Control and status
registers
The SCI receiver and transmitter can operate either independently or simultaneously.