Z-World OP7100, User Manual

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OP7100 42 s Hardware
Z180 Serial Ports
The
Z180
’s two independent, full-duplex asynchronous serial channels
have a separate baud-rate generator for each channel. The baud rate can be
divided down from the microprocessor clock, or from an external clock for
either or both channels.
The serial ports have a multiprocessor communications feature. When
enabled, this feature adds an extra bit to the transmitted character (where
the parity bit would normally go). Receiving
Z180
s can be programmed to
ignore all received characters except those with the extra multiprocessing
bits enabled. This provides a
1
-byte attention message that can be used to
wake up a processor without the processor having to intelligently monitor
all traffic on a shared communications link.
The block diagram in Figure 3-21 shows Serial Channel 0. Serial Chan-
nel 1 is similar, but control lines for
/RTS
and
/DCD
do not exist. The five
unshaded registers shown in Figure 3-21 are directly accessible as internal
registers.
Figure 3-21. Z180 Serial Channel 0
Microprocessor Internal Bus
RDR0 TDR0
TSR0 RXA0 TXA0
Shift Register Out Shift Register In
Baud-Rate
Generator
CKA0
CNTLA0
STAT0
CNTLB0
/RTS0
/CTS0
/DCD0
RSR0