ZiLOG Z-80 SIB User Manual page 38

If
external sync has been specified
in the
mode instruction,
a
"one"
applied
to the
syndet
(input)
for at
least one RxC-
cycle will synchronize the USART.
Parity
and
overrun errors
are
treated
the same
in
the
synchronous
as in the
asynchronous
mode.
Framing errors do
not apply
in
the synchronous format.
The
processor may command
the
receiver
to
enter the hunt mode
with
a
command instruction which sets enable hunt
(EH) if
synchronization
is
lost.
TRANS^5IT/RECEIVER FORMAT SYNCHRONOUS MODE
CPU BYTES
(5-8
bits/char)
Data Characters
Assembled Serial Data Output
(TxD)
4
Sync
Char
1
Sync
Char
2
Data Characters
{\
TRANSMIT FORMAT
Serial Data Input
(RxD)
Sync
Char
1
Sync
Char
2
CPU BYTES
(5-8
bits/char)
Data Characters
AS
Data Characters
\s
RECEIVE FORMAT
30