AN00010.TXT

Advanced Communication Board Developer's Toolkit 1995
    

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Subject: External Synchronous Communications.

Synchronous Communications is implemented in many different protocols. Some
synchronous protocols rely on a character synchronization to be performed
by a external device. The SCC can be programmed for external sync mode,
however, the ACB adapter will need to be modified to utilize external sync.
The modification consist of a single jumper from the /SYNC pin on the SCC
to the source of the sync signal proved by the synchronizing device. If
the interface that is being communicated with does not provide a sync signal,
the /SYNC pin may be tied to the RTS signal. With this configuration, the
SCC will act as a shift register and all bits will be clocked into the
RX FIFO on an active clock edge. Please note that no character synchronization
is performed by the SCC. With some obscure protocols, this method of
communications is the only option of receiving the data. The SCC has been 
used with protocols that only provide a clock signal when the data is
valid. This protocol and external sync application are not normally supported
by the SCC, but if the data rate is at a moderate level, the system may be 
able to communicate with these obscure protocols. Most external
synchronous communications protocols vary in synchronizing signals and
methods. If further assistance is needed, please contact the technical 
support at the numbers listed in the README.TXT file located in the root 
directory of this diskette.