6100 MPS-B Programming Manual

WRITING APPLICATIONS THAT USE 6100 MPS-B
Cancelling a Request
There are several requests that can assist the application in
dealing with errors:
• The STATION CONTROL request lets you change the retry count
for the line. Increasing the retry count can reduce the
incidence of error by giving the station more chances to
succeed in each operation.
• The FETCH STATISTICS request retrieves line quality
information and other data useful for evaluating problems.
• The CONTROL request can be used to issue a Send EOT to reset
the line following a READ error.
NOTE
An application can cause error behavior by including in its
output buffer a control character that shouldn’t be there.
For example, if a message contains an embedded ETX
character, that character will cause repeated LRC errors.
Once the repeat count is exhausted, the request completes
with an error.
If the application keeps getting errors but nothing seems
to be wrong with the line, use CMI to trace frames and look
for embedded control characters. Trace the frames as they
leave the I/O process, not as they reach the line; a trace
of the line captures only the beginning and end of the
text.
CANCELLING A REQUEST
The CP6100 I/O Process supports the GUARDIAN CANCEL procedure
call, but 6100 MPS-B does not support a request to cancel a
specified earlier request.
Do not use the GUARDIAN CANCEL or CANCELREQ procedure calls with
6100 MPS-B.
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