6100 MPS-B Programming Manual

WRITING APPLICATIONS THAT USE 6100 MPS-B
Request Queuing
REQUEST QUEUING
Queued I/O reqeusts are not permitted by 6100 MPS-B. However, at
any given time, 6100 MPS-B can retain one READ and one WRITE
request. Note that if your application process issues a WRITE
request when a READ request is in progress, control over the
possibility of receiving a message acknowledgement is diminished.
In this case, if a message was received from a station, the next
WRITE request will send an ACK to the station prior to sending
its own data transmission.
To maintain control over the line--that is, to be able to send an
ACK or NAK--the application process should issue only one I/O
request at a time. A Halt Poll request can be used to terminate
a READ request before issuing a WRITE request.
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