6100 MPS-B Programming Manual

INTRODUCTION TO 6100 MPS-B
Station Types
A file system WRITEREAD procedure with a task request formatted
in the buffer is used for communication on the link. The
response to the request is returned in the buffer. Your
application process is responsible for providing the appropriate
request and for correctly interpreting the response to the
request.
The rules for interaction between the stations on the link are
determined by several factors, including station types, message
formats, and line configuration options. The rest of this
section discusses these topics.
NOTE
Differences between the Burroughs Multipoint protocol, ADM-2
Multipoint protocol, and NCR Multipoint protocol are
indicated in the text.
Station Types
6100 MPS-B, running in the LIU, is designated as the supervisory
station. The supervisory station has sole responsibility for the
successful transfer of messages. It may assume "master" status
to deliver a message to one or more tributary "slave" stations
(selection), or it may give master status to one of the tributary
stations, by assuming slave status, to accept data (polling).
Selection
There are two basic forms of selection--Select with response and
Fast Select.
Select with Response. 6100 MPS-B may select a single tributary
station by sending a selection sequence terminated with ENQ. The
selected tributary station may respond with an optional prefix
followed by ACK if it is ready to receive data, or with an
optional prefix followed by NAK if it is not ready to receive
data.
If 6100 MPS-B receives NAK, an invalid response, or no response,
the select operation is retried repeatedly until an ACK, a valid
response, or the retry count specified for the line is exhausted.
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