6100 MPS-B Programming Manual

WRITING APPLICATIONS THAT USE 6100 MPS-B
Closing the Line
Your application process can also define the number of times to
traverse the poll/select list when polling. This is called non-
continuous polling. The polling process terminates when the
traverse poll list count is reached. Note that polling also
terminates whenever a station responds with a message, or an
error is encountered.
An explicit Halt Poll request should be issued by your
application process prior to any WRITE request. Note that this
use of the Halt Poll request gives your application greater
control over the line because an explicit negative acknowledge-
ment (EOT) can be sent by the application in response to the
polled data from a station. However, 6100 MPS-B can be
configured to allow a WRITE request to be processed without a
prior Halt Poll request. This is accomplished by specifying a
value other than zero for the line configuration MPSBPACE
parameter (see "SET CONFIGURATION Request" and "STATION CONTROL
Requests" later in this section).
To select and transmit a message to a station or group of
stations, the application makes a WRITEREAD call containing a
WRITE request. Depending on the modifier included with the
request, several select categories are available. These
categories include select station, select and enable station,
free-format select, and ENVOY-format select.
The READ request and WRITE request are described later in this
section.
CLOSING THE LINE
An application that finishes its use of the line should issue a
call to the CLOSE procedure to correspond to each one of its OPEN
calls. In fact, if an application no longer needs all of its
outstanding OPEN calls, it should close as many as possible, to
make room for other openers. There is a limit of 15 concurrent
OPEN calls for a specific line.
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