6100 MPS-B Programming Manual

WRITING APPLICATIONS THAT USE 6100 MPS-B
Setting Line Parameters
In the call to the OPEN procedure, you specify several important
parameters. In the flags word, there are bits to indicate shared
or exclusive access to the line; if more than one process pair
will have the line open concurrently, or if one process pair will
open the line more than once, you must specify shared access.
There are bits to specify read/write, read-only, or write-only
access to the line; for 6100 MPS-B, you must specify read/write
access. The bits used to specify wait/nowait I/O may be set to
zero (wait I/O) or to a value 1 through 15 (nowait I/O) although
6100 MPS-B does not support queued I/O requests (see "Request
Queuing").
A parameter separate from the flags is sync depth; it determines
whether, if the primary CP6100 process goes down, GUARDIAN routes
a new request automatically to the backup process. (The
alternative is to reject the request and have the application
retry it.) You should specify a sync depth of zero with CP6100.
SETTING LINE PARAMETERS
Most applications don’t have to set the line configuration
parameters. Rather, you define the parameters for system
generation (SYSGEN), and include AUTOCONF among them. The effect
of AUTOCONF is to download the line configuration from the host
on the first call to OPEN after 6100 MPS-B is downloaded. If at
some point all openers close the line, configuration occurs again
on the next call to OPEN.
If you haven’t specified AUTOCONF, or if an application requires
a change in the line configuration, the application makes a
WRITEREAD call containing a SET CONFIGURATION request. A subset
of line configuration parameter values (Connect Timeout, Timeout,
Poll Interval, Retries, and Pace) can be changed using a STATION
CONTROL Alter Line request. The values supplied in these
requests need not match those in the SYSGEN configuration file.
(The SYSGEN configuration file should reflect the configuration
you use most frequently.)
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