HELP
An object that waits for a service request
from a specified HP-IB interface.  This
feature is available in HP VEE-Test only.

USE
Use Wait For SRQ to trap and process an HP-IB
service request.  Wait For SRQ must be armed
(by activating the sequence input pin) before
it can detect each service request.

The interface select code specified in
Wait For SRQ must correspond to an installed
HP-IB interface; the first HP-IB interface is
usually at select code 7.

Be certain that you have properly
configured at least one instrument to
generate an SRQ to avoid waiting
indefinitely.

LOCATION
I/O ==> Advanced HP-IB ==> Wait For SRQ

NOTES
You may wish to use Serial Poll to determine
which instrument connected to the HP-IB
interface generated the SRQ.

Typical use of Wait For SRQ is to have it
at the beginning of a separate thread.

The thread with SRQ is idle until a
service request is received.  No other
threads or subthreads execute as long as the
thread hosted by Wait For SRQ is completed.

Wait for SRQ "sleeps" after it has been
activated and before it has detected an SRQ
event.  This means that other objects on any
other thread that are able to operate, can do
so until an SRQ is detected.

If continually rearmed, Wait For SRQ
continues to operate if the device that
asserted the SRQ does not drop the line.
This is usually accomplished by a serial poll
(SPOLL) of said device during the execution
of the subthread, since polling the asserting
device generally clears the SRQ.

When more than one Wait For SRQ object is
active at the same time, it is not which one
first detects the SRQ event.  However, when
each Wait For SRQ looks for a unique device
(or set of devices) the subthread logic which
polls that device (or devices) determines
whether or not to service the SRQ.

If a second SRQ is executed while a
previous subthread hosted by a Wait For SRQ,
any service for that SRQ is postponed until
the first subthread completes.  

SEE ALSO
Advanced HP-IB, Bus I/O Monitor, and 
HP-IB Serial Poll.
