Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Fri, 07 Sep 2007 09:37:33 -0500

Heinrich du Toit wrote:

Why is CreateUser called twice with different asynUser's ??
I've seen this dual-called behaviour of DrvUser before in my other
drivers. This time I would like to figure it out :)

An asynUser is a structure that Asyn uses to hold information about an
individual I/O transaction (the name is unfortunate, it's not very
descriptive of what it really does). Asyn needs one of these for each
independent transaction that could conceivably be active at once â
typically that will be one or possibly two per record as Mark Rivers
described, but that choice is completely up to whatever is connecting to
the port. Your port code should be written to accept any number of
asynUser objects presented to it; the Asyn code provides the locking and
queuing that ensures only one of them can be active at any time.
- Andrew
--
When a distinguished but elderly scientist states that something is
possible, he is almost certainly right.  When he states that something
is impossible, he is very probably wrong.  -- Arthur C. Clarke

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System