j_osh_o wrote:
I want to listen for unsolicited messages while I make a write. I am using LabVIEW7.0. Is this possible with GPIB? When I set up VISA events and wait for SRQ, I find that I cannot issue a VISA write even if the write is in a different for loop (different thread). My understanding is that the SRQ is a common wire in the GPIB cable, and that it should theoretically be possible to have the controller write data to a listener and keep an eye on the SRQ line at the same time.
This is not possible. The Wait for SRQ locks the bus until tmo or SRQ. Similarily, the Wait for Event locks the entire bus. The GPIB standard was developed with the principle that interdevice timing and syncronization could be achieved for any bus and that the state of the several devices on a bus is relatable.
In you case you seem to have an intrument that does not really follow this paradigm. Its unsolicited messages make it hog the bus and they do get in the way of traffic to other instruments.
Yet, there is a solution. Just like in any traffic system, if there is a need for increased capacity you build another lane. Hang a second GPIB bus dedicated to your "HOV" instrument. There is almost no limit to the number of GPIB busses you can support from LabVIEW.
"Should be" isn't "Is" -Jay
