Delayed END status on ibrd talking to an EXFO IQ-203

[thechickenshed]

Hi,

My problem started in a VB6 program but has been confirmed using NI-Spy and NI-MAX to talk to an EXFO IQ-203 mainframe and logging the results.

Using NI-MAX I connect to the EXFO and issue a *IDN? command (the actual query is irrelevant to the problem) and hit the QUERY button. This issues a write followed by a read and the result returns immediately as expected - no problem. So then I hit the WRITE button followed by the READ button, causing the write command to be issued followed by a read. The response string is returned immediately, as shown by NI-Spy, but the status doesn't show an END condition for about 30 seconds.

The NI-Spy log shows that the results from the 2 operations, QUERY and WRITE/READ, are identical.

This problem does not occur with any other instrument I have on the bus, but does occur with both EXFO units.

Regards.

[LoganS]

Can you post the spy log(s) that you had?  Are you using asynchronous reads/writes or synchronous reads/writes?  Can you post a spy capture that shows successful reads/writes to other instruments? 

Logan S.

[thechickenshed]

Hi,

Problem solved.  It appears that for these units (EXFO IQ-203) if there is a delay of more than 20mSec between the write and the read then the unit only responds on a timeout. Hence the reason the QUERY command on NI-MAX works but an individual WRITE followed by READ doesn't (obvious really when you think about it but late Friday night isn't the best time!)

Regards.