Are AI single scan and counter control wait incompatible??

Question

System: LabVIEW RT on 8175 controller with 6052E PXI DAQ card. LabVIEW 6.1 on Win 2000 as the development environment.
I have an application requiring GPS synchronized hardware loop timing for the time critical thread. The loop controls a variety of functions including analog output, simple event counting and analog inputs from several channels. Analog output and counter sub-vis work great in this type of loop.
However, implementing AI single scan in a loop using counter control wait disrupts the loop timing counter. The loop completes only one iteration and then generates a timeout error. The attached vi represents a simple implementation that I think should work, but doesn't. Can anyone tell m
e what I'm doing wrong?? I haven't yet located any specific information on this topic in the discussion forum.
Thanks.
Attachments:
CntrCntrl_AI_LoopTest.vi ‏100 KB

Answer 1

Thanks for your comments. Unfortunately, I can't open your attachment since it's version 7 and I only have version 6.1. But I know what you're saying.
I'd really like to know why the test vi I submitted doesn't work. It crashes my system every time with a timeout error on the counter. Remove the AI single scan node and the loop runs fine. And of course, AI single scan works fine in a different loop using something like "wait till next ms multiple" timing. But when I put the two together they crash.
I didn't mention much about the GPS sync, but you're correct that I'm using a disciplined 10 kHz pulse signal from my GPS timecode generator as the source for the loop control counter. I also have a 6608 counter card with a real time clock synched to I
RIG-B providing timestamps for each loop iteration. Besides AI, other tasks which must occur within the loop are setting an analog output and reading/resetting an event counter. Everything except the AI works fine.
I suppose I can use the same pulse train driving the loop timing for the AI scan clock. I'll give that a try and see what happens. It's just that the AI single scan seemed like an easier implementation.
Maybe someone at NI can tell me why the AI and counter wait aren't working?? Do I have a hardware/driver problem or is this a fundamental incompatibility??
Thanks again.