Why should intensive use of VXI bus by one instrument cause I/O errors by others?

[Believer]

We have a MXI-2 controlled system which has a Digitizer card and an AWG (arb waveform generator) card.

When the Digitizer is not acquiring, then the AWG card works perfectly without error.

However as soon as the digitizer starts to acquire (and so much bus activity) then the other card (or any other card) cannot do a memory operation without failing with IO error 0xBFFF003E. Typically it's a ViMoveIn or ViMoveOut (the width of 8, 16, or 32 makes no difference) that causes the error.

If I run Spy in the background, the failures still occur, but they are not as frequent.

I'm surprised that VISA does not handle the apparent conflict. Is there anything we can do to avoid this?

Thanks,

Ronnie

[Believer]

Well, after experimenting with various settings I discovered that I had to Disable DMA on the MXI-2 Controller (the PCI tab).

This solves the problem but I'm not sure why.

Any illumination on the issue would be appreciated.

[Chris_R.]

Hi Ronnie,

This is a known issue with rev A of the MITE chip on the PCI-MXI-2 card when doing DMA transfers. This issue is typically seen with faster PCs and has to do with the retry behavior of the rev A chip.  The best workaround is exactly what you did: disable DMA and use programmable I/O instead.

Please let me know if you have any questions or need any clarification.  Have a great day!

Message Edited by Chris_R. on 06-06-2006 04:53 PM