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VXI-USB viMoveInXX errors

When I call viMoveIn using a VXI-USB controller the data returned is sometimes corrupted.
I don't have this error with any other VXI controller including the Prodac USB.
Both 16 and 32 bit transfers are getting errors.
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Message 1 of 19
Could you be more specific?  What are you expecting to see?  What are you actually seeing?  What drivers are you using (NI-VXI, NI-VISA)?  Are you using LabVIEW to communicate or some other ADE?  Have you taken a SPY capture of the function calls that are made?  What OS are you working on?  Are the function calls actually erroring out or are they "successful" in that no error codes are returned?  Have you done any other trouble shooting other than replacing the VXI-USB with a USB module from Prodac?
Please let us know.
Logan S.
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Message 2 of 19

Turns out that the VXI-USB bus timing is slightly different than all the other controllers and exposed a bug in the VXI card I was troubleshooting.


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I am having a similar problem.  How did you discover that the bus timing was the issue? 

Best regards,


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Message 4 of 19

Hi K. Coggins,

You mentioned that you are having a similar issue.  Does this mean that you are also receiving corrupted data when using a VXI-USB device?  Does this also occur when calling viMoveIn?  Have you tried any of the suggestions Logan S. made above?  The more information you can give me about the errors you are having, as well as the hardware and software you are using, would be extremely helpful.

For more information on VXI bus timing, take a look at the following links:

http://digital.ni.com/public.nsf/allkb/B7E440E8BD0D50DC862571B5004E6947?OpenDocument  http://zone.ni.com/devzone/cda/tut/p/id/4365

I hope this helps a little.  Give me as much information as possible, and I will look into the issue a little further.

Lauren L.

Message Edited by Lauren L on 10-22-2007 08:36 AM

Applications Engineering
National Instruments
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Message 5 of 19

Hi Lauren,

The issue K. Coggins is referring to involves ViIn16 calls returning bad data. We have a HP xw4400 PC running XP and NI-4.0 software. The chassis is a Racal 1261b with a NI VXI-USB slot 0 controller. The instrument having issue is an Ascor switch matrix. This instrument uses a controller card in the VXI chassis to control relays in a separate card cage (Not VXI). The secondary card cage consists of 13 slots which are all populated. The bad data problem does not occur when only 11 slots are populated. I'm suspecting that there is a memory management issue here but do not know how to proceed.

Ni-Spy reports no errors. This instrument does not have any problems when running with a MXI-2 controller.

Any suggestions would be great.


M. Beene

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Message 6 of 19

Hi M. Beene,

What kind of 'bad data' are you getting specifically?  Is it providing you with unexpected data, or is it skipping data points?  The more information you can give me, the better chance I will have at figuring out the issue.

USB devices do not have the same transfer rate as a MXI connection, so it sounds like the most likely possibility is that it is getting backed-up when you have so many relays in the cage.  The USB device has a max transfer rate of 32 Mb/s, while MXI-2 has a max transfer rate of 38 Mb/s.  As far as I can see this is the most likely cause of the issue you are seeing.  Is it necessary that you use a USB device, or could you set up your system using the MXI-2 cable you tested with? 

I hope this helps a little, but if you need more specific information, give me a little more information on the data you have been receiving.


Lauren L.

Applications Engineering
National Instruments
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Message 7 of 19
Each relay is controlled by a single bit in a register. The registers are accessed by ViIn16/ViOut16 calls. The test controls one relay at a time. Each time a bit is set/cleared the register is read following the write and the data compared to determine if the relay was set correctly. The data clearly shows that the correct bit is being set properly but that other bits are being corrupted (ie. the are indicating that other relays changed state).
The use of the USB controller was decided by the customer. I have suggested that they change to the MXI-2 controller and they are considering it. I was just hoping to understand what the differences were between the controllers and how this is affecting the driver.
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Message 8 of 19

Hi Mark,

Since I do not have all the details of the application, my best recommendation is to take a look at the data sheet for each of the products.  Because the system operates correctly when using a MXI-2 connector, it certainly makes it seem that the issue lies in the performance specs for each device.

VXI-USB: http://www.ni.com/pdf/products/us/20044601201101dlr.pdf

VXI-MXI-2: http://www.ni.com/pdf/products/us/2vxi694.pdf

I will continue to look into this, but at the moment, my best suggestion is to take a look at these.


Lauren L.

Applications Engineering
National Instruments
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Message 9 of 19


The customer has decided to move everything to MXI-2 so this will be a non-issue. No point in you spending any more time on it.



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Message 10 of 19