GPIB Timeout Errors (EABO) after Upgrading to Faster Computers

Issue Details

I recently upgraded from an old computer to a faster, newer computer. I may have also upgraded my GPIB board. On the old computer, I was able to communicate with my instrument just fine, but on the new computer I experience EABO timeout errors with the same program.

If I use the Interactive Control (IBIC) to talk to my instrument, everything works fine. The problem only seems to occur when I access my GPIB device programmatically. What might be happening?

Solution

If you are experiencing intermittent timeouts or other communication problems, and you are using an older GPIB instrument, then your device may not be fully compliant with the IEEE 488 specification. This is usually the case if communications worked fine on slower computers, but timeout errors occur on faster computers.

Certain older instruments communicate with the GPIB board in such a way that they indicate they are able to receive data before they have the capability. This behavior makes them appear faster with older computers, but throws off the bus timing with faster computers.

You may be able to resolve the timing problems with one of the following steps:

1. introducing delays between GPIB commands 
2. increasing the timeout value in your LabVIEW VIs
3. changing the GPIB bus timing to the slowest setting in the GPIB Configuration Utility.

The third option is less effective because it only affects the time the GPIB controller waits before valid data is on the bus and the data valid (DAV) line is asserted.

Note: DAV assertion is a step in the GPIB handshaking that occurs each time a byte of information is sent to the device.

If these steps do not fix the timing problem, or you experience other types of sporadic communication problems, you may need to modify your instrument's GPIB interface so it complies with the IEEE 488 specification. See the GPIB Support pages in the Related Links for additional suggestions.