Chapter 4 Debugging Your ApplicationNI-488.2 User Manual for Windows 4-4 www.natinst.comTiming ErrorsIf your application fails, but the same calls issued interactively in theInteractive Control utility are successful, your program might be issuingthe NI-488.2 calls too quickly for your device to process and respond tothem. This problem can also result in corrupted or incomplete data. Thisshould only be a problem with older, non-standard GPIB devices.To check if your interactively issued NI-488.2 calls succeed, use theInteractive Control utility. To start the Interactive Control utility, completethe following steps:1. Select Start»Programs»National Instruments NI-488.2»ExploreGPIB to start Measurement & Automation Explorer.2. Expand the Devices and Interfaces directory by clicking on the + nextto the folder.3. Right-click on your GPIB interface and select Interactive Controlfrom the drop-down menu that appears.4. At the command prompt, type NI-488.2 API calls to communicateinteractively with the your instrument. For example, you might useibdev, ibclr, ibwrt, ibrd, and ibonl.To view the online help for Interactive Control, type help at the InteractiveControl command prompt.A well-behaved IEEE 488 device does not experience timing errors. If yourdevice is not well-behaved, you can test for and resolve the timing error bysingle-stepping through your program and inserting finite delays betweeneach NI-488.2 call. One way to do this is to have your device communicateits status whenever possible. Although this method is not possible withmany devices, it is usually the best option. Your delays are controlled by thedevice and your application can adjust itself and work independently onany platform. Other delay mechanisms probably exhibit differing behaviorson different platforms and thus might not eliminate timing errors.
