some common questions from a beginner

[jey]

1.whenever i use ibwait with mask bits ATN ,DCAS etc through interactive control, EARG(invalid argument) error is showing up.why?

2.what are the compatibility issues bet IEEE 488(.1),IEEE 488.2 and HPIB.Could i use IEEE488.2 calls like DevClear,findListeners ,remoteEnable etc over a NI PCI-GPIB bus having instruments with different versions of IEEE488?.

3.what is the difference between between DevClear call and
any device specific calls like preset or clear?

4.Using GPIB-ENET requires any change in the application software which has been developed using general GPIB 488 and 488.2 commands ;not VISA calls?

5.what exactly will be the form of Read data(ASCII bytes)?
Does every call will be having unique format with different delimiters between tokens?Do i need to know the the output format of every read command i make?

Regards,
Jay

[ScottieB]

Jey,

1. ATN and DCAS can only be "IBWAIT-ed" for on a board-level descriptor opened with IBFIND. If you are using it with a device level descriptor opened with IBDEV, you will get EARG.

2. IEEE 488.2 is a superset of IEEE 488.1. The details of all the enhancements of 488.2 are too much to go into here, but you can probably use all of the calls you mention without problems on IEEE 488.1 and HPIB devices. For example, DevClear will send SDC (selected device clear) to the address you specify. All 488.1 instruments should understand SDC. Exactly what they clear, however, is left up to the device manufacturer.

3. This depends on the device. IEEE 488.2 specifies what DevClear should do if the device is 488.2-compliant (such as clear the output buffer and some other things) but I have no idea what your device might do with its own "clear" command.

4. No, using a GPIB-ENET versus a PCI-GPIB does not require any application software change (neither does using VISA).

5. Data returned from IBRD() or Receive() will be a number of bytes. Each instrument may return different data formats for different commands. Some instruments may return binary data to be interpretted as 16 bit numbers or something similar. Most instruments will return plain ASCII text. You do need to know your instrument in order to properly interpret this data.

Hope this helps.

Scott Brown
GPIB Software
National Instruments

[jey]

Thanks ScottieB.I 've got some useful info from your answers .