User`s guide

80 Agilent VISA User’s Guide

3 Programming with VISA

Trapping Errors

This section provides guidelines for trapping errors,

including:

• Trapping Errors

• Exception Events

Trapping Errors

The sample programs in this guide show specific VISA

functionality and do not include error trapping. Error

trapping, however, is good programming practice and is

recommended in all your VISA application programs. To trap

VISA errors you must check for VI_SUCCESS after each

VISA function call.

If you want to ignore WARNINGS, you can test to see if err

is less than (<) VI_SUCCESS. Since WARNINGS are greater

than VI_SUCCESS and ERRORS are less than VI_SUCCESS,

err_handler would only be called when the function returns

an ERROR. For example:

if(err < VI_SUCCESS) err_handler (vi, err);

Sample: Checking for VI_SUCCESS

This sample illustrates checking for VI_SUCCESS. If

VI_SUCCESS is not returned, an error handler (written by

the programmer) is called. This must be done with each

VISA function call.

ViStatus err;

err=viPrintf(vi, "*RST\n");

if (err < VI_SUCCESS) err_handler(vi, err);