(Compare) 10: Don't Care Regions

A related function to the masking signals is don’t care regions. Sometimes you may not want to compare certain regions in time on a particular signal. One case would be on a bus signal where the actual data did not matter. If you want the compare function to skip a particular section, then just turn the waveform into a valid region on the reference signal.

To create a don’t care region:

•On the test.pin2 reference signal (not the compare signal), click in the high segment to select it.

dont_care_valid_btn

•Press the VAL button in the button bar at the top of the waveform window. This will change the waveform to a valid waveform.

•Press the Compare button to apply the changes and perform the comparison.

dont_care

•Notice that the difference is no longer flagged, because the don't care segment on the reference signal blocks the compare.