Introduction

The ModelSim Waveform Comparison feature allows you to compare the current live simulation against a reference dataset (.wlf file), compare two datasets, or compare different parts of the current live simulation. You can view the results of these comparisons in the Wave and List windows and generate a text file of the results in the Main window.

With the Waveform Comparison feature you can:

• specify the signals or regions to be compared,
• define tolerances for timing differences,
• set a start time and end time for the comparison,
• limit the comparison to a specific number of timing differences, and
• step through a succession of timing differences via buttons in the Wave window.

By default, Waveform Comparison computes the timing differences between test signals and reference signals from time zero to the end of the shortest dataset, or to the end of the current live simulation. But you can also specify an optional start time and end time, or you can limit the comparison to a specific number of encountered timing differences. In addition, you can exclude windows of time with -when conditions in either the clock definitions or in the compare add command. The display will indicate intervals of time during which no attempt was made to compute differences.

All waveform differences encountered in the waveform comparison are summarized and listed in the transcript area of the Main window. Waveform differences are also displayed in the Wave and List windows (see Wave window display and List window display). Icons in the toolbar of the Wave window allow you to step forward and backward through successive differences. Or, you can use the Tab and Shift-Tab keys on your keyboard to move to the next or previous difference of a selected signal.

You can also write a list of the differences to a file using the compare info command.

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