ModelSim SE User's Manual - Electrical and Computer Engineering

UM-276 9 - Waveform analysis
Specifying the comparison method
ModelSim SE User’s Manual
The Waveform Compare feature provides two comparison methods:
Continuous comparison – Test signals ar e compared to reference signals at each
transition of the reference. Timing differences between the test and reference signals are
shown with rectangular red markers in the Wave window and yellow markers in the List
window.
Clocked comparisons – Signals are compared only at or just after an edge on some signal.
In this mode, you define one or more clocks. The test signal is compared to a reference
signal and both are sampled relative to the defined clock. The clock can be defined as the
rising or falling edge (or either edge) of a particular signal plus a user-specified delay.
The design need not have any events occurring at the specified clock time. Differences
between test signals and the clock are highlighted with red diamonds in the Wave
window.
To specify the comparison method, select Tools > Waveform Compare > Options and
select the Comparison Method tab.
Continuous comparison
Continuous comparisons are the default. You have the option of specifying leading and
trailing tolerances and a when expression that must evaluate to "true" or 1 at the signal edge
for the comparison to become effective. See "Add Signal Options dialog" (GR-244) for more
details on this dialog.