User guide

14-19
Negative Timing Checks
• If the operands in these expressions are the original reference
and data signals and not the delayed versions, then you want VCS
to evaluate these expressions when there are value changes on
the original reference and data signals. To specify evaluating
these expressions when the original reference and data signals
change value, include the +NTC2 compile-time option.
Toggling the Notifier Register
VCS waits for a timing violation to occur on the delayed versions of
the reference and data signals before toggling the notifier register.
Toggling means the following value changes:
• X to 0
• 0 to 1
• 1 to 0
VCS does not change the value of the notifier register if you have
assigned a Z value to it.
SDF Backannotation to Negative Timing Checks
You can backannotate negative setup and hold limits from SDF files
to $setuphold timing checks and negative recovery and removal
limits from SDF files to $recrem timing checks, if the following
conditions are met:
• You included the arguments for the names of the delayed
reference and data signals in the timing checks.