User guide

7-9
VCD and VPD File Utilities
-when expression
Reports differences only when the given when expression is true.
Initially this expression can consist only of scalar signals,
combined via and, or, xor, xnor, and not operators and employ
parentheses to group these expressions. You must fully specify
the complete path (from root) for all signals used in expressions.
-synch signal
Checks for differences only when the given signal changes value.
In effect, the given signal is a "clock" for value change diffing,
where diffs are only checked for on transitions (any) of this signal.
-synch0 signal
As -sync (above) except that it checks for diffs when the given
signal transitions to ’0’.
-synch1
As -sync (above) except that it checks for diffs only when the
given signal transitions to ’1’.
Note:
The -max, -min and -when options must all be true in order for
vcdiff to report a value change difference.