User guide

14-20
Negative Timing Checks
• You compiled your design with the +neg_tchk compile-time
option.
• For all $setuphold timing checks the positive setup or hold limit
is greater than the negative setup or hold limit.
• For all $recrem timing checks the positive recovery or removal
limit is greater than the negative recovery or removal limit.
As documented in the OVI SDF3.0 specification:
• TIMINGCHECK statements in the SDF file backannotate timing
checks in the model which match the edge and condition
arguments in the SDF statement.
• If the SDF statement specifies SCOND or CCOND expressions, they
must match the corresponding timestamp_cond or
timecheck_cond in the timing check declaration for
backannotation to occur.
• If there is no SCOND or CCOND expressions in the SDF statement,
all timing checks that otherwise match are backannotated.
How VCS Calculates Delays
This section describes how VCS calculates the delays of the delayed
versions of reference and data signals. It does not describe how you
use negative timing checks; it is supplemental material intended for
users who would like to read more about how negative timing checks
work in VCS.