User guide

21-50
OpenVera Native Testbench
By default, VCS does not create automatic bins for ’X’ or ’Z’ values
of a coverage point. For example, if a coverage point is a 4 bit
bit-vector and the auto_bin_max attribute is set to 64 (default), then
by default the total number of possible bins for the coverage point is
16 (2
4
). On the other hand, if VCS coverage is sampling the
coverage point when it has ’X’ or ’Z’ values (auto_bin_include_xz
attribute of the sample is set to ON or 1), then the total number of
possible bins for the 4 bit bit-vector is 64 (MIN(auto_bin_max
attribute, 4
4
)). Finally, if the auto_bin_max attribute is set to 5, then
the total number of possible bins for the 4 bit bit-vector is 5.
VCS computes the coverage number of a cross as the number of
bins (of that cross) with the at_least number of hits divided by the
total number of bins for that cross (multiplied by 100). By default, the
number of possible bins for a cross is the sum of the user-defined
bins and the number of possible automatically generated bins for
that cross. The number of possible automatically generated bins is
the product of the number of possible bins for each of the samples
being crossed.
Reporting and Querying Coverage Numbers
Testbench coverage is reported in the coverage HTML and text
reports (see “Unified Coverage Reporting” on page 21-53 for
details). The reports also include detailed information for each
coverage group as well as the samples and crosses of each group.
You can also query for the testbench coverage during the VCS run.
This allows you to react to the coverage statistics dynamically (for
example, stop the VCS run when the testbench achieves a particular
coverage).