User guide

12-22
Delays and Timing
There are other modes that you can specify:
• If you include the +delay_mode_unit compile-time option, VCS
ignores the module path delays and changes the delay
specification in all primitive instantiation and continuous
assignment statements to the shortest time precision argument
of all the ‘timescale compiler directives in the source code. (The
default time unit and time precision argument of the ‘timescale
compiler directive is 1 s). In Example 12-11 the ‘timescale
compiler directive has a precision argument of 1 ns. VCS might
use this 1 ns as the delay, but if the module definition is used in
a larger design and there is another ‘timescale compiler
directive in the source code with a finer precision argument, then
VCS uses the finer precision argument.
• If you include the +delay_mode_zero compile-time option, VCS
changes all delay specifications and module path delays to zero.
• If you include none of the compile-time options described in this
section, when, as in Example 12-11, the module path delay does
not equal the distributed delays along the path, VCS uses the
longer of the two.