User guide

12-13
Delays and Timing
Figure 12-5 shows the waveforms for the input and output ports for
an instance of a module that models a buffer with a ten time unit
module path delay. The vcs command line contains the following
compile-time options:
+pulse_e/0 +pulse_r/0
Specifying 0 percentages here means that the trailing edge of all
pulses can change the second scheduled event on the output.
Specifying 0 does not mean that all pulses propagate to the output
because this implementation has its own way of filtering out short
pulses.
Figure 12-5 Pulse Control with Inertial Delays
In the example illustrated in Figure 12-5 the following occurs:
1. At time 20 the input port transitions to 0. This schedules a
transition to 0 on the output port at time 30, ten time units later as
specified by the module path delay. This is the first scheduled
event on the output port. This event is not tentative, it will occur.
2. At time 23 the input port toggles to 1. This schedules a transition
to 1 on the output port at time 33. This is the second scheduled
event on the output port. This event is tentative.