User guide

4-20
Waveform Window
Delta Cycle Recording for VHDL
You can enable the capture of delta cycle information before
simulating your design and not during runtime. To capture delta cycle
information, set the VPDDELTACAPTURE variable to ON or OFF
(default is OFF) in the .synopsys_vss.setup file or use the command
line switch -vpddeltacapture on|off when simulating.
When viewing the simulation results in the waveform window, you can
observe changes at the delta cycle level by pointing at a signal
transition with the mouse and using the right-mouse button. A popup
menu appears, select the Expand time option to open up the series
of transitions to show the sequence of delta cycle changes.
The trade-off for capturing delta cycle information is longer simulation
runtime and larger VPD databases. Therefore, use this feature only
for debugging delta delay problems.
Expand and Collapse Times
To expand a time to view delta cycle information:
1. Right click on the edge of a waveform that includes a delta-cycle
event to open the Waveform Pane CSM.
2. Select Expand Time.
You can collapse either all delta cycle regions or a selected delta cycle
region. To collapse all delta cycle regions, right click anywhere in the
Waveform Pane and select Collapse All Time from the CSM. To
collapse a single delta cycle region, right click in the region to open
the Waveform Pane CSM and select Collapse Time.