User guide

17-31
VCD+ (vpd) File Generation
VCD+ On/Off PLI Rules
• VCD+ On/Off PLI system tasks follow these basic rules.
• vcdpluson and vcdplusoff tasks may be inserted in source
code or entered at the simulator interactive prompt.
• vcdpluson and vcdplusoff tasks accept one level but multiple
scopes/signals as arguments.
• vcdpluson and vcdplusoff tasks when applied to the same
signal(s) toggle the recording on and off. The count for each signal
is accumulative; (+,-). ..on/..on/..off leaves the signal recording on.
For example using the hierarchy of
Figure 17-8, the following
command sequence will still report on Module D since it was
added twice but only removed once.
$vcdpluson(A); $vcdpluson(B); $vcdplusoff(D);
• On large designs, you should selectively turn signal data capture
(dumping) on or off. Multiple use of vcdpluson and vcdplusoff
allow on and off selection
• vcdpluson and vcdplusoff tasks executed in the same
simulation time period may execute in any order. To ensure that
one or the other executes last, separate them by at least one
simulation time unit.
• Signals that are turned off may have signal value changes
recorded if a higher/ lower level of the same signal is turned on.