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AR# 3124

Foundation F1.x Simulator: Selective preset feature may disrupt the operation of counters, state machines


Keywords: selective preset, simulate, simulator, counter

Urgency: Standard

General Description:
Executing a Selective preset feature occasionally disrupts the
functionality of state machines or counters.

After assigning D inputs of the counter flip-flops to some
value (i.e. ff) using this feature, execute a preset, and step.
Then, the counter either gets stuck at the preset value or
starts counting incorrectly.

This happens to feedback-looped flip-flops (such as counters).


For selective preset functionality, follow these steps instead.

1. Use Signal->Add Signals to select all D pins of flip-flops
that you want to set the preset value to:
a. To select a flip flop pin, navigate the design hierarchy
displayed on the right hand side of the Component Selection
b. When the desired flip flop is listed in the center pane,
double-click on it to bring up a list of pins for this
flip flop on the right side.
c. Now, double-click on the D input pin to add it to the
Waveform Viewer.
2. Use Signal->Add Stimulators to assign stimulus (preset
values) to all of these D inputs.
3. Step the simulation once.
4. Disable the stimulators by selecting the signal and clicking
on the DS button in the Stimulator Selection window.
5. Now keep stepping the simulation.
AR# 3124
Date Created 11/25/1997
Last Updated 04/04/2000
Status Archive
Type General Article