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AR# 1286

Foundation Simulator: simulating bi-directional signals


Keywords: Simulation, Bi-directional

Urgency: Standard

General Description: How do I setup simulation stimulus so that
I can properly simulate a bidirectional pin?



Use the 'Chip Controlled' (CC) mode when simulating
bidirectional signals. This will allow a chip (symbol)
output to override the test vector.

For example:

You are simulating a bidirectional pin BIDIR, and have
applied a stimulator to BIDIR. You want this stimulus to
appear on BIDIR when the 3-state buffer is disabled.

Now, when the 3-state buffer is enabled, you want to view its
output on BIDIR, but the input test vector is overriding
the output.

Using CC mode on the BIDIR stimulator will allow the output
of the 3-state buffer to override the stimulus.

To apply the CC mode to a stimulator, select the signal in
the Waveform Viewer, and either click on the CC button in the
Stimulator Selection Window, or select Stimulator->Chip
Controlled Mode.

Stimulators that are in 'Override' (OV) mode are displayed
in red in the Waveform Viewer. Stimulators that are in CC
mode are displayed in black.


If using a CMD (script) file, use the 'release' command to
release the bidirectional pin.


h DATA #assigns input stimulus to bidi pin DATA
l EN #tri-states output enable
h EN #enables output so that data is driven OUT onto DATA
r DATA #releases bidi pin DATA so that data may be driven out
AR# 1286
Date Created 09/29/1996
Last Updated 08/11/2003
Status Archive
Type General Article