AR# 1286: Foundation Simulator: simulating bi-directional signals
Foundation Simulator: simulating bi-directional signals
Keywords: Simulation, Bi-directional
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.
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 sim 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 sim