I am kind of confused how is bidirectional pin displayed in the Waveform Simulation. In my waveform file I have A as an bidirectional pin but when I run simulation one more pin name appears called A~result. I guess that's the output and the other one which is displayed as A is input in simulation. But I need to know more like, are those pins supposed to be displaying same waveform? If not which one is a true waveform. I am trying to find some help on this in Quartus but I cannot see it.
This is taken from the Quartus II online help and should answer your questions.
This is copy-n-paste from the Quartus II Help file. (do "Search" for "simulating bidirectional pin" from the Quartus II Help)
======================================================================== Guidelines for Simulating Bidirectional Nodes
See Also Using Vector Files with the Simulator
When simulating a vector file that contains bidirectional nodes, use the following guidelines:
A bidirectional node is represented in a Vector Waveform File (.vwf) by two channels: one channel represents the input to the bidirectional node, the other channel represents the output from the bidirectional node. You can enter the input channel into the VWF by adding the bidirectional node to the VWF using the Node Finder dialog box, or you can insert the bidirectional node into the VWF using the Insert Node or Bus command (Edit menu).
If the Automatically add pins to simulation output waveforms option is turned on, the Simulator automatically creates the corresponding output channel for the bidirectional node, named ~result, after simulation is complete. This channel contains the logic levels of the output channel during simulation. Alternatively, you can manually create the output channel and specify the expected logic levels for the output channel. If you manually create the channel, you must name the channel ~result, and follow the additional guidelines below about specifying the logic levels of bidirectional nodes.
I am having one more doubt now. If I place an Oscilloscope on the Bidirectional Pin, what would I see? Will it be any form of combination of A and A~result or it will be A~result only. Can I use MAX3000 family EPLD for this sort of application?
My understanding is that the bidirectional pin will only have one set of values on it and therefore on the oscilloscope you will measure what is present. The diagram should explain this. If OE = '1' for example then whatever the value of A is should be present otherwise, it should be whatever some other entity placed on that pin.
_____ OE | |/| ___/ |___ A | \ | | \| Z --| | |\ |___| \___ Y | / |/
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