FPGA Central

Hello all,

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.

Your help is appreciated
Drew

Hi Drew,

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 <bidir node name>~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 <bidir node name>~result, and follow the additional guidelines
below about specifying the logic levels of bidirectional nodes.

Hope this helps.

- Subroto Datta
Altera Corp.


"Drew" <[email protected]> wrote in message
news:[email protected] om...
> Hello all,
>
> 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.
>
> Your help is appreciated
> Drew

Thanks a lot Subroto,

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?

Thanks,
Dhruvish

[email protected] (Drew) wrote in message news:<[email protected] com>...
> Thanks a lot Subroto,
>
> 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?
>
> Thanks,
> Dhruvish

Dhruvish,

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
| /
|/