Is it possible to peek internal signals in testers?

[Shafiur Rahman]

Hi, I've been looking for a way to peek on the internal signals of a module that isn't connected to the IO. I tried peek(c.state) in PeekPokeTester. It cannot observe the value of the internal signal. Is it possible to peek internal states/wires using any of the testers?

My use case: I have several submodules that should exchange messages between them in certain order to output the final result. To ensure that the messages follow proper ordering, I print all events, parse, and run a script over them. It would be simpler if I could monitor the internal signals between them in my test code.
Thanks.

[wacha]

Hello,

With InterpretiveTester it is more or less possible, with PeekPokeTester afaik not.

Gabor

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[Shafiur Rahman]

Thanks. I will look into InterpretiveTester.
Though, OrderedDecoupledHWIOTester suits my use case better. Since I need this for only one big test for the top-level module and I would only eavesdrop in the signals, I might channel the debug signals through the IO. It might work for me if there is some way to keep some wires during testing but discard them during final compilation.

[wacha]

Keep in mind, that InterpretiveTester has its quirks:

- you have to pass the signal name as a string, so not as "safe" as a PeekPokeTester

- on many not toplevel io signals - internal signals - it sometimes throws exceptions saying "the value not found". I don't know if this is a bug or a feature.

So it is possible, but not very stable.

Gabor

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