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Verilog A: Generate different $random values for each Monte Carlo iteration

MC20250412421 25 days ago

Hi everyone !

I have a Verilog A block that uses the $random function as is (without any seed defined inside the Verilog A code). I have noticed while running Monte Carlo (default settings) that the Verilog A would always generate the exact same $random values for each MC iteration.
I assume it is because the Monte Carlo seed which is 12345 is being fed into the Verilog A $random function ?
If that's the case, what is the best way to generate $random values that are different for each MC iteration ?

Thanks in advance for your answers !

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JankoK 24 days ago

Hi,

Interesting question...

I guess you could do something similar to this:

How to do Monte Carlo mismatch variation on a VerilogA model

That model deck is just a separate .scs (model file) where you add your statements (don't forget to include it in you Model Libraries). You can also define process{} too, for process variations, under that statistical statement.

Let me know if it worked.

Disclaimer: I have not tried this myself.

BR

/Janko
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MC20250412421 24 days ago in reply to JankoK

Thanks a bunch for that answer !

While Andrew's answer was a simpler solution for my problem (just having a different seed for each MC run), you showed me something I had no idea how to do before and that I'll be using from now on.

So again, thanks a lot for that and have a great day !
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MC20250412421 24 days ago in reply to JankoK

Thanks a bunch for that answer !

While Andrew's answer was a simpler solution for my problem (just having a different seed for each MC run), you showed me something I had no idea how to do before and that I'll be using from now on.

So again, thanks a lot for that and have a great day !
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