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A stochastic model in Verilog A for Monte Carlo simulation

UUinfini

 Hello Guys,

I have a problem for Veriglog A in Cadence, I hope you can help me. In fact I need to elaborate a stochastic model by coding in Verilog A executed under Cadence. My aim is to offer a model with which the customers can do the Monte Carlo Analysis. But I used the functions like "$random", "$temperature" etc. to generate a seed for obtaining a parameter which changes each time of simulation. But finally it changes just according to the real time of simulation, but not according to different times of simulation. Do you have any experiences like this? Thank you for you response.

Best regards,

UU

Parents
  • Andrew Beckett

    Not sure what you mean by "it doesn't work". I created a simple circuit containing an instance of source, and then ran a monte carlo analysis:

    include "source.scs"

    I1 (a b c) source
    r1 (a 0) resistor r=1k
    r2 (b 0) resistor r=1k
    r3 (c 0) resistor r=1k

    monte montecarlo numruns=10 variations=mismatch savefamilyplots=yes {
       tran tran stop=10n
    }

    This outputs a lot of stuff, but in particular it says (for each iteration of the monte carlo):

     hello,I'm glad to meet you -3.38873
    hello,I'm glad to meet you -3.38873
    hello,I'm glad to meet you -3.38873
    .hello,I'm glad to meet you -3.38873
    ..hello,I'm glad to meet you -3.38873
    ...hello,I'm glad to meet you -3.38873

    and then later:

         gmin = 1 pS                                           


    hello,I'm glad to meet you 2.42183
    hello,I'm glad to meet you 2.42183
    hello,I'm glad to meet you 2.42183
    .hello,I'm glad to meet you 2.42183
    ..hello,I'm glad to meet you 2.42183

    (you're strobing on each timestep iteration, so because I ran a transient, it strobes multiple times).

    Because I ran with saving family plots, you can see your signal b in the monte carlo (see attached picture).

    Andrew.

Reply
  • Andrew Beckett

    Not sure what you mean by "it doesn't work". I created a simple circuit containing an instance of source, and then ran a monte carlo analysis:

    include "source.scs"

    I1 (a b c) source
    r1 (a 0) resistor r=1k
    r2 (b 0) resistor r=1k
    r3 (c 0) resistor r=1k

    monte montecarlo numruns=10 variations=mismatch savefamilyplots=yes {
       tran tran stop=10n
    }

    This outputs a lot of stuff, but in particular it says (for each iteration of the monte carlo):

     hello,I'm glad to meet you -3.38873
    hello,I'm glad to meet you -3.38873
    hello,I'm glad to meet you -3.38873
    .hello,I'm glad to meet you -3.38873
    ..hello,I'm glad to meet you -3.38873
    ...hello,I'm glad to meet you -3.38873

    and then later:

         gmin = 1 pS                                           


    hello,I'm glad to meet you 2.42183
    hello,I'm glad to meet you 2.42183
    hello,I'm glad to meet you 2.42183
    .hello,I'm glad to meet you 2.42183
    ..hello,I'm glad to meet you 2.42183

    (you're strobing on each timestep iteration, so because I ran a transient, it strobes multiple times).

    Because I ran with saving family plots, you can see your signal b in the monte carlo (see attached picture).

    Andrew.

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