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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

    You need to use the cds_inherited_parameter attribute on a parameter which you are going to have a mismatch definition of in the statistics block. For example, this VerilogA module:

    `include "disciplines.vams"

    module res(vp, vn);

    inout vp, vn;

    electrical vp, vn;

    (* cds_inherited_parameter *) parameter real monteres = 0;

    parameter real r = 1k;

    localparam real r_effective = r + monteres; // nominal resistance plus

    // monte-carlo mismatch effect

    analog

    V(vp, vn) <+ (r_effective)*I(vp, vn);

    endmodule

    And I'm simulating this from this netlist:

    //
    parameters monteres=0

    statistics {
      mismatch {
        vary monteres dist=gauss std=5
      }
    }

    R1 (n1 0) res
    I1 (n1 0) isource dc=1m

    ahdl_include "monteres.va"

    monte montecarlo numruns=10 variations=mismatch {
       dc dc
       export vdc=oceanEval("v(\"n1\" ?result 'dc)")
    }

    Regards,

    Andrew.

Reply
  • Andrew Beckett

    You need to use the cds_inherited_parameter attribute on a parameter which you are going to have a mismatch definition of in the statistics block. For example, this VerilogA module:

    `include "disciplines.vams"

    module res(vp, vn);

    inout vp, vn;

    electrical vp, vn;

    (* cds_inherited_parameter *) parameter real monteres = 0;

    parameter real r = 1k;

    localparam real r_effective = r + monteres; // nominal resistance plus

    // monte-carlo mismatch effect

    analog

    V(vp, vn) <+ (r_effective)*I(vp, vn);

    endmodule

    And I'm simulating this from this netlist:

    //
    parameters monteres=0

    statistics {
      mismatch {
        vary monteres dist=gauss std=5
      }
    }

    R1 (n1 0) res
    I1 (n1 0) isource dc=1m

    ahdl_include "monteres.va"

    monte montecarlo numruns=10 variations=mismatch {
       dc dc
       export vdc=oceanEval("v(\"n1\" ?result 'dc)")
    }

    Regards,

    Andrew.

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