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Usage of (* cds_inherited_parameter *)

chenchen

Hi all,

I try the simple case in Verilog-A document and I want to obtain "different" values of mismatch parameter in single Verilog-A module.

// I want to use "single" random variable for different parameters w/ mismatch

// variation.scs

section my_variation

parameters monteres=0

statistics {

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

endsection my_variation

//////////////////////////////////////////////////////////

// pseudo code 

include "variation.scs"  my_variation

(* cds_inherited_parameter *) parameter real monteres = 0;
parameter real r = 1k;

localparam real r1_effective = r + monteres; 

localparam real r2_effective = r + monteres; 

V(vp1, vn1) <+ (r1_effective)*I(vp1, vn1);

V(vp2, vn2) <+ (r2_effective)*I(vp2, vn2);

//////////////////////////////////////////////////////////

I expect two different random values of r1_effective and r2_effective, but I just got one random value during each Monte Carlo iteration ( r1_effective=r2_effective)

Anyone knows what is correct usage for such cases? (I want r1_effective != r2_effective)

Many thanks.

Parents

  • Having lots of instances of the Verilog-A is almost certainly less efficient than having a single instance with many parameters. The only problem with having a huge number of mismatch parameters is that these need to be generated for every instance in the design (not just the instances that use them), so that's also expensive. However, given the fact that the random numbers are generated for each mismatch parameter and for each instance, there's no getting around this fact...

    Maybe you should contact customer support so that we can talk in more detail about your unusual requirements.

    Regards,

    Andrew.

Reply

  • Having lots of instances of the Verilog-A is almost certainly less efficient than having a single instance with many parameters. The only problem with having a huge number of mismatch parameters is that these need to be generated for every instance in the design (not just the instances that use them), so that's also expensive. However, given the fact that the random numbers are generated for each mismatch parameter and for each instance, there's no getting around this fact...

    Maybe you should contact customer support so that we can talk in more detail about your unusual requirements.

    Regards,

    Andrew.

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