Hi,

The following code for a 2-stage RC filter in the following code works ok.

Code:

`include "discipline.h"

module rc_ladder(in, out, gnd) ;
  inout in,out,gnd;
  electrical in,out, mid,gnd;

  parameter r=1k ;
  parameter c=1n ;

  analog begin
      // stage 1
      I(in,mid) <+ V(in,mid) / r;
      I(mid,gnd) <+ ddt( V(mid,gnd) * c );

      // stage 2
      I(mid,out) <+ V(mid,out) / r;
      I(out,gnd) <+ ddt( V(out,gnd) * c );
  end
endmodule 

The next step would be use a for loop to create as many stages as I want. I tried using the following code, but fails at compile.

Code:

`include "discipline.h"

module rc_ladder_forloop(c[0],c[2], gnd) ;
  inout c[0],c[2], gnd;
  electrical [0:2] c;
  electrical gnd;

  parameter r=1k ;
  parameter c=1n ;
  
  genvar k;

  analog begin
      for (k=1; k<2;k=k+1) begin
        I(c[k],c[k+1]) <+ V(c[k],c[k+1]) / r;
        I(c[k+1],gnd) <+ ddt( V(c[k+1],gnd) * c );
      end
  end
endmodule 

Any suggestions on how to fix this?

The next step would be to pass the number of stages as a parameter. Would that be possible? and how?

Thanks in advance.

Regards, sorgin

Thanks BOE,

I was already using the genvar method, but missed a couple of other things.

I managed to get it working even including the parameterized number of stages. The following code shows the working model, at least for smartspice.

Code:

`include "discipline.h"

module rc_ladder(in, out, gnd) ;
  inout in,out,gnd;
  electrical in,out, mid,gnd;

  parameter r=1k ;
  parameter c=1n ;

  analog begin
    // stage 1
    I(in,mid) <+ V(in,mid) / r;
    I(mid,gnd) <+ ddt( V(mid,gnd) * c );

    // stage 2
    I(mid,out) <+ V(mid,out) / r;
    I(out,gnd) <+ ddt( V(out,gnd) * c );
  end
endmodule

// parameterized version using a for loop with genvar

module rc_ladder_forloop(in, out, gnd) ;

  parameter integer steps = 2;

  inout in,out,gnd;

  electrical [0:steps] con;
  electrical in, out, gnd;

  parameter r=1k ;
  parameter c=1n ;
  
  genvar k;

  analog begin
    for (k=0 ; k < steps ; k = k+1 ) begin
      I(con[k],con[k+1]) <+ V(con[k],con[k+1]) / r;
      I(con[k+1],gnd) <+ ddt( V(con[k+1],gnd) * c );
    end
    V(con[0],gnd) <+ V(in,gnd);
    V(out,gnd) <+ V(con[steps],gnd);
  end
endmodule 

and the netlist should be as follows:

Code:

Test RC-ladder loops

.verilog "./test.vams"

v1 in 0 PWL(0 0 5u 10 20u 10)

** Uncomment only one of the following two lines
** First line: fixed 2 stage RC ladder
** Second line: parameterized n-stage RC ladder

*YVLG_ladder in out 0 rc_ladder
YVLG_ladder in out 0 rc_ladder_forloop steps = 2

.tran 1n 20u
.iplot v(out)