Hi,
Can anyone help me with my problem.
I am  trying to change a parameter in my testbench and pass it to my design module. Basically I am working on processes variations on a device.
I am passing the parameter by using assign statement in my main module. I am trying to compile my program as many times as I change the parameter. But when I try to do change my parameter in always block, my parameter changes parallel with the input voltage. So, I am able to compile it only once. Can someone help me with this?
Thank you,
Sindhura

I am using Cadence sim vision 08.20-s014.
I am using verilog AMS for programming.


my test bench is as follows:

module testbench();
 electrical gnd,in;
 ground gnd;
 real index;

real length1;

  m_linear # (.mu(1e-10)) m1(in,gnd);

initial length1 = 50e-9;
always
     begin
     #(2)
     length1 = length1 + 50e-9;
     end
// Create a pulse voltage source as input to the design
       vsource #(.type("pulse"), .val0(1),.val1(-1), .period(20m)) v0(in,gnd);
     
endmodule


and in the design module I am implementing


module m_linear(Vp, Vn);
input Vp;
output Vn;
electrical Vp, Vn;

wreal length;// = 50e-9 from (-inf:inf);     //

real Vm;                                           // Terminal voltage
real Im;                                           // Current

parameter real deltaT=1u;//for example.
integer fptr;

assign length = testbench.length1;
analog begin

 Vm = V(Vp, Vn);

 // Calculate the current
 Im=Vm/length;

 I(Vp, Vn) <+ Im;


@(initial_step) begin
fptr =$fopen("/home/sxm7139/Desktop/Memristor/test.txt");
end

@(timer(1p,deltaT)) begin
$fstrobe(fptr,"%g %g",length,Im);
end

@(final_step) $fclose(fptr);
end
endmodule

Sindhura,
why do you use wreal for length? I'd expect a real for that.

B O E

Hi Boe,

If I use real I am getting the following error..
Err: A reg is not a legal lvalue in this context
I am using it in continuous assign statement so it can't be a real.

Regards,
Sindhura

Sindhura,

I expected a real at line Code:

Im=Vm/length; 

but didn't think about the assign statement. Perhaps you should convert the wreal to a real?

B O E

I still don't understand what you are trying to do.

Why do you have a pulse source, if you don't want the input voltage and length to be changing at the same time?  (Why not a dc source?)

What's the timescale for #(2) -- is it much longer than the 20m period of your pulse source?  (I usually work with Verilog-A, so my digital knowledge is limited.)

How does length change in your real design?  For the example you showed, one could set length in the analog block
 length = (1 + floor($abstime / 2 )) * 50e-9;
(I'm not sure of the units on "2").  Every 2 seconds, length will step up by 50n.  I guess you get 100 periods of your 20ms pulse source this way.

Do you want 100+ instances, each with a different L?

Or do you want 1 instance, but to run a simulation that is 100 times some unit duration, and change L after each unit duration?

Or do you want to call your simulator 100+ times to run the simulation?