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Verilog force assign
von Bruno (Guest)

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Hi,
I face a problem when I try to force a signal in my Verilog testbench

My v file is:
module test(I);
  input I;
  wire tmp;
  wire NB;
  assign NB = I;
  assign tmp = NB;
endmodule

My testbench is:
module tb();
reg in;
test test(in);
 initial begin
      in = 1;
      #10;
       force tb.test.I = 1'b0;
      #20;
       release tb.test.I;
      #20;
      $finish;
   end //initial
endmodule // tb_scu

When I look at the simu result, signal I is following my force/release 
but NB (and therefore tmp) is not.
I am really unable to figure out the problem.
Does anyone see something wrong or have an idea?

Tahnks a lot.
Br

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Re: Verilog force assign
von Harald (Guest)

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Bruno,
in case this works

test test(in);
 initial begin
      in = 1;
      #10;
      in = 0;
      #20;
      in = 1;
      #20;
      $finish;
   end //initial

I also would assume that this is a simulator issue. I don't see any 
reason why the forced value should not be propagated through the assign 
statement. What simulator are you using?

Harald

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Re: Verilog force assign
von Bruno (Guest)

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Thanks for your answer.

Yes your piece of code works.
I was using iverilog,
I tried with cver, it works now.
Then it is a icarus verilog simulator related issue.
Thanks a lot fo your help !

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