Icarus Simulation and View Waveforms with GTKWave simple tutorial

[blooz]

First you need to download the Free Waveform viewer GTKwave
h**p://gtkwave.sourceforge.net/

then Generate a VCD file


Files

//Testbench

//Save as countertb.v
////////////////////////////////
`timescale 1ns/1ns


module countertb();

reg clk;
reg reset;

wire [3:0] q;

counter instance0(.clk(clk),.q(q),.reset(reset));

initial
begin
clk=1'b0;
reset=1'b1;
#10 reset=1'b0;
#1600 ;
$finish;
end

initial
begin
forever #20 clk=~clk;
end

initial
begin
$monitor("time=>%tns q=>%b",$time,q);
$dumpfile(counter_wave.vcd);
$dumpvars();
end

endmodule



//Save As counter.v
///////////////////////////


// 4 bit Counter


module counter(clk,q,reset);
input clk;
input reset;
output reg [3:0] q;
initial
begin
q=4'b0000;
end

always@( posedge clk)
begin
if (reset==1'b1)
q=4'b0000;
else
q=q+1;

end

endmodule



step

1.Compile and simulate in Icarus verilog

iverilog -o result counter.v countertb.v

vvp result

2.Simulation results are visible and a VCD file will be produced ,we have named it as
counter_wave.vcd


3.run
gtkwave counter_wave.vcd

then a graphical window will be shown

screen shots are given in the pictures section