Discussion 1 Tools

Objective: Iverilog and Gtkwave in Ubuntu and Ubuntu on WSL (Ubuntu in Windows)

Linux and X11

To Enable WSL first, do the following:

• Install Ubuntu 18.04 LTS from Windows App Store
• Install VcXsrv from this link https://sourceforge.net/projects/vcxsrv/ or https://wiki.ubuntu.com/WSL (Advanced Topic section)
• Open XLaunch (VcXsrv) and change the Display number to 0 then hit Next and Finish the setup without changing any other settings

Use the following commands in Ubuntu terminal

sudo apt update
export DISPLAY=:0  
sudo apt install x11-apps (installing xeyes)
use xeyes (to see if the Xserver is working)
sudo apt install emacs (text editor)
sudo apt-get install -y iverilog
sudo apt-get install -y gtkwave

• In Ubuntu terminal, you can access your windows drives using cd /mnt/<drive>

The commands follow commands can be used to compile, run, and examine saved waveforms if any

iverilog -o <compiled_output_filename> <verilog_input_file1.v> <verilog_input_file2.v> ...
vvp <compiled_output_filename> # To run
gtkwave <dumpfile.vcd> # To check the waveform

Iverilog and Gtkwave native for Windows

Can be downloaded from this link - https://bleyer.org/icarus/
While installing make sure that Gtkwave is selected

If running Linux on your own computer, install iverilog
For ubuntu:

sudo apt install iverilog

sudo apt install gtkwave

If running on lab computers you can use my installation of iverilog

alias iverilog /afs/umbc.edu/users/r/o/robucci/pub/iverilog/bin/iverilog
alias vvp /afs/umbc.edu/users/r/o/robucci/pub/iverilog/bin/vvp

iverilog Example

create a file named hello_world.v, using your favorite editor

module hello_world;
initial $display("hello world");
endmodule

Verilog Simulations works by compiling a host-native binary for simulation. Do this:

iverilog hello_world.v

That creates creates a.out. Verify this by listing the directory contents:

ls

In some environments you can directly run ./a.out,

./a.out

while for others you'll use vvp:

vvp ./a.out

GTKWave Example

modify hello_world.v

module hello_world;
initial $display("hello world");

   reg clk;
   initial clk=0;
   always #5 clk=~clk;

   initial #100 $finish;

   initial begin
      $dumpfile("hello_world.vcd");      
      $dumpvars;
      
   end
  
endmodule // hello_world

rerun the simulation as before

you should get a message that a waveform file has been generated:

hello world
VCD info: dumpfile hello_world.vcd opened for output.

Run gtkwave:

gtkwave hello_world.vcd

At the end of the video, the right → and left ← arrow keyboard keys are used to move the time cursor to the next and previous transitions.