[[:|gEDA]] >> [[Documentation]] >> [[icarus|Icarus Verilog]] >> [[|Getting Started]]

====== Getting Started with Icarus Verilog ======

Icarus Verilog is a Verilog compiler. It is suitable for use as a
simulator, and, to some degree, synthesizer. Icarus Verilog runs under
Linux and a variety of UNIX systems, as well as Windows as a command
line tool, so the instructions are generally applicable to all
environments. Note that this is only a quick start. For more detailed
documentation, see the manual page for the iverilog command.


===== Hello, World! =====

The first thing you want to do as a user is learn how to compile and
execute even the most trivial design. For the purposes of simulation,
we use as our example //the// most trivial simulation:

<code verilog "hello.vl">
module main;

initial
  begin
    $display("Hello, World");
    $finish ;
  end

endmodule
</code>

[[http://wiki.geda-project.org/_export/code/geda:icarus_quick_start?codeblock=0|Download]] this program,
or copy it from the Icarus Verilog examples directory.
Next, compile it with a command like this:

	% iverilog -o hello hello.vl

The results of this compile are placed into the file ''hello'', as the
''-o'' flag tells the compiler where to place the compiled result. Next,
execute the compiled program like so:

	% vvp hello
	Hello, World

And there it is, the program has been executed. So what happened? The
first step, the ''iverilog'' command, read and interpreted the source
file, then generated a compiled result. The compiled form may be
selected by command line switches, but the default form is the VVP
format, which is actually run by the ''vvp'' command.

The ''iverilog'' and ''vvp'' commands are the only commands that users
use to invoke Icarus Verilog. What the compiler actually does is
controlled by command line switches. In our little example, we asked
the compiler to compile the source program to the default vvp form,
which is in turn executed by the vvp program.


===== Windows Install =====

The easiest way to install under Windows is to get a precompiled
installer for the version you wish to install. Icarus Verilog is
distributed for Windows users as a self-installing ''.exe''. Just execute
the installer and follow the instructions. During the install, take
note of the directory where the program is installed: for example,
''C:\iverilog'' is a good place to install.

Once the binary is installed, you need to add the bin directory to
your execution path. The executables you need are in ''C:\iverilog\bin'',
where the ''C:\iverilog'' part is actually the root of where you
installed the package. The programs are in the bin subdirectory. Put
this directory in your ''PATH'' environment variable, and the above
commands become accessible to you at the command line prompt, or even
in batch files.


===== Linux Install =====

Under Linux, the install is even easier. For RedHat and Mandrake based
systems, there is the appropriate RPM file. Just install the package
with the ''rpm -U <file>'' command. Debian users should get Icarus
Verilog packages from the main Debian software site.


===== Install From Source =====

In this case, see [[icarus_readme|The Icarus Verilog Compilation System]]
and other documentation that comes with the source.