Simply RISC S1 Core - Simulation Environment
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To run a simulation using the free software Icarus Verilog
simulator use the following commands:

  build_icarus
  run_icarus

If you want to use a commercial tool such as Synopsys VCS then
set up your PATH enviroment variable so that you are able to
find the "vcs" executable, and then type in the following
commands:

  build_vcs
  run_vcs

Within this design the only visible difference between Icarus
and VCS is the speed: the commercial tool could be hundreds of
times faster than its FLOSS counterpart; but with Icarus if
you have time to wait for some minutes you will obtain exactly
the same results just using free software.

At the end of the simulation you can look at the logfile and
at the waveforms placed at the following paths:

  run/sim/icarus/sim.log
  run/sim/icarus/trace.vcd

  run/sim/vcs/sim.log
  run/sim/vcs/trace.vcd

Obviously if you do not have access to a commercial tool you
can use GTKWave to look at the waveforms: for instance from
the top-level directory just type in the following command:

  gtkwave run/sim/icarus/trace.vcd &

and then from "File|Read Save File" choose the file named
"tools/src/gtkwave.sav".