Awlsim is a free Step 7 compatible AWL/STL Soft-PLC written in Python.

Depending on the host machine and the Python interpreter used, it achieves
good performance of several thousand to millions of AWL/STL instructions
per second. German and english AWL/STL mnemonics are supported.

Awlsim can emulate CPUs with two and four accumulator registers (S7-3xx and
S7-4xx).

Compatibility to S7 hardware is taken seriously by the awlsim project. We want
to be as close as possible to the real PLC hardware with our AWL/STL code
execution. For this reason awlsim ships an extensive selftest suite. Missing
features and differences between awlsim and Step 7 are documented in the
COMPATIBILITY.txt and TODO.txt files. If you find any undocumented bugs and
incompatibilities to a real PLC CPU, please contact us.

Awlsim is Open Source Free Software licensed under the GNU General Public
License v2+. That means it's available in full source code and you are
encouraged to improve it and contribute your changes back to the community.
Awlsim is free of charge, too.


The official website of awlsim is:
http://bues.ch/cms/hacking/awlsim.html