Step 7 AWL/STL PLC simulator
Image preview of awlsimgui.png

Awlsim is a free Step 7 AWL/STL PLC simulator 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.

The current focus is the S7-3xx and S7-4xx family of PLC CPUs (2 and 4 accu).

Simulation accuracy is taken seriously by the awlsim project. We want to be as close as possible to the real PLC hardware with our simulation. 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.

Awlsim requires two software packages to be installed before it can be used:

Please install Python and PySide to their default install locations.

After the dependencies have been installed, the awlsim-X.X.tar.gz archive can be extracted.

After extracting the tar.gz archive, simply run the awlsim-win.bat file. The graphical user interface of awlsim should appear.

If you did not install a dependency correctly, or if there is any other problem, an error message will be printed to the console window that also appears.

Alternatively, you may download the awlsim win32.exe installer file and install awlsim into the system. But this is not a requirement. Awlsim can run without install.

Awlsim runs on any platform that supports Python and PySide, which includes Linux and Mac OS X.

Awlsim runs on Python 2.7 and Python 3.2 or later (CPython).

The awlsim core and thus the command line interface 'awlsimcli' and the core server 'awlsim-server' also run on these alternative Python interpreters:

It is possible to compile the awlsim core and coreserver with Cython. Cython is an optimizing static compiler for the Python language.
If Cython is installed, the ./ build run will also build the optimized awlsim package in addition to the standard Python modules. The package will be called awlsim_cython, so both the optimized build and the original Python-code can be installed simultaneously.
To use the awlsim_cython core, set the AWLSIMCYTHON environment variable to 1 before running awlsim. For example run awlsimcli like this:
This will also work with awlsimgui.
Using the compiled awlsim_cython core will result in a performance gain of over five percent, compared to the pure Python core.

Awlsim includes an experimental hardware access layer for connecting the awlsim S7-CPU to real PROFIBUS-DP slave hardware. It does this by providing an interface to the Raspberry Pi PROFIBUS module.

The hardware access layer module is loaded and executed with the new -H command to awlsimcli.
For example: awlsimcli -D -H pyprofibus program.awl
The pyprofibus module has some module options. See the --help and --hardware-info pyprofibus options to awlsimcli for details.

The pyprofibus module is highly experimental at this time. It lacks a lot of flexibility, but it does work.

Needless to say, the Raspberry Pi PROFIBUS module must be installed before the awlsim pyprofibus hardware access layer can be used. Otherwise to following error will occur:

  [PyProfibus hardware module] Failed to import PROFIBUS protocol stack module 'pyprofibus':
    No module named 'pyprofibus'

A LinuxCNC HAL module is included in awlsim. With this module it is possible to use awlsim as a non-realtime S7-compatible PLC backend.

To use awlsim in LinuxCNC, a HAL configuration file has to be added to your LinuxCNC configuration. See the LinuxCNC Integrators Manual on how to add HAL-files. An example HAL-file is included in the awlsim package as awlsimhw_linuxcnc/awlsim.hal
See this .hal file for additional information.

Latest bleeding edge awlsim can be downloaded using the Git version control system as follows:

git clone git://

or by downloading the awlsim snapshot archive.
To browse the Git repository online, go to the gitweb interface.
A mirror of the repository is available on Github.

Thanks to everybody testing awlsim and reporting bugs and differences between awlsim and the original STEP-7 AWL/STL language implementation.

Thanks to the lecturers at Balthasar Neumann Technikum Trier for their fine lectures in PLC automation.

Copyright (C) Michael Büsch
Licensed under the terms of the GNU General Public License version 2. See the sourcecode for details.

Updated: Saturday 26 July 2014 22:54 (UTC)
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