Step 7 AWL/STL/PLC simulator
Awlsim is a free Step 7 AWL/STL/PLC simulator.
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. S7-300 and S7-400 CPUs (with 2 and 4 accus) are supported.
Awlsim has got a hardware interface with existing PROFIBUS-DP (proof-of-concept) and LinuxCNC plug-in modules.