Verification of PLC Properties Based on Formal Semantics in Coq
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- Blech J.O., Ould Biha S. (2011) Verification of PLC Properties Based on Formal Semantics in Coq. In: Barthe G., Pardo A., Schneider G. (eds) Software Engineering and Formal Methods. SEFM 2011. Lecture Notes in Computer Science, vol 7041. Springer, Berlin, Heidelberg
Programmable Logic Controllers (PLC) are widely used in embedded systems for the industrial automation domain. We propose a formal semantics of two languages defined in the IEC 61131-3 standard for PLC programming. The first one is the Instruction List (IL) language, an assembly like language. The second one is the Sequential Function Charts (SFC) language, a graphical high-level language that allows to describe the main control-flow of the system. A PLC system description may comprise SFC and IL code. We formalized the semantics in the proof assistant Coq. Furthermore, we present an associated tool for automatically generating SFC representations from a graphical description – the text based IL code can be handled in Coq directly – and its usage for verification purposes. We demonstrate our approach to prove safety properties of a PLC in a real industrial demonstrator.
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