Verification of PLC programs written in FBD with VIS

Abstract

Verification of programmable logic controller (PLC) programs written in IEC 61131-3 function block diagram (FBD) is essential in the transition from the use of traditional relay-based analog systems to PLC-based digital systems. This paper describes effective use of the well-known verification tool VIS for automatic verification of behavioral equivalences between successive FBD revisions. We formally defined FBD semantics as a state-transition system, developed semantic-preserving translation rules from FBD to Verilog prograins, implemented a software tool to support the process, and conducted a case study on a subset of FBDs for APR-1400 reactor protection system design.