Exception Handling in Programmable Controllers with Denotational Model

The paper introduces a customized approach to handle failures in IEC 61131–3 programmable controllers. The solution assumes the utilization of a virtual machine as a runtime environment to execute control code in an isolated manner. A formal model of the runtime is presented, employing denotational semantics. Subsequently, the model is expanded by incorporating new procedures that enable the handling of runtime exceptions using ST code constructs. This formal model serves as the foundation for implementing the exception infrastructure in the CPDev development environment. The research presented in the paper, driven by industry demands, aims to facilitate the development of more reliable and resilient control systems, capable of effectively dealing with failures.