On the systematic method of conditional control program execution by a PLC

The paper presents an original idea of the selective control program execution that allows significant response time reduction. The exhaustive analysis of the PLC program performance is given. An analytic approach explains the idea of the selective control program evaluation and gives the requirements for its feasibility. There is presented a systematic and formal method of program analysis based on a data flow graph approach. The method generates acyclic graph from the control program that is subject of optimization, variable allocation and instruction generation. The graph approach allows determining variables dependencies and task partitioning required by selective program execution. The method utilize the hardware supported variable changes detection. It is transparent for system operation and enables evaluation of blocks that require update.