A real-time communication protocol with contention-resolving algorithm for programmable controllers

In this paper, a communication protocol far real-time distributed programmable controllers is proposed. An architecture for the real-time distributed system which consists of small PCs is proposed. A basic execution cycle of the sequence control tasks executed by the PCs is defined. The workload model which includes the execution period and time constraints is proposed. A contention-resolving algorithm is suggested in order to provide deterministic communication delays. Based on the workload model, the response time characteristic of the proposed communication protocol is investigated and compared with those of three well-known communication protocols. It is shown that the proposed real-time communication protocol provides better performance than the other protocols