WCRT-reducing scheduling algorithm for programmable logic controllers with remote I/Os

떨어진 입출력 장치를 가지는 프로그래머블 로직 콘트롤러를 위한 스케쥴링 알고리즘

In this paper, a scheduling algorithm is proposed for a programmable logic controller(PLC) with remote I/Os, assuming the multi-tasking facilities. Since sequence programs are executed on the application processor and I/O data are transmitted by the network processor concurrently, the proposed algorithm schedules the data transmission as well as the sequence program execution. The suggested algorithm guarantees the bounded WCRT(worst case response time), which is the one third of the WCRT in the absence of scheduling. Computer simulation shows that the algorithm can be easily applied to a real PLC without critical constraints on utilization of resources and inter-relation among tasks.