Response Time Driven Scheduling for Real-time Programmable Logic Controllers with Network-based I/o Systems

High performance programmable logic controllers(PLCs) are time critical systems that require deadline-guaranteed response time. This paper describes a processor and network scheduling method for real-time PLCs supporting networkbased I/O systems and multi-tasking facilities. This enhances schedulability under the pre-de ned response time constraints, by adjusting the period as well as the release time of tasks, together with I/O data transmission. A generalized architectural and behavioral model is developed to yield a precise time-performance speci cation re ecting accurate eld condition. This scheme synchronizes I/O data transmission and task execution in a network processor and an application processor, respectively.