IMPROVING FLEXIBILITY AND RESPONSIVENESS IN FTT-CAN WITH A SCHEDULING COPROCESSOR

摘要

Fieldbus distributed systems are increasingly required to accommodate on-line changes in the messages they convey. The FTT-CAN protocol relies on the planning scheduler to achieve this kind of flexibility, but its response time to changes in the message set is severely limited by the plan duration which cannot be set arbitrarily short. This paper presents a scheduling coprocessor solution for FTT-CAN, aimed at improving its flexibility and responsiveness. The coprocessor generates message schedules according to one of three different scheduling policies, includes an on-line schedulability analyser function and can be used also in other fieldbuses using centralised scheduling. The paper focuses on the coprocessor functionality and interface. Preliminary performance figures showing its feasibility are also presented.