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Paper Details

Multi-priority scheduling for transputer-based real-time control

Authors: Welch, Peter H.


A major requirement of real-time control applications is a set of cyclic processes — one for each "control-law". Each process must be managed so that it completes each cycle within a fixed time. The rate at which each process cycles will be constant, but will generally be different for different processes.Current transputer hardware provides very fast pre-emptive scheduling for two static priority levels, with "round-robin" management within each level. This is not sufficient to manage securely more than one such control-law per transputer — even at very low processor loadings. Efficient classical solutions (e.g. "rate-monotonic" or "deadline" scheduling) require multiple and time-varying priorities.This paper shows how to implement such solutions simply, and with an acceptable level of overhead, on the existing (and future) generation of transputer. Other promising scheduling methods are discussed. All solutions are expressed in occam with no assembler inserts and no security rules violated — the intended applications are safety-critical! Real performance figures are reported.Finally, a method of proving (or dis-proving) the security of any particular set of process loadings, operating under any particular scheduling algorithm, is described.


OUG-13: Real-Time Systems with Transputers, Hussein S. M. Zedan, 1990, pp 198 - 214 published by IOS Press, Amsterdam

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