Software Engineering Institute

The correctness of a real-time system with hard deadline requirements depends both on the logical correctness and on the timing correctness of the system. The principles of rate monotonic scheduling have proven to be very useful in providing a framework for designing, analyzing, and modifying the timing and concurrency aspects of real-time systems. This paper illustrates how to build a mathematical model of the schedulability of a real-time system, taking into consideration such factors as preemption, synchronization, non-preemptibility, interrupts, and process idle time. In particular, this paper illustrates how these principles can be applied to input/output interfaces (e.g., to devices or local area networks) to predict the timing behavior of various design alternatives.