Software architecture for hard real-time applications: Cyclic executives vs. fixed priority executives

Abstract

We contrast the software architecture of a hard real-time application using a fixed priority task structure against the software architecture of the same system using a cyclic executive structure to satisfy hard real-time deadlines in response to a set of embedded system requirements. We identify the perceived and actual advantages and disadvantages of both approaches, consider the types of applications which can take advantage of these approaches, and make recommendations related to the attributes of such applications that might be needed with both approaches. We conclude that the fixed priority approach, when priorities are assigned using rate monotonic priorities, generally dominates the cyclic executive approach for hard real-time systems.