Software Engineering Institute

Hard-real time systems have consistently proven to be some of the most difficult for successful software implementation. Attributes often associated with the intractable nature of real-time are concurrency, severe timing constraints, the complexity of real-world devices, and limited resources. In this experiment, an actual embedded hard real-time application (Inertial Navigation Set, AN/WSN-5) is simulated and ported to a variety of target processors. The effort is specifically directed at investigating the capability of ADA for providing program development solutions in the hard real-time regime. Special emphasis is focused on applying the built-in concurrency capabilities of ADA. The effort contends with typical cross-targeting issues such as board-level execution and memory configuration, device communications, and runtime debugging of the application. This report presents the top-level design of the application and addresses the solution in terms of a concurrency abstraction. Beginning with a classical data flow analysis of the requirements ADA tasks are derived from analyzable categories, specifically periodics, aperiodics, and servers. This classification scheme is predicated on work actively being conducted on a scheduling technique that quantifies the effect of task preemption and blocking, behavior fundamental to the concept of parallelism in ADA. In a corollary report, a schedulability analysis of the INS is described within the framework of the task set developed in this top-level design.