The Cardiac Pacemaker

Abstract

A cardiac pacemaker example is used to compare and contrast the Synchronous Reactive (SR) programming model of SystemJ with the SCJ programming model. Our pacemaker is implemented in the synchronous subset of the Globally Asynchronous Locally Synchronous (GALS) SystemJ, which extends the Java language with reactivity, concurrency and real-time constructs based on a formal mathematical framework. The use of different programming models results in different design choices and implementations. The SR programming model is driven by a logical clock, which clearly demarcates the state boundaries and is ideal for formal verification of functional and real-time properties. Unlike the preemptive scheduling model prescribed by the SCJ specification, the SystemJ program execution model is atomic and non-preemptive between two logical ticks, and as such it is statically schedulable without the need for a runtime scheduler. To check the effectiveness of the SystemJ approach, we implemented the cardiac pacemaker on three different execution platforms that demonstrate feasibility of guaranteed real-time of the pacemaker execution with a fraction of the used processor's resources.