KEP2 (Kiel Esterel Processor 2): The Esterel Processor

The concurrent synchronous language Esterel allows to program reactive systems in an abstract, concise manner. Several preemption operators, such as suspension or weak and strong abortion, are provided to directly express reactive behavior with a deterministic, mathematically precise semantics, without the inherent need for the support of a resource-consuming, typically non-deterministic operating system. An Esterel program is typically first translated into other, non-synchronous high-level languages, such as VHDL or C, and then compiled further into hardware or software. Another approach that has been proposed recently is the direct execution of Esterel-like instructions with a customized processor, which promises the flexibility of a software solution with an efficiency close to a hardware implementation. However, the instruction sets and implementations of the processor architectures proposed so far still have some limitations regarding their completeness, efficiency, and adherence to the original Esterel semantics. This paper presents a novel processor architecture, the Kiel Esterel Processor, which addresses these shortcomings. In particular, it provides a complete, semantically accurate implementation of the Esterel preemption primitives, most of which can be expressed directly with a single machine instruction