The Kiel Esterel Processor - A Semi-Custom, Configurable Reactive Processor

Abstract

The synchronous language Esterel is an established language for
developing reactive systems. It gives an abstract, well-defined
and executable description of the application, and can be
synthesized into hardware and software. Typically, an Esterel
program is first translated into other, lower-level languages
(such as VHDL or C), and then compiled further. However, there is
also the alternative of executing Esterel-like instructions
directly. For example, in the REFLIX and RePIC projects, Roop et
al.\ have augmented traditional processors with custom hardware to
execute Esterel instructions. This patch strategy is a convenient
approach, but has some shortages.

We present the Kiel Esterel Processor (KEP), a semi-custom, configurable reactive processor for the direct execution of Esterel programs.  It consists of a reactive core and scalable peripheral elements. KEP supports standard Esterel statements directly, except (so far) for the concurrency operator. Valued signals and counter functions in Esterel statements are supported by KEP. Due to its control path and its cooperation with elements, KEP obeys exact Esterel (preemption and priority) rules, including for example abort/weak abort (nests).