HW/SW co-design for Esterel processing

We present a co-synthesis approach that accelerates reactive software processing by moving the calculation of complex expressions into external combinational hardware. The starting point is a system model written in the synchronous language Esterel, which can be mapped to both hardware and software. Our approach performs the partitioning at the source-code level and preserves the original, strictly synchronous semantics. It is thus platform-independent and allows to use standard simulation and synthesis tools. Furthermore, the source-level partitioning approach presented here should be applicable to non-reactive processing platforms as well. However, the challenge is to partition the program without changing its meaning under any circumstances. In particular, signal scopes and interpartition signal dependencies must be maintained, which rules out a naïve top-level partitioning. We have implemented the co-synthesis approach based on the Columbia Esterel Compiler and have validated it on the Kiel Esterel Processor. As the experimental results confirm, this can significantly reduce execution times and energy consumption per reaction, with minimal additional hardware requirements.