Mixing Signals and Modes in Synchronous Data-flow Systems

Synchronous data-flow languages such as Scade/Lustre manage infinite sequences, or streams, as primitive values making them naturally adapted to the description of data-dominated systems. Their conservative extension with means to define control-structures or modes has been a long-term research topic through which several solutions have emerged. In this paper, we pursue this effort and generalize exist-ing solutions by providing two constructs: a general form of state machines called parameterized state machines, and valued signals, as can be found in Esterel. Parameterized state machines greatly reduce the reliance on error-prone mechanisms such as shared memory in automaton-based programming. Signals provide a new way of programming with multi-rate data in synchronous data-flow languages. Together, they allow for a much more direct and natural programming of systems that combine data-flow and state-machines. The proposed extension is fully implemented in the new Lucid Synchrone compiler. Categories and Subject Descriptors C.3 [Special-purpose and application-based systems]: Real-time and embedded systems; D.3.2 [Language classi-fications]: Data-flow languages; F.3.2 [Semantics of pro-gramming languages]: Operational semantic