A conservative extension of synchronous data-flow with state machines

This paper presents an extension of a synchronous data-flow language such as Lustre with imperative features expressed in terms of powerful state machine a ̀ la SyncChart. This extension is fully conservative in the sense that all the pro-grams from the basic language still make sense in the ex-tended language and their semantics is preserved. From a syntactical point of view this extension consists in hierarchical state machines that may carry at each hierarchy level a bunch of equations. This proposition is an alternative to the joint use of Simulink and Stateflow but improves it by allowing a fine grain mix of both styles. The central idea of the paper is to base this extension on the use of clocks, translating imperative constructs into well clocked data-flow programs from the basic language. This clock directed approach is an easy way to define a seman-tics for the extension, it is light to implement in an exist-ing compiler and experiments show that the generated code compete favorably with ad-hoc techniques. The proposed extension has been implemented in the ReLuC compiler of Scade/Lustre and in the Lucid Synchrone compiler. Categories and Subject Descriptors C.3 [Special-purpose and application-based systems]: Real-time and embedded systems; D.3.2 [Language clas-sifications]: Data-flow language