Abstract: We present cyclo dynamic data flow (CDDF), a new data flow model for real time digital signal processing (DSP) applications. CDDF is an extension of cyclo static dataflow (CSDF) (G. Bilsen et al.; M. Engels et al., 1994) that keeps the interesting properties like analyzability and efficient compile time scheduling, while introducing data dependent control flow to improve the expressivity. The semantics are constructed such that extra knowledge about the internals of the actors, which is known to the programmer, can be expressed both in a natural way, and in a syntax that can be analyzed by automatic tools. We describe the proposed model in the context of already existing data flow languages, demonstrate its schedulability and its improved analyzability as compared to the Boolean data flow model (J.T. Buck, 1993).