This paper extends the existing synchronous dataflow (SDF) model to provide dynamic behavior and top down design with compile time deadlock detection and bounded buffer memory.We propose a new dataflow model called constant rate dataflow with intermediate ports (CRDF-IP) in which a component (or actor) can send and receive data to/from another actor through intermediate port during its execution. Since an actor can call another actor multiple times per execution, dynamic behaviors are easily specified without introducing run-time scheduler. Moreover, top-down design can be achieved by extracting a sub-actor from the top actor.This paper has proved that deadlock detection and buffer size computation can be performed at compile in CRDF-IP model. The proposed model has been implemented in a system level design platform in which H.263 video encoding algorithm is specified.