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.It is not easy to specify a general algorithm in SDF since it does not allow dynamic behaviors such as if-then-else, for-loop and while-loop, and top-down design which provides progressive algorithm improvement, even though SDF model provides static analysis of deadlock detection, compile time buffer size computation and efficient code generation. In order to solve these problems without any performance degradation,we propose a new dataflow model called constant rate dataflow with intermediate ports (CRDF-IP). In the proposed model, 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 requiring a run-time scheduler.Moreover, top-down design can be achieved by extracting a sub-actor from a top actor. This paper proves that deadlock detection and buffer size computation can be performed at compile time 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.