PCC: a modeling technique for mixed control/data flow systems

Many signal processing systems make use of event driven mechanisms-typically based on finite state machines (FSMs)-to control the operation of the computationally intensive (data flow) parts. The state machines in turn are often fueled by external inputs as well as by feedback from the signal processing portions of the system. Packet-based transmission systems are a good example for such a close interaction between data and control flow. For a smooth design flow with a maximum degree of modularity it is of crucial importance to be able to model the complete functionality of the system, containing both control and data flow, within one single design environment. While the degree of abstraction should be sufficiently high to model and simulate efficiently, the link to implementation has to be fully supported. For these reasons we developed a computational model that integrates the specification of control and data flow. It combines the notion of multirate dynamic data flow graphs with event driven process activation. Thus, it maintains the flexibility and expressive power of data flow representations while enabling designers to efficiently control these operations by incorporating control automata that may have been designed using protocol compilers or state machine tools.