Experience with formal methods implementing the PROFIBUS FMS and DP protocol for industrial applications

The paper presents our experience using the formal description technique Estelle for the protocol development cycle in the area of real time industrial communication systems. As a real world application, the PROFIBUS parts FMS and DP of the European fieldbus standard were completely implemented using formal models. These implementations are successfully used in industrial applications and embedded systems. Our development method, results, and experiences during the development process are discussed. A closed, tool based method is the overall aim concerning the development life cycle to support the requirement definition as well as the implementation of the product code with final testing. To meet these needs, our approach defines some assumptions and constraints using the syntactic and semantic model of the specification language Estelle, aspects of the modelling process concerning the architecture, handling data abstraction and encapsulation of the specification language vs. real time data flow in the product code implementation, synchronous vs. asynchronous communications to local interfaces (e.g. physical layer or partly data link layer ASIC) and dealing with special local events like timeouts and interrupts in the specification and in the real time execution environment. The paper discusses advantages and also critical points using the formal way of the protocol development cycle. In theory, it is quite clear that formal description techniques enhance quality. Therefore, we discuss this approach from the user's point of view.