Research And Realization Of Foundation Fieldbus Message Specification

The fieldbus is one of the hotspot in the automation control area. The fieldbus control system based on it becomes the mainstream of control system step by step. Foundation fieldbus is a fieldbus technology that has good market outlook. It is widely supported by the instrument manufacturers in the process automation area. Fieldbus message specification is one layer of the protocol stack. The content of it is introduced in this paper. Then, the method of how to design the software is also given based on the nucleus real-time operating system. This paper aims to find out the method that is proper to accomplish the function of fieldbus message specification layer.Firstly, the structure of foundation fieldbus system model is analysied. The function of each layer and their relationship is introduced in this paper. For the comprehension of the protocol stack some important concepts are also introduced. Through the analysis the overall of the protocol stack can be understanded.Secondly, the paper presents the content of the fieldbus message specification layer. It describes the services of the fieldbus message specification. Then, it studies the principle of encode and decode and the state machine of this layer. Because fieldbus message specification layer is one layer of the protocol stack, this paper researches the communication characteristic of foundation fieldbus.Finally, the software design of fieldbus message specification layer is presented. The design is based on nucleus plus which is a widely used real time operation system. It gives the solutions of how to write the software to accomplished protocol's services. Considered of the communication characteristic of the foundation fieldbus, the interfaces between fieldbus message specification layer and other layers is designed to meet the practical used.Although the protocol of foundation fieldbus is very complicated, the content of it can be understanded by detailed analysis. The software that accord with the protocol can be programmed. When the software is programmed, the communication characteristic must be considered and the software can accord with the need of practical use.