Evolution of Standard Fieldbus Networks

Until the late 1970s communication in the factory environment was based, where it existed, on proprietary solutions; field devices could not be monitored or programmed from a remote station, different cells could not communicate with each other, and so on. In such a situation neither open solutions nor integration could be achieved. The first attempt to define a standard protocol for field communication in the factory environment was made at the beginning of 1980s. It originated in a joint effort of the International Electrotechnical Committee (IEC) and the Instrumentation Society of America (lSA). In order to facilitate progress and to ensure that the two standards were developed at the same rate, joint IEC/ISA meetings were held. The project is known as IEC 1158/ISA SP 50 Fieldbus. The slow rate at which the international standardization activity was progressing and the growing needs of the industrial users led some groups of companies operating in the industrial automation field to define their own protocols mainly for factory communication and field communication. From among the proprietary proposals there are two which are particularly interesting: the FIP (Field Instrumentation Protocol) proposal, sponsored by a team of French companies, and the PROFlBUS (PROcess FleldBUS) proposal, supponed by a team of German companies. The PROFIBUS and FIP teams developed components and/or products satisfying their norms and also defined a suitable protocol. This commercial strategy facilitated the diffusion of the FIP and PROFlBUS protocols which have become national standards in France and Germany, respectively. In such a way these two protocols have begun to influence IEC/ISA Fieldbus international standardization activity; at the moment fieldbus has not yet been completely standardized but many of its mechanisms are derived from FIP or PROFlBUS or both. It is for these reasons that this chapter considers those three protocols, even though many other proposals and field communication models have been proposed during the last few years.