PROFIBUS (PROcess FleldBUS) is an open fieldbus standard developed in 1989 catering to the needs of both process automation and factory manufacturing automation. Initially developed by Siemens, it is particularly suitable for fast, time-critical applications and also involves complex communications. It is an open, vendor-independent (thus providing interoperability) fieldbus standard, adhering to the Open Systems Interconnection/ International Standards Organization (OSI/ISO) model for communication. It supports single cable wiring having multi-input sensor blocks, intelligent devices operator interfaces, and smaller subnetworks such as AS-i. It is based on the German National Standard DIN 19 245 Parts 1 and 2 and also has been ratified by the European National Standard EN 50170 Vol. 2. Three PROFIBUS versions are available: PROFIBUS-FMS, PROFIBUS-PA, and PROFIBUS-DP. The general PROFIBUS features are tabulated in Table 8.1.