ProfiBus PA/DP/FMS overview

This chapter provides an insight into the PROcess FIeld BUS (Profibus) networking standard and its several versions. Profibus is a widely accepted international networking standard, commonly found in process control and in large assembly and material handling machines. It supports single-cable wiring of multi-input sensor blocks, pneumatic valves, complex intelligent devices, smaller sub-networks (such as AS-i), and operator interfaces. It is an open, vendor-independent standard and adheres to the OSI model and ensures that devices from a variety of different vendors can communicate together easily and effectively. It has been standardized under the German National standard as DIN 19 245 Parts 1 and 2 and, in addition, has also been ratified under the European national standard EN 50170 Volume 2. Profibus DP (distributed peripheral) allows the use of multiple master devices, in which case each slave device is assigned to one master. This means that multiple masters can read inputs from the device but only one master can write outputs to that device. Profibus FMS (fieldbus message specification) is a peer-to-peer messaging format, which allows masters to communicate with one another. The Profibus PA protocol is the same as the latest Profibus DP with V1 diagnostic extensions, except that voltage and current levels are reduced to meet the requirements of intrinsic safety (class I division II) for the process industry.