process field bus (PROFIBUS)
Profibus is a standardized fieldbus for industrial automation and manufacturing technology. It is manufacturer-independent, has an open concept, is internationally standardized in EN 50170, EN 50254, IEC 61158 and DIN 19245 and has a hierarchical structure with the levels: Sensors/Actuators, Field level and Process level.
On the field level, the digitalsignals of the sensors and actuators are transmitted via the AS-Interface. Via this sensor/ actuator network in bus technology, the supply voltage of 24 V for the end components and the data signals are transmitted via a common transmission medium.
The distributed peripheral units, such as the I/O modules, measuring transducers, the control units for valves and motors, and the operator consoles of the administrators are located at the field level. The process data are transmitted cyclically, while alarm signals, parameters and diagnostic data can also be transmitted anticyclically.
At the cell level are the programmable controllers, which communicate with each other. On this functional level, large data packets with powerful communication functions must be transmitted. In addition, Profibus systems should be integrated into the company's communication infrastructure, Internet and Intranet, using common network and transport protocols. Therefore, Profibus relies on Ethernet as the transmission method in automation.
The Profibus concept works in master- slave mode with the token passingaccess method, where the slaves are only allowed to access the Profibus when requested by the masters. There are several masters, which exchange the access authorization among each other. As in the Token Ring, each master has a predecessor station and a successor station and receives the token after a fixed runtime. The transmission rates are between 9.6 kbit/s and 500 kbit/s, the number of participants is unlimited and the frame length is 246 bytes. The Profibus, which is networked to Profinet, is available in several variants: Profibus-FMS, Profibus-DP and Profibus-PA.
The Profibus activities are supported by the Profibus User Organization (PNO), the largest fieldbus organization.