PROFIBUS is a fieldbus communication standard in the automation technology. The universal fieldbus is mainly used in manufacturing-, process- and building automation and has been standardized in IEC 61158 and IEC 61784. The so-called line topology is used for the PROFIBUS. The maximum number of BUS participants is limited to 126 and the individual BUS segments are divided into 32 participants. Repeaters amplify the signal between the individual segments. The PROFIBUS fieldbus is a master/slave system.
The master, usually only one in the system, sends data as an active participant according to its cycle. In addition, it requests data from passive participants, the so-called slaves, cyclically. The slaves, such as IO modules or drives, only acknowledge or forward process data to the master and therefore have no access to the bus. In principle, several masters can also be connected to a PROFIBUS fieldbus. Fixed slaves are then assigned to the masters and the access of the two masters to the bus is synchronized via a token. Up to 244 bytes of data can be transferred per bus user.