Calcolo dei tempi di Ciclo nelle Reti Profibus DP

Profibus DP is a fieldbus designed for use at low level of factory automation systems, where it performs high speed data exchanging between process controllers and field devices, such as sensors and actuators, in a master-slave configuration. The standardisation process of Profibus DP began with the German national standard DIN 19245 part 3, issued in 1994. Subsequently it was included, together with other fieldbuses, in the European Standard EN50170. Finally, at the beginning of 2000, a complete (and revised) version of Profibus DP became part of the IEC 61158 international fieldbus standard. The standard specifies mainly three types of possible configurations for Profibus DP networks: Mono-master (only one DP master device) , Multi-master (more than one DP master device) and Combi-master (presence of other masters implementing a different protocol). This paper analyses in detail the behaviour of the network giving an analytical calculation of the cycle time. Moreover it takes into consideration the presence of acyclic messages of various type and gives an evaluation of their effects on the cycle time.