On the performances of two popular fieldbuses

CAN and PROFIBUS-DP are two very popular fieldbuses, which can be profitably used also as control networks for distributed systems where a controller is connected to a number of simple devices. In this paper, the use of CAN and PROFIBUS-DP as a communication support for event-driven systems is considered and their performances are evaluated from this point of view. Only those aspects of these two networks which are relevant in the scenario of event-driven automation systems are taken into account and formulas are derived to evaluate the responsiveness and throughput which can be achieved in a number of situations. The results obtained with our analysis show that even though the performances of the two kinds of fieldbuses are very similar, it is convenient to use CAN in small-size systems while PROFIBUS-DP is more suited to poll-based applications.