Fieldbus networks aim at the interconnection of field devices such assensors, actuators and small controllers. Therefore, they are an effectivetechnology upon which Distributed Computer Controlled Systems (DCCS) canbe built. DCCS impose strict timeliness requirements to the communicationnetwork. In essence, by timeliness requirements we mean that traffic must besent and received within a bounded interval, otherwise a timing fault is said tooccur. P-NET is a multi-master fieldbus standard based on a virtual tokenpassing scheme. In P-NET each master is allowed to transmit only one messageper token visit, which means that in the worst-case the communication responsetime could be derived considering that the token is fully utilised by all stations.However, such analysis can be proved to be quite pessimistic. In this paper wepropose a more sophisticated P-NET timing analysis model, which considersthe actual token utilisation by different masters. The major contribution of thismodel is to provide a less pessimistic, and thus more accurate, analysis for theevaluation of the worst-case communication response time in P-NET fieldbusnetworks.
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