A Communication Support for Real-Time Distributed Computer Controlled Systems
Eduardo Tovar, Francisco Vasques · 1998
In this paper, we analyse the ability of P-NET [1] fieldbus to cope with the timing requirements of a Distributed Computer Control System (DCCS), where messages associated to discrete events should be made available within a maximum bound time. The main objective of this work is to analyse how the network access and queueing delays, imposed by P-NET's virtual token Medium Access Control (MAC) mechanism, affect the realtime behaviour of the supported DCCS. 1. Introduction Within industrial communication systems, fieldbus networks are specially devoted for the interconnection of process controllers, sensors and actuators, at the lower levels of the factory automation hierarchy (figure 1). Among other characteristics, these hierarchical levels have dissimilar message flows. It is possible to classify [2] such flows, carried by the communication systems, according to: . the required response time, that is, how quickly messages must be transferred; . their length, that is, the amount o...