New Efficient Communication Services for ISO 11898 Networks

Fieldbus networks should be able to support several kinds of data exchanges, which are characterised by very different requirements. The most popular solutions available today have been designed with some sets of specific needs in mind and usually, they are not always able to satisfy, equally well, the different kinds of communications which can be found in the industrial and process control environments. Often, system integrators and designers are forced to trade responsiveness (needed in event-driven systems) for efficiency (mostly required in systems which are based on the periodic polling of the controlled devices), or vice-versa. In this paper, a modification of the basic ISO 11898 protocol is described which supports some new transmission services that significantly increase the communication efficiency for periodic exchanges of process data and for messages devoted to high level functions. These services maintain a good degree of compatibility with the original protocol and do not affect its very good responsiveness and flexibility.