Synchronous model for Fieldbus applications

The aim of this paper is to show how the synchronous approach that is used in classical distributed systems can be adopted for designing Fieldbus applications. Generally, control applications can be classified into two different hierarchy levels, namely control loop at lower and supervisory control at higher level. The lower level systems are sampled systems and the higher level systems handle the logical part of the control that cannot be treated by the sampled systems. In this paper, the authors concentrate on applications that belong to the class of sampled systems. Typically, these applications have short response times (few milliseconds) and therefore, impose hard real-time constraints on the Fieldbus. The synchronous model that the authors propose is kept simple in order to permit efficient implementations. As a second contribution, the authors study the influence of real-time aspects of the application on the proposed synchronous model. Examples demonstrate the practical utility of the authors´ model