Device descriptions: The key to fieldbus interoperability
M. Santori · InTech · 1995
The subject of interoperability and fieldbus is a complicated one. Both the definition of and the need for interoperability are subject to some debate. Is it merely the ability to substitute one device for another, or does interoperability imply some greater flexibility in configuring and modifying control systems? In the realm of the Fieldbus Foundation fieldbus, interoperability is embodied in a key technology: device descriptions. A device description (DD) is a clear, unambiguous description of a field device; precisely defining the features, parameters, and operation of the device so a host system can communicate with it. DDs provide both interoperability, by defining the capabilities of typical devices, and product innovation, by giving device manufacturers a common mechanism for describing the functionality included in their devices. Users need not understand the technical working of DDs to derive their benefits. Many readers, however, are curious about how this technology works. This article gives a brief introduction to DDs from a technical perspective. The best place to start is by taking a look at the overall fieldbus architecture. Fieldbus, like any data network, is constructed from a set of communication layers. Each layer performs a specific function required for hosts and devices tomore » communicate on the fieldbus network. For most users, the only layers to be concerned with are the Physical Layer, which defines how you physically wire a network, and the User Layer. The User Layer defines how a user views the world of the fieldbus network and field devices on the network. 7 figs.« less