Technical system comprising hardware and software that makes possible communication and the exchange of data between the devices connected to it (Figure F 8). The devices are primarily sensors, actuators, valves and process-related components, as well as control terminals and interfaces to other bus systems. These days the inter-machine communication that generally uses the 7-layer ISO/OSI architecture model is limited in fieldbus to layer 1 (physical layer), layer 2 (data link layer) and layer 7 (application layer).
As the hardware for communication, in fieldbus e.g. the serial interface RS 485 or optical fibres are often used. The communication is co-ordinated by serial protocols (software) that ensure signal transmission with the correct timing, a high level of immunity to interference and flexibility in relation to the number of bus users, speed and type of data transmitted.
These days in industrial drive and control technology numerous fieldbus systems are available, e.g. ASI (communication and electrical control are transported on the same cable), CAN bus, Interbus, Profibus DP among others. Fieldbuses are to some extent already standardised, e.g. in DIN 19 245. The usage of fieldbuses significantly reduces the wiring effort in control systems, as all devices are connected to the same cable. The fieldbus is an important element for the development of decentral control systems and intelligent sensors, actuators and systems.
Figure F 8: Communication architecture