General Information about Fieldbus Systems

Industrial data communication by serial bus systems is the core of every distributed control and IO system. Serial bus systems designed for real-time data communication are called Fieldbuses. Fieldbuses are industrial networks for deterministic real-time data communication between bus masters, distributed actors and sensors.

They are designed for low latency and low transmission volumes. The packet sizes of fieldbuses are in general in the range of 1 to 200-300 bytes. The transmission speed can be choosen in a wide range from e.g. 12Mbit/s down to 1200bit/s. This flexibility of transmission speed is a big advantage against Ethernet based networks, e.g.

The useable segment length depends on the transmission speed, transmission media, and the topology of the individual fieldbus. In general, high transmission speed decreases the segment length of bus oriented fieldbuses to a length of 50 to 100 meters; low transmission speed allows a segment length in the range of a few kilometers.

Fieldbuses with a ring topology like INTERBUS or EtherCAT are working often with a physical extension in the range of kilometers because of the signal refreshing which is done by the fieldbus modules. Fiber optical transmission medias allow in general extended segment lengths and increased noise immunity. The Fieldbus Comparison shows a collection of the most important fieldbuses, their core attributes and their relationship to standards.

STEINHOFF offers support packages for PC based control systems with fieldbuses running QNX 4.25 RTOS, QNX Neutrino RTOS v. 6.3 , RTAI-Linux and Linux. If you are interested in INTEGRITY or VxWorks based packages, please contact us.