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Implementing stars and decoupling segments

With topology components such as CAN repeaters, hubs, bridges, and switches, high bandwidths can be realized even in large CAN network architectures. These components even enable star and tree topologies instead of the usual linear bus structure.

(Photo: Ixxat)

CAN REPEATERS PRIMARILY SERVE the physical connection of two or more segments of a CAN system and for long stubs. The hubs (repeater with more than two CAN ports) allow for the implementation of tree and star topologies. Repeaters and hubs do not in general influence the real-time behavior of a system. An application scenario: three pitch controllers in a wind turbine shall communicate with the master controller via CAN.

The standard line topology of CAN is not equal to the task. However, CAN repeaters enable star connections to the individual wind-turbine blades. They also establish galvanic isolation and thereby improve lightning protection. In case of unexpected failures in the network, faulty segments can be taken off the network by means of an integrated monitoring function in order to maintain reliable communication between the other network participants.

As soon as the failure has been repaired, the restored segment is reconnected without interruptions. CAN systems linked via a repeater represent autonomous electrical segments with optimum signal termination – thus, topologies can be realized which would be impossible with a simple linear bus topology for the danger of electrical reflections.

(The full article “Tapping the full potential of CAN with topology components” by Frank Pastors (Ixxat) has been published in CAN Newsletter 1/2012)


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