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Repeater

Introduction Repeater

Repeaters are used to establish a physical coupling of two or more segments of a CAN bus system. They can be used to implement tree or star topologies as well as for long drop lines. In addition, network segments can be electrically decoupled using a galvanically isolated repeater.

The lines coupled by the repeater are independent electric segments that can be optimally terminated in terms of signals. In this way topologies can be implemented that are not possible with a pure line of the bus due to electrical reflections.

According to the transceiver output capacities, the division of a CAN system into several subsystems, connected via CAN repeaters, increases the maximum number of bus nodes.

As signaling is not directed in CAN, the repeater logic has to translate the signals of the segment received into the other and has to ensure that the input signals are not back-coupled. In terms of signals, the repeater corresponds to a line with relevant delay time. Therefore, it cannot be used to extend a CAN system.

Using repeaters does not influence the real-time behavior of a system because in terms of transmission behavior it corresponds to a network that consists only of lines.

Another application of repeaters is the coupling of different physical CAN layers by means of high/low-speed repeaters, optical repeaters, or optical star couplers.

The repeaters offered by IXXAT have an additional monitoring function. Connected network segments that are disturbed by permanent dominant levels are detected and automatically disconnected, thus allowing the remaining network to continue functioning normally. After the fault has been eliminated, the operation of a disconnected segment is detected and the segment is automatically reconnected to the network.

IXXAT also offers the repeater technology for licensed integration into customer hardware.

Conventional bus structure of CAN Networks - Overview

Conventional bus structure
The distance between the two nodes
furthest apart (1/9) is 220 meters

Extended CAN bus structure with drop line - Overview

Extended structure with drop line
The distance between the two nodes
furthest apart (1/6 or 6/9) is 150 meters