Control Area Network

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Control Area Network, or CAN (sometimes called CAN Bus), is the chosen networking method for Layout Command Control.

For this article and to be consistent, the term CAN will be used for Control Area Network.

Zimo employs the CAN Bus to network their DCC systems.

History of CAN and LCC

CAN found adoption with the automobile industry.

The reason for this is the bus is noise tolerant, an industry standard, and designed for the 12­/24V world.

CAN can operate over a wide speed range, with a linear trade off between bus speeds and bus lengths. The OpenLCB engineers selected a 125Kb rate and 1000’ maximum bus length as a compromise for model railroad use. Unlike other Peer to ­Peer systems, CAN can operate at a 100% data throughput rate with error free collision resolution.

Disadvantages of CAN

The relatively high CAN bus speed does not allow free form network design. A CAN network segment requires a linear bus with terminations at each end. Timing and other electrical limitations mean that a single CAN segment is limited to 40 or fewer physical nodes. There are solutions to expand a CAN network into multiple segments.

CAN supports several different cabling and connector standards. Some require large (and costly) connectors. Often CAN will use the DB­9 connectors found on RS­232 serial cables. Another CAN connector option uses RJ45 connectors and cables, as wired Ethernet does.

The OpenLCB engineers opted for RJ45 connectors because of relative low cost and availability world wide. The 4 wire pairs of an Ethernet cable also allow for additional options such as power and other signals in addition to the CAN signal pair itself.