Correct Wiring of Electrically Isolated CAN Networks
CPCI-CAN/200
Hardware Manual Doc.-Nr.: C.2035.21/ Rev. 2.2
Page 21 of 31
7.2.2 Device Cabling
Figure 5:
Example of proper wiring with single shielded double twisted pair cables
7.2.3 Branching
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In principle the CAN bus has to be realized in a line. The participants are connected to the
main CAN bus line via short cable stubs. This is normally realised by so called T-
connectors. When using esd's CAN-T-Connector (order no.: C.1311.03) it should be noted
that the shield potential of the conductive DSUB housing is not looped through this T-
Connector type. Thus, the shielding is interrupted. Therefore, you have to take adequate
measures to connect the shield potentials, as described in the manual of the CAN-T-
Connector. For further information on this read the CAN-T-Connector Manual (order no.:
C.1311.21).
Alternatively, a T-connector can be used, in which the shield potential is looped through,
e.g. the DSUB9 connector from ERNI (ERBIC CAN BUS MAX, order no.:154039).
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If a mixed application of single twisted and double twisted cables is unavoidable, take care
that the CAN_GND line is not interrupted!
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Deviations from the bus structure can be realized by the usage of repeaters.
7.2.4 Termination
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A termination resistor has to be connected at both ends of the CAN bus.
If an integrated CAN termination resistor which is equipped at the CAN interface at the end
of the bus is connected, this one has to be used for termination instead of an external CAN
termination plug.
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9-pin DSUB-termination connectors with integrated termination resistor and contact pins
and socket contacts are available from esd (order no. C.1303.01).
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9-pin DSUB-connectors with integrated switchable termination resistor can be ordered e.g.
from ERNI (ERBIC CAN BUS MAX, socket contacts, order no.:154039).
