Bus Termination - ABB FCAN-01 User Manual

Bus termination

Bus termination is required to prevent signal reflections from the
bus cable ends. The adapter module is not equipped with internal
bus termination. Therefore the first and last nodes of the bus must
be included with bus termination. Termination is done by
connecting one resistor between the CAN_H and CAN_L signals.
The nominal value for the terminating resistor is 120 ohms. The
resistors can be connected between the CAN_H and CAN_L wires
or a D-SUB connector with a built-on termination can be used.
In the following diagram, the built-on terminations of the D-SUB
connectors at the first and last nodes are switched on.
CANopen
node
Term.
ON
In the following diagram, the bus line is terminated with 121 ohm,
1 % (E96) resistors connected between the CAN_L and CAN_H
wires at each end.
CANopen
node
121 ohm
1%
Metal Film
1/4 W
Note: Further information on CANopen wiring is available from
www.can-cia.org.
CANopen
node
Term.
OFF
CANopen
node
Electrical installation 33
CANopen
node
Term.
OFF
CANopen
...
node
CAN_H
CAN_L
CANopen
node
Term.
ON
121 ohm
1%
Metal Film
1/4 W