Bus Termination - ABB FCAN-01 User Manual

Bus termination

Bus termination is required to prevent signal reflections from the
bus cable ends. The FCAN-01 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 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
resistors connected between the CAN_L and CAN_H wires at
each end.
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
CANopen
node
Term.
OFF
CANopen
node
• • •
CAN_H
CAN_L
CANopen
node
Term.
ON
CANopen
node
121 ohm
1%
Metal Film
1/4 W
Electrical installation
43