National Instruments NI 9861, Operating Instructions Manual, Page: 7 / 20

© National Instruments Corp. 7 NI 9861 Operating Instructions
CAN Bus Topology and Termination
A CAN bus consists of two or more CAN nodes cabled together.
The CAN_H and CAN_L pins of each node are connected to the
main CAN bus cable through a short connection known as a “stub.”
The pair of signal wires, CAN_H and CAN_L, constitutes a
transmission line. Every device on a low-speed/fault tolerant CAN
network requires a termination resistor for each CAN data line:
R
RTH
for CAN_H and R
RTL
for CAN_L.
Figure 1 shows a simplified diagram of a CAN bus with multiple
CAN nodes and proper termination resistor (R
t
) locations.
Figure 1. CAN Bus Topology and Termination Resistor Locations
RTL CAN_L RTH CAN_H RTL CAN_L RTH CAN_H RTL CAN_L RTH CAN_H
CAN_H
CAN_L
Low-Speed/Fault-Tolerant
CAN Device
Low-Speed/Fault-Tolerant
CAN Device
Low-Speed/Fault-Tolerant
CAN Device
R
t
R
t
R
t
R
t
R
t
R
t