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National Instruments Corp.
7
NI 9882 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. If the transmission line is not terminated,
each signal change on the bus causes reflections that may cause
communication errors. Because the CAN bus is bidirectional, both
ends of the cable must be terminated. However, this requirement
does not mean that every node on the bus should have a termination
resistor; only the two nodes at the far end of the cable should have
termination resistors.
Figure 1 shows a simplified diagram of a CAN bus with multiple
CAN nodes and proper termination resistor (R
t
) locations.
