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Determining the Necessary Termination
Resistance for the Board
Unlike High-Speed CAN, Low-Speed/Fault-Tolerant CAN
requires termination at the Low-Speed/Fault-Tolerant CAN
transceiver instead of on the cable itself. Termination requires
two resistors, RTH for CAN_H and RTL for CAN_L. This
configuration allows the NXP Fault-Tolerant CAN transceiver to
detect and recover from bus faults. It is important to determine
the overall termination of the existing network, or the termination
of the individual device, before connecting it to a Low-Speed/
Fault-Tolerant port. NXP recommends an overall RTH and RTL
termination of 100 to 500 Ω (each) for a properly terminated low-
speed network.
Termination on the low-speed/fault-tolerant ports of the NI 9861
is set through the NI-XNET software to either 1 kΩ or 5 kΩ.
Number of CAN Nodes
The maximum number of nodes depends on the electrical
characteristics of the nodes on the network. If all of the nodes
meet the requirements of Low-Speed/Fault-Tolerant CAN, up to
32 nodes may be connected to the bus.
NI 9861 Getting Started Guide
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© National Instruments
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