AppendixB CablingRequirements for PXI-8460 Low-Speed CAN
©NationalInstruments Corporation B-5 PXI-846xand NI-CAN for Windows NT
Low-Speed Termination
Everydevice on the low-speed CAN network requires a termination
resistorfor each CAN data line: RRTH for CAN_H and RRTL for CAN_L.
FigureB -4 showstermination resistor placement in a low-speed CAN
network.
FigureB-4. Termination Resistor Placement for Low-Speed CAN
Thefollowing sections explain how to determine the correct resistor values
for your PXI-8460, and howto r eplace those resistors, if necessary.

Determining the Necessary TerminationR esistance for YourBoard

Unlikehigh-speed CAN, low-speed CAN requires termination at the
low-speedCAN transceiver instead of on the cable. The termination
requiresone resistor for eachCAN line. This configurationallows the
Philipsfault-tolerant CAN transceiver to detect any of sevennetwork faults.
Youcanuse your PXI-84 60 to connect to a low-speedCAN network having
from twoto 32 nodes as specifiedby Philips (including the port on the
PXI-8460as a no de). Youcan also use the PXI-8460 to communicate with
individuallow-speed CAN devices. It is important to determine the overall
terminationof your existing network, or the termination of you r individual
device,before connecting it to a PXI-8460 port.Phi lips recommends an
overallRTH and RTL termination of 100 to 500 Ω(each) for a properly
terminated low-speednetwork .The overallnetwork termination may be
determined as follows:
Low-speed
CANDevice
RTL CAN_L RTH CAN_H
Low-speed
CANDevice
RTL CAN_L RTH CAN_H
Low-speed
CANDevice
RTL CAN_L RTH CAN_H
CAN_H
CAN_L
1
RRTHoverall†
-------------------------- 1
RRTHnode 1
------------------------ 1
RRTHnode 2
------------------------ 1
RRTHnode 3
------------------------ 1
RRTH node n
-------------------------+++=