NI-XNET CAN HS/FD Transceiver Cable Instructions
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© National Instruments
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13
Termination Resistors
The termination resistors (R
t
) should match the nominal
impedance of the CAN cable and therefore comply with the values
in Table 3. The onboard, software-selectable termination has a
nominal value of 120
Ω
. If you are not using the onboard
termination, use the values listed in Table 3.
Cable Lengths
The cabling characteristics and desired bit transmission rates affect
the allowable cable length. You can find detailed cable length
recommendations in the ISO 11898, CiA DS 102, and DeviceNet
specifications.
ISO 11898 specifies 40 m total cable length with a maximum
stub length of 0.3 m for a bit rate of 1 Mb/s. The ISO 11898
specification says that significantly longer cable lengths may be
Table 3.
Termination Resistor Specification
Characteristic
Value
Condition
Termination resistor, R
t
100
Ω
min,
120
Ω
nominal,
130
Ω
max
Minimum power
dissipation: 220 mW