National Instruments PXI-846x Computer Hardware User Manual


 
Appendix B Cabling Requirements for PXI-8460 Low-Speed CAN
PXI-846x and NI-CAN for Windows NT B-6 ni.com
Philips also recommends an individual device RTH and RTL termination of
500 to 16 k. The PXI-8460 board ships with mounted RTH and RTL
values of 510 ±5% per port. The PXI-8460 kit also includes a pair of
15 k ±5% resistors for each port. After determining the termination of
your existing network or device, you can use the following formula to
indicate which value should be placed on your PXI-8460 board in order to
produce the proper overall RTH and RTL termination of 100 to 500 upon
connection of the board:
*R
RTH overall
should be between 100 and 500
**R
RTH oflow-speed CANinterface
=510±5% (mounted) or 15 k±5% (in kit)
R
RTH
= R
RTL
As the formula indicates, the 510 ±5% shipped on your board will work
with properly terminated networkshaving atotal RTH and RTL termination
of 125 to 500 , or individual devices having an RTH and RTL termination
of 500 to 16 k. For communication with a network having an overall
RTH and RTL termination of 100 to 125 , you will need to replace the
510 resistors with the 15 kresistors in the kit. Please refer to the next
section, Replacing the Termination Resistors.
R
RTH overall*
1
1
R
RTH of low-speed CAN interface**
-----------------------------------------------------------------
1
R
RTH of existing network or device
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