Appendix B
Cabling Requirements for PXI-8460 Low-Speed CAN
PXI-846x and NI-CAN for Windows 98/95
B-6
ni.com
Philips also recommends an individual device RTH and RTL termination of
500
Ω
to 16 k
Ω
. The PXI-8460 board ships with mounted RTH and RTL
values of 510
Ω
±5% per port. The PXI-8460 kit also includes a pair of
15 k
Ω
±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
Ω
upon
connection of the board:
*
R
RTH overall
should be between 100 and 500
Ω
**
R
RTH of low-speed CAN interface
= 510
Ω
±5% (mounted) or 15 k
Ω
±5% (in kit)
†
R
RTH
=
R
RTL
As the formula indicates, the 510
Ω
±5% shipped on your board will work
with properly terminated networks having a total RTH and RTL termination
of 125 to 500
Ω
, or individual devices having an RTH and RTL termination
of 500
Ω
to 16 k
Ω
. For communication with a network having an overall
RTH and RTL termination of 100 to 125
Ω
, you will need to replace the
510
Ω
resistors with the 15 k
Ω
resistors 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
--------------------------------------------------------------
+
-------------------------------------------------------------------------------------------------------------------------------------------
=
