OPERATING INSTRUCTIONS
NI 9852
2-Port, Low-Speed/Fault-Tolerant CAN Module
These operating instructions describe how to use the National
Instruments (NI) 9852 module. For information about installing,
configuring, and programming your system, refer to your system
documentation. The NI 9852 module requires the NI 985x software
(version 1.2 or higher) to be installed. The latest version of the
NI 985x software is located at
Note The safety guidelines and specifications in this
ni.com/downloads.
document are specific to the NI 9852. The other
components in your system may not meet the same safety
ratings and specifications. Refer to the documentation for
each component in your system to determine the safety
ratings and specifications for the entire system.
Safety Guidelines
Operate the NI 9852 only as described in these operating
instructions.
Hot Surface This icon denotes that the component may be
hot. Touching this component may result in bodily injury.
NI 9852 Operating Instructions 2 ni.com
Safety Guidelines for Hazardous Locations
The NI 9852 is suitable for use in Class I, Division 2, Groups A, B,
C, D, and T4 hazardous locations; Class 1, Zone 2, AEx nA II T4
and Ex nA II T4 hazardous locations; and nonhazardous locations
only. Follow these guidelines if you are installing the NI 9852 in a
potentially explosive environment. Not following these guidelines
may result in serious injury or death.
Caution Do not disconnect I/O-side wires or connectors
unless power has been switched off or the area is known
to be nonhazardous.
Caution Do not remove modules unless power has been
switched off or the area is known to be nonhazardous.
Caution Substitution of components may impair
suitability for Class I, Division 2.
Caution For Zone 2 applications, install the
CompactRIO system in an enclosure rated to at least
IP 54 as defined by IEC 60529 and EN 60529.
© National Instruments Corp. 3 NI 9852 Operating Instructions
Caution For Zone 2 applications, install a protection
device between the CAN signals and the NI 9852 CAN
pins. The device must prevent the CAN Port-to-COM
voltage from exceeding 55 V if there is a transient
overvoltage condition.
Special Conditions for Hazardous Locations Use in Europe
This equipment has been evaluated as EEx nA II T4 equipment
under DEMKO Certificate No. 03 ATEX 0324020X. Each module
is marked II 3G and is suitable for use in Zone 2 hazardous
locations.
Wiring the NI 9852
The NI 9852 has two 9-pin male D-Sub connectors that provide
connections to a CAN bus. Each port on the NI 9852 has pins for
CAN_H and CAN_L, to which you connect the CAN bus signals.
These signals should be connected using twisted-pair cable.
NI 9852 Operating Instructions 4 ni.com
Each port has two isolated common pins (COM) that are internally
connected to the isolated reference of the module and serve as the
reference ground for CAN_H and CAN_L. Connect the CAN bus
reference ground (sometimes referred to as CAN_V–) to the COM
pin. Each port also has an optional shield pin, SHLD, that can be
connected to a shielded CAN cable. Connecting SHLD may
improve signal integrity and EMC performance in a noisy
environment.
Both of the ports on the NI 9852 require an external power supply
of +8 V to +36 V to operate. Supply power from the CAN bus to
the V
pin on CAN0, and the V
SUP0
pin on CAN1.
SUP1
Pinouts for CAN0 and CAN1 of the NI 9852 are listed in Table 1
and Table 2.
© National Instruments Corp. 5 NI 9852 Operating Instructions
Table 1. Pin Assignments for CAN0
Connector Pin Signal
1 No Connection (NC)
2 CAN_L
3 COM0
6
7
8
9
1
2
3
4
5
4 NC
5 SHLD
6 COM0
7 CAN_H
8 NC
9 V
NI 9852 Operating Instructions 6 ni.com
SUP0
Table 2. Pin Assignments for CAN1
Connector Pin Signal
1 No Connection (NC)
2 CAN_L
3 COM1
6
7
8
9
1
2
3
4
5
4 NC
5 SHLD
6 COM1
7 CAN_H
8 NC
9 V
© National Instruments Corp. 7 NI 9852 Operating Instructions
SUP1
CAN Bus Topology and Termination
A CAN bus consists of two or more CAN nodes cabled together.
The CAN_H and CAN_L pins of each node are connected to the
main CAN bus cable through a short connection known as a “stub.”
The pair of signal wires, CAN_H and CAN_L constitutes a
transmission line. Every device on a low-speed/fault-tolerant CAN
network requires a termination resistor for each CAN data line:
R
for CAN_H and R
RTH
Figure 1 shows a simplified diagram of a low-speed/fault-tolerant
CAN bus with termination resistor placements.
NI 9852 Operating Instructions 8 ni.com
for CAN_L.
RTL
Low-speed/Fault-Tolerant
CAN Device
RTL CAN_L RTH CAN_H RTL CAN_L RTH CAN_H RTL CAN_L RTH CAN_H
Low-speed/Fault-Tolerant
CAN_H
CAN_L
CAN Device
Low-speed/Fault-Tolerant
CAN Device
Figure 1. CAN Bus Topology and Termination Resistor Locations
Connecting a CAN Bus to the NI 9852
Each port of the NI 9852 can be connected to any location on a
CAN bus. Figure 2 shows one example of the connection of CAN0
of the NI 9852 directly to one CAN node, and CAN1 directly to
another CAN node. CAN0 and CAN1 require an external power
supply on the CAN bus.
© National Instruments Corp. 9 NI 9852 Operating Instructions
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