National Instruments NI 9853 User Manual
OPERATING INSTRUCTIONS
NI 9853
2-Port, High-Speed CAN Module
These operating instructions describe how to use the National
Instruments (NI) 9853 module. For information about installing,
configuring, and programming your system, refer to your system
documentation. The NI 9853 module requires the NI 9853 software
to be installed. The latest version of the NI 9853 software is located
at
ni.com/downloads.
Note The safety guidelines and specifications in this
document are specific to the NI 9853. 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 9853 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 9853 Operating Instructions 2 ni.com
Safety Guidelines for Hazardous Locations
The NI 9853 is suitable for use in Class I, Division 2, Groups A, B,
C, D, T4 hazardous locations; Class I, 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 9853 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 9853 Operating Instructions
Caution For Zone 2 applications, install a protection
device between the CAN signals and the NI 9853 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 Safe 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 9853
The NI 9853 has two 9-pin male D-Sub connectors that provide
connections to a CAN bus. Each port on the NI 9853 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.
Each port has two 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. You can connect the
CAN bus reference ground (sometimes referred to as CAN_V–) to
NI 9853 Operating Instructions 4 ni.com
one or both of the COM pins. 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.
CAN0 of the NI 9853 is internally powered, and therefore requires
no external power supply. CAN1 requires an external power supply
of +8 to +25 V to operate. Supply power to the V
pin of CAN1
SUP
from the CAN bus.
Note Although CAN0 of the NI 9853 does not require an
external power supply to operate, it can be connected to a
powered CAN bus without being damaged.
Pinouts for CAN0 and CAN1 of the NI 9853 are listed in Table 1
and Table 2.
Table 4 lists recommended termination resistor values.
© National Instruments Corp. 5 NI 9853 Operating Instructions
Table 1. Pin Assignments for CAN0
Connector Pin Signal
1 No Connection (NC)
2 CAN_L
3 COM
6
7
8
9
1
2
3
4
5
4 NC
5 SHLD
6 COM
7 CAN_H
8 NC
9 NC
NI 9853 Operating Instructions 6 ni.com
Table 2. Pin Assignments for CAN1
Connector Pin Signal
1 No Connection (NC)
2 CAN_L
3 COM
6
7
8
9
1
2
3
4
5
4 NC
5 SHLD
6 COM
7 CAN_H
8 NC
9 V
© National Instruments Corp. 7 NI 9853 Operating Instructions
SUP
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. If the transmission line is not terminated,
each signal change on the bus causes reflections that may cause
communication errors. Because the CAN bus is bidirectional, both
ends of the cable must be terminated. However, this requirement
does not mean that every node on the bus should have a termination
resistor—only the nodes at the end of the cable should have
termination resistors.
Figure 1 shows a simplified diagram of a CAN bus with multiple
CAN nodes, and proper termination resistor (R
NI 9853 Operating Instructions 8 ni.com
) locations.
t
Bus Cable Length
CAN
Node
CAN_H
R
t
CAN_L
CAN_H
CAN_L
CAN
R
t
Node
Stub
Length
CAN_L
CAN_L
CAN
Node
CAN_H
CAN_H
CAN
Node
Figure 1. CAN Bus Topology and Termination Resistor Locations
© National Instruments Corp. 9 NI 9853 Operating Instructions
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