National Instruments NI 9871, RS422, RS-485 User Manual

OPERATING INSTRUCTIONS AND SPECIFICATIONS

NI 9871

4-Port, RS485/RS422 Serial Module

This document describes how to use the National Instruments 9871
and includes specifications and pin assignments for the NI 9871.
Vis it ni.com/info and enter rdsoftwareversion to determine
which software you need for the modules you are using. For
information about installing, configuring, and programming the
system, refer to the system documentation. Visit
enter

cseriesdoc for information about C Series documentation.

Note The safety guidelines and specifications in this

ni.com/info and

document are specific to the NI 9871. The other
components in the system might not meet the same safety
ratings and specifications. Refer to the documentation for
each component in the system to determine the safety
ratings and specifications for the entire system. Visit

ni.com/info and enter cseriesdoc for information

about C Series documentation.

Safety Guidelines

Operate the NI 9871 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 9871 Operating Instructions 2 ni.com

Safety Guidelines for Hazardous Locations

The NI 9871 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 9871 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 9871 Operating Instructions

Caution For Zone 2 applications, install a protection

device between the RS485/RS422 signal cables and the
NI 9871 RJ-50 jacks (ports 1– 4). The device must
prevent the RS485/RS422 signal-to-signal or
signal-to-COM voltage from exceeding 23 V if there is a
transient overvoltage condition.

Caution For Zone 2 applications, install a protection

device between the external power supply and the
NI 9871 V
V

-to-COM voltage from exceeding 39 V if there is a

sup

and COM pins. The device must prevent the

sup

transient overvoltage condition.

Special Conditions for Hazardous Locations in Europe

This equipment has been evaluated as Ex nA IIC T4 equipment
under DEMKO Certificate No. 07 ATEX 0626664X. Each module
is marked II 3G and is suitable for use in Zone 2 hazardous
locations. If you are using the NI 9871 in Gas Group IIC hazardous
locations or in ambient temperatures of –40 °C ≤ Ta ≤ 70 °C, you
must use the device in an NI chassis or controller that has been
evaluated as EEx nC IIC T4, Ex nA IIC T4, or Ex nL IIC T4
equipment.

NI 9871 Operating Instructions 4 ni.com

Special Conditions for Marine Applications

Some modules are Lloyd’s Register (LR) Type Approved for
marine applications. To verify Lloyd’s Register certification, visit

ni.com/certification and search for the LR certificate, or

look for the Lloyd’s Register mark on the module.

Caution To meet radio frequency emission requirements

for marine applications, use shielded cables and install
the system in a metal enclosure. Suppression ferrites
must be installed on power supply inputs near power
entries to modules and controllers. Power supply and
module cables must be separated on opposite sides of the
enclosure and must enter and exit through opposing
enclosure walls.

© National Instruments Corp. 5 NI 9871 Operating Instructions

Wiring the NI 9871

The NI 9871 has four RJ-50 receptacles that provide connections
for four RS485/RS422 devices.

Table 1. RS485/RS422 Port Pinout

RJ50 Jack

* These signals are shared by all four RJ-50 connectors on the NI 9871.

NI 9871 Operating Instructions 6 ni.com

RJ-50 Pin Signal Name*

1 No Connect

2 TXD–

3 TXD+

1

NC

2

TXD–

3

TXD+

4

RTS–

5

CTS–

6

RXD–

7

RXD+

8

RTS+

9

CTS+

10

COM

4 RTS –

5 CTS–

6 RXD–

7 RXD+

8 RTS +

9 CTS+

10 GND

The cables included with your kit convert the RJ-50 pinout to the
standard NI pinout, as shown in Table 2.

Table 2. Pin Assignments for RS485/RS422 DB-9 Male Connector

Connector Pin Signal

1 GND

2 CTS+

3 RT S+

6
7
8
9

© National Instruments Corp. 7 NI 9871 Operating Instructions

1
2
3
4
5

4 RXD+

5 RXD–

6 CTS–

7 RT S–

8 TXD+

9 TXD–

You must connect an external power supply to the NI 9871.
This power supply provides the power for the RS485/RS422
transceivers on the module. You can use the included female
four-position pigtail to connect to an external voltage source.
Figure 1 lists the connections between an external voltage source
(of +8 V to +28 V) and the NI 9871.

2

4

3

1V

SUP

2V

SUP

1

3 COM 4COM

Figure 1. Four-Position External Power Connector

NI 9871 Operating Instructions 8 ni.com