National Instruments NI 9871, RS422, RS485

NI 9871 Operating Instructions 8 ni.com

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.

Figure1 lists the connections between an external voltage source

(of +8 V to +28 V) and the NI 9871.

Figure 1. Four-Position External Power Connector

SUP 2V

SUP 3COM 4COM

Contents

Main Safety Guidelines Safety Guidelines for Hazardous Locations Special Conditions for Hazardous Locations in Europe Special Conditions for Marine Applications 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 RJ-50 Pin Signal Name* Table 2. Pin Assignments for RS485/RS422 DB-9 Male Connector Connector Pin Signal Page Page Page RS485 Bus Topology and Termination RS485 terminators are available at ni.com/serial. Figure 4. 4-Wire Full-Duplex Multidrop Network Using Terminating Resistors Figure 5. 2-Wire Multidrop Network Using Terminating Resistors RS485 Transceiver Control NI 9871 Hardware Overview Sleep Mode (CompactRIO Only) Specifications Power Requirements Physical Characteristics Safety Maximum Voltage Isolation Voltages Hazardous Locations Safety Standards Electromagnetic Compatibility CE Compliance Online Product Certification Shock and Vibration Environmental Environmental Management Waste Electrical and Electronic Equipment (WEEE) RoHS Where to Go for Support Page 372277B-01 Sep08