National Instruments NI 9871, RS422, RS485 NI 9871 Hardware Overview

NI 9871 Operating Instructions 12 ni.com

Refer to Table3 for a listing of TX and RX enable conditions for

the different RS485 transceiver control modes.

NI 9871 Hardware Overview

The NI 9871 has four independent RS485/RS422 ports that are

isolated from the other modules in the system. Each port is fully

compatible with the ANSI/EIA/TIA-485 standard.

Table 3. Transceiver Control Pin Conditions

Enable 4-Wire

2-Wire

DTR/Echo DTR/No Echo Auto

TX On DTR DTR TX

RX On On DTR# TX#

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