Emerson Wireless 1420 Gateway Reference Manual page 25

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Reference Manual

00809-0200-4420

Note

Unless dual Ethernet ports were specified at the time of order, the secondary Ethernet port

(Ethernet 2) will not be active.

3.4.3

RS-485

The Gateway may be ordered with an optional RS-485 (serial) connection

referenced by the A and B Serial Modbus terminals. This connection is used to

communicate Modbus RTU on an RS-485 data bus.

Use 18 AWG single twisted shielded pair wiring to connect the Gateway to the RS-485 data

bus. The total bus length should not exceed 4000 ft. (1220 m). Connect the Tx + (positive,

transmit) wire to terminal A and the Rx - (negative, receive) wire to terminal B. The wiring

shield should be trimmed close and insulated from touching the Gateway enclosure or

other terminations. Only terminated at one end typically at the power supply end.

If the existing data bus uses a 4 wire Full Duplex configuration, see

a 2-wire Half Duplex configuration.

Figure 3-8: Convert from Full to Half Duplex

Emerson.com/Rosemount

Installation

September 2020

(Figure

3-6). It is

Figure 3-8

to convert to

(A)

(B)

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