Remote Communications 6.1 Rs232; Application; Connections - Honeywell ERX350 User Manual

6 Remote Communications
6.1 RS232/ 485
6.1 RS232/ 485

6.1.1 Application

ERX350 is capable of communicating with a number of types of external devices, such as cellular or
land- line modems, and RTUs. ERX350 supports the following protocols: MI Protocol, Modbus RTU,
Modbus ASCII. The description of those protocols is beyond the scope of this manual, although a basic
discussion of Modbus operation is presented later in this chapter. This section describes the physical
connections and instrument configuration parameters that are required.

6.1.2 Connections

Wiring connections are made to TB4, see below:
For RS-232, only 3-wire communications is supported: pin 1 TXD (Transmit Data), pin 2 RXD (Receive
Data), and pin 5 GND (Ground). (The TB4 RTS/CTS connections are not used.) TXD and RXD are labelled
as a DTE device (ERX350 transmits on TXD).
For RS-485, use TB4 pin 1 (TXD) as line A, pin 2 (RXD) as line B, and pin 5 (GND) as Ground.
The RS-232 and RS-485 standard specifications should be consulted for the proper wire type, maximum
cable length, etc.
Honeywell
2023
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