RKI Instruments Beacon 410 - Manual (Page 58)

54 • Overview Beacon 410 Gas Monitor Operator’s Manual
Chapter 9: RS-485 Modbus Output
Overview
This chapter describes the Beacon 410’s RS-485 Modbus output and how to configure the
Beacon 410 to make use of it. It also discusses how to wire the Beacon 410 into a Modbus
system.
The Beacon 410 provides an RS-485 serial communications interface. It is a Modbus
Slave Device, supporting 2-wire RS-485 Modbus RTU serial communications.
Wiring the Beacon 410 in a Modbus
System
The Beacon 410 is a 2-wire Modbus RTU device. When wiring the Beacon 410 into a
Modbus system, adhere to standard Modbus wiring practices per the Modbus Over Serial
Line Specification and Implementation Guide V1.0 or later. This document can be found
online at www.modbus.org/specs.php.
The Modbus protocol supports a maximum of 247 unique slave addresses (1-247). The
Beacon 410’s line driver provides for up to 32 Beacon 410s (or some combination of
Beacon 410s and other Modbus slave devices such as the RKI Instruments M2) to be
connected together without the need for a repeater. Figure 15 & Figure 16 below illustrate
typical Beacon 410 wiring configurations. If more than 32 Beacon 410s (or Beacon 410s
and other slave devices) need to be connected together, an RS-485 repeater(s) should be
used such that no more than 32 Beacon 410s reside on any given network segment.
The MODBUS terminals are located on the controller terminal strip (See Figure 1). The
following signals are available at the Modbus terminals:
Table 10: Modbus Terminal Signals
Modbus Terminal Label
(RS-485 Name)
Modbus Signal Name
A D0
B D1
C Common