Modbus Communications; Introduction; Communications Settings; Analog Input Registers - Emerson MRLDS-250 Installation And Operation Manual

7
MODBUS
Communications
7.1.

Introduction

The MRLDS-250 gas detector can be configured to
communicate on an RS-485 network using 
MODBUS-RTU protocol. Before configuring the gas
detector for MODBUS communications, be sure your
network connection is complete and your network 
termination switches are set appropriately. Refer to
Section 3, Wiring and Configuration for details.
7.3.

Analog Input Registers

Analog input registers are read only and use 
function code 04.
Reg Description
1000 Concentration gas level
1001 Concentration gas level
1002 Reserved
1003 Full scale detector level
1004 Alarm setpoint (% full
scale)
1005 Gas detector timer
1006 Node address
1007 Software version
1008 Reserved
1009 Reserved
1010 Reserved
1011 Reserved
1012 16-bit fault code
Table 7-1 - Analog Input Registers
24 • MRLDS-250 Infrared Gas Detector I&O Manual
7.2.
There are 255 selections available to be set
electronically, from addresses 1 to 255 inclusive. 
MODBUS data with a zero in the address field is 
received by all detectors (regardless of the address 
selected) to enable the master device to broadcast 
simultaneously to all the detectors.
Refer to the specifications section for information on
RS-485 network communications parameters such as
data bits, stop bits, and more.
Range Units
0-100 %FS
0-65, 535 PPM
0-65, 535 PPM
0-100 %
0-65, 535 hours
1-247 none
none
0-65535 none
Communications
Settings
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