5. COMMUNICATION [MODBUS RTU] PROTOCOL
5.1 Introduction
The unit can be connected in MODBUS/RTU communication data link protocol to messaging
structure, widely used to establish master - slave communications between devices. Each
device must have unique No. node address. Before starting any communication, choose a
baud rate compatible to the host device. A Modbus data sent from a master to slave tells the
selected slave what to do and what information to send back. The MODBUS/RTU protocol
works with RS232, RS485 and RS422 standards
5.2 MODBUS Configuration Basic settings
The Basic settings for RS-485 Modbus protocol are as follows :
Band rate
Start bit
Data bit
Stop bit
Parity
9600
1
8
1
none
5.3 Register addresses for MODBUS / RTU Protocol
The addressees for RS-485 Modbus protocol are as follows :
5.4 MODBUS system schematic.
DATA+
READ ONLY
SR. NO.
1
PROCESS VALUE [PV]
PARAMETER
ABSOLUTE ADDRESS
ACCESS TYPE
40001
READ / WRITE
3
SET POINT-1 [SP1]
40003
READ ONLY
2
DECIMAL POINT
40002
READ / WRITE
4
SET POINT-2 [SP2]
40004
READ ONLY
5
RELAY-1 STATUS
40005
READ ONLY
6
RELAY-2 STATUS
40006
The system schematic for RS-485 Modbus protocol are as follows :
DATA-
Ethernet
RS-232
or
RS-485
CONVERTER
D- D+
1 2
UT-102 Device-1
D- D+
1 2
D- D+
1 2
D- D+
1 2
RS-485 BUS
ADD:1
ADD:2
ADD:3
ADD:N
RS-485 BUS
Upto 128
devices
UT-102 Device-2
UT-102 Device-3
UT-102 Device-128
2 core 1 sq/mm shielded cable
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All content are subject to change without notice
due to continuous improvements.
Doc. Ref. 1410/R04/0819
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12
UT-102
UNIVERSAL PROCESS INDICATOR & CONTROLLER
COMPUTER- SCADA
Summary of Contents for UT-102
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