Doc ID : ADR111A_IM_01
Ref ID : ADR111A/IM/CS
Rev No. : 04
Page No. : 76 of 127
ADR111A /
ADR211A
7
SCADA COMMUNICATIONS
7.1
MODBUS
This section describes how the MODBUS standard is applied to the RT platform. It is not a
description of the standard itself. The level at which this section is written assumes that the
reader is already familiar with the MODBUS standard.
The MODBUS protocol is a master/slave protocol, defined and administered by the
MODBUS Organization. For further information on MODBUS and the protocol specifications
please see the Modbus web site (
Overview: Physical Connection and Link Layer
For connecting on MODBUS use:
Rear serial port - for permanent SCADA connection via RS422/ RS485
The MODBUS interface uses ‘RTU’ mode communication rather than ‘ASCII’ mode as this
provides more efficient use of the communication bandwidth. This mode of communication is
defined by the MODBUS standard.
The IED address and baud rate can be selected using the relay front panel.
When using a serial interface, the data format is: 1 start bit, 8 data bits, 1 stop bit (a total of
10 bits per character).
7.1.1
MODBUS Protocol Map
7.1.1.1
Function Codes supported:
Code
Function Name
Addresses starts with
02
Read Input Status
1x addresses
03
Read Holding Registers
4x addresses
04
Read Input Registers
3x addresses
05
Force Single Coil
0x addresses
16
Preset Multiple Registers
4x addresses
Summary of Contents for ADR111A
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