DKM-411 Modbus Application Manual V3.0
(15.01.2017)
- 3 -
The Modbus communication is widely used in the connection of industrial control units to various
management systems for remote monitoring and control. It has begun the basic industry standard in the
last decades.
The unit offers the possibility of MODBUS communication through below carriers:
-RS485 serial port, with adjustable baud rate between 2400 and 115200 bauds
-MODBUS-TCP/IP through Ethernet port (10/100Mb)
-MODBUS-TCP/IP through GSM-GPRS modem. (84/42kb)
Detailed description about the MODBUS protocol is found in the document “
Modicon Modbus Protocol
Reference Guide
”
.
This document may be downloaded at: www.modbus.org/docs/PI_MBUS_300.pdf
Detailed description about the MODBUS-TCP/IP
protocol is found in the document “
MODBUS
APPLICATION PROTOCOL SPECIFICATION
”
.
This document may be downloaded at:
http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
The MODBUS properties of the unit are:
-Data transfer mode: RTU
-Serial data: selectable baud rate, 8 bit data, no parity, 1 bit stop
-Modbus-TCP/IP: Ethernet 10/100Mb or GPRS Class 10.
-Supported functions:
-Function 3 (Read multiple registers)
-Function 6 (Write single register)
-Function 16 (Write multiple registers)
Each register consists of 2 bytes (16 bits). A larger data structure will contain multiple registers.
The Modbus communications requires a slave address to be assigned to each device in the Modbus
network. This address ranges between 1 and 240 and allows the addressing of different slave devices in
the same network.
Devices using Modbus-TCP/IP with different IP or port
addresses may use any slave address. It is advised to set
these slave addresses to the default setting which is 1.
Each device in the same RS-485 serial network must be
assigned a different slave address. Otherwise the Modbus
communications will not be performed.
MODBUS CONFIGURATION
MODBUS COMMUNICATION BASICS
