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ET-2200 Series Ethernet I/O Modules
6. Modbus Information
The ET-2200 series is a family of IP-based Modbus I/O devices that allow you to remotely control
DI/DO terminals via an Ethernet connection and uses a master-slave communication technique in
which only one device (the master) can initiate a transaction (called queries), while other devices
(slaves) respond by either supplying the requested data to the master or by taking the action
requested in the query.
Most SCADA (Supervisory Control and Data Acquisition) and HMI software, such as Citect (Schneider
Electric), ICONICS, iFIX, InduSoft, Intouch, Entivity Studio, Entivity Live, Entivity VLC, Trace Mode,
Wizcon (ElUTIONS), and Wonderware, etc. can be used to easily integrate serial devices via the
Modbus protocol.
6.1
What is Modbus TCP/IP?
Modbus is a communication protocol that was developed by Modicon Inc. in 1979. Detailed
information regarding the Modbus protocol can be found at: http://www.modbus.org.
The different versions of the Modbus protocol used today include Modbus RTU, which is based on
serial communication interfaces such as RS-485 and RS-232, as well as Modbus ASCII and Modbus
TCP, which uses the Modbus RTU protocol embedded into TCP packets.
Modbus TCP is an internet protocol. The protocol embeds a Modbus frame into a TCP frame so that
a connection-oriented approach is obtained, thereby making it more reliable. The master queries
the slave and the slave responds with a reply. The protocol is open and, hence, highly scalable.
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