User`s manual

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There are three most common Modbus versions, Modbus ASCII, Modbus RTU
and Modbus TCP. Ethernet based device, Industrial Ethernet Switch for
example, supports Modbus TCP that it can be polled through Ethernet. Thus
the Modbus TCP master can read or write the Modbus registers provided by
the Industrial Ethernet Switch.
The MDI-110 Managed DIN-Rail Ethernet Switch has implement Modbus/TCP
register in the firmware. Those register mapping to some of Ethernet Switchs’
operating information, includes description, IP address, power status, interface
status, interface information and inbound/outbound packet statistics. With the
register supports, user can read the information through their own Modbus
TCP based progress/ display/ monitor applications and monitor the status of
the switch easily.
The configuration of Modbus/TCP only present in CLI management mode and
the no extra user interface for Web configuration.
5.3.1 Modbus Function Code
The Modbus TCP device uses a subset of the standard Modbus TCP function
code to access device-dependent information. Modbus TCP function code is
defined as below.
FC
Name
Usage
01
Read Coils
Read the state of a digital output
02
Read Input Status
Read the state of a digital input
03
Read Holding Register
Read holding register in 16-bits register
format