Acrel APM Series User Manual

46
Modbus-TCP/IP
1. General communication architecture
A communicating system over MODBUS TCP/IP may include different types of device:
A MODBUS TCP/IP Client and Server devices connected to a TCP/IP network.
The Interconnection devices like bridge, router or gateway for interconnection between
the TCP/IP network and a serial line sub-network which permit connections of MODBUS Serial
line Client and Server end devices.
Figure 1: MODBUS TCP/IP communication architecture）
The MODBUS protocol defines a simple Protocol Data Unit (PDU) independent of the
underlying communication layers. The mapping of MODBUS protocol on specific buses or
networks can introduce some additional fields on the Application Data Unit (ADU).
The client that initiates a MODBUS transaction builds the MODBUS Application Data Unit.
The function code indicates to the server which kind of action to perform.
Figure 2: General MODBUS frame
2. MODBUS On TCP/IP Application Data Unit
This section describes the encapsulation of a MODBUS request or response when it is
carried on a MODBUS TCP/IP network.

Acrel APM Series Specifications

General

Brand	Acrel
Model	APM Series
Category	Measuring Instruments
Language	English