JAVA, as a cross platform programming language, is widely used in various fields, including industrial automation. At the same time, PLC, as the core equipment in the field of industrial automation, is responsible for controlling various process flows. Therefore, the communication between JAVA and PLC is a very important topic in the field of industrial automation.
1. Introduction to Java Language
Java is an object-oriented programming language that supports network computing. Java language has absorbed the advantages of Smalltalk language and C++language, and added other features such as support and
Develop programming, network communication, and multimedia data control.
The excellent features of the Java language make Java applications incredibly robust and reliable, which also reduces the maintenance costs of application systems.
Java's comprehensive support for object technology and the embedded APIs in the Java platform can shorten the development time of application systems and reduce costs.
The compile once, run everywhere feature of Java enables it to provide an open structure that can be used anywhere and a low-cost way to transfer information between multiple platforms.
2. Serial Communication between PLC and Computer
The S7-200 PLC has a very powerful networking function and can connect programmers, human-machine interface devices, or other PLCs. The communication interface of the S7-200 series PLC is a 9-pin RS-485 signal connection
port, which can be connected to a computer through a PC/PPI cable or connected to a network with other PLCs through a SINEC-L2 interface.
Connect PLC and computer through COM port to complete serial communication. Serial ports can easily achieve long-distance
communication by sending data with one wire and receiving data with another wire.
3. Design of PLC Communication Program for Lower level Machine PLC Communication is a crucial issue in practical PLC applications. Various communication functions can be achieved using the S7-200 programmable communication port mode, which can fully realize many very complex functions.


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