PLC是專為工業(yè)自動操控而開發(fā)的裝置，通常PLC選用面向操控過程，面向問題的“自然言語”編程。不同廠家的產(chǎn)品選用的編程言語不同，這些編程言語有梯形圖、句子表、操控系統(tǒng)流程圖等。為了增強PLC的各種運算功用，有的PLC還配有BASIC言語，并正在探究用其他言語來編程。
日本的FANUC公司、立石公司、三菱公司、富士公司等所出產(chǎn)的PLC產(chǎn)品，都選用梯形圖編程。在用編程器向PLC輸入程序時，一般簡易編程器都選用編碼表輸入，大型編程器也可用梯形圖直接輸入。在很多的PLC產(chǎn)品中，由于制作廠家不同，其指令系統(tǒng)的表明辦法和句子表中的助記符也不盡相同，但原理是徹底相同的。在本書中我們以FANUC-PMC-L為例，對適用于數(shù)控機床操控的PLC指令作一介紹。在FANUC系列的PLC中，規(guī)格型號不一起，只是功用指令的數(shù)目有所不同，如北京機床研究所與FANUC公司合作開發(fā)的FANUC-BESK PLC-B功用指令23條，除此以外，指令系統(tǒng)是徹底一樣的。
PLC is a device specially developed for industrial automatic control. Usually, PLC adopts "natural language" programming which is oriented to the control process and problems. Different manufacturers' products use different programming languages, such as ladder diagram, sentence table, control system flow chart, etc. In order to enhance the various computing functions of PLC, some PLCs are also equipped with basic language, and are exploring programming with other high-end languages.
The PLC products produced by FANUC company, Lishi company, Mitsubishi company and Fuji company in Japan all use ladder diagram programming. When using programmers to input programs to PLC, generally simple programmers use code table input, and large programmers can also use ladder diagram to input directly. In many PLC products, due to different manufacturers, the indication method of its instruction system and the mnemonic in the sentence table are also different, but the principle is completely the same. In this book, we take fanuc-pmc-l as an example to introduce the PLC instructions applicable to the control of CNC machine tools. In FANUC series PLC, the specifications and models are different, but the number of function instructions is different. For example, the fanuc-besk plc-b function instructions developed by Beijing Machine Tool Research Institute in cooperation with FANUC company are 23. In addition, the instruction system is completely the same.