PLC的程序编制1、编程元件PLC是采用软件编制程序来实现控制要求的。编程时要使用到各种编程元件，它们可提供无数个动合和动断触点。编程元件是指输入存放器、输出存放器、位存储器、定时器、计数器、通用存放器、数据存放器及特殊功能存储器等。PLC部这些存储器的作用和继电接触控制系统中使用的继电器十分相似，也有“线圈”与“触点”，但它们不是“硬”继电器，而是PLC存储器的存储单元。当写入该单元的逻辑状态为“1°时，那么表示相应继电器线圈得电，其动合触点闭合，动断触点断开。所以，部的这些继电器称之为“软”继电器。ALD指令也简称与块指令，ALD也是无操作目标元件,是一个程序步指令。
PR9376010-011
编程语言所谓程序编制，就是用户根据控制对象的要求，利用PLC厂家提供的程序编制语言，将一个控制要求描述出来的过程.PLC较常用的编程语言是梯形图语言和指令语句表语言,且两者常常联合使用。梯形图(语言)梯形图是一种从继电接触控制电路图演变而来的图形语言。它是借助类似于继电器的动合、动断触点、线圈以及串、并联等术语和符号，根据控制要求联接而成的表示PLC输入和输出之间逻辑关系的图形，直观易懂。指令语句表指令语句表是一种用指令助记符来编制PLC程序的语言，它类似于计算机的汇编语言，但比汇编语言易懂易学，若干条指令组成的程序就是指令语句表。
PR9376010-011
—条指令语句是由步序、指令语和作用器件编号三部分组成。基本指令简介—、标准触点指令LD动合触点指令，表示一个与输入母线相连的动合触点指令,即动合触点逻辑运算起始。LDN动断触点指令，表示一个与输入母线相连的动断触点指令，即动断触点逻辑运算起始。二、串联电路块的并联连接指令OLD两个或两个以上的接点串联连接的电路叫串联电路块。串联电路块并联连接时，分支开始用LD、LDN指令，分支结束用OLD指令。OLD指令与后述的ALD指令均为无目标元件指令;而两条无目标元件指令的步长都为一个程序步。OLD有时也简称或块指令。三、并联电路的串联连接指令ALD两个或两个以上接点并联电路称为并联电路块分支电路并联电路块与前面电路串联连接时，使用ALD指令。分支的起点用LD、LDN指令，并联电路结束后,使用ALD指令与前面电路串联。ALD指令也简称与块指令。
PR9376010-011
Programming of PLC 1. The programming element PLC uses software programming to achieve control requirements. When programming, various programming components need to be used, which can provide countless dynamic closing and dynamic breaking contacts. Programming components refer to input storage, output storage, bit memory, timer, counter, universal storage, data storage, and special function memory. The function of these memories in the PLC department is very similar to the relays used in relay contact control systems, with “coils” and “contacts”, but they are not “hard” relays, but rather storage units of the PLC memory. When the logical state written to the unit is “1 °,” it indicates that the corresponding relay coil is energized, its closing contact is closed, and the breaking contact is open. Therefore, these relays are called “soft” relays. The ALD instruction, also known as the block instruction, is also a program step instruction without an operational target component
PR9376010-011
Programming language is the process in which users describe a control requirement based on the requirements of the control object using the programming language provided by the PLC manufacturer. The most commonly used programming languages for PLC are ladder diagram language and instruction statement table language, and the two are often used in combination. Ladder diagram (language) Ladder diagram is a graphical language that has evolved from relay contact control circuit diagrams. It is a graphical representation of the logical relationship between PLC input and output, which is connected according to control requirements using terms and symbols such as dynamic closing, dynamic breaking contacts, coils, and series and parallel connections, similar to relays. It is intuitive and easy to understand. Instruction statement table is a language that uses instruction mnemonics to program PLC programs. It is similar to the assembly language of a computer, but easier to understand and learn than assembly language. A program composed of several instructions is an instruction statement table
PR9376010-011
An instruction statement is composed of three parts: step sequence, instruction language, and action device number. Introduction to Basic Instructions – Standard Contact Instruction LD Moving Contact Instruction, which represents a moving contact instruction connected to the input bus, that is, the logical operation of the moving contact begins. LDN dynamic breaking contact command represents a dynamic breaking contact command connected to the input bus, that is, the logical operation of the dynamic breaking contact starts. 2、 The parallel connection instruction of a series circuit block is called a series circuit block, where two or more contacts are connected in series. When series circuit blocks are connected in parallel, LD and LDN instructions are used at the beginning of the branch, and OLD instructions are used at the end of the branch. The OLD instruction and the ALD instruction described later are both target free component instructions; The step size of both target free component instructions is one program step. OLD is sometimes abbreviated as a block instruction. 3、 The series connection instruction ALD for parallel circuits. A parallel circuit with two or more contacts is called a parallel circuit block. When a parallel circuit block is connected in series with a previous circuit, the ALD instruction is used. The starting point of the branch is using LD and LDN instructions, and after the parallel circuit ends, ALD instructions are used to connect in series with the previous circuit. The ALD instruction is also abbreviated as a block instruction
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