XV-440-10TVB-1-13-1 工业显示屏模块 EATON 广泛应用于工业自动化

XV-440-10TVB-1-13-1 工业显示屏模块 EATON 广泛应用于工业自动化

1.PLC的硬件组成
PLC硬件系统的基本结构如下
PLC的主机由CPU、存储器（EPROM、RAM）、输入/输出单元、外设I/O接口、通信接口及电源组成。对于整体式PLC，这些部件都在同一个机壳内。而对于模块式PLC，各部件独立封装，称为模块，各模块通过机架和电缆连接在一起。主机内的各个部分均通过电源总线、控制总线、地址总线和数据总线连接，根据实际控制对象的需要配备一定的外部设备，构成不同的PLC控制系统。常用的外部设备有编程器、打印机、EPROM写入器等。PLC可以配置通信模块与上位机及其他的PLC进行通信，构成PLC的分布式控制系统。
下面分别介绍PLC的各组成部分及其作用，以便用户进一步了解PLC的控制原理和工作过程。
（1）CPU
CPU是PLC的控制中枢，PLC在CPU的控制下有条不紊地协调工作，从而实现对现场的各个设备进行控制。CPU由微处理器和控制器组成，它可以实现逻辑运算和数学运算，协调控制系统内部各部分的工作。
控制器的作用是控制整个微处理器的各个部件有条不紊的进行工作，它的基本功能就是从内存中读取指令和执行指令。
（2）存储器
PLC配有两种存储器，即系统存储器和用户存储器。系统存储器用来存放系统管理程序，用户不能访问和修改这部分存储器的内容。用户存储器用来存放编制的应用程序和工作数据状态。存放工作数据状态的用户存储器部分也称为数据存储区，它包括输入/输出数据映像区、定时器/计数器预置数和当前值的数据区及存放中间结果的缓冲区。
PLC的存储器主要包括以下几种。 

XV-440-10TVB-1-13-1 工业显示屏模块 EATON 广泛应用于工业自动化

1. Hardware composition of PLC
The basic structure of PLC hardware system is as follows
The PLC host consists of CPU, memory (EPROM, RAM), input/output unit, peripheral I/O interface, communication interface and power supply. For integral PLCS, these components are all in the same housing. For modular PLC, the components are packaged independently, called modules, and the modules are connected together through racks and cables. Each part of the host is connected through the power bus, control bus, address bus and data bus, and is equipped with certain external devices according to the needs of the actual control object to form different PLC control systems. Commonly used external devices are programmers, printers, EPROM writers and so on. PLC can be configured with communication module to communicate with the host computer and other PLC to form a distributed control system of PLC.
The following are the components of PLC and their functions, so that users can further understand the control principle and working process of PLC.
(1) CPU
The CPU is the control center of the PLC, and the PLC works methodically under the control of the CPU, so as to achieve the control of each device on the site. The CPU is composed of a microprocessor and a controller, which can realize logical and mathematical operations and coordinate the work of various parts of the control system.
The role of the controller is to control the entire microprocessor each part of the orderly work, its basic function is to read instructions from the memory and execute instructions.
(2) Memory
PLC is equipped with two kinds of memory, namely system memory and user memory. The system memory is used to store the system management program, and users cannot access and modify the contents of this part of the memory. User memory is used to store the state of the programmed application and working data. The part of the user memory that stores the state of the working data is also called the data store, which includes the input/output data image area, the data area of the timer/counter preset number and the current value, and the buffer to store the intermediate results.
PLC memory mainly includes the following types.

XV-440-10TVB-1-13-1 工业显示屏模块 EATON 广泛应用于工业自动化