3BSE018283R1 ABB

The hardware system of PLC is mainly composed of host computer,input/output expansion unit and external equipment,and each part is connected by bus.The host is mainly composed of central processing unit(CPU),memory,input/output circuit,external device interface,and power supply.

Like a general-purpose computer,the central processing unit(CPU)is the core component of the PLC,and its main function is to control the entire system to run in unison.It interprets and executes user and system programs,and completes all control,processing,communication,and other functions assigned by running user and system programs.Its main functions are as follows.

PLC的硬件系统主要由主机、输入／输出扩展单元、外部设备组成，各部分之间通过总线连接。其中主机主要由中央处理单元(CPU)、存储器、输入／输出电路、外部设备接口、电源几大部分组成。

与通用计算机一样，中央处理单元(CPU)是PLC的核心部件，它的主要作用是控制整个系统协调一致地运行。它解释并执行用户及系统程序，并通过运行用户及系统程序完成所有控制、处理、通信以及所赋予的其他功能。它的主要功能有以下几点。