The basic structure of PLC and DCS is the same.PLC has developed to this day and has been fully transplanted to the computer system control,and the traditional programmer has long been eliminated.PLCs for small applications generally use touch screens,and PLCs for large-scale applications use computer systems in an all-round way.Like DCS,the controller and IO station use field bus(generally based on the RS485 or RS232 asynchronous serial communication protocol),if there is no expansion requirement between the controller and the computer,that is to say,only one computer is used.In this case,this bus communication is also used.But if more than one computer is used,the system structure will be the same as DCS,and the upper computer platform uses the Ethernet structure.This is one of the reasons why the PLC has become larger and the concept of DCS is blurred.
PLC与DCS的基本结构是一样的。PLC发展到今天，已经全面移植到计算机系统控制上了，传统的编程器早就被淘汰。小型应用的PLC一般使用触摸屏，大规模应用的PLC全面使用计算机系统。和DCS一样，控制器与IO站使用现场总线（一般都是基于RS485或RS232异步串口通讯协议的总线方式），控制器与计算机之间如果没有扩展的要求，也就是说只使用一台计算机的情况下，也会使用这个总线通讯。但如果有不止一台的计算机使用，系统结构就会和DCS一样，上位机平台使用以太网结构。这是PLC大型化后和DCS概念模糊的原因之一。
