In automatic control systems,mounting traditional button switches in wide range may use a lot of wires,and leads to the waste of resources. In order to solve this problem,a kind of intelligent button switch which is different from the traditional mechanical button switch has been designed.It can be used online via public bus,the character information output represents the status of switch,and the function of button can be displayed in Chinese characters or other characters by miniature LCD.The displayed content can be modified via bus communication. The intelligent button switches can work together online in more quantity and long distance through a special RS-422 bus with two-way relay function.Through designing the bus hardware and the protocol with two-way preemptive sending and caching sending mechanisms,there is no data conflict and data loss when all the switches on the bus send data at the same time,so as to achieve real-time performance and reliability of the switch group.The design of intelligent button switch make the basic component of button switch become a terminal of distributed control system, which conforms to the design concept of modern programmable distributed control system.%在自动控制系统中,大范围安装传统按钮开关会使用大量导线,造成资源浪费.为解决此问题,设计了一种有别于传统机械式按钮开关的智能按钮开关.该智能按钮开关可通过公共总线联机使用,输出字符信息来表示开关状态,并可通过微型LCD显示汉字或其他字符,以标示按钮功能.显示的内容可通过总线通信修改.智能按钮开关通过一种特殊的、带双向中继功能的RS-422总线,实现了较多数量、较远距离的联机工作.通过设计带有双向抢占发送和缓存发送机制的总线硬件和协议,使挂载在总线上的所有智能按钮开关不会因同时发送数据而发生冲突、造成数据丢失,实现了智能按钮开关组的实时性和可靠性.该设计使按钮开关这种基本元件成为分布式控制系统的一种终端,符合现代可编程分布式控制系统的设计理念.
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