设计软件在每按一次单脉冲按钮产生一个正脉冲使8255产生一次中断请求，让CPU进行一次中断服务：读取拨动开关状态，设定3中状态，每种状态屏幕显示不同信息，例如“1”状态屏幕显示“DOING ONE”，“2”显示“TWO”，“8”显示“EXIT”-Design software in a single pulse button, a positive pulse to make 8255 to generate an interrupt request to allow the CPU to an interrupt service: Read toggle switch state, set the 3 state, each state of the screen to display different information, such as a status screen display " DOING ONE" , " 2"　" TWO,"　8 " display"　EXIT "