实验电路如图25，按虚线连接电路：CLK0接1MHz，GATE0，GATE1，接+5V，OUT0接CLK1，OUT1接PA0，PC0接继电器驱动电路的开关输入端Ik。继电器常开触点串联一个220V灯泡，接交流220V。编程使用8253定时，让继电器周而复始的闭合5秒钟（指示灯灯亮），断开5秒钟（指示灯灯灭）-The experimental circuit shown in Figure 25, connected by dotted line circuit: CLK0 connected 1MHz, GATE0, GATE1, then+5 V, OUT0 then CLK1, OUT1 connected PA0, PC0 then switch relay drive circuit input Ik. Relay normally open contact in series a 220V light bulb, then AC 220V. Programming using the 8253 timer, so that the relay closed cycle of 5 seconds (LED lights), off 5 seconds (LED OFF)