用实验电路板上的PIC16F877A控制一个发光二极管来模拟航标灯工作。模拟航标灯以精确的1Hz频率闪烁，其中关闭时间为0.5s，发光时间也是0.5s。要求1Hz闪烁频率的长期误差达到20ppm以下。-Breadboard PIC16F877A control to simulate a light-emitting diode beacon lights work. Analog beacon lights to the precise frequency of 1Hz blinking, closing time 0.5s, the luminous time is 0.5s. The 1Hz flashing frequency of long-term error reaches below 20ppm.