说明：  本程序使用6个数码管和一个单片机做成的一个倒计时器秒表，实现时 分 秒的实时显示 外加1302作为实时时钟芯片
(The program uses six digital control and a single chip device made of a countdown stopwatch, to achieve real-time display when the minutes and seconds plus 1302 as a real time clock chip)