0-99秒表，有开始，停止，暂停，清空键； 当按下暂停键，把当前的时间位存入24C02， 能够把存进去的值读出显示在数码管上-0-99 stopwatch, start, stop, pause, clear key When the pause button is pressed, the current time bit is stored in the 24C02, To be able to read the values displayed on the digita