1.　　用51单片机内部的定时器实现秒计数，用两个七段LED显示器上显示秒时间，用一个按键控制秒表的计数和清零。

2.　　按键入口选用P1口。

3.　　按键采用软件去抖动。

4.　　七段显示器接口采用串行口扩张并行口，显示方式为静态显示。

-With 51 MCU internal timer to count seconds and display the second time with two seven-segment LED display, a button control the stopwatch count and cleared. (2) the the key entrance selection of P1 port. 3 Key software to jitter. 4 seven-segment display interface parallel port, serial port expansion, display as a static display.