秒表设计

用89C51设计一个2位的LED数码管显示“秒表”，显示时间为00~99秒，每秒自动加1，计满显示“FF”。另设计一个“开始”按键和一个“停止”按键，按“开始”键显示秒数从00开始，按“停止”键，保持实时时间，停计时。-Stopwatch design with 89C51 design a two LED digital tube display, " stopwatch" , show time is 00 to 99 seconds, 1 second automatic, expiry display " FF" . Another design a " start"　button and a " stop"　button, click " Start"　button to display the number of seconds from 00 starts, press the " Stop"　button, keeping real-time, stop the timer.