用单片机实现的简单的交通灯功能 在十字路口 各有一组交通灯 和一个时钟系统 时钟系统由2个led数码管组成 采用并行输出方式-Using single chip to achieve a simple function of the traffic lights at the crossroads have a set of traffic lights and a clock system, clock system led by the two tubes parallel digital