VHDL实现的交通灯程序，可以定时南北和东西方向的交通灯信号，控制红黄绿各灯亮的时间，并考虑紧急情况如有救护车通过-VHDL procedures realize the traffic lights, you can regularly north-south and east-west direction of the traffic lights signal control red, yellow, and green lights all the time, and to consid