用VHDL编写的交通灯显示程序，功能是实现主次干道显示不同时间的绿灯，并在数码管上显示相应时间倒计时，仿真波形已经成功。-Written by VHDL of traffic light show program, the function is to realize primary and secondary road show different time of the green, and in the digital display on the corresponding time c