xilinx完成一个模拟的十字路*通信号灯，主干道上的绿灯时间为30s，支干道的绿灯时间为30s，且交通灯从绿变红时，有6s黄灯亮的时间间隔。当然每种状态的倒计时的时间值应显示到LED数码管上。-Xilinx completed in a simulated traffic lights at a crossroads, a main road on the green time for the 30s, branch roads green time for 30s, and red tra