说明：  数字电子技术课程，设计交通灯。 所要设计的交通信号灯控制电路要能够适用于由一条主干道和一条支干道的汇合点形成的十字交叉路口。能够做到主、支干道的红绿灯闪亮的时间不完全相同，在绿灯跳变红灯的过程中能够用黄灯进行过渡，使得行驶过程中的车辆有足够的时间停下来。还要求在主、支干道各设立一组计时显示器，能够显示相应的红、黄、绿倒计时。可以利用VHDL语言合理设计系统功能，使红黄绿灯的转换有一个准确的时间间隔和转换顺序
(Digital electronic technology course and design of traffic lights. The design of traffic signals to control circuit to be able to apply to a trunk road and a branch from the trunk of the convergence point of intersection are formed. Able to do the main and branch roads are not exactly the same time, traffic lights flashing, the green light to red light in the process of transition to the transition with a yellow light, making the process of moving vehicles have enough time to stop. Also called in the main, supported the establishment of a group of roads each time display, can display the corresponding red, yellow, green countdown. VHDL language can be used rational design system function, so that the conversion has a red, yellow, green precise time interval and the conversion sequence)