1). 用红、绿、黄三色发光二极管作信号灯。主干道为东西向，有红、绿、黄三个灯；支干道为南北向，也有红、绿、黄三个灯。红灯亮禁止通行；绿灯亮允许通行；黄灯亮则给行驶中的车辆有时间停靠到禁行线之外。

2).由于主干道车辆较多而支干道车辆较少，所以主干道绿灯时间较长。当主干道允许通行亮绿灯时，支干道亮红灯。而支干道允许通行亮绿灯时，主干道亮红灯，两者交替重复。主干道每次放行50秒，支干道每次放行30秒。

在每次由亮绿灯变成亮红灯的转换过程中间，需要亮5秒的黄灯作为过渡，以使行驶中的车辆有时间停靠到禁行线以外。

3). 能实现正常的、即时显示功能。用DE2上的四个七段数码管作为倒计时显示器。分别显示东西、南北方向的红灯、绿灯、黄灯时间。

4).能实现特殊状态的功能显示。设S为特殊状态的传感器信号，当Ｓ=1时，进入特殊状态。当Ｓ=0时，退出特殊状态。按S后，能实现特殊状态功能：

（1）显示器闪烁；

（2）计数器停止计数并保持在原来的数据；

（3）东西、南北路口均显示红灯状态；

（4）特殊状态结束后，能继续对时间进行计数。

5).能实现总体清零功能。按下R后，系统实现总清零，计数器由初始状态开始计数，对应状态的指示灯亮。

-1). With red, green, yellow three-color light-emitting diodes for lights. For the east-west trunk road, has red, green, yellow three lights　support for the north-south trunk road, there are red, green, yellow three lights. Red light curfew　green permit passage　yellow light is to the moving vehicles have the time of call to cut outside the lane.

2). Because of the trunk road vehicles more vehicles and less trunk extension, so a longer green time of a main road. When the main road access permit a green light when the trunk road red sticks. Permit access roads and support a green light when the trunk road red, the two alternating repetition. Allowed 50 seconds for each trunk, branch trunk release each 30 seconds.

At each green light into red by the conversion process between the need for five seconds of yellow light as a transitional measure to enable the moving vehicles have the time of call to ban outside lane.

3). To achieve a normal, real-time display. Using DE2 four seventh