设计一个十字路口的交通灯控制系统

要求：工作顺序为东西方向红灯亮45秒，前40秒南北方向绿灯亮，后5秒黄灯亮。然后南北方向红灯亮45秒，前40秒东西方向绿灯亮，后5秒黄灯亮。依次重复。有紧急事件时允许将某方向一直开绿灯或者开红灯，另外允许特定情况两方向均为红灯，车辆禁行，比如十字路口恶性交通事故时，东西，南北两个方向均有两位数码管适时显示该方向亮灯时间。-Design a crossroads of traffic light control system requirements: Working in order of east-west direction the red light 45 seconds, the former north-south direction for 40 seconds, green light, yellow light after 5 seconds. North-south direction and then the red light 45 seconds, 40 seconds east-west direction before the green light, yellow light after 5 seconds. Followed by repetition. The event of emergency allows a certain direction has been given the green light or the opening of a red light, while allowing the direction of a particular situation are two red lights, vehicles forbidden lines, such as the crossroads of malignant accident, the things in both directions north and south are two digital tube in due course of time showed that the direction of lighting.