本次实现主要是实现红绿灯能完成 9 秒倒计时，以 18F452 单片机为中心，

通过 1 个数码管和 8 盏信号灯控制交通。首先是南北方向绿灯亮，东西方向红灯

亮，数码管开始倒计时；当倒计时为 0 时，状态改变为南北方向红灯亮，东西方

向绿灯亮，然后重复上述过程。-This realization is mainly the realization of traffic lights to complete the 9 seconds countdown, with 18F452 MCU as the center,

Control traffic through the 1 digital tube and 8 signal lamps. The first is the north south direction of the green light, red light east-west direction

Light, digital tube countdown　when the countdown reaches 0, the state changed to red light north-south direction, East and West

To the green light, and then repeat the process.