十字路口车辆穿梭，行人熙攘，车行车道，人行人道，有条不紊。那么靠什么来实现这井然秩序呢？靠的就是交通信号灯的自动指挥系统。交通信号灯控制方式很多。本系统采用MSC-51系列单片机ATSC51和可编程并行I/O接口芯片8255A为中心器件来设计交通灯控制器，实现了能根据实际车流量通过8051芯片的P1口设置红、绿灯燃亮时间的功能；红绿灯循环点亮，倒计时剩5秒时黄灯闪烁警示（交通灯信号通过PA口输出，显示时间直接通过8255的PC口输出至双位数码管）；车辆闯红灯报警；绿灯时间可检测车流量并可通过双位数码管显示。本系统实用性强、操作简单、扩展功能强。过上、下限温度时，进行声音（蜂鸣器）报警。-Crossroads shuttle vehicles, pedestrians bustling, car dealers driveway, walkway person, methodical. So rely on to achieve this orderly order it? Rely on automatic command system traffic lights. Traffic signal control many ways. The system uses the MSC-51 series MCU ATSC51 and programmable parallel I/O interface chip 8255A-centric device designed to traffic light controller realized according to the actual traffic flow through the P1 port 8051 set of red, green kindle time function　traffic light cycle light, countdown five seconds flashing yellow warning (traffic light signal through the PA output, display time directly through the 8255 PC port output to double-digit LED)　vehicles ran a red light alarm　green time can detect vehicles Traffic and through the double-digit digital display. The system is practical, simple operation, expand strong function. Over the upper and lower temperature, for sound (buzzer) alarms.