说明：  这是用单片机实现的多功能数字钟,通过8255扩展端口,AD0809将模拟信号转换成数字信号进行处理,可以比较精确的测出电压值.
(This is the MCU multifunction digital clock, through the 8255 expansion port, AD0809 a conversion of analog signals into digital signal processing, more precise measuring the voltage values.)