protues与keil实现，at89c52完成，自己编写的电压表，adc0809芯片实现，上有adc0809资料，静态显示电压精确至小数点后两位-protues and keil achieve, at89c52 completed, I have written voltmeter, adc0809 chip, there adc0809 information on static display voltage is accurate to two decimal places