According to the concept that analog to digital converters are defined as external RAM of single chip computer,three typical connections between AT89S51 single chip computer and ADC0809 analog to digital converter are introduced.

• 根据模数转换器定位为单片机的外部RAM单元的概念；介绍了AT89S51单片机与ADC0809模数转换器三种典型连接电路及程序编制.