在单片机与外部环境通信的时候，就需要有一种转换器来把模拟信号变为数字信号，以便能够输送给单片机进行处理。而单片机送出的控制信号，也必须经过变换器变成模拟信号，才能为控制电路所接受。这种变换器就称为数模(D／A)转换器和模数(A／D)转换器。-In single-chip communication with the external environment when the need for a converter to the analog signal into digital signal in order to be able to transfer to the single chip for processing. The single-chip control signals sent also to go through into the analog signal converter can be accepted for the control circuit. This is called digital-to-analog converter (D/A) converters and analog-to-digital (A/D) converters.