用C8051F040实现DA（模拟-数字）变换。C8051F040集成了12位精度的DA转换器。-With the C8051F040 to achieve DA (analog- digital) conversion. C8051F040 integrates a 12-bit accuracy of the DA converter.

SPI串行输出控制DA变换，实现函数信号发生器的功能，有方波，正弦波，三角波三种可调，输出波形，频率都是可调的！-SPI serial output control DA conversion, to achieve the function signal generator functions, well-wave, sine wave, triangle wave of three adjustable, output waveform, frequency is adjustable!

D/A转换是把数字量转换成模拟量的变换，从D/A输出的是模拟电压信号。产生锯齿波和三角波只需由A存放的数字量的增减来控制；要产生正弦波，较简单的手段是造一张正弦数字量表。取值范围为一个周期，采样点愈多，精度愈高些-D/A converter is to convert the analog digital transformation, from the D/A output is an analog voltage signal. Sawtooth and triangle wave gene

SPI口单片机控制AD和DA变换的汇编程序，51单片机通用-The SPI port SCM control the AD and DA conversion assembler, 51 MCU Universal