说明：  本程序主要用于DDS算法的验证,可以生成正弦波，占空比可调的方波，三角波；其中频率控制字可调，生成波形的频率也可调。
(This procedure is mainly used for verification DDS algorithm, can generate sine wave with adjustable duty cycle square wave, triangle wave including adjustable frequency control word to generate adjustable frequency waveform.)