说明：  对AD9959英文数据手册进行了详尽的翻译，并标注出了一些很重要的功能、结构，能加快初学者入门速度，提高编程效率。
(This paper makes a detailed translation of AD9959 English data book, and marks out some very important functions and structures, which can speed up the beginners' entry speed and improve the programming efficiency.)