说明：  我的查表算法思路是这样的 ： 1、构造N个二维数组（N＝你需要输入的最大频率值位数，例如你需要精确到10HZ，最高30MHZ，那么就有10M位、1M位、100K位、10K位、1K位、100HZ位、10HZ位，共7位，所以N=7）。 2、根据你所用的芯片型号，和晶振频率，计算出每个频率位0-9时的控制字。 3、使用时，把你频率的每一位控制字，查表读出，并相加（特别需要注意进位也需要处理）。 4、把加出的4字节控制字，送DDS。
(My idea of look-up table algorithm is this: one, construction of two-dimensional array of N months (N = you need to enter the median value of maximum frequency, for example, you need accurate to 10HZ, the highest 30MHZ, then there is 10M bit, 1M bit, 100K-bit, 10K-bit, 1K-bit, 100HZ-bit, 10HZ, and a total of 7, so N = 7). 2, based on your use of the chip model, and the crystal frequency, calculated for each frequency control digital word at the time 0-9. 3, when used, you control the frequency of every word, look-up table read out, and the sum of (the special needs of attention also needs to deal with binary). 4, the increase of the 4-byte control word sent to DDS.)