DDS

             AD9956 chip.

           The output voltage of the pin cp-out of the 36 pin of the ad9956 chip is 0, which leads to the low vibration frequency of the VCO. The output voltage of the pin cp-out of the 36 pin shoule be 3.3v,However, the chip can be programmed and work. The working voltage of the charge pump is 3.3v, which is no problem.So I can't find where the problem is.