AD9959 SPI Problem


I am using AD9959 DDS.I am trying to communicate it with SPI.

I am trying to configure it as below:

SET_RST;     // Make reset pin high

CLR_RST;     // Make reset pin low

SET_CS;     // Make CS pin high

SET_IOUPD;     // Make IO_UPDATE pin high

CLR_IOUPD;     // Make IO_UPDATE pin high

SET_SDIO3;     // Make SDIO3 pin high

P0 to P3;     Low

CLK_MODE_SEL = 1.8 v;

After this I am trying to write as below:

1.pull the CS to Low

2.write the bytes (when probed only the MOSI pin is transmitting without any clock i.e the ClK pin of the SPI stays high every time. Not able to bring CLK Low.)

I isolated AD9959 and my controller, then i am able to see CLK and MOSI both fine.

Unable to point where the problem is.

Please check the attached schematics not sure if anything needs to be changed.