I'm trying to program the AD9910 evaluation board through the SPI interface. However, when the jumpers are configured to allow external control of the DDS, the SYNC_CLK signal disappears after a fraction of a second when the board is powered up. If I configure the jumpers for control of the DDS by the evaluation board micro-controller the SYNC_CLK signal is as expected.
I haven't found anything in the manual that may explain this behavior. What may be wrong?