Phase shift on two sinus waves with Aduc7129

How can I detect a phase shift between a reference sinus and a phase shift sinus with my Aduc7129 controller.

Is there a chance to detect the intern ref. sinus without measureing it with the ADC.

I would like to meausure the zero crossing of the two sinus and so get the phase shift.

Or can I start at a given phase with controlling the DDSPhs register?

Is there anybody who can help me?

Thanks Marcus