NA: AD9913: DDS IC, whats the serial protocol?

1. This IC datasheet page 22/32 says that the serial interface for this chip is flexible and can be integrated with any of the standards. SDIO is one single line! But SPI has unidirectional lines provided for each of the master and slave combinations! What can I call such a format?
2. How do you simulate a non periodic clock? By non periodic clock I mean, how do you pause the clock in between as shown on 22/32 and simulate the same on GPIF 2 interface?