How to use Fast Lock mode in AD9361?


Rencently I'm lenrning to use the Fast Lock mode of AD9361,because I want to shorten the time to change the frequency.But when I follow the datasheet to complete the operation step by step,RX LO frequency has not changed.

The way I used Fastlock is to use drive instructions to modify the value of the registers like the picture below.

I can make sure that the Reference frequency and the SynthLUT I used is the same as in the datasheet,so I don’t understand the reason for this phenomenon, I hope someone can answer,thanks.