ad9523 spi write problem

I'm using ad9523 chip for clock generation.

The problem is that, spi write doesn't work except register 0x000.

(The condition of spi write(in 100khz, high 1.8V amplitude) is one byte transfer, registering channel divide.)

After spi write, when I read the spi data(activating SDO pin), all the value except 0x000 register, are default value.

I want to know why spi write only work at register 0x000.