ADF5902 Can not configure R7 Register

Hello: 

     We use ADF5902, but we can not configure R7 register.  We program 5902 registers by ADF5902_data initialization sequence. 

The step 9 , We program R7 with value "0x01800827",  but we read R7 , the value is "0x00000000".   We read the other register is all right.