I use AD9650 in my design, it is 105MHz, now I can read reg #001, I can also read and write other reg.
But I can not write reg #00B, any value write to it when read is 0x00, I can make sure my work on SPI is OK, Why?
This particular register requires an additional WRITE operation to transfer its content. See datasheet below.
Page 39 of the datasheet describe the Transfer Register Map.