I am troubleshooting a design that uses the AD9889B connected to an ARM9 processor. I am able to read and write to the AD9889B using the I2C bus and receive ACKs but am unable to read anything back from the device except zeros. I have the A0 line pulled low using address 0x72 and have also tried pulling A0 high and using address 0x7A but get the same results. When I pull the HDP line I expect to see bits set in registers 0x41, 0x42 and 0x96 but see no change. What am I doing wrong? Is there some sort of initialization process that must be done before attempting to read these registers?