I am now programming the AD9858 with series communication. But every time after the AD9858 powers up, the first command sent by series port always fails to correctly execute. For example, if I send the command to both disable 2GHz divider and shut down SYNCLK output, the chip will only disable the 2GHz divider but does not disable the SYNCLK output. I have to hardware reset the chip and then every command can be executed correctly. Is there something I need to pay attention when I first send command after the chip powers up? Or clear any register before sending the command?