In ADAU1772's datasheet it is written (page 41):
"If an invalid subaddress is issued by the user, the ADAU1772 does
not issue an acknowledge and returns to the idle condition."
I have checked it, I tried writing to registers of subaddress like 0xFFFF, 0xCCFF and so on (address values that are not mentioned in datasheet). I use oscilloscope to monitor SDA and SCL and I think something is wrong cause my ADAU issued acknowledge after each weird subaddress.
What can be a reason of such behaviour ?