ADAU17xx Data Readback format

Hello All,

I have an ADAU17xx part talking to a microcontroller in my application. I'm trying to use the readback tool to read out some rms values from the codec over the I2C bus. I read that the format of this data is 5.23 here Numeric Formats [Analog Devices Wiki]

Lets take an example:-

From within Sigmastudio, I notice that the value 0x0F, 0x81, 0xB1, 0xC2 gets converted to -0.98676....

I cannot understand how that would be.

0x0F and 0x81 would mean that the 5 bit integer part is 11111 thereby making it -1 in decimal (negative twos complement) :-

   0        F        8       1

0000 (1111 1)000 0001

Yet the converted value in Sigmastudio is -0.98676....

What am I missing ?

Thanks for your time.

K