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data format confusion, 2.14? or  5.23?

Question asked by michaelc21 on Jan 4, 2010
Latest reply on Jan 8, 2010 by BrettG
Branched to a new discussion

hi, I am a new guy with ADI dsp. I am using the 1940, and the board is EVAL-AD1940AZ.

I just design a simple project, to control the volume.

I just don't know the data format of the  "Single Volume Control".

When I adjust the slew,  the capture window will show the data,  the "data" filed is  5 bytes (HEX).

When I make it to  +20dB,  the  data is:  0x00,  0x85,  0x00,  0x000x00

                      when 0 dB,  the data is : 0x00,  0x80,  0x80,  0x00,  0x00

                      when -80dB, the data is: 0x00,  0x80,  0x00,  0x03 ,0x47,

 

Why it should be so ?

 

I read the datasheet  of 1940, the 0x00, 0x8x,  i konw it , may be it is  "Constant Time Ramp Data Write",

datasheet  Page20~22.

But the datafiled , I  confused!

I know the format  of 5.23,  but the 2.14??  Above data right? Why it should like this?

 

The attach is  the project file.

Thank you.

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