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AIC3106 control registers question

Donald Reay
Expert 1545 points

I've been experimenting with writing to the page 1 control registers in the AIC3106 and have had success configuring the audio effects filters

by writing different values to the appropriate page 1 registers.

However, when it comes to configuring the DAC de-emphasis and ADC high pass filters I've not been so successful.

I can't seem to alter (write) the values in the control registers for these filters (page 1, registers 21-26, 47-52, 65-76).

Are these registers writeable?

Additionally, I am confused by the data sheet SLAS509E. It states that the reset values for the ADC high pass filter coefficients

are identical to the reset values for the DAC de-emphasis filter coefficients. If I read the DAC de-emphasis filter coefficient registers I see the

reset values given in the datasheet. If I read the ADC high pass filter coefficient registers I get different values - values that make more sense

as representing high pass filters.

I don't understand either how the selection of high pass filter -3dB frequencies relates to the values in the ADC high pass filter coefficient registers.

I can see/measure different high pass filter characteristics corresponding to different values that I write to bits 7-4 in page 0 register 12, i.e. if I

enable the ADC high pass filters with different -3dB frequencies. Are these -3dB frequencies different because different filter coefficients are used

or due to some other mechanism?

For a given selection of -3dB frequency, I see a different filter characteristic depending on how I have set bits 7-6 in page 0 register 107. This is supposed to select

either 'default' or 'programmable' coefficients - but I don't understand what are the 'default' vs. 'programmable' coefficients? Are either of these coefficient sets

the ones represented in page 1 registers 65-76? Are the 'default' coefficients the reset values of page 1 registers 65-76?

Given that I seem unable to change the values in page 1 registers but that by selecting 'default' or 'programmable'

coefficients via page 0 register 107, it appears that there are two different sets of coefficients available. Alternatively,

does the selection of 'default' or 'programmable' coefficients using page 0 register 107 interact in some way with the choice of -3db frequency set using

page 0 register 12?

Hope this makes sense!

  • 0
    Expert 1545 points

    Perhaps should avoid posting in the heat of battle.

    It appears that I can write to the aforementioned page 1 registers.

    To answer my own question, page 0 register 12 disables or enables ADC high pass filter. If enabled, and default parameters selected using page 0 register 107 then one of three different ADC high pass filters is implemented - independent of values in page 1 registers 65-76. Evidently, the 'default coefficients' are not the 'reset values' and must be being read from somewhere other than page 1 registers 65-76. If enabled, and programmable  parameters selected using page 0 register 107 then values in page 1 registers 65-76 are used.

    The reset values for page 1 registers 65-76 shown in the SLAS509E datasheet do, however, appear to be incorrect. The actual reset values implement a high pass filter not unlike the default f(3dB) = 0.0045*fs option.