AD1981B

Rev. C | Page 25 of 32

Bit

Mnemonic

Function

biquad 1 coef a2 BCA[5:0] = 011110

biquad 1 coef b1 BCA[5:0] = 100010

biquad 1 coef b2 BCA[5:0] = 100001

biquad 2 coef a0 BCA[5:0] = 100101

biquad 2 coef a1 BCA[5:0] = 100100

biquad 2 coef a2 BCA[5:0] = 100011

biquad 2 coef b1 BCA[5:0] = 100111

biquad 2 coef b2 BCA[5:0] = 100110

biquad 3 coef a0 BCA[5:0] = 101010

biquad 3 coef a1 BCA[5:0] = 101001

biquad 3 coef a2 BCA[5:0] = 101000

biquad 3 coef b1 BCA[5:0] = 101100

biquad 3 coef b2 BCA[5:0] = 101011

biquad 4 coef a0 BCA[5:0] = 101111

biquad 4 coef a1 BCA[5:0] = 101110

biquad 4 coef a2 BCA[5:0] = 101101

biquad 4 coef b1 BCA[5:0] = 110001

biquad 4 coef b2 BCA[5:0] = 110000

biquad 5 coef a0 BCA[5:0] = 110100

biquad 5 coef a1 BCA[5:0] = 110011

biquad 5 coef a2 BCA[5:0] = 110010

biquad 5 coef b1 BCA[5:0] = 110110

biquad 5 coef b2 BCA[5:0] = 110101

biquad 6 coef a0 BCA[5:0] = 111001

biquad 6 coef a1 BCA[5:0] = 111000

biquad 6 coef a2 BCA[5:0] = 110111

biquad 6 coef b1 BCA[5:0] = 111011

biquad 6 coef b2 BCA[5:0] = 111010

CHS

Channel Select

CHS = 0 selects the left-channel coefficient’s data block.

CHS = 1 selects the right-channel coefficient’s data block.

SYM

Symmetry

When set to 1, this bit indicates that the left and right-channel coefficients are equal. This shortens

the coefficients’ setup sequence, because only the left-channel coefficients need to be addressed

and set up. The right-channel coefficients are fetched from the left-channel memory.

MAD

LBEN

Mixer ADC Loopback

Enable

Enables mixer ADC data to be summed into the PCM stream.

0 = No loopback allowed (default).

1 = Enable loopback.

EQM

Equalizer Mute

When set to 1, this bit disables the equalizer function (allows all data to pass through). The reset

default sets this bit to 1, disabling the equalizer function until the biquad coefficients can be

properly set.