AD1985

Rev. A | Page 30 of 48

PCM L/R ADC Rate Register (Index 0x32)

Reg Num Name

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

Default

0x32

PCM L/R ADC Rate SRA15 SRA14 SRA13 SRA12 SRA11 SRA10 SRA9 SRA8 SRA7 SRA6 SRA5 SRA4 SRA3 SRA2 SRA1 SRA0 0xBB80

This read/write sample rate control register contains 16-bit unsigned values, representing the rate of operation in Hz.

SR[15:0]

Sample Rate. The sampling frequency range is from 7 kHz (0x1B58) to 48 kHz (0xBB80) in 1 Hz increments. The codec may

not function correctly if frequencies are written outside this range. If 0 is written to ASCVRA (Register 0x2A), then the

sample rate is reset to 48 kHz.

Center/LFE Volume Register (Index 0x36)

Reg Num

Name

D15

D14 D13 D12 D11 D10 D9

D8

D7

D6 D5 D4

D3

D2

D1

D0

Default

0x36

Center/LFE Volume

LFEM X

X

LFE4 LFE3 LFE2 LFE1 LFE0 CNTM X

X

CNT4 CNT3 CNT2 CNT1 CNT0 0x8080

This register controls the center and LFE output volumes and

mute bits. The volume register contains five bits, generating 32

volume levels with increments of 1.5 dB each.

AC ’97 defines the 6-bit volume registers, therefore, to maintain

compatibility whenever the D5 or D13 bit is set to 1, its

respective lower five volume bits are automatically set to 1 by

codec logic. On read-back, all lower five bits will read 1s

whenever this bit is set to 1.

Note that depending on the state of the AC 97NC bit in

Register 0x76, this register operates as follows:

• For AC'97NC = 0, the register controls the center and LFE

output pin attenuators. The range is 0 dB to −46.5 dB.

• For AC97NC = 1, the register controls the center and LFE

DAC gain/attenuators. The range is +12 dB to −34.5 dB.

CNT[4:0]

Center Volume Control.

CNTM

Center Volume Mute. When this bit is set to 1, the channel is muted.

LFE[4:0]

LFE Volume Control.

LFEM

LFE Volume Mute. When this bit is set to 1, the channel is muted.

Note that when the CSWP bit (Register 0x74) is set to 1, the definition of these volume controls for left and right are swapped, i.e., LFE[4:0] and LFEM control center

volume/mute, and CNT[4:0] and CNTM control LFE volume/mute.

CNT/LFE[5:0]

CNTM (LFEM)

Write

Readback

Function with AC97NC = 0

Function with AC97NC = 1

0

00 0000

00 0000

0 dB Gain

+12 dB Gain

0

00 1111

00 1111

−22.5 dB Gain

−10.5 dB Gain

0

01 1111

01 1111

−46.5 dB Gain

−34.5 dB Gain

0

1x xxxx

01 1111

−46.5 dB Gain

Indeterminate1

1

xx xxxx

xx xxxx

Muted, −∞ dB Gain

Muted, −∞ dB Gain

Note: x in the above table is a wild card, meaning the value has no effect.

indeterminate, since the five LSBs are listed as wild cards.