AD1985 Analog Devices, AD1985 Datasheet - Page 30

• Manufacturer Part Number: AD1985
• Description: AC'97 2.3 Soundmax Codec W/jack Sensing
• Manufacturer: Analog Devices

AD1985
PCM ADC Rate Register (Index 0x32)
Reg Num
0x32
This read/write sample rate control register contains 16-bit unsigned values, representing the rate of operation in Hz.
SR[15:0]
CENTER/LFE Volume Control Register (Index 0x36)
Reg Num Name
0x36
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. Because AC ’97
defines 6-bit volume registers, 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.
CNT[4:0]
CNTM
LFE[4:0]
LFEM
Note: 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, CNT[4:0] and CNTM control LFE volume/mute.
CNTM (LMEM)
0
0
0
0
1
Note: x in the above table is a wild card, meaning the value has no effect.
1
indeterminate since the five LSBs are listed as wild cards.
When AC97NC is set to 1, there is only a 5-bit gain/attenuator to control, so the sixth bit, i.e., the MSB, does not control anything. Therefore, the 5-bit gain setting is
Name
PCM L/R ADC Rate SRA15 SRA14 SRA13 SRA12 SRA11 SRA10 SRA9 SRA8 SRA7 SRA6 SRA5 SRA4 SRA3 SRA2 SRA1 SRA0 0xBB80
Center/LFE volume
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 (Reg 0x2A), then the sample
rate is reset to 48 kHz.
WRITE
00 0000
00 1111
01 1111
1x xxxx
xx xxxx
CENTER Volume Control.
CENTER Volume Mute. When this bit is set to 1, the channel is muted.
LFE Volume Control.
LFE Volume Mute. When this bit is set to 1, the channel is muted.
CNT5 (LFE5)–CNT0 (LFE0)
D15
D15
LFEM X
D14
READBACK
00 0000
00 1111
01 1111
01 1111
xx xxxx
D14 D13 D12 D11 D10 D9
D13
X
D12
LFE4 LFE3 LFE2 LFE1 LFE0 CNTM X X CNT4 CNT3 CNT2 CNT1 CNT0 0x8080
Function with AC97NC = 0
0 dB Gain
–22.5 dB Gain
–46.5 dB Gain
–46.5 dB Gain
Muted, -∝ dB Gain
D11
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D10
D9
Note that depending on the state of the AC 97NC bit in Register
0x76, this register operates as follows:
D8
D8
For AC97NC = 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.
D7
D7
Function with AC97NC = 1
+12 dB Gain
–10.5 dB Gain
–34.5 dB Gain
Indeterminate
Muted, -∝ dB Gain
D6 D5 D4
D6
D5
D4
1
D3
D3
D2
D2
D1
D1
D0
D0
Default
Default