ad1985jstz-reel Analog Devices, Inc., ad1985jstz-reel Datasheet - Page 30

• Manufacturer Part Number: ad1985jstz-reel
• Description: Ac ?97 Soundmax Codec
• Manufacturer: Analog Devices, Inc.

Reg Num Name
0x32
Reg Num
0x36
AD1985
PCM L/R ADC Rate Register (Index 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 Register (Index 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.
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.
CNT[4:0]
CNTM
LFE[4:0]
LFEM
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.
CNTM (LFEM)
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
PCM L/R ADC Rate SRA15 SRA14 SRA13 SRA12 SRA11 SRA10 SRA9 SRA8 SRA7 SRA6 SRA5 SRA4 SRA3 SRA2 SRA1 SRA0 0xBB80
Name
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 (Register 0x2A), then the
sample rate is reset to 48 kHz.
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.
Write
00 0000
00 1111
01 1111
1x xxxx
xx xxxx
D15
CNT/LFE[5:0]
D15 D14 D13 D12 D11 D10 D9
LFEM X
D14
Readback
00 0000
00 1111
01 1111
01 1111
xx xxxx
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
Rev. A | Page 30 of 48
D10
D9
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
• For AC97NC = 1, the register controls the center and LFE
D8
output pin attenuators. The range is 0 dB to −46.5 dB.
DAC gain/attenuators. The range is +12 dB to −34.5 dB.
D8
D7
D7
D6
D6 D5 D4
D5
Function with AC97NC = 1
+12 dB Gain
−10.5 dB Gain
−34.5 dB Gain
Indeterminate
Muted, −∞ dB Gain
D4
D3
D3
D2
D2
1
D1
D1
D0
D0
Default
Default