wm9708 Wolfson Microelectronics plc, wm9708 Datasheet - Page 27

• Manufacturer Part Number: wm9708
• Description: Ac?97 Revision 2.1 Audio Codec
• Manufacturer: Wolfson Microelectronics plc

Production Data
VENDOR RESERVED REGISTERS (INDEX 5Ah - 7Ah)
w
REGISTER 2Ah – EXTENDED AUDIO STATUS AND CONTROL REGISTER
The Extended Audio Status and Control Register is a read/write register that provides status and
control of the extended audio features.
Table 13 Extended Audio Status and Control Register
REGISTER 2Ch TO 32h – AUDIO SAMPLE RATE CONTROL REGISTERS
These registers are read/write registers that are written to, to select alternative sample rates for the
audio PCM converters. Default is the 48ks/s rate. Note that only Revision 2.1 recommended rates
are supported by the WM9708, selection of any other unsupported rates will cause the rate to default
to the nearest supported rate, and the supported rate value to be latched and so read back.
REGISTERS 36h AND 38h – 6 CHANNEL VOLUME CONTROL
These read/write registers control the output volume of the optional four PCM channels. (not
supported by the WM9708)
These registers are vendor specific. Do not write to these registers unless the Vendor ID register has
been checked first to ensure that the driver knows the source of the AC ‘97 component.
VENDOR SPECIFIC REGISTER (INDEX 5Ch)
The WM9708 can be programmed to automute the DACs. By setting the mute bit, the WM9708 will
mute the DACs when it detects a continuous sequence of 1024 zeros.
VENDOR SPECIFIC GAIN CONTROL REGISTERS – (INDEX 72h)
This register controls the gain and mute functions applied to the mixer path. This PGA is not
accommodated in the Intel specification, but is required in order to allow the option of simultaneous
recording of the mixer output and playback of DAC signals. The function is as per the other mixer
PGA’s. However, the default value of the register is not-muted. If it is not used it will be transparent to
the user.
VENDOR ID REGISTERS (INDEX 7Ch TO 7Eh)
This register is for specific vendor identification if so desired. The ID method is Microsoft’s Plug and
Play Vendor ID code. The first character of that ID is F7 to F0, the second character S7 to S0, and
the third T7 to T0. These three characters are ASCII encoded. The REV7 to REV0 field is for the
Vendor Revision number. In the WM9708 the vendor ID is set to WML3.
Wolfson is a registered Microsoft Plug and Play vendor.
VENDOR ID REGISTERS (INDEX 74h)
This register describes how data is mapped to the AC’97 DACs. Register 74h can be used to change
the incoming DAC data slots that are used by the on-board DACs. This allows software control of
multiple codecs. If used it is recommended that the ID is configured before any other registers and
before the data is applied to the system.
DATA BIT
MADC
CDAC
SDAC
LDAC
VRM
VRA
DRA
PRK
PRJ
PRL
PRI
FUNCTION
Enables variable rate audio mode
Enable double rate audio mode
Enables variable rate Mic ADC
Indicates centre DAC ready
Indicates surround DAC ready
Indicates LFE DAC ready
Indicates Mic ADC ready
Set to turn off centre DAC
Set to turn off surround DACs
Set to turn off LFE DACs
Set to turn off Mic ADC
READ/WRITE
Read/write
Read/write
Read/write
Read/write
Read/write
Read/write
Read/write
Read
Read
Read
Read
PD, Rev 4.2, August 2009
WM9708 SUPPORT
Yes
No
No
No
No
No
No
No
No
No
No
WM9708
27