wm9704q Wolfson Microelectronics plc, wm9704q Datasheet - Page 25

• Manufacturer Part Number: wm9704q
• Description: 4-channel Surround Sound Codec
• Manufacturer: Wolfson Microelectronics plc

Production Data
WOLFSON MICROELECTRONICS LTD
Support for the MSB of the volume level is not provided by the WM9704Q. If the MSB is written to,
then the WM9704Q detects when that bit is set and sets all 4 LSBs to 1s. Example: If the driver
writes a 1xxxxx the WM9704Q interprets that as x11111. It will also respond when read with x11111
rather than 1xxxxx, the value written to it. The driver can use this feature to detect if support for the
6th bit is there or not.
The default value of both the mono and the stereo registers is 8000h (1000 0000 0000 0000), which
corresponds to 0dB gain with mute on.
Table 11 Volume Register Function
MASTER TONE CONTROL REGISTERS (INDEX 08h)
Optional register for support of tone controls (bass and treble). The WM9704Q does not support bass
and treble and writing to this register will have no effect, reading will result in all don’t care values.
PC BEEP REGISTER (INDEX 0Ah)
This controls the level for the PC-beep input. Each step corresponds to approximately 3dB of
attenuation. The MSB of the register is the mute bit. When this bit is set to 1 the level for that channel
is set at -
WM9704Q defaults to the PC-beep path being muted, except during reset when the path is open, so
an external speaker should be provided within the PC to alert the user to power on self-test
problems.
Table 12 PC-beep Register Function
ANALOGUE MIXER INPUT GAIN REGISTERS (INDEX 0Ch - 18h)
This controls the gain/attenuation for each of the analogue inputs. Each step corresponds to
approximately 1.5dB. The MSB of the register is the mute bit. When this bit is set to 1 the level for
that channel is set at -
REGISTER 0Eh (MIC VOLUME REGISTER)
This has an extra bit that is for a 20dB boost. When bit 6 is set to 1 the 20dB boost is on. The default
value is 8008, which corresponds to 0dB gain with mute on.
The default value for the mono registers is 8008h, which corresponds to 0dB gain with mute on. The
default value for stereo registers is 8808h, which corresponds to 0dB gain with mute on.
Table 13 Mixer Gain Control Register Function
MUTE
MUTE
MUTE
0
0
0
1
0
0
1
0
0
0
1
dB.
MX4...MX0
GX4...GX0
PV3...PV0
0 0000
0 0001
1 1111
00000
01000
11111
x xxxx
xxxxx
0000
1111
xxxx
dB. (See Table 13).
FUNCTION
0dB attenuation
1.5dB attenuation
46.5dB attenuation
FUNCTION
0dB attenuation
45dB attenuation
FUNCTION
+12dB gain
0dB gain
-34.5dB gain
-
dB attenuation
dB attenuation
dB gain
PD Rev 2.3 January 2001
WM9704Q
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