wm9704q Wolfson Microelectronics plc, wm9704q Datasheet - Page 15

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

Production Data
GAIN CONTROL REGISTER LOCATION VERSUS MODE AND ID
MASTER/SLAVE ID0/1 SUPPORT
WOLFSON MICROELECTRONICS LTD
The following table shows which registers control which DAC rates, versus Mode and ID selected
Table 4 Variable Rate Register Location Versus Mode and ID
Depending on what mode and ID the device is operated in, the various gain control registers have
locations in the register map that may change. For example, if the Codec is configured as ID 10, it
means that the device will be converting the rear surround DAC data. Therefore in this case the
surround DAC volume word written to register 38h is now used to control the master volume control,
rather than the normal master volume 02h.
In addition, in this case when the surround volume mute control is written as de-mute, then mute in
the DAC PGA register 18h is automatically over-ridden, to avoid the user having to make an
unexpected additional write to register 18h to de-mute the DAC PGA.
Table 5 Gain Control Register Location Versus Mode and ID
WM9704Q supports operation as either a master or a slave codec. Configuration of the device as
either a master or as a slave, is selected by tying the ID pins CID0 and CID1, pins 45 and 46 on the
package.
Fundamentally, a device identified as a master (ID = 00) produces BITCLK as an output, whereas a
slave (any other ID) must be provided with BITCLK as an input. This has the obvious implication that
if the master device on an AC link is disabled, the slave devices cannot function.
The AC’97 Revision 2.1 specification defines that the ID pins have inverting sense, and are provided
with internal weak pull ups. Therefore, if no connections are made to the CID0/1 pins, then the pins
pull hi and an ID = 00 is selected, i.e. master. External connects to ground will select other IDs.
Front Mixer
Rear Mixer
Front DAC
Rev 2.1
mode (00)
Rev 2.1 6-
channel
mode (01)
Quad
mode (10)
Rear DAC
Volume
Volume
MODE
Front
Rear
PGA
PGA
PGA
CODEC
00 and 01
00 and 01
00 and 01
10
11
10
11
10
11
10
11
10
11
10
11
0x
0x
0x
0x
0x
0x
ID
ID
10
11
10
11
10
11
CONTROL
REG
18h
70h
72h
74h
02h
38h
36h
04h
2Ch (centre) and 30h (LFE)
2Ch (centre) and 30h (LFE)
2Ch (centre) and 30h (LFE)
REV 2.1 MODE (0X)
FRONT DAC RATE
REGISTER
Muted (bit15) Rev 2.1
Permanently muted
AND with 38h,7,15
AND with 36h,7,15
Not-muted (bit15)
muted (7 and 15)
muted (7 and 15)
MUTE DEFAULT
and powered off
switch enabled
2Ch
2Ch
2Ch
2Eh
2Eh
2Eh
Muted (bit15)
Muted (bit15)
Muted (15)
REAR DAC RATE
CONTROL
REGISTER
REG
18h
70h
72h
74h
02h
38h
36h
38h
02h
38h
2Eh
2Ch
2Eh
QUAD MODE (10)
PD Rev 2.3 January 2001
AND with 38h,7,15
AND with 36h,7,15
AND with 38h,7,15
Not-muted (bit15)
AND with 02h, 15
Not-muted (bit15)
Not-muted (bit15)
muted (7 and 15)
muted (7 and 15)
Muted (7 and 15)
muted (7 and 15)
MUTE DEFAULT
Muted (bit15)
Muted (15)
muted (15)
WM9704Q
ADC RATE
REG
32h
32h
32h
15