wm9715l Wolfson Microelectronics plc, wm9715l Datasheet - Page 37

• Manufacturer Part Number: wm9715l
• Description: Ac?97 Audio And Touchpanel Codec
• Manufacturer: Wolfson Microelectronics plc

Production Data
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VARIABLE RATE AUDIO / SAMPLE RATE CONVERSION
By using an AC’97 Rev2.2 compliant audio interface, the WM9715L can record and playback at all
commonly used audio sample rates, and offer full split-rate support (i.e. the DAC, ADC and
AUXDAC sample rates are completely independent of each other – any combination is possible).
The default sample rate is 48kHz. If the VRA bit in register 2Ah is set and the appropriate block is
enabled, then other sample rates can be selected by writing to registers 2Ch, 32h and 2Eh. The AC-
Link continues to run at 48k frames per second irrespective of the sample rate selected. However, if
the sample rate is less than 48kHz, then some frames do not carry an audio sample.
Table 22 Audio Sample Rate Control
When the audio ADC is disabled, its sample rate cannot be changed (i.e. writing to the ADCSR bits
has no effect). The following sequence of register writes is therefore recommended for changing the
ADC sample rate:
2Ah
Extended
Audio
Stat/Ctrl
2Ch
Audio DAC
Sample Rate
32h
Audio ADC
Sample Rate
2Eh
AUXDAC
Sample Rate
REGISTER
ADDRESS
1.
2.
3.
4.
Set PD11 and/or PD12 = 0 in register 24h as appropriate for
left/right/stereo ADC operation
Set PR0 = 0 in register 26h to enable the audio ADC(s)
Set VRA = 1 in register 2Ah to enable Variable Rate Audio
Set ADCSR in register 32h to the appropriate value for the
desired sample rate
0
15:0
15:0
15:0
BIT
VRA
DACSR
ADCSR
AUXDAC
SR
LABEL
0 (OFF)
BB80h
(48kHz)
BB80h
(48kHz)
BB80h
(48kHz)
DEFAULT
Variable Rate Audio
0: OFF (DAC and ADC run at 48kHz)
1: ON (sample rates determined by
registers 2Ch, 2Eh and 32h)
Audio DAC sample rate
1F40h: 8kHz
2B11h: 11.025kHz
2EE0h: 12kHz
3E80h: 16kHz
5622h: 22.05kHz
5DC0h: 24kHz
7D00h: 32kHz
AC44h: 44.1kHz
BB80h: 48kHz
Any other value defaults to the nearest
supported sample rate
Audio ADC sample rate
similar to DACSR
Note writing to these bits has no effect
when ADC is disabled
AUXDAC sample rate
similar to DACSR
DESCRIPTION
PD Rev 4.0 December 2007
WM9715L
37