WM1811A Datasheet, PDF (199/328 Pages) Wolfson Microelectronics plc – Multi-Channel Audio Hub CODEC for Smartphones

Production Data
WM1811A
SAMPLE RATE CONVERSION
The WM1811A supports two main digital audio interfaces, AIF1 and AIF2. These interfaces are
configured independently and may operate entirely asynchronously to each other. The WM1811A
performs stereo full-duplex sample rate conversion between the audio interfaces, allowing digital
audio to be routed between the interfaces, and allowing asynchronous audio data to be mixed
together.
The Sample Rate Converters (SRCs) are configured automatically within the WM1811A, and no user
settings are required. The SRCs are enabled automatically when required and are disabled at other
times. Synchronisation between the audio interfaces is not instantaneous when the clocking or sample
rate configurations are updated; the lock status of the SRCs is signalled via the GPIO or Interrupt
circuits, as described in “General Purpose Input/Output” and “Interrupts”.
Separate clocks can be used for AIF1 and AIF2, allowing asynchronous operation on these interfaces.
The digital mixing core is clocked by SYSCLK, which is linked to either AIF1CLK or AIF2CLK, as
described in “Clocking and Sample Rates”. The digital mixing core is, therefore, always synchronised
to AIF1, or to AIF2, or to both interfaces at once.
SAMPLE RATE CONVERTER 1 (SRC1)
SRC1 performs sample rate conversion of digital audio data input to the WM1811A. Sample Rate
Conversion is required when digital audio data is received on an audio interface that is not
synchronised to the digital mixing core.
SRC1 is automatically configured on AIF1 or AIF2, depending on the selected Clocking and Sample
Rate configuration. Note that SRC1 cannot convert input data on AIF1 and AIF2 simultaneously.
The SRC1 Lock status indicates when audio data can be received on the interface channel that is not
synchronised to the digital mixing core. No audio will be present on this signal path until SRC1 Lock is
achieved.
SAMPLE RATE CONVERTER 2 (SRC2)
SRC2 performs sample rate conversion of digital audio data output from the WM1811A. Sample Rate
Conversion is required when digital audio data is transmitted on an audio interface that is not
synchronised to the digital mixing core.
SRC2 is automatically configured on AIF1 or AIF2, depending on the selected Clocking and Sample
Rate configuration. Note that SRC2 cannot convert output data on AIF1 and AIF2 simultaneously.
The SRC2 Lock status indicates when audio data can be transmitted on the interface channel that is
not synchronised to the digital mixing core. No audio will be present on this signal path until SRC2
Lock is achieved.
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PD, November 2013, Rev 4.1
199