Pre-Production
WM8850
Mono Streams
All converters are stereo. Where an input converter (ADC, S/PDIF Rx) is associated with a mono
stream, only the left channel (channel 0) will be sent on the HDA Link.
In mono mode, right channel modules in the ADC will be disabled to save power.
Where an output converter (DAC, S/PDIF Tx) is associated with a mono stream, both left and right
channels render the same samples. If both left and right DAC outputs are not desired, the unwanted
channel can be muted.
A stream is assumed to be mono when its Chan control in the Stream Format Verb is set to 0. The
Channel control in the Converter Stream, Channel Verb should be set to 0, although any setting of
this register gives the same behaviour in mono mode.
ILLEGAL REGISTER VALUES
Should the user set verb registers to illegal, unsupported or reserved values, WM8850 behaviour is
undefined.
Writing to Reserved registers has no effect.
RESPONSE FIELD
Valid Bit
Bit [35] of the Response Field is defined as the Valid Bit. Section 7.3.1 of the HDA specification
states: “A 1 in the Valid bit position indicates the Response Filed contains a valid response, which the
controller will place in the RIRB; a 0 indicates there is no response.”
The WM8850 will set the Valid Bit for all responses, except null responses.
We define a null response as a response to a command that contains an invalid verb (a command
where NID=0h, and Verb=0h), or a response to a command with a CODEC address (CAd) that does
not match the WM8850 CAd. Either of these commands can be considered as a null command.
We define a non-defined command as a command that has no meaning (i.e. a NID that is not within
the WM8850, or a Verb ID that is not supported for the given node). The WM8850 will set the Valid
Bit for non-defined commands.
PP, April 2011, Rev 3.2
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