92HD66B Datasheet, PDF (15/286 Pages) Integrated Device Technology – FOUR CHANNEL HD AUDIO CODECS

92HD66B
FOUR CHANNEL HD AUDIO CODECS WITH DUAL CAPLESS HEADPHONE AMPLIFIERS
2.5. SPDIF Input
SPDIF IN can operate at 44.1 KHz, 48 KHz, or 96 KHz, and implements internal Jack Sensing (Port
presence Detect).
A sophisticated digital PLL allows automatic rate detection and accurate data recovery. The ability to
directly accept consumer SPDIF voltage levels eliminates the need for costly external receiver ICs.
Status flags from the input stream are updated only after the entire valid block has been received (or
at least when all bits of a particular status flag have been received) to ensure that software does not
read an invalid mixture of old and new data.
In general, the SPDIF input block does not alter the data received. However, it is sometimes neces-
sary to alter the data when the converter widget settings do not match the stream format. The follow-
ing table outlines a few cases and the expected behavior.
Port presence detect for SPDIF_IN operates differently from other ports. Once the PLL has locked
and valid framing (no errors) has been detected, then the port presence detect bit is set. In D3, and
D3 without a clock, it is not possible to check for proper framing. Monitoring of activity (rising and fall-
ing edges) is sufficient to verify a change in connectivity in D3. If no clock is present, then the internal
oscillator is used until a clock is restored. When the HD Audio bus is in a low power state (reset
asserted and clock stopped) the CODEC will generate a Power State Change Request when a
change in SPDIF_IN port connectivity is sensed and then generate an unsolicited response after the
HD Audio link has been brought out of a low power state and the device has been enumerated. Per
HDA015-B, this will take less than 10mS.
Conflict
Behavior
Resolution
Converter widget rate does not
equal the stream rate
Although the SPDIF input block is designed
to handle inputs slightly above or below the
programmed rate, samples may be lost if
the input rate is much higher than the rate
programmed into the converter widget.
Program the converter widget with the
same rate as indicated by the input stream.
Converter widget programmed
for a word length less than the
word length provided by the
input stream
If the input stream indicates non PCM data,
the data will be truncated to the requested
word length. If LPCM data is indicated in the
input stream, the CODEC will round the
received data to the requested length.¹
Program the converter widget with the word
length indicated in the input stream.
Converter widget programmed
with a word length greater than
the word length provided by
the input stream.
Regardless of content, 24 bits per channel
of data will be transferred from the SPDIF
input stream to the HD Audio bus interface.
Truncation or rounding to the requested
word length will be handled as described as
above. Any non-zero data in the incoming
stream will cause problems.
Program the converter widget with the word
length indicated in the input stream.
Although not recommended, application or
driver software may program the converter
widget with a word length of 24 bits,
truncate the input to the word length
indicated by the input stream, then right
extend the data using 0s to the desired
word length.
Table 7. SPDIF Behavior
1. Rounding may be disabled by setting the disable bit (AFG vendor specific verb -see widget list) or setting the
SPDIF_IN converter widget Frmt StrmType field to 1 (non-PCM)
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