WM8802
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IEC61937, DTS-CD/LD DETECTION FLAG OUTPUT
A function to output IEC61937 and DTS-CD/LD detection flags for non-PCM data is provided.
When the UNPCM non-PCM signal output setting is selected, as well as an indication on the AUDIO
pin, an interrupt signal is output from INT upon detection of an IEC61937 or DTS-CD/LD sync signal.
Non-PCM signal details can be known by reading this information from the output register.
The IEC61937 sync signal is detected and output when channel status bit 1 is non-PCM data ("1").
The IEC61937 sync signal is not output if bit 1 is PCM data (“0”).
DTS-CD/LD sync signal detection is done based on the sync pattern and the base frequency. In the
case of DTS-ES data detection, output is performed when the DTS5.1 channel sync signal is
detected and the DTS-ES sync pattern has been verified.
The IEC61937 and DTS-CD/LD detection flags are cleared when fs has changed or upon occurrence
of a PLL lock error or data error.
Since the DTS sync signal is provided within the audio data, digital data with the same code as the
DTS sync signal may in rare cases exist for regular CD/LD records that are not recorded in the DTS
format. Protection using the sync pattern or base frequency is provided so that such data is not
misinterpreted as DTS-CD/LD detection flags. The detection sequence is shown below.
Input data
NO
Bit 1 detection
Bit 1 = 1
YES
DTS-CD/LD
SYNC
detection
NO
NO
PaPb
detection
YES
YES
Frame counter
reset
Frame counter
start
Frame counter
start
Frame counter
reset
PaPb
detection
during 4096
frames
Frame count
512, 1024, 2048, 4096
SYNC detection
NO
NO
YES
YES
DTS-CD/LD flag
not valid
INT lowered
IEC61937
flag
DTS-CD/LD flag OK
INT lowered
IEC61937 flag OK
INT lowered
*
Frame count hold
x2 count detection
expansion
PaPb
detection
during 4096
frames
NO
Depending on the frame count,
the subsequent detection count
is expanded up to x2.
*
YES
Frame count
512, 1024, 2048, 4096
SYNC detection
NO
*
IEC61937 data
hold
Periodic fluctuation is supported.
1st count
2nd count
YES
512 => 512 or 1024
1024 => 1024 or 2048
2048 => 2048 or 4096
4096 => 4096
DTS-CD/LD
data hold
Figure 24 Detection Flag Output Flowchart
PP Rev 1.1 April 2004
32
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
