WM8850
Pre-Production
The generation of the Non Audio Flag is controllable in one of two ways:
The non-audio code (as defined in IEC-61937) is received by the WM8850. The value of the
/AUDIO channel status bit is ignored. The Non Audio Flag will clear after 4096 consecutive
S/PDIF frames have been received without the non-audio code being present.
The non-audio code (as defined in IEC-61937) is received by the WM8850 and the /AUDIO
channel status bit is set to 1. The Non Audio Flag will clear after 4096 consecutive S/PDIF
frames have been received without the non-audio code being present, or it will clear
immediately if the /AUDIO channel status bit is cleared.
The required function of the Non Audio Flag is set by the NA_CNTRL field as part of the Overwrite
Control Verb.
SET VERB
BIT
BITFIELD
NAME
DEFAULT
DESCRIPTION
793h
2
NA_CNTRL
1
Controls the generation of the Non-Audio Flag:
0 = Asserted when the non-audio code (as
defined in IEC-61937) is detected
1 = Asserted when the non-audio code (as
defined in IEC-61937) is detected and the
/AUDIO channel status bit is set
When the Non Audio Flag is asserted, the WM8850 can be configured to overwrite the recovered
data samples with zeros using the vendor-specific Overwrite Control Verb.
SET VERB
BIT
BITFIELD
NAME
DEFAULT
DESCRIPTION
793h
1
NA_OVWR_
EN
0
Enables data overwrite when the Non Audio
Flag is asserted:
0 = Do not overwrite
1 = Overwrite data with zeros
Notes:
1. When in Software Formatted S/PDIF Mode, only the 24-bit payload can be overwritten
2. When SRC1 is being used NA_OVWR_EN is set to 1 automatically by the WM8850 and
becomes read-only
The WM8850 can detect a S/PDIF received data error. A received data error can be the result of a
parity error, a bi-phase encoding error or by receiving out of sequence pre-ambles. Using the vendor-
specific Overwrite Control Verb it is possible to configure with WM8850 to automatically overwrite
erroneous samples with zeros when a data error is detected and therefore the received sample is
erroneous:
SET VERB
BIT
BITFIELD
NAME
DEFAULT
DESCRIPTION
793h
0
DE_OVWR_
EN
1
Enables data overwrite when a data error is
detected:
0 = Do not overwrite erroneous sample
1 = Overwrite erroneous sample with zeros
Note: When in Software Formatted S/PDIF Mode, all 32-bits of the stream sample are overwritten
Note that the vendor-specific S/PDIF Verb supported by the S/PDIF Rx node is described in the
“S/PDIF Receive using SRC1” section below.
PP, April 2011, Rev 3.2
62
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
