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The user bits from the channel A and B subframes are simply strung
together. For more information, please refer to the AES3 standard.
CHANNEL
CHANNEL
X
Y
1
FRAME 191
Figure C-4. S/PDIF Block Structure
The data carried by the SPDIF interfaceis transmitted serially. In order to
identify the assorted bits of information the data stream is divided into
frames, each of which are 64 time slots (or 128 unit intervals
(Figure
C-4). Since the time slots correspond with the data bits, the frame
is often described as being 64 bits in length.
A frame is uniquely composed of two subframes. The first subframe nor-
mally starts with preamble X. However, the preamble changes to preamble
Z once every 192 frames. This defines the block of frames structure used
to organize the channel status information. The second subframe always
starts with preamble Y.
Subframe Format
Each frame consists of two subframes.
a subframe, which consists of 32 time slots numbered 0 to 31. A subframe
is 64 unit intervals in length. The first four time slots of each subframe
carry the preamble information. The preamble marks the subframe start
1
The unit interval is the minimum time interval between condition changes of a data transmission sig-
nal.
ADSP-2136x SHARC Processor Hardware Reference
www.BDTIC.com/ADI
for the ADSP-21362/3/4/5/6 Processors
CHANNEL
Z
Y
2
1
SUBFRAME
SUBFRAME
1
FRAME 0
START OF
BLOCK
Audio Frame Formats
CHANNEL
CHANNEL
X
Y
2
1
2
FRAME 1
Figure C-5
shows an illustration of
CHANNEL
2
1
) in length
C-11
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