RM0390 Rev 4 899/1328
RM0390 SPDIF receiver interface (SPDIFRX)
929
For linear coded audio applications, the first sub-frame (left or “A” channel in stereophonic
operation and primary channel in monophonic operation) normally starts with preamble “M”.
However, the preamble changes to preamble “B” once every 192 frames to identify the start
of the block structure used to organize the channel status and user information. The second
sub-frame (right or “B” channel in stereophonic operation and secondary channel in
monophonic operation) always starts with preamble “W”.
A S/PDIF block contains 192 pairs of sub-frames of 32 bits.
Figure 340. S/PDIF block format
Synchronization preambles
The preambles patterns are inverted or not according to the previous half-bit value. This
previous half-bit value is the level of the line before enabling a transfer for the first “B”
preamble of the first frame. For the others preambles, this previous half-bit value is the
second half-bit of the parity bit of the previous sub-frame. The preambles patterns B, M and
W are described in the Figure 341.
Figure 341. S/PDIF Preambles
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