uda1355h-n2 NXP Semiconductors, uda1355h-n2 Datasheet - Page 31

• Manufacturer Part Number: uda1355h-n2
• Description: Stereo Audio Codec With Spdif Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9
9.1
The digital signal is coded using Biphase Mark Code
(BMC), which is a kind of phase modulation. In this
scheme, a logic 1 in the data corresponds to two
zero-crossings in the coded signal, and a logic 0 to one
zero-crossing. An example of the encoding is given in
Fig.11.
2003 Apr 10
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Stereo audio codec with SPDIF interface
clock
BMC
SPDIF SIGNAL FORMAT
data
SPDIF channel encoding
0
M
sync
preamble
Fig.11 Biphase mark encoding.
channel 1
frame 191
3 4
W
S
B
L
channel 2
auxiliary
7 8
B
sub-frame
L
S
B
channel 1
frame 0
Fig.12 SPDIF signal format
Fig.13 Sub-frame format
MGU606
W
sub-frame
channel 2
audio sample word
31
M
9.2
The SPDIF signal format is shown in Fig.12. A PCM signal
is transmitted in sequential blocks. Each block consists
of 192 frames. Each frame contains two sub-frames, one
for each channel. Each subframe is preceded by a
preamble. There are three types of preambles: B, M
and W. Preambles can be spotted easily in an SPDIF
bitstream because these sequences never occur in the
channel parts of a valid SPDIF bitstream.
The sub-frame format is represented by Fig.13.
A sub-frame contains a single audio sample word which
may be 24 bits wide, a validity bit which indicates whether
the sample is valid, a bit containing user data, a bit
indicating the channel status and a parity bit for this
sub-frame.
The data bits 31 to 4 in each sub-frame are encoded using
a BMC scheme. The sync preamble contains a violation of
the BMC scheme and can be detected. Table 15 indicates
the values of the preambles.
channel 1
SPDIF hierarchical layers
block
channel 2
channel status
validity flag
user data
parity bit
M
channel 1
frame 191
27 28
M
S
B
Preliminary specification
V
W
UDA1355H
U
channel 2
MGU608
MGU607
C
31
P