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Philips Semiconductors
CMOS digital decoding IC with RAM for
Compact Disc
EBU interface
The biphase-mark digital output signal at pin DOBM is in accordance with the format defined by the "IEC 958 "
specification.
Three different modes can be selected via the EBU output control register (address 1010).
Table 6 EBU output modes
EBU CONTROL
REGISTER DATA
X X 1 1
X X 0 0
X X 1 0
F
ORMAT
The digital audio output consists of 32-bit words (subframes) transmitted in biphase-mark code (two transitions for a
logic 1 and one transition for a logic 0). Words are transmitted in blocks of 384 (see Table 7).
Table 7 EBU word format
WORD
Sync
Auxiliary
Error flags
Audio sample
Validity flag
User data
Channel status
Parity bit
S
YNC
The sync word is formed by violation of the biphase rule
and therefore does not contain any data. Its length is
equivalent to 4 data bits. The three different sync patterns
indicate the following situations:
Sync B:
– Start of a block (384 words), word contains left
sample.
Sync M:
– Word contains left sample (no block start).
Sync W:
– Word contains right sample.
1998 Feb 16
EBU OUTPUT AT DOBM PIN
DOBM pin held LOW
data taken before concealment, mute and fade
data taken after concealment, mute and fade
BITS
0 to 3
4 to 7
4
8 to 27
28
29
30
31
not used; normally zero
CFLG error and interpolation flags when bit 3 of EBU control
register is set to logic 1
first 4 bits not used (always zero)
valid = logic 0
used for subcode data (Q-to-W)
control bits and category code
even parity for bits 4 to 30
A
UDIO SAMPLE
Left and right samples are transmitted alternately.
V
ALIDITY FLAG
Audio samples are flagged (bit 28 = logic 1) if an error has
been detected but was non-correctable. This flag remains
the same even if data is taken after concealment.
U
SER DATA
Subcode bits Q-to-W from the subcode section are
transmitted via the user data bit. This data is asynchronous
with the block rate.
19
Product specification
EBU VALIDITY FLAG (BIT 28)
HIGH if data is non-correctable
(concealment flag)
HIGH if data is non-correctable
(concealment flag)
FUNCTION
SAA7345
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