SAA7824 Datasheet, PDF (23/89 Pages) NXP Semiconductors – CD audio decoder, digital servo and filterless DAC with integrated pre-amp and laser control (PhonIC)

Philips Semiconductors
CD audio decoder, digital servo and filterless
DAC with integrated pre-amp and laser control
Product specification
SAA7824
7.11 EBU interface
The bi-phase mark digital output signal at pin DOBM is in
accordance with the format defined by the IEC 60958
specification. Three different modes can be selected via
decoder register A:
• DOBM pin held LOW
• Data taken before concealment, mute and fade (must
always be used for CD-ROM modes)
• Data taken after concealment, mute and fade.
An additional mute function is available via shadow
register 7 (bank 1) and decoder register 0 and C. They
provide the following:
• Hard mute: immediate mute of the audio sample in the
ROM mode at 1×, 2× or 4×
• Soft mute: 3 ms ramp up or ramp down of the audio
samples in the 1× audio mode
• Bypass: switches the EBU mute function out of the EBU
signal path.
7.11.1 FORMAT
The digital audio output consists of 32-bit words
(‘subframes’) transmitted in bi-phase mark code (two
transitions for a logic 1 and one transition for a logic 0).
Words are transmitted in blocks of 384. The EBU frame
format is given in Table 8.
Table 8 EBU frame format; see also Table 9
FUNCTION
Sync
Auxiliary
Error flags
Audio sample
Validity flag
User data
Channel status
BITS
0 to 3
4 to 7
4
8 to 27
28
29
30
DESCRIPTION
−
not used; normally zero
CFLG error and interpolation flags when selected by register A
first 4 bits not used (always zero); twos complement; LSB = bit 12, MSB = bit 27
valid = logic 0
used for subcode data (Q-to-W)
control bits and category code
Table 9 Description of EBU frame function
FUNCTION
Sync
Audio sample
Validity flag
User data
Channel status
DESCRIPTION
The sync word is formed by violation of the bi-phase rule and therefore does not contain any data.
Its length is equivalent to 4 data bits. The 3 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) and sync W; word contains right sample.
Left and right samples are transmitted alternately.
Audio samples are flagged (bit 28 = 1) if an error has been detected but was uncorrectable. This
flag remains the same even if data is taken after concealment.
Subcode bits Q-to-W from the subcode section are transmitted via the user data bit. This data is
asynchronous with the block rate.
The channel status bit is the same for left and right words. Therefore a block of 384 words contains
192 channel status bits. The category code is always CD. The bit assignment is given in Table 10.
2003 Oct 01
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