adav802 Analog Devices, Inc., adav802 Datasheet - Page 21

• Manufacturer Part Number: adav802
• Description: Audio Codec For Recordable Dvd
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
Serial Digital Audio Transmission Standards
The ADAV802 can receive and transmit SPDIF, AES/EBU and
IEC-958 serial streams. SPDIF is a consumer audio standard
and AES/EBU is a professional audio standard. IEC-958 has
both consumer and professional definitions. This data sheet is
not intended to fully define or to provide a tutorial for these
standards, please contact the international standards setting
bodies for the full specifications.
All of these digital audio serial communication schemes encode
audio data and audio control information using the biphase-
mark method. This encoding method minimizes the dc content
of the transmitted signal. As can be seen from Figure 23 ones in
the original data end up with midcell transitions in the biphase-
mark encoded data, while zeros in the original data do not. Note
that the biphase-mark encoded data always has a transition
between bit boundaries.
Digital audio communication schemes use “preambles” to
distinguish between channels (called “subframes”) and between
longer term control information blocks (called “frames”).
Preambles are particular biphase-mark patterns, which contains
encodeing violations that allow the receiver to uniquely
recognize them. These patterns, and their relationship to frames
and subframes, are shown in Figure 24 and Figure 25.
(2 TIMES BIT RATE)
Z
X
Y
BIPHASE-MARK
11100010 OR 00011101
11100100 OR 00011011
11101000 OR 00010111
BIPHASE PATTERNS
CLOCK
DATA
DATA
Figure 24. Biphase-Mark Encoded Preambles
82nF
Figure 22. DIR loop Filter Components
AVDD
Figure 23. Biphase-Mark Encoding
0
+
750Ω
2.2µF
1
LEFT
RIGHT
LEFT AND C.S. BLOCKSTART
DIR_LF
BLOCK
1
DIR
CHANNEL
1
0
0
Rev. Pr G | Page 21 of 53
The biphase-mark encoding violations are shown in Figure 26.
Note that all three preambles include encoding violations.
Ordinarily, the biphase-mark encoding method results in a
polarity transition between bit boundaries.
The serial digital audio communication scheme are organized
using a frame and subframe construction. There are two
subframes per frame (ordinarily the left and right channel).
Each subframe includes the appropriate four bit preamble, up to
24 bits of audio data, a “validity” (V) bit, a “user” (U) bit, a
“channel status” (C) bit and an even “parity” (P) bit. The channel
status bits and the user bits accumulate over many frames to
convey control information. The channel status bits accumulate
over a 192 frame period (called a channel status block). The
user bits accumulate over 1176 frames when the interconnect is
implementing the so-called “subcode” scheme (EIAJ CP-2401).
The organization of the channel status block, frames and
subframes are shown in Figure 27 and Figure 28.
N = 0x20 for Receiver Channel Status Buffer
N = 0x38 for Transmitter Channel Status Buffer
Address
X
(N+5) to
(N+23)
N+1
N+2
N+3
N+4
LEFT CH
N
FRAME 191
PREAMBLE Z
PREAMBLE X
PREAMBLE Y
Y
7
Reserved
Channel
RIGHT CH
Figure 25. Preambles, Frames and Subframes
Status
Channel Number
6
Reserved
Z LEFT CH
FRAME
Figure 26. Preambles
SUB-
Figure 27. Consumer
1
1
1
Accuracy
5
PREAMBLES
Clock
FRAME 0
Category Code
Emphasis
1
1
1
Y
1
4
1
1
Data Bits
RIGHT CH
Reserved
FRAME
SUB-
0
0
0
3
0
0
1
Sampling Frequency
X
Copy-
0
1
0
right
Source Number
LEFT CH
Word Length
2
1
0
0
FRAME 1
Audio
Non-
0
0
0
ADAV802
Y
1
RIGHT CH
Pro/Con
=0
0