ADAV802_15 datasheet(21/53 Pages) AD

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Preliminary Technical Data

ADAV802

Rev. Pr G | Page 21 of 53

DIR

BLOCK

DIR_LF

2.2µF

750

Ω

82nF

AVDD

Figure 22. DIR loop Filter Components

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.

CLOCK

(2 TIMES BIT RATE)

DATA

BIPHASE-MARK

DATA

Figure 23. Biphase-Mark Encoding

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.

BIPHASE PATTERNS

11100010 OR 00011101

11100100 OR 00011011

11101000 OR 00010111

LEFT

RIGHT

LEFT AND C.S. BLOCKSTART

CHANNEL

Figure 24. Biphase-Mark Encoded Preambles

LEFT CH

XRIGHT CH

YZ LEFT CH

RIGHT CH

YLEFT CH

XRIGHT CH

SUB-

FRAME

SUB-

FRAME

FRAME 0

FRAME 1

FRAME 191

PREAMBLES

Figure 25. Preambles, Frames and Subframes

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.

PREAMBLE X

1100

010

PREAMBLE Y

PREAMBLE Z

Figure 26. Preambles

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.

Channel

Status

Emphasis

Copy-

right

Non-

Audio

Pro/Con

Address

Category Code

Channel Number

Source Number

Reserved

Clock

Accuracy

Sampling Frequency

Word Length

Reserved

N+1

N+2

N+3

N+4

(N+5) to

(N+23)

Data Bits

N = 0x20 for Receiver Channel Status Buffer

N = 0x38 for Transmitter Channel Status Buffer

Figure 27. Consumer

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