AK4683_07 Datasheet, PDF (57/84 Pages) Asahi Kasei Microsystems – Asynchronous Multi-Channel Audio CODEC with DIR/T

[AK4683]
■ Non-PCM (AC-3, MPEG, etc.) and DTS-CD Bitstream Detection
The AK4683 has a Non-PCM steam auto-detection function. When the 32bit mode Non-PCM preamble based on Dolby
“AC-3 Data Stream in IEC60958 Interface” is detected, the AUTO bit goes “1”. The 96bit sync code consists of 0x0000,
0x0000, 0x0000, 0x0000, 0xF872 and 0x4E1F. Detection of this pattern will set the AUTO bit “1”. Once the AUTO bit
is set “1”, it will remain “1” until 4096 frames pass through the chip without additional sync pattern being detected.
When those preambles are detected, the burst preambles Pc and Pd that follow those sync codes are stored to registers.
The AK4683 also has the DTS-CD bitstream auto-detection function. When The AK4683 detects DTS-CD bitstreams,
DTSCD bit goes to “1”. When the next sync code does not come within 4096 flames, DTSCD bit goes to “0” until
when the AK4683 detects the stream again.
■ Burst Preambles in non-PCM Bitstreams
sub-frame of IEC60958
0
34
78
preamble
Aux.
11 12
LSB
0
16 bits of bitstream
27 28 29 30 31
MSB V U C P
15
Pa Pb Pc Pd
Burst_payload
repetition time of the burst
stuffing
Figure 37. Data structure in IEC60958
Preamble word
Pa
Pb
Pc
Pd
Length of field
16 bits
16 bits
16 bits
16 bits
Contents
sync word 1
sync word 2
Burst info
Length code
Value
0xF872
0x4E1F
see Table 61
Numbers of bits
Table 60. Burst preamble words
MS0427-E-02
- 57 -
2007/04