ASAHI KASEI
[AK4122]
Non-PCM (AC-3, MPEG, etc.) and DTS-CD Bitstream Detection
The DIR of the AK4122 has a Non-PCM steam auto-detection function. When the 32-bit mode Non-PCM preamble
based on Dolby “AC-3 Data Stream in IEC60958 Interface” is detected, the NPCM bit goes to “1”. The 96-bit sync code
consists of 0x0000, 0x0000, 0x0000, 0x0000, 0xF872 and 0x4E1F. Detection of this pattern will set the NPCM to “1”.
Once the NPCM is set to “1”, it will remain “1” until 4096 frames pass through the chip without an additional sync pattern
being detected (Timing diagram: Figure 27 and Figure 28). When those preambles are detected, the burst preambles Pc
and Pd (Pc: burst information, Pd: length code; Refer to Table 22, 23) that follow those sync codes are stored to registers.
The AK4122 also has a DTS-CD bitstream auto-detection function. When AK4122 detects DTS-CD bitstream, the
DTSCD bit goes to “1”. If the next sync code does not occur within 4096 frames, the DTSCD bit goes to “0” until either
the AK4122 detects the stream again. OR’ed value of the NPCM and DTSCD bits are output to the AUTO bit. The
AK4122 detects 14bit sync word and 16bit sync word of a DTS-CD bitstream, the detection function can be set ON/OFF
by DTS14 and DTS16 bit.
Serial Control Interface
The internal registers may be either written or read by the 4-wire µP interface pins: CSN, CCLK, CDTI & CDTO. The
data on this interface consists of Chip address (2bits, C1/0 are fixed to “00”), Read/Write (1bit), Register address (MSB
first, 5bits) and Control data (MSB first, 8bits). Address and data is clocked in on the rising edge of CCLK and data is
clocked out on the falling edge. For write operations, data is latched after the 16th rising edge of CCLK, after a
high-to-low transition of CSN. For read operations, the CDTO output goes to high impedance after a low-to-high
transition of CSN. The maximum speed of CCLK is 5MHz. The chip address is fixed to “00”. The access to the chip
address except for “00” is invalid. PDN pin = “L” resets the registers to their default values. Read/Write can be access
without MCLK, BICK and , LRCK.
CSN
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
CCLK
CDTI
C1
C0 R/W A4
A3
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
Write
Read
Hi-Z
CDTO
CDTI
C1
C0 R/W A4
A3
A2
A1
A0
Hi-Z
Hi-Z
CDTO
D7
D6
D5
D4
D3
D2
D1
D0
C1 - C0 : Chip Address (Fixed to "00")
R/W : READ / WRITE ("1" : WRITE, "0" : READ)
A4 - A0 : Register Address
D7 - D0 : Control Data
Figure 25. Control I/F Timing
MS0267-E-02
2004/07
- 35 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
