[AK4117]
MS0157-E-04 2010/08
- 10 -
OPERATION OVERVIEW
■ Non-PCM (AC-3, MPEG, etc.) and DTS-CD Bitstream Detection
The AK4117 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 (burst
information:
Table 10) and Pd (length code: Table 11) that follow those sync codes are stored to registers. The AK4117
also has a DTS-CD bitstream auto-detection function. When AK4117 detects DTS-CD bitstreams, 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 AK4117 detects
the stream again. OR’ed value of the NPCM and DTSCD bits are output to the AUTO bit. The AK4117 detects 14bit
sync word of a DTS-CD bitstream, while it does not detect 16bit sync word (0x7FFE8001).
■ 192kHz Clock Recovery
The on-chip, low jitter PLL has a wide lock range of 32kHz to 192kHz and a lock time of less than 20ms. The AK4117
has a sampling frequency detect function (32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz and 192kHz) that uses
either clock comparison against the X’tal oscillator or the channel status information. The PLL loses lock when the
received sync interval is incorrect.
■ Clock Operation Mode
The AK4117 has two sources for MCKO and SDTO.
1) MCKO and SDTO source is recovered by PLL from RX input.
2) MCKO source is X’tal or External clock. SDTO source is DAUX input.
The CM1-0 bits select the clock operation mode (
Table 1). In Mode 2, the clock source is switched from PLL to X'tal
when the PLL loses lock. In Mode3, even though the clock source is fixed to X'tal, the PLL is also operating. This allows
the monitoring of recovered data such as C bits. For Mode2 and 3, it is recommended that the X’tal frequency and PLL
recovery frequency be set differently.
Mode CM1 CM0 UNLCK PLL X'tal Clock source SDTO
0 0 0 - ON ON(Note) PLL RX Default
1 0 1 - OFF ON X'tal DAUX
0 ON ON PLL RX
2 1 0
1 ON ON X'tal DAUX
3 1 1 - ON ON X'tal DAUX
ON: Oscillation (Power-up), OFF: STOP (Power-down)
Note : When the X’tal is not used as clock comparison for fs detection (i.e. XTL1,0= “1,1”), the X’tal is off.
Table 1. Clock Operation Mode select
