Rainbow Electronics AT89C51SND1C - Manual (Page 62)

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AT8xC51SND1C
4109E–8051–06/03
MP3 Decoder
The AT8xC51SND1C implement a MPEG I/II audio layer 3 decoder better known as
MP3 decoder.
In MPEG I (ISO 11172-3) three layers of compression have been standardized support-
ing three sampling frequencies: 48, 44.1, and 32 kHz. Among these layers, layer 3
allows highest compression rate of about 12:1 while still maintaining CD audio quality.
For example, 3 minutes of CD audio (16-bit PCM, 44.1 kHz) data, which needs about
32M bytes of storage, can be encoded into only 2.7M bytes of MPEG I audio layer 3
data.
In MPEG II (ISO 13818-3), three additional sampling frequencies: 24, 22.05, and 16 kHz
are supported for low bit rates applications.
The AT8xC51SND1C can decode in real-time the MPEG I audio layer 3 encoded data
into a PCM audio data, and also supports MPEG II audio layer 3 additional frequencies.
Additional features are supported by the AT8xC51SND1C MP3 decoder such as volume
control, bass, medium, and treble controls, bass boost effect and ancillary data
extraction.
Decoder
Description The C51 core interfaces to the MP3 decoder through nine special function registers:
MP3CON, the MP3 Control register (see Table 72); MP3STA, the MP3 Status register
(see Table 73); MP3DAT, the MP3 Data register (see Table 74); MP3ANC, the Ancillary
Data register (see Table 76); MP3VOL and MP3VOR, the MP3 Volume Left and Right
Control registers (see Table 77 and Table 78); MP3BAS, MP3MED, and MP3TRE, the
MP3 Bass, Medium, and Treble Control registers (see Table 79, Table 80, and
Table 81); and MPCLK, the MP3 Clock Divider register (see Table 82).
Figure 42 shows the MP3 decoder block diagram.
Figure 42. MP3 Decoder Block Diagram
MPEN
MP3CON.7
MP3
CLOCK
Audio Data
From C51
1K Bytes
8
MPxREQ
MP3STA1.n
Header Checker
Stereo Processor
Huffman Decoder
IMDCT
Side Information
ERRxxx
MP3STA.5:3
16
Sub-band
Synthesis Decoded Data
To Audio Interface
Anti-Aliasing
MPFS1:0
MP3STA.2:1
Dequantizer
MPVER
MP3STA.0
MPBBST
MP3CON.6
MP3VOL MP3VOR MP3BAS MP3MED MP3TRE
Ancillary Buffer
MP3ANC
Frame Buffer
MP3DAT