Specifications

12
AT83SND2CMP3
7524D–MP3–07/07
MP3 Decoder The product implements 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 AT83SND2CMP3 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 AT83SND2CMP3 MP3 decoder such as vol-
ume control, bass, medium, and treble controls, bass boost effect and ancillary data
extraction.
Decoder
Description The core interfaces to the MP3 decoder through nine special function registers:
MP3CON, the MP3 Control register; MP3STA, the MP3 Status register; MP3DAT, the
MP3 Data register; MP3ANC, the Ancillary Data register; MP3VOL and MP3VOR, the
MP3 Volume Left and Right Control registers; MP3BAS, MP3MED, and MP3TRE, the
MP3 Bass, Medium, and Treble Control registers; and MPCLK, the MP3 Clock Divider
register.
Figure 9 shows the MP3 decoder block diagram.
Figure 9. 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