Rainbow Electronics AT89C51SND1C - Manual (Page 65)

65
AT8xC51SND1C
4109E–8051–06/03
Frame Information The MP3 frame header contains information on the audio data contained in the frame.
These informations is made available in the MP3STA register for you information.
MPVER and MPFS1:0 bits allow decoding of the sampling frequency according to
Table 71. MPVER bit gives the MPEG version (2 or 1).
Table 71. MP3 Frame Frequency Sampling
Ancillary Data MP3 frames also contain data bits called ancillary data. These data are made available
in the MP3ANC register for each frame. As shown in Figure 45, the ancillary data are
available by Bytes when MPANC flag in MP3STA register is set. MPANC flag is set
when the ancillary buffer is not empty (at least one ancillary data is available) and is
cleared only when there is no more ancillary data in the buffer. This flag can generate an
interrupt as explained in Section "Interrupt", page 66. When set, software must read all
Bytes to empty the ancillary buffer.
Figure 45. Ancillary Data Block Diagram
MPVER MPFS1 MPFS0 Fs (kHz)
0 0 0 22.05 (MPEG II)
0 0 1 24 (MPEG II)
0 1 0 16 (MPEG II)
0 1 1 Reserved
1 0 0 44.1 (MPEG I)
1 0 1 48 (MPEG I)
1 1 0 32 (MPEG I)
1 1 1 Reserved
Ancillary
Data To C51
8
MP3ANC
8
MPANC
MP3STA.7
7-Byte
Ancillary Buffer