Rainbow Electronics aP8942A - Manual (Page 5)

Integrated Circuits Inc. aP8942A
Ver 2.0 Dec 6, 2006 5
VOICE SECTION COMBINATIONS
Voice files created by the PC base developing system are stored in the built-in EPROM of the
aP8942A chip as a number of fixed length Voice Blocks. Voice Blocks are then selected and
grouped into Voice Groups for playback. Up to 32 Voice Groups are allowed. A Voice Block
Table is used to store the information of combinations of Voice Blocks and then group them
together to form Voice Group.
Chip aP8942A
Memory size 1M bits
Max no. of Voice Block 252
No. of bytes per Voice Block 512
Max. no. of Voice Group 32
No. of Voice Table entries 960
Voice Length (@ 6KHz 4-bit ADPCM) 42 sec
Example of Voice Block Combination
Assume here we have three voice files, they are “How are You?”, Sound Effect and Music. Each
of the voice file is divided into a number of fixed length Voice Block and stored into the memory.
Voice File 1 - “How are You?” is stored in Voice Block B0 to B12.
Voice File 2 - Sound Effect is stored in Voice Block B13 to B15.
Voice File 3 - Music is Voice Block B16 to B40.
Voice Blocks are grouped together using Voice Table to form Voice Group for playback:
Group no. Voice Group contents Voice Table Entries
Group 1
“How are You?”
B0 … B12
Group 2 Sound Effect + “How are You?” B13 … B15 + B0 … B12
Group 3
“How are You?” + Music
B0 … B12 + B16 … B40
Group 4 Music B16 … B40
Voice Data Compression
Voice File data is stored in the on-chip EPROM as either 4-bit ADPCM or 8-bit PCM format.
Voice data stored as 4-bit ADPCM provides 2:1 data compression which can save 50% of memory
space. On the other hand, voice data are stored as 8-bit PCM format means no data compression is
employed but voice playback quality will be better.