FEDL2250DIGEST-09

OKI Semiconductor

ML2250 family

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Voice Synthesis Algorithm

The ML2250 family contains 5 algorithm types to match the characteristic of playback voice: 2-bit ADPCM2

algorithm, 4-bit ADPCM 2 algorithm, 8-bit PCM algorithm, 8-bit non-linear PCM algorithm, and 16-bit PCM

algorithm.

Key feature of each algorithm is described in the table below.

Voice synthesis algorithm

Applied waveform

Feature

Oki 2-bit ADPCM2

Normal voice waveform

Oki

’s specific speech synthesis algorithm of low

bit rate with improved 2-bit ADPCM.

Oki 4-bit ADPCM2

Normal voice waveform

Oki

’s specific speech synthesis algorithm of

improved waveform follow-up with improved

4-bit ADPCM.

Oki 8-bit Nonlinear PCM

High-frequency

components

inclusive sound effect etc.

Algorithm which plays back mid-range of

waveform as 10-bit equivalent voice quality.

8-bit PCM

High-frequency

components

inclusive sound effect etc.

Normal 8-bit PCM algorithm

16-bit PCM

High-frequency

components

inclusive sound effect etc.

Normal 16-bit PCM algorithm

Memory Allocation and Creating Voice Data

The ROM is partitioned into4 data areas: voice (i.e., phrase) control area, test area, voice area, and phrase control

table area.

The voice control area manages the ROM’s voice data. It controls the start/end addresses of voice data, usage/not

usage of the phrase control table function and so on. The voice control area stores voice control data for 256

phrases.

The test area stores the data for testing.

The voice area stores the actual waveform data.

The phrase control table area stores data for effective use of voice data. As for the details, please refer to the Phrase

Control Table Function.

There is no phrase control table area if the phrase control table is not used.

The ROM data is created using a development tool.

Voice control area

(16 Kbit Fixed)

Test area

Voice area

Phrase Control Table area

Depends on creation of ROM

data.

0x00000

0x007FF

0x00800

max: 0x1FFFF

max: 0x1FFFF

ROM Addresses (ML2252)

0x00807

0x00808