ISD3900
Publication Release Date: Dec 10, 2013
- 39 -
Revision 1.5
12.3
D
EVICE
C
ONFIGURATION
R
EGISTERS
The configuration of the ISD3900 is achieved by forty-eight configuration registers, CFG0-CFG2F as
detailed below.
Please note that registers 0x19~0x1F have no default value, and user should configure these registers
in both POI VM and PU VM to customized value or suggested initial value to avoid undesired
consequences. See register 0x19 ~ 0x1F configuration for details.
2
Table 12-8 CFG0 Register
CFG0 Configuration Register
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
SR[2:0]
CMP[4:0]
011
00100
Default 0x64:
4-bit ADPCM
Ratio to Fs = 4
ISD provides a powerful software tool, Voice Prompt Editor, to help the user build their project and
ease the configuration of the ISD3900.
Configuration register CFG0 controls the sample rate and compression algorithm during message
record operations. It can also override sample rate setting for playback by setting bit 0 of CFG1 high.
SR[2:0]=CFG0[7:5] controls the sample rate and CMP[4:0]=CFG0[4:0] controls the compression. An
explanation of these follows below.
Table 12-9 CFG0 Register Compression Type.
Compression
Type
Bit rate
(bits/sample)
CMP[4:0]
(Dec)
(Hex)
ADPCM
2
2
0x02
ADPCM
3
3
0x03
ADPCM
4
4
0x04
ADPCM
5
5
0x05
µ-Law
6
16
0x10
µ-Law
7
17
0x11
µ-Law
8
18
0x12
Dµ-Law
6
20
0x14
2
Note: Register 0x1C and 0x1E are excluded because register 0x1C is read-
only and register 0x1E doesn’t exist.