AMBE2000 Datasheet, PDF (35/47 Pages) List of Unclassifed Manufacturers – VOCODER CHIP

AMBE-2000™ Vocoder Chip
User’s Manual Version 3.0
6 A/D-D-A Interface
6.1 A/D-D/A Overview
The interface from the analog world of speech and the AMBE-2000™ is typically an A/D-D/A chip. Selection of the A/D-D/A
chip should be made carefully, with a preference given to 16 bit linear devices. Additionally, consideration should be given for
signal to noise ratios and filtering characteristics typically built into many such devices. Generally speaking, the flatter the
frequency response over the voice spectrum (20-4000Hz) the better the overall system will sound.
The AMBE-2000™ Vocoder Chip operates with a speech data sample rate of 8kHz for both the A/D and D/A interfaces. This
8kHz data is input and output using a serial port on the AMBE-2000.
In order to simplify the process of configuring the interface to the A/D-D/A chip, a number of preset configurations can be
chosen through the CODEC_SEL[1-0] pins shown in Table 6-A. These preset configurations control signal directions for the
interface as well as the sequence of programming words for the programmable devices, specifically the AD7331AR.
6.2 Configuring the A/D-D/A Interface using CODEC_SEL[1-0]
In order to simplify the process of configuring the A/D-D/A interface certain preset configurations are available to the user.
Selection of these preset modes is made through the 3 hardware pins CODEC_SEL[1-0]. In Table 6-A, the 2 digit binary value
for CODEC_SEL[1-0] corresponds to the levels present on the hardware pins, with a 0 corresponding to GND, and a 1
corresponding to VCC.
Table 6-A CODEC_SEL[1-0] : A/D-D/A Hardware Configuration Values
A/D-D/A Type
Generic 16 bit Linear
8Khz
Analog Devices 7331
32kHz
Generic µlaw 8kHz
Generic Alaw 8kHz
CODEC_SEL[1-0]
pins
85,84
00b
01b
10b
11b
page 35
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