AMBE-2000 Digital Voice Systems, Inc., AMBE-2000 Datasheet - Page 37

• Manufacturer Part Number: AMBE-2000
• Description: 2.0 - 9.6 KBPS Single ic For Toll-quality, Low Data Rate, Real Time Speech Compression
• Manufacturer: Digital Voice Systems, Inc.

6
6.1
The interface from the analog world of speech to 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 companding and sampling rates
as well as the sequence of programming words for the programmable devices, specifically the AD73311.
6.2
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 2 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 V
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A/D-D-A Interface
A/D-D/A Overview
Configuring the A/D-D/A Interface using CODEC_SEL [1-0]
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Table 6-A CODEC_SEL [1-0]: A/D-D/A Hardware Configuration Values
CC
.
A/D-D/A Type
Generic 16 bit Linear 8Khz
Analog Devices 73311
32kHz
Generic µlaw 8kHz
Generic Alaw 8kHz
AMBE-2000™ Vocoder Chip
User’s Manual Version 4.0
CODEC_SEL[1-0]
85,84
pins
00b
01b
10b
11b
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