AMBE-2000 Digital Voice Systems, Inc., AMBE-2000 Datasheet - Page 27

• 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.

5.2.1
The decoder uses the header information to synchronize with the beginning of each 20 millisecond frame. This 16-bit word
MUST be 0x13EC.
5.2.2
Set the 8-bit Power Control ID field to 0x00 for normal use. For Power Down Mode, set this value to 0x55. This causes the
AMBE-2000™ to enter low power mode. To exit low power mode, the device must be reset through the hardware.
5.2.3
Use the 8-bit control word to set various functions.
Lost Frame Indicator: Setting the Lost Frame Indicator bit to a 1 will cause the AMBE-2000™ decoder to construct the
voice frame using the parameters from the previous frame. This is an effective way to mask the effects of short periods of data
loss. The user should set this bit when channel data is lost or corrupted. It works by replacing the frame of corrupted data with
the previous, intact, frame.
Comfort Noise Insertion (CNI): Setting the CNI bit will cause the decoder to output a frame of comfort noise. This bit is
used with systems that are capable of discontinuous transmission (DTX).
5.2.4
Rate Info 0, Rate Info 1, Rate Info 2, Rate Info 3, Rate Info 4
The initial rate of the AMBE-2000™ is set through the hardware pins RATE_SEL [4-0] (see Section 7.2 and Tables 7-A and 7-
B). After resetting the device, the coding rate can be modified for both the encoder and the decoder by sending a framed packet
to the input channel interface. The Rate Selector control field (described in section 5.2.9) determines where to apply the rate
change.
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0x00
0x55
Lost Frame
ID
Indicator
Framed Input: Word 0 : Header
Framed Input: Word 1 : Power Control ID
Framed Input: Word 1 : Control Word 1
Framed Input: Words 2-6 : Rate Information
7: MSB
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Unused
Low Power Mode
6
Voice Data
Type
Table 5-A Framed Input: Power Control ID Values Summary
Table 5-B Control Word 1 Format
Unused
5
Control Word 1 – 8-bits (See Table 1-F)
AMBE-2000™ Vocoder Chip
User’s Manual Version 4.0
Unused
This ID value instructs AMBE-2000™ to operate in normal fashion
When this mode is activated the AMBE-2000™ Vocoder Chip will go into a mode,
which conserves power, where no voice packets are being processed.
4
Unused
3
Unused
2
Description
CNI
1
Unused
0 : LSB
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