AMBE2000 Datasheet, PDF (38/47 Pages) List of Unclassifed Manufacturers – VOCODER CHIP

7 Special Functions
AMBE-2000™ Vocoder Chip
User’s Manual Version 3.0
7.1 Hardware vs. Software Selection Note
Many of the functions of the AMBE-2000™ can be accessed through both a hardware and software interfaces to the device.
The following hardware inputs, CHANN_SEL[1-0], RATE_SEL[4-0], CODEC_SEL[1-0], VAD_EN, ECHOCAN_EN, and
SLEEP_EN, are only accessed for input during the first 200 microseconds after a hardware reset on RESETN. For predictable
operation these signals must remain stable over this time period. After this initialization period the functions that these pins
access can only be reconfigured through the Control Word interface described in section 5.3.4. Changes on these pins after the
200 microseconds initialization period after reset are ignored, unless another reset is performed.
7.2 Coding Rate Selection
The Voice coding rate as well as the FEC coding rate can be selected individually on the AMBE-2000™. These rates are
selected by using a Control Word as described in section 5.3.4, or through hardware pins RATE_SEL[4-0] subject to the
restrictions in section 7.1. The five input pins RATE_SEL[4-0] give 16 preconfigured voice/FEC rates. The voice and FEC
rates are individually configurable in 50 bit per second intervals. If rates other than these are desired then the Control Word
method of configuring the rates must be used.
Table 7-A Rate Selection Using Rate Info 0-4, compatible w/ AMBE-1000™
RATE_SEL4
Pin
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
RATE_SEL3
Pin
0
0
0
1
1
1
0
0
0
1
1
1
1
1
0
0
RATE_SEL2
Pin
0
1
0
0
1
1
0
1
0
0
0
0
1
1
1
1
RATE_SEL1
Pin
0
0
0
1
1
1
1
1
1
0
1
0
0
0
0
1
RATE_SEL0
Pin
0
1
1
1
1
0
1
1
0
0
0
1
0
1
0
0
Speech Rate
(bps)
2400
2350
3600
3350
4000
3750
4800
4550
3600
3100
4150
4400
7750
4650
9600
4850
FEC Rate
(bps)
0
50
0
250
0
250
0
250
1200
1700
2250
2800
250
3350
0
4750
Total Rate
(bps)
2400
3600
4000
4800
6400
7200
8000
9600
page 38
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