AMBE2000 ETC, AMBE2000 Datasheet - Page 26

• Manufacturer Part Number: AMBE2000
• Description: VOCODER CHIP
• Manufacturer: ETC

5.2.3 Formatted Input : Word 1 : Control Word 1
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. This bit should be set by the user 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 Formatted Input : Words 2-6 : Rate Info 0, Rate Info 1, Rate Info 2, Rate Info 3,
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 then be modified for both the encoder and the decoder through the Unformatted
channel interface. The Rate Selector control field (describe in section) determines where to apply the rate change.
The AMBE-2000 used these five words to set the source and FEC coding rates. Tables 5-C and 5-D list predefined value for
various source and FEC rates. The software configurations in Table 4-C are compatible for use with the AMBE-1000™. If
compatibility is not an issue, use the software codes in Table 4-D to select speech and FEC rates to optimize use of the AMBE-
2000™.
Rate Info 0
0x9030
0x9348
0x9243
0x934b
0x9348
0xab50
0xab60
0xab5b
0x923e
0xab53
0xab58
0xab5d
0xab16
0x902f
0xbf9b
0xbfc0
Indicator
7: MSB
Frame
Rate Info 4
Lost
Table 5-C Rate Selection Using Rate Info 0-4, compatible w/ AMBE-1000™
Rate Info 1
0x0000
0x0000
0x0000
0x0080
0x0000
0x0080
0x0000
0x0080
0x2030
0x2800
0x3000
0x0080
0x3400
0x0000
0x2c00
0xe400
Unused
6
Rate Info 2
Table 5-B Control Word 1 Format
Unused
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
Control Word 1 – 8-bits (See Table 1-F)
Confidential Proprietary, Subject to Change
5
User’s Manual Version 3.0
Unused
Rate Info 3
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0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
4
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Unused
Rate Info 4
3
0x4330
0x6930
0x5348
0x3950
0x3950
0x7960
0x6860
0x7060
0x7460
0x5680
0x4490
0x49a0
0x31a0
0x72c0
0x67c0
0x6f48
Unused
Speech Rate
2
(bps)
2400
2350
3600
3350
4000
3750
4800
4550
3600
3100
4150
4400
7750
4650
9600
4850
CNI
1
FEC Rate
(bps)
1200
1700
2250
2800
3350
4750
250
250
250
250
50
0
0
0
0
0
Unused
0 : LSB
Total Rate
(bps)
2400
3600
4000
4800
6400
7200
8000
9600