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June 2004
The Speech Compression Specialists
Implementing the AMBE-2000/2020™ Vocoder Chip
at Data Rate 2350 bps Voice and 50 bps FEC
for Compatibility with the AMBE-1000™ Vocoder Chip
This white paper describes the procedure for implementing the AMBE-2000/2020™ in a
special mode that is compatible to AMBE-1000™ Vocoder Chip at 2350 bps voice and 50
bps FEC.
This procedure is
ONLY
required when interoperating with the AMBE-1000™ Vocoder Chip
at this specific rate (2350 voice + 50 bps FEC). All other rate configurations function as
described in the AMBE-2000/2020™ Vocoder Chip Manual.
When implementing this compatible mode on the AMBE-2000/2020™ Vocoder Chip if the
data rate is fixed and does not change, it is recommended to set the rate via the Rate_Sel
configuration pins (Pins 74, 73 72, 71, 70) as shown in Table 1. By hardwiring these pins the
procedure outlined below can be avoided.
AMBE-2000/2020™ Rate Selection Using Hardwired Rate Info 0-4, compatible w/ AMBE-1000™
RATE_SEL4
Pin 74
RATE_SEL3
Pin 73
RATE_SEL2
Pin 72
RATE_SEL1
Pin 71
RATE_SEL0
Pin 70
Speech Rate
(bps)
FEC Rate (bps)
Total Rate
(bps)
0
0
1
0
1
2350
50
2400
Table 1.
Compatible Mode Procedure Step 1.
To enable the AMBE-2000/2020™ to interoperate with the AMBE-1000™ Vocoder Chip at
the rate of 2350 bps voice + 50 bps FEC, first send the packet described in Table 2.
First Packet
Word #
Value
Description
0 0x13ec Header
1
0x0002
Power Control ID/Control Word 1
2 0x902f Rate
0
3 0x0000 Rate
1
4 0x0000 Rate
2
5 0x0000 Rate
3
6
0x6930
Rate 4
7 0x0000 Unused
8 0x0000 Unused
9 0x0000 Unused
10 0x0000 DTMF
Control
11
0x0000
Control Word 2
12-23
Channel Data for AMBE® voice decoder
Table 2.
