User`s manual

AMBE-2000™ Vocoder Chip
User’s Manual Version 4.9
DVSI Confidential Proprietary, Subject to Change Page 63
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8.7 Special Rate 2350 bps Voice / 50 bps FEC AMBE-1000™ Vocoder Chip
Compatible Mode
The following procedure is 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.