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234 Littleton Road Tel: (978) 392-0002 email: info@dvsinc.com
The Speech Compression Specialists
Westford, MA 01886 Fax: (978) 392-8866 web: www.dvsinc.com
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
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.
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)
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.
Page 1 of 2 June 2004
First Packet
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AMBE-2000/2020™ Vocoder Interoperability at 2350 bps
June 2004
Compatible Mode Procedure Step 2.
The next packet should be identical to the packet described in Table 3.
Special Control Packet
Word # Value Description
0 0x13ec Header
1 0x0700 Special Control packet
2 0x0834 Special control data
3 0x0005 Special control data
4 0x11bf Special control data
5 0x0005 Special control data
6 0x0000 Must be 0x0000
7 0x0000 Must be 0x0000
8 0x0000 Must be 0x0000
9 0x0000 Must be 0x0000
10 0x0000 Must be 0x0000
11 0x0000 Must be 0x0000
12-23 Channel Data for AMBE® voice decoder
Table 3.
Compatible Mode Procedure Step 3.
After the packets detailed in Table 2 and Table 3 are sent into the AMBE-2000/2020™
Vocoder Chip the RIS bits in Control Word 2 must be set to 0x3 for each subsequent packet.
If the rate is changed or the device is reset, the above procedure (steps 1, 2 and 3) must be
repeated.
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Decoder Output Volume Control
Table 4.
Page 2 of 2 June 2004
Control Word 2 – (16-bits)
Unused
Unused
0
0
VAD
Unused
0
SL EC RIS