AMBE-2000™ Vocoder Chip Users Manual
Version 4.92, June, 08
DVSI Confidential Proprietary, Subject to Change
Page 47
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Word #
Value
Description
0
0x13ec
Header
1
0x07xx
Slip Control Packet ID, xx=CWD1 (See table 5-B) Typical value xx=00
2
0x12c9
Slip Control indicator for AMBE-2020™
3
0x009f
Slip Control data
4
0x0000
Must be 0x0000
5
0x0000
Must be 0x0000
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 7D: Slip Control Packet
Method 1 - Internal Slip Control
This is the simplest method of slip control and is the default method provided slip control is enabled (SLIP_EN is high) on
the chip. In this method the vocoder chip’s internal slip adjustment of 160 to 161 sample per frame is used. In order to
work properly, the system designer must set-up the sample rate and packet timing so that the following constraint is met:
160 < Average-Frame-Interval * (1 +/- Frame-Drift) * Sample-Rate * (1 +/- Sample-Drift) < 161
For example using an Average-Frame-Interval = 20 ms, and assuming 100 parts per million oscillator accuracy (i.e Frame-
Drift = Sample-Drift = .0001), then the above constraint requires:
8002 Hz < Sample-Rate < 8048 Hz.
In practice Sample-Rate=8002 Hz would be preferred since it is closer to the nominal value of 8000 Hz.
In another example the Sample-Rate = 8000 Hz. as provided by a PCM source. Again assuming 100 parts per million
oscillator accuracy for both clocks (i.e. Frame-Drift = Sample-Drift = .0001), then the above constraint requires:
20.0041 ms. < Average-Frame–Interval < 20.1209 ms.
This can be achieved by slightly decreasing the channel bit rate or adding an extra bit into the channel bit stream every
several voice frames.
