AMBE-2000™ Vocoder Chip

User’s Manual Version 3.0

page 30

Confidential Proprietary, Subject to Change

5.3.1 Formatted Output : Word 0 : Header

The header is a 16 bit word that begins each valid frame corresponding to 20 milliseconds of speech. This field will always be

0x13EC.

5.3.2 Formatted Output : Word 1 : ID (Power Control)

The encoder will always use 0x00 in the 8-bit field of an output frame.

5.3.3 Formatted Output : Word 1 :Control Word 1

This 8-bit control word indicates the activity of various functions.

Table 5-J Control Word 1 Format

Control Word 1 – 8-bits (See Table 1-A)

7: MSB

6

5

4

3

2

1

0 : LSB

Unused

Unused

Decoder

Frame

Repeat

Decoder

Silence

Detect

Unused

Unused

Encoder

Silence

Detect

Encoder

DTMF

Detect

Decoder Frame Repeat: When the Decoder Frame Repeat flag is set to 1, the decoder is reporting that the last frame decoded

was a repeat of the previous frame.

Decoder Silence Detect: When the Decoder Silence Detect flag is set to 1, the decoder is reporting that the last frame decoded

was a comfort noise frame.

Encoder DTMF Detect: The Encoder DTMF Detected Flag will be set to a 1 when the encoder detects a DTMF tone. The

DTMF Detect option is controlled by the DTMF Detect/Generate bits in control Word 10 described in section 5.2.8 enable the

DTMF Detect option.

Silence Detect: The Encoder Silence Detected Flag will be set to 1 when no voice activity is detected. The Silence Detect

option is controlled by and can be disabled by the VAD as described in section 5.2.9.

5.3.4 Formatted Output : Words 2-6 : Rate Info 0, Rate Info 1, Rate Info 2, Rate Info 3,

Rate Info 4.

Words 2-6 in the packet indicate the rate at which the AMBE-2000™ encoder is operating . These words are output. See

tables 5-C and 5-D for corresponding values.

5.3.5 Formatted Output: Word 7 : Bit Error Rate

This status field is used for the decoder to report bit error information. The 16 bit number output is used to compute the BER

using the following calculation

% BER = (Word 7) / (32768)

5.3.6 Formatted Output : Word 10 : DTMF Control

This word corresponds to the DTMF Detection capabilities of the vocoder. It uniquely identifies specific tones recognized by

the encoder. See table 5-J for a list of tones and their corresponding values.