Digital Voice Systems AMBE-3000 Specifications download pdf (Page 47)

AMBE-3000F™ Vocoder Chip Users Manual

Version 3.4, April, 2014

O Management

3 C

NI_FRAME

Comfort Noise Insertion Enable. If CNI_FRAME=1,

then the Decoder ignores any channel data provided to

it and inserts comfort noise using the latest silence

frame that was received by the decoder. (or the default

silence frame if no silence frames have been received

yet).

0 at reset.

4-6 Reserved.4-Reserved.6

7 CP_SELECT

Compand Select.

If companding is enabled and CP_SELECT=0, then u-

law companding is selected. If companding is

enabled, and CP_SELECT=1 then a-law companding

is selected. If companding is not enabled, then this bit

has no effect.

After reset, this

bit is initialized

using the setting

from the

CP_SELECT pin.

8 CP_ENABLE

Compand Enable

If CP_ENABLE=1, then companding is enabled

(either a-law or u-law, depending on the setting of

CP_SELECT). If CP_ENABLE=0, then companding

is disabled and all speech samples are 16-bit linear.

After reset, this

bit is initialized

using the setting

from the

CP_ENABLE pin.

9-13 Reserved.9-Reserved.13

14 TS_ENABLE

Tone Synthesis Enable. If TS_ENABLE=1, then the

Decoder ignores any channel data provided to it and

synthesizes the specified tone.

0 at reset.

15 Reserved.15

Table 15 DCMODE_IN Flags

The I/O handler also passes a frame of channel data, if available, to the decoder once every 20 ms. The decoder produces

160±4 speech samples for every 20 ms frame. In addition to outputting speech samples for each 20 ms frame, the decoder

outputs a 16-bit status word named DCMODE_OUT. The DCMODE_OUT flags are as specified in Table 16

DCM

ODE_OUT Flags. If the I/O handler does not have a frame of channel data to pass to the decoder at the scheduled time,

then t

he I/O Handler forces the decoder to perform a frame repeat by setting the appropriate bit in DCMODE_IN for that frame

only.

Bit

Number

Bit Name Bit description

0 Reserved.0 Reserved

1 VOICE_ACTIVE

The decoder sets VOICE_ACTIVE=1 if the decoder synthesized a voice

frame or a tone frame. If the decoder synthesized a comfort noise frame,

then it sets VOICE_ACTIVE=0. The decoder can synthesize comfort

noise in the following circumstances:

(a) a comfort noise frame (silence frame) was received by the decoder.

(b) The decoder FEC (if enabled) found too many errors.

2-4 Reserved.2-Reserved.4

5 DATA_INVALID

The decoder sets this bit whenever it performs a frame repeat. It also sets

this bit if it inserted comfort noise due to channel errors or missing frames.

The decoder will set DATA_INVALID=0 if it received a valid (voice,

silence, or tone frame).

6-14 Reserved.6-Reserved.14

15 TONE_FRAME The decoder sets this bit whenever it decodes a tone frame.

Table 16 DCMODE_OUT Flags

(Subject to Change) Page 37

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