CMX649E3 CML Microcircuits, CMX649E3 Datasheet - Page 32

• Manufacturer Part Number: CMX649E3
• Description: ADM Codec
• Manufacturer: CML Microcircuits

ADM Codec
Local Decoder
Output Select
(Bits 10 – 9)
Track Offset
(Bit 8)
Encoder VAD
Decay Time
Constant
(Bits 7 – 5)
Encoder VAD
Attack Time
Constant
(Bits 4 – 3)
Encoder VAD
Output Source
(Bits 2 – 1)
2002 CML Microsystems Plc
For the Encoder this bit should normally be set to a logic 1 to allow analog offsets to
be automatically compensated. When running the encoder as a digital ADM to PCM
transcoder this bit should be set to 0 since the local ADM decoder runs outside a
feedback loop.
When enabling offset tracking ensure the encoder ADM input selection is either
feedback from the comparator or for PCM to ADM transcoding. Also load the
ENCODE OFFSET LEVEL Register ($E3) with a small positive constant. And if
transcode feedback is selected then the PCM filter must also be set to interpolate.
These bits allow selection of the Voice Activity Detector decay time constant.
Allows selection of the Voice Activity Detector attack time constant.
Allows selection of the Voice Activity Detector output source.
Bit 10
Bit 7
Bit 4
Bit 2
0
0
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
Bit 9
Bit 6
Bit 3
Bit 1
0
1
0
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
ADM estimator output drives local decoder
output.
ADM estimator output summed with PCM
interpolation filter output drives local
decoder output.
For encoder, ADM output tracks sum of MIC
input analog signal plus a PCM signal input
over the C-BUS interface.
Direct PCM test mode.
Interpolated PCM output.
(VAD Decay Time Constant)/4
(VAD Decay Time Constant)/8
(VAD Decay Time Constant)/16
(VAD Decay Time Constant)/32
Nominal VAD operation.
ADM bits are driven over VAD pin at the ADM bit
rate (may be useful when transcoding or verifying
proper application of the burst interface).
VAD output driven to 0.
VAD output driven to 1.
Bit 5
0
1
0
1
0
1
0
1
Selected Local Decoder Output
Attack Time Constant (ms)
128/(Bit Rate)
256/(Bit Rate)
512/(Bit Rate)
1024/(Bit Rate)
2048/(Bit Rate)
4096/(Bit Rate)
8192/(Bit Rate)
16384/(Bit Rate)
Decay Time Constant (ms), Bit Rate in kbps
32
VAD Output
CMX649
D/649/1