CMX649 CML Microcircuits, CMX649 Datasheet - Page 34

• Manufacturer Part Number: CMX649
• Description: ADM Codec
• Manufacturer: CML Microcircuits

ADM Codec
ENCODE VAD THRESHOLD Register ($E2)
Encode VAD
Threshold
(Bits 15 – 0)
ENCODE OFFSET LEVEL Register ($E3)
Encode Offset
Input
(Bits 15 - 0)
ENCODE DAC INPUT Register ($E7)
Encode DAC
Input
(Bits 15 – 0)
ENCODE ADM INPUT TEST Register ($E8)
Encoder ADM
Input Test
(Bits 7 – 0)
2003 CML Microsystems Plc
These bits directly program the threshold of detection for the Voice Activity Detector.
The number programmed into this register can range from $0 to $7FFF (0 to 32767).
The equation for the VAD threshold is:
These bits allow for an offset amount to be directly programmed. This offset amount
is useful in trimming out offsets that may occur in the on-chip analog circuitry. The
number format is 2’s complement and ranges from $8000 through $0000 to $7FFF
(-32768 to 32767).
The equation for the direct offset value is:
For normal Encoder operation this register should be loaded with a small positive
constant (eg in the range [2-16]) and bit 8 of the ENCODER MODE AND SETUP
Register ($E0) should be set to logic 1. The programmed offset will be summed with
the encoder input signal. If offset compensation is not required, bit 8 of the register
$E0 should be set to logic 0 and the ENCODE OFFSET LEVEL Register should also
be set to logic 0.
Offset compensation can be suspended by loading this register with 0 while leaving
Bit 8 of register $E0 true. This holds the current offset estimate constant. The offset
estimate can be read out via the ENCODE OFFSET LEVEL OUTPUT Register
($E5).
This register allows direct access to the encoder DAC input. The number format is
2’s complement and ranges from $8000 through $0000 to $7FFF (-32768 to 32767).
This register allows ADM bits to be written via C-BUS for transcoding from ADM to
PCM. An interrupt can be enabled to inform a micro-controller when the register
needs reloading.
Register
Register
Value
Value
34
(DAC
(DAC
(Signal
Full
Full
(Offset
Detection
Scale
Scale
Voltage)
Reference
Reference
Threshold)
2
18
Voltage)
Voltage)
2
15
CMX649
D/649/2