MT9122 Zarlink Semiconductor, MT9122 Datasheet - Page 5

• Manufacturer Part Number: MT9122
• Description: Dual Voice Echo CANceller (ITU-T G165 Compliant) With Disable Tone Detection
• Manufacturer: Zarlink Semiconductor

Data Sheet
Functional Description
The MT9122 architecture contains two individually
controlled echo cancellers (Echo Canceller A and B).
They can be set in three distinct configurations:
Normal, Back-to-Back and Extended Delay (see
Figure 3). Under Normal configuration, the two echo
cancellers are positioned in parallel providing 64
millisecond echo cancellation in two channels
simultaneously. In Back-to-Back configuration, the
two echo cancellers are positioned to cancel echo
coming from both directions in a single channel. In
Extended-Delay
cancellers are internally cascaded into one 128
millisecond echo canceller.
Each echo canceller contains the following main
elements (see Figure 1).
•
•
•
•
•
Adaptive Filter for estimating the echo channel
Subtracter for cancelling the echo
Double-Talk detector for disabling the filter
adaptation during periods of double-talk
Non-Linear Processor for suppression of
residual echo
Disable Tone Detectors for detecting valid
disable tones at the input of receive and send
paths
echo
path B
Rout
echo
path A
Sin
PORT 2
a) Normal Configuration (64ms)
configuration,
channel B
channel A
channel B
channel A
E.C.A
E.C.B
Filter (64ms)
Filter (64ms)
Adaptive
Adaptive
-
-
+
+
the
Optional -12dB pad
Optional -12dB pad
Figure 3 - Device Configuration
two
echo
PORT 1
Sout
Rin
•
•
•
•
•
The
Controllerless and Controller. Controllerless mode is
intended for applications where customization is not
required. Controller mode allows access to all
registers for customizing the MT9122 operation.
Refer to Table 7 for a complete list. Controller mode
is selected when CONFIG1 and CONFIG2 pins are
both connected to Vss.
Each echo canceller in the MT9122 has four
functional states: Mute, Bypass, Disable Adaptation
and Enable Adaptation. These are explained in the
section entitled Echo Canceller Functional States.
Narrow-Band Detector for preventing Adaptive
Filter divergence caused by narrow-band
signals
Offset Null filters for removing the DC
component in PCM channels
12dB attenuator for signal attenuation
Serial controller interface compatible with
Motorola, National and Intel microcontrollers
PCM encoder/decoder compatible with µ/A-Law
ITU-T G.711, µ/A-Law Sign-Mag or linear 2’s
complement coding
PORT 2
Rout
MT9122
echo
path
Sin
echo
b) Extended Delay Configuration (128ms)
path A
PORT 2
c) Back-to-Back Configuration (64ms)
Rout
Sin
Filter (64ms)
Adaptive
E.C.A
has
-
channel A
channel A
+
E.C.A
Optional -12dB pad
two
Optional -12dB pad
Adaptive Filter
(128 ms)
modes
-
+
Filter (64ms)
Optional -12dB pad
Adaptive
E.C.B
+
of
MT9122
-
operation:
PORT 1
PORT 1
echo
path
Sout
Rin
Sout
Rin
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