MT9123AE Zarlink Semiconductor, MT9123AE Datasheet - Page 5

• Manufacturer Part Number: MT9123AE
• Description: Description = Dual Voice Echo CANceller ( Itu-t G165 Compliant) ;; Package Type = Pdip ;; No. Of Pins = 28
• Manufacturer: Zarlink Semiconductor

Data Sheet
Functional Description
The MT9123 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
Narrow-Band Detector for preventing Adaptive
Filter divergence caused by narrow-band
signals
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 MT9123 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 MT9123 has four
functional states: Mute, Bypass, Disable Adaptation
and Enable Adaptation. These are explained in the
section entitled Echo Canceller Functional States.
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
MT9123
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
MT9123
-
operation:
PORT 1
PORT 1
echo
path
Sout
Rin
Sout
Rin
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