MT9300 Mitel Networks Corporation, MT9300 Datasheet - Page 7

• Manufacturer Part Number: MT9300
• Description: Multi-channel Voice Echo CANceller
• Manufacturer: Mitel Networks Corporation

Advance Information
in the Status Registers. Following the detection of a
disable tone (TD bit high) on a given channel, the
external controller must switch the echo canceller
from Enable Adaptation to Bypass state.
Narrow Band Signal Detector (NBSD)
Single or dual frequency tones (i.e. DTMF tones)
present in the receive input (Rin) of the echo
canceller for a prolonged period of time may cause
the Adaptive Filter to diverge. The Narrow Band
Signal Detector (NBSD) is designed to prevent this
divergence by detecting single or dual tones of
arbitrary frequency, phase, and amplitude. When
narrow band signals are detected, the adaptation
process is halted but the echo canceller continues to
cancel echo.
The NBSD can be disabled by setting the NBDis bit
to “1” in Control Register 2.
Offset Null Filter
Adaptive filters in general do not operate properly
when a DC offset is present at any inputs. To remove
the DC component, the MT9300 incorporates Offset
Null filters in both Rin and Sin inputs.
The offset null filters can be disabled by setting the
HPFDis bit to “1” in Control Register 2.
PORT2
echo
path B
echo
path A
Rout
Sin
a) Normal Configuration (64ms)
channel B
channel A
channel B
channel A
E.C.A
E.C.B
Filter (64ms)
Filter (64ms)
Adaptive
Adaptive
-
-
+
+
Optional -12dB pad
Optional -12dB pad
Figure 5 - Device configuration
PORT1
Sout
Rin
Device Configuration
The
cancellers divided into 16 groups. Each group has
two echo cancellers which can be individually
controlled (Echo Canceller A and B). They can be set
in three distinct configurations: Normal, Back-to-
Back, and Extended Delay. See Figure 5.
Normal Configuration
In Normal configuration, the two echo cancellers
(Echo Canceller A and B) are positioned in parallel,
as shown in Figure 5a, providing 64 milliseconds of
echo cancellation in two channels simultaneously.
Back-to-Back Configuration
In
cancellers from the same group are positioned to
cancel echo coming from both directions in a single
channel
cancellation. See Figure 5c. This configuration uses
only one timeslot on PORT1 and PORT2 and the
second timeslot normally associated with ECB
contains undefined data. Back-to-Back configuration
allows a no-glue interface for applications where
bidirectional echo cancellation is required.
Back-to-Back configuration is selected by writing “1”
into the BBM bit of both Control Register A1 and
Control Register B1 of a given group of echo
cancellers. Table 2 shows the 16 groups of 2
PORT2
Rout
echo
path
Sin
Back-to-Back
echo
path A
b) Extended Delay Configuration (128ms)
MT9300
PORT2
c) Back-to-Back Configuration (64ms)
Rout
Sin
Filter (64ms)
providing
Adaptive
E.C.A
-
channel A
channel A
+
E.C.A
architecture
Optional -12dB pad
configuration,
Optional -12dB pad
Adaptive Filter
full-duplex
(128 ms)
-
+
Filter (64ms)
Optional -12dB pad
Adaptive
contains
E.C.B
+
the
-
MT9300
64ms
two
32
PORT1
echo
path
PORT1
Sout
Rin
Sout
Rin
echo
echo
echo
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