MT93L04 Zarlink Semiconductor, MT93L04 Datasheet - Page 27

• Manufacturer Part Number: MT93L04
• Description: 128-channel Voice Echo Canceller
• Manufacturer: Zarlink Semiconductor

MT93L04
Data Sheet
Back-to-Back Configuration
In Back-to-Back configuration, the two echo cancellers from the same group are positioned to cancel echo coming
from both directions in a single channel providing full-duplex 64 ms echo cancellation. See Figure 6c. 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 cancellers that can be configured
into Back-to-Back.
Examples of Back-to-Back configuration include positioning one group of echo cancellers between a CODEC and a
transmission device or between two codecs for echo control on analog trunks.
Extended Delay configuration
In this configuration, the two echo cancellers from the same group are internally cascaded into one 128
milliseconds echo canceller. See Figure 6b. This configuration uses only one timeslot on PORT1 and PORT2 and
the second timeslot normally associated with ECB contains undefined data.
Extended Delay configuration is selected by writing “1” into the ExtDl bit in Echo Canceller A, Control Register A1.
For a given group, only Echo Canceller A, Control Register A1, has the ExtDl bit. Control Register B1, bit-0 must
always be set to zero.
Table 2 shows the 16 groups of 2 cancellers that can each be configured into 64 ms or 128 ms echo tail capacity.
Echo Canceller Functional States
Each echo canceller has four functional states: Mute, Bypass, Disable Adaptation and Enable Adaptation.
Mute
In Normal and in Extended Delay configurations, writing a “1” into the MuteR bit replaces Rin with quiet code which
is applied to both the Adaptive Filter and Rout. Writing a “1” into the MuteS bit replaces the Sout PCM data with
quiet code.
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