zl50211 Zarlink Semiconductor, zl50211 Datasheet - Page 15

• Manufacturer Part Number: zl50211
• Description: 256 Channel Voice Echo Canceller
• Manufacturer: Zarlink Semiconductor

2.2
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 64ms echo cancellation. See Figure 7. This
configuration uses only one timeslot on PORT1 and PORT2 and the second timeslot normally associated with ECB
contains zero code. 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 a “1” into the BBM bit of Control Register 1 for both Echo
Canceller A and Echo Canceller B for a given group of echo canceller. Table 4 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.
Back-to-Back Configuration
Figure 7 - Back-to-Back Device Configuration (64 ms)
PORT2
echo
path B
Rout
echo
path A
Sin
Figure 6 - Normal Device Configuration (64 ms)
PORT2
Rout
echo
path
Sin
ECA
Filter (64ms)
channel B
channel A
channel B
channel A
Adaptive
ECA
ECB
-
Zarlink Semiconductor Inc.
+
ZL50211
Filter (64ms)
Filter (64ms)
Adaptive
Adaptive
-
-
15
+
+
Filter (64ms)
Adaptive
ECB
+
-
echo
path
PORT1
Sout
Rin
PORT1
Sout
Rin
Data Sheet