6
61291004L2-5, Issue 2
61291004L2-5B
TRDDB Bidirectional Loopback Support
The TRDDB will execute a bidirectional loopback
when performing a DS0 loopback at the TRDDB
(
Figure 7
). If the TROCU-R detects a bidirectional
loopback during power up synchronization, the
TROCU-R allows data to pass on the 4-wire interface
by entering pass-thru mode (Figure 7). This allows a
standard portable DDS test set, connected to the 4-
wire customer interface of the TROCU-R, to verify
the integrity of the 2-wire loop by transmitting a test
pattern and examining the returning data for
synchronization and errors. The TRDDB LBK
indicator will illuminate during a TRDDB
bidirectional loopback in pass-thru mode. The
latching and alternating loopback sequences are
defined in
Table 5
and
Table 6.
Table 6. Alternating Loopback Activation
Sequence
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DSU/
CSU
TR
OCU-R
TRDDB
MOS
Bidirectional
loopback
Figure 8. TRDDB Bidirectional Loopback
Normal Mode
If a DS0 loopback is invoked after the TROCU-R
achieves synchronization, some TROCU-R units will
not pass or receive data from the CPE or DDS test set.
These OCU-Rs will send a MUX-Out-Of-Sync code
downstream on the 4-wire customer loop. This is
consistent with current DDS testing methods and is
referred to as the bidirectional loopback normal mode
(
Figure 8
). For testing purposes, the installer may
choose to initiate the TROCU-R pass-thru mode. Once
the bidirectional loopback is executed in normal
mode, unseat and reseat the TROCU-R and allow the
unit to train. Once trained, the unit will revert to
pass-thru mode for further testing.
Figure 7. TRDDB Bidirectional Loopback
Pass-Thru Mode
Test
Unit
TR
OCU-R
TRDDB
Data
Pass-Thru
Bidirectional
loopback
Содержание Total Reach TRDDB
Страница 10: ...10 61291004L2 5 Issue 2 61291004L2 5B ...
