IDT82P2916 Datasheet, PDF (50/138 Pages) Integrated Device Technology – 16-Channel High-Density T1/E1/J1 Line Interface Unit

IDT82P2916
16-CHANNEL HIGH-DENSITY T1/E1/J1 LINE INTERFACE UNIT
3.5.8.4 Dual Loopback
Dual Loopback refers to the simultaneous implementation of Remote
Loopback and Digital Loopback. Two kinds of combinations are
supported:
• Manual Remote Loopback + Manual Digital Loopback;
• Manual Remote Loopback + Automatic Digital Loopback.
Note that when Digital Loopback is active, automatic Remote Loop-
back is unavailable as the pattern detection is within the digital loop.
In Dual Loopback mode, the data stream received from the line side
outputs from the RJA (if enabled), loops to the Waveform Shaper inter-
nally and does not output to the system side. The data stream to be
transmitted from the system side outputs from the TJA (if enabled),
loops to the Decoder (if enabled) internally and does not output to the
line side. LLOS, AIS detection in the receive path monitors the data
stream received from the line side. The BPV/CV, EXZ and pattern detec-
tion in the receive path monitors the digital looped data. The BPV/CV,
EXZ, SLOS, AIS and pattern detection in the transmit path monitors the
data stream input from the system side.
Manual Remote Loopback + Manual Digital Loopback
This combination of Dual Loopback is enabled when both manual
Remote Loopback and manual Digital Loopback are enabled. Manual
Remote Loopback is enabled by the RLP bit (b1, LOOP,...). Manual
Digital Loopback is enabled by the DLP bit (b2, LOOP,...).
In this condition, the priority of the diagnostic facilities in the receive
path is: pattern generation > digital looped data; the priority of the diag-
nostic facilities in the transmit path is: remote looped data > pattern
generation. AIS generation is disabled in both the receive path and the
transmit path.
Refer to Figure-31.
Manual Remote Loopback + Automatic Digital Loopback
This combination of Dual Loopback is enabled when both manual
Remote Loopback and automatic Digital Loopback are enabled. Manual
Remote Loopback is enabled by the RLP bit (b1, LOOP,...). Automatic
Digital Loopback is enabled when the pattern detection is assigned in
the transmit path (i.e., the PD_POS bit (b3, PD,...) is ‘1’) and the
AUTOLP bit (b3, LOOP,...) is ‘1’. The corresponding channel will enter
Digital Loopback when the activate IB code is detected in the transmit
path for more than 5.1 sec.; and will return from Digital Loopback when
the deactivate IB code is detected in the transmit path for more than 5.1
sec. Refer to section Inband Loopback (IB) Detection on page 43 for
details. When automatic Digital Loopback is active, setting the AUTOLP
bit (b3, LOOP,...) back to ‘0’ will also stop automatic Digital Loopback.
The setting of the PD_POS bit (b3, PD,...) should not be changed during
automatic Digital Loopback. The AUTOLP_S bit (b7, STAT0,...) indicates
the automatic Digital Loopback status.
In this condition, the priority of the diagnostic facilities in the receive
path is: pattern generation > digital looped data. AIS generation in both
the receive path and the transmit path, the pattern generation in the
transmit path are disabled.
Refer to Figure-32.
Functional Description
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April 24, 2010