IDT82P2821 Datasheet, PDF (54/151 Pages) Integrated Device Technology – 21(+1) Channel High-Density T1/E1/J1 Line Interface Unit

IDT82P2821
21(+1) CHANNEL HIGH-DENSITY T1/E1/J1 LINE INTERFACE UNIT
3.5.8 LOOPBACK
There are four kinds of loopback:
• Analog Loopback
• Remote Loopback
• Digital Loopback
• Dual Loopback
Refer to Figure-1 for loopback location.
3.5.8.1 Analog Loopback
Analog Loopback is enabled by the ALP bit (b0, LOOP,...). The data
stream to be transmitted on the TTIPn/TRINGn pins is internally looped
to the RTIPn/RRINGn pins.
In Analog Loopback mode, the data stream to be transmitted is still
output to the line side, while the data stream received from the line side
is covered by the Analog Loopback data.
Anytime when Analog Loopback is set, the other loopbacks (i.e.,
Digital Loopback and Remote Loopback) are disabled.
In Analog Loopback, the priority of the diagnostic facilities in the
receive path is: pattern generation > looped data. AIS generation is
disabled in both the receive path and the transmit path. Refer to Figure-
32.
LLOS detection
Analog
Loopback
AIS generation
X
X
AIS generation
BPV/CV, EXZ,
AIS, pattern
detection
Pattern generation
Pattern generation
BPV/CV, EXZ,
SLOS, AIS, pattern
detection
Rx path
Tx path
Figure-32 Priority Of Diagnostic Facilities During Analog Loopback
Functional Description
54
January 11, 2007