Advance Data Sheet, Rev. 2
April 1999
TLIU04C1 Quad T1/E1 Line Interface
41
Lucent Technologies Inc.
Microprocessor Mode
(continued)
Loopbacks
The device has three independent loopback paths that are activated using LOOPA and LOOPB (registers 6—9, bits
3 and 4) as shown in Table 17. The locations of these loopbacks are illustrated in Figure 3 on page 19.
Table 17. Loopback Control
* During the transmit AIS condition, the looped data will be the transmitted data from the
system and not the all-ones signal.
Transmit AIS request is ignored.
Full Local Loopback (FLLOOP)
A full local loopback (FLLOOP) connects the transmit line driver input to the receiver analog front-end circuitry.
Valid transmit output data continues to be sent to the network. If the transmit AIS (all-ones signal) is sent to the net-
work, the looped data is not affected. The ALOS alarm continues to monitor the receive line interface signal while
DLOS monitors the looped data.
See Digital Loss of Signal (DLOS) Alarm section on page 21 regarding the behavior of the DLOS alarm upon acti-
vation of FLLOOP
Remote Loopback (RLOOP)
A remote loopback (RLOOP) connects the recovered clock and retimed data to the transmitter at the system inter-
face and sends the data back to the line. The receiver front end, clock/data recovery, encoder/decoder (if enabled)
jitter attenuator (if enabled), and transmit driver circuitry are all exercised during this loopback. The transmit clock,
transmit data, and XAIS inputs are ignored. Valid receive output data continues to be sent to the system interface.
This loopback mode is very useful for isolating failures between systems.
See Loss of Transmit Clock (LOTC) Alarm and Transmit Driver Monitor (TDM) Alarm on page 30 regarding the
behavior of the LOTC and TDM alarms upon activation and deactivation of RLOOP
Digital Local Loopback (DLLOOP)
A digital local loopback (DLLOOP) connects the transmit clock and data through the encoder/decoder pair to the
receive clock and data output pins at the system interface. This loopback is operational if the encoder/decoder pair
is enabled or disabled. The AIS signal can be transmitted without any effect on the looped signal.
Operation
Symbol
LOOPA
LOOPB
Normal
Full Local Loopback
Remote Loopback
Digital Local Loopback
—
0
0
1
1
0
1
0
1
FLLOOP*
RLOOP
DLLOOP