XRT86VL38
PRELIMINARY
xr
OCTAL T1/E1/J1 FRAMER/LIU COMBO
REV. P1.0.6
321
5.1.3
Digital Loopback
With digital loopback activated, the transmit input data at TCLK/TPOS/TNEG is looped back to the receive
output data at RCLK/RPOS/RNEG. The digital loopback mode includes the Transmit JA (if enabled). The
receive input data at RTIP/RRING is ignored while valid transmit output data continues to be sent to the line. A
simplified block diagram of digital loopback is shown in Figure 34.
5.1.4
Dual Loopback
With dual loopback activated, the remote loopback is combined with the digital loopback. A simplified block
diagram of dual loopback is shown in Figure 35.
5.1.5
Framer Remote Line Loopback
The Framer Remote Line Loopback is almost identical to the LIU physical interface Remote Loopback. The
digital data enters the framer interface, however does not enter the framing blocks. The main difference
between the Remote loopback and the Framer Remote Line loopback is that the receive digital data from the
LIU is allowed to pass through the LIU Decoder/Encoder circuitry before returning to the line interface. A
simplified block diagram of framer remote line loopback is shown in Figure 36.
F
IGURE
34. S
IMPLIFIED
B
LOCK
D
IAGRAM
OF
D
IGITAL
L
OOPBACK
F
IGURE
35. S
IMPLIFIED
B
LOCK
D
IAGRAM
OF
D
UAL
L
OOPBACK
Encoder
Decoder
Timing
Control
Data and
Clock
Recovery
JA
JA
Tx
Rx
TAOS
NLC/PRBS/QRSS
TTIP
TRING
RTIP
RRING
TCLK
TPOS
TNEG
RCLK
RPOS
RNEG
Encoder
Decoder
Timing
Control
Data and
Clock
Recovery
JA
JA
Tx
Rx
TAOS
NLC/PRBS/QRSS
TTIP
TRING
RTIP
RRING
TCLK
TPOS
TNEG
RCLK
RPOS
RNEG