Datasheet

DS26518 8-Port T1/E1/J1 Transceiver
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9.12.6 LIU Loopbacks
The DS26518 provides four LIU loopbacks for diagnostic purposes: Analog Loopback, Local Loopback, Remote
Loopback 1, and Remote Loopback 2. Dual Loopback is a combination of Local Loopback and Remote Loopback
1. In the loopback diagrams that follow, TSERn, TCLKn, RSERn, and RCLKn are inputs/outputs from the framer.
Figure 9-28. Loopback Diagram
Jitter
Attenuator
(in RX path)
RSER
Jitter
Attenuator
(in TX path)
Local Loopback
Jitter
Attenuator
can be
assigned to
receive path
or transmit
path or
disabled
RTIP
RRING
TTIP
TRING
JACLK
Master Clock
PLL
MCLK
RCLK
Analog Loopback
Remote 2 Loopback
Remote 1 Loopback
TSER
TCLK
RX LIU
TX LIU TX FORMATTER
RX FRAMER
9.12.6.1 Analog Loopback
The analog output of the transmitter TTIPn and TRINGn is looped back to RTIPn and RRINGn of the receiver. Data
at RTIPn and RRINGn is ignored in analog loopback. This is shown in the
Figure 9-29.
Figure 9-29. Analog Loopback
Line
Driver
Transmit
Framer
Optional
Jitter
A
ttenuato
r
Transmit
Digital
Transmit
A
nalog
TCLK
Receive
Framer
Optional
Jitter
A
ttenuato
r
Receive
Digital
Receive
Analog
RCLK
RTIP
RRING
TSER
RSER
TTIP
TRING