XRT82D20 Datasheet, PDF (25/27 Pages) Exar Corporation – SINGLE CHANNEL E1 LINE INTERFACE UNIT

XRT82D20 SINGLE CHANNEL LINE INTERFACE UNIT
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REV. 1.0.7
2.2 THE REMOTE LOOP BACK MODE
When the XRT82D20 is configured to operate in the
Remote Loop-Back Mode, the XRT82D20 will ignore
any signals that are input to the TPOS and TNEG in-
put pins. The XRT82D20 will receive the incoming
line signals, via the RTIP and RRing input pins. This
data will be processed through the entire Receive
Section (within the XRT82D20) and will output to the
Receive Terminal Equipment via the RPOS and
RNEG output pins. Additionally, this data will also be
internally looped back to the Transmit Input Interface
block within the Transmit Section. At this point, this
data will be routed through the remainder of the
Transmit Section of the XRT82D20 and will be trans-
mitted out onto the line via the TTIP and TRing output
pins.
Figure 19, illustrates the path that the data takes
(within the XRT82D20) when the chip is configured to
operate in the Remote Loop-Back Mode.
FIGURE 19. ILLUSTRATION OF THE REMOTE LOOP-BACK PATH, WITHIN THE XRT82D20
TClk
TPOS
TNEG
RClk
RPOS
RNEG
HDB3
Encoder
MUX
Remote
Loopback
HDB3
Decoder
MUX
Tx Pulse
Shaper
Line
Driver
Jitter Attenuator
Data &
Timing
Recovery
LOS
Detect
Data
Slicer
Peak
Detector
Timing
Generator
TTIP
TRing
RLOS
RTIP
RRing
MClk
NOTE: During Remote Loop-Back operation, any data
which is input via the RTIP and RRING input pins, will also
be output to the Terminal Equipment, via the RPOS and
RNEG output pins.
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