XRT73LC04A_08 Datasheet, PDF (53/64 Pages) Exar Corporation – 4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT

XRT73LC04A
REV. 1.0.2
4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
b. Operating in the Hardware Mode.
To configure Channel (n) to operate in the Digital Lo-
cal Loop-Back Mode, pull both the LLB input pin and
the RLB input pin "High".
4.3 THE REMOTE LOOP-BACK MODE
When a given channel is configured to operate in the
Remote Loop-Back Mode, the channel ignores any
signals that are input to the TPData and TNData input
pins. The channel receives the incoming line signal
via the RTIP and RRing input pins. This data is pro-
cessed through the entire Receive Section and is out-
put to the Receive Terminal Equipment via the RPOS,
RNEG and RxClk output pins. Additionally, this data
is also internally looped back into the Pulse-Shaping
block within the Transmit Section. At this point, this
data is routed through the remainder of the Transmit
Section of the channel and transmitted out onto the
line via the TTIP_(n) and TRing_(n) output pins.
Figure 35 illustrates the path that the data takes when
the chip is configured to operate in the Remote Loop-
Back Mode.
FIGURE 35. THE REMOTE LOOP-BACK PATH, WITHIN A GIVEN CHANNEL
RLOL_(n) EXClk_(n)
RTIP_(n)
RRing_(n)
REQEN_(n)
LOSTHR_(n)
SDI
SDO
SClk
CS/(SR/DR)
REGR
TTIP_(n)
TRing_(n)
TxLEV_(n)
TxOFF_(n)
DMO_(n)
AGC/
Equalizer
Slicer
Clock
Recovery
Peak
Detector
LOS Detector
Data
Recovery
Serial
Processor
Interface
Remote
Loop-Back Path
Loop MUX
Invert
HDB3/
B3ZS
Decoder
Pulse
Shaping
HDB3/
B3ZS
Encoder
Device
Monitor
Transmit
Logic
Duty Cycle Adjust
RxClk_(n)
RPOS_(n)
RNEG_(n)
LCV_(n)
RLOS_(n)
LLB_(n)
RLB_(n)
TAOS_(n)
TPData_(n)
TNData_(n)
TxClk_(n)
MTIP_(n)
MRing_(n)
Notes: 1. (n) = 0, 1, 2, or 3 for respective Channels
2. Serial Processor Interface input pins are shared by the four Channels in HOST Mode and redefined in
Hardware Mode.
Configure a channel to operate in the Remote Loop-
Back Mode by employing either one of the following
two steps
a. Operating in the HOST Mode
To configure Channel (n) to operate in the Remote
Loop-Back Mode, write a "1" into the RLB bit-field,
and a "0" into the LLB bit-field, within Command Reg-
ister CR4.
COMMAND REGISTER CR4-(n)
D4
D3
D2
D1
D0
X STS-1/DS3_(n) E3_(n) LLB_(n) RLB_(n)
X
X
X
0
1
b. Operating in the Hardware Mode
To configure Channel(n) to operate in the Remote
Loop-Back Mode, pull both the RLB_(n) input pin to
“High" and the LLB_(n) input pin to "Low".
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