XRT73LC04A
4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. 1.0.1
b. Operating in the Hardware Mode.
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.
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-
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)
AGC/
Equalizer
Clock
Recovery
Slicer
Invert
RxClk_(n)
RRing_(n)
REQEN_(n)
Peak
Detector
Data
Recovery
RPOS_(n)
RNEG_(n)
LCV_(n)
HDB3/
B3ZS
Decoder
LOS Detector
LOSTHR_(n)
SDI
RLOS_(n)
LLB_(n)
RLB_(n)
SDO
Serial
Processor
Interface
Remote
Loop-Back Path
SClk
Loop MUX
CS/(SR/DR)
REGR
TAOS_(n)
TPData_(n)
TNData_(n)
TxClk_(n)
TTIP_(n)
HDB3/
B3ZS
Encoder
Transmit
Logic
Pulse
Shaping
Duty Cycle Adjust
TRing_(n)
TxLEV_(n)
TxOFF_(n)
DMO_(n)
MTIP_(n)
Device
Monitor
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
COMMAND REGISTER CR4-(n)
D4
X
D3
D2
D1
D0
a. Operating in the HOST Mode
STS-1/DS3_(n)
X
E3_(n) LLB_(n) RLB_(n)
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.
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".
49
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