XRT73L03 Datasheet, PDF (51/62 Pages) Exar Corporation – 3 CHANNEL E3/DS3/STS-1 LINE INTERFCE UNIT

áç
PRELIMINARY
3 CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT XRT73L03
REV. P1.0.13
4.3 THE REMOTE LOOP-BACK MODE
When a given channel of the XRT73L03 is configured
to operate in the Remote Loop-Back Mode, the chan-
nel ignores any signals that are input to the TPData
and TNData input pins. The channel receives the in-
coming line signal via the RTIP and RRing input pins.
This data is processed through the entire Receive
Section of the channel and outputs to the Receive
Terminal Equipment via the RPOS, RNEG and RxClk
output pins. Additionally, this data is internally looped
back into the Pulse-Shaping block in 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 31 illustrates the path the data takes in the
XRT73L03 when the chip is configured to operate in
the Remote Loop-Back Mode.
FIGURE 31. THE REMOTE LOOP-BACK PATH IN A GIVEN XRT73L03 CHANNEL
RLOL(n) EXClk(n)
RTIP(n)
RRing(n)
REQEN(n
)
LOSTHR(n)
SDI
SDO
SClk
CS
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
Notes: 1. (n) = 1, 2 or 3 for respective Channels
2. Serial Processor Interface input pins are shared by the three Channels in HOST Mode and redefined in
Hardware Mode.
RxClk(n)
RPOS(n)
RNEG(n)
LCV(n)
ENDECDIS
RLOS(n)
LLB(n)
RLB(n)
TAOS(n)
TPData(n)
TNData(n)
TxClk(n)
MTIP(n)
MRing(n)
To configure a channel to operate in the Remote
Loop-Back Mode employ either one of the following
two steps
a. Operating in the HOST Mode
To configure Channel (n), write a "1" into the RLB bit-
field and a "0" into the LLB bit-field in Command Reg-
ister CR4.
COMMAND REGISTER CR4-(n)
D4
D3
D2
D1
D0
X STS-1/DS3_Ch(n) E3_Ch(n) LLB(n) RLB(n)
X
X
X
0
1
b. Operating in the Hardware Mode
To configure Channel(n), pull both the RLB input pin
(pin 35, 53 or 43) to “High" and the LLB input pin (pin
34, 54 or 42) to "Low".
4.4 TXOFF FEATURES
The Transmit Section of each Channel in the
XRT73L03 can be shut off. When this feature is in-
voked, the Transmit Section of the configured channel
is shut-off and the Transmit Output signals TTIP(n)
and TRing(n) are tri-stated. This feature is useful for
system redundancy conditions or during diagnostic
testing.
a. Operating in the Hardware Mode
48