XRT75L00D Datasheet, PDF (32/92 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

XRT75L00D
E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER
FIGURE 16. TRANSMIT DRIVER MONITOR SET-UP.
TxPO S
TxN E G
T x L in e C lk
TxPO S
TxN EG
T x L in e C lk
T T IP
T P D a ta
T N D a ta
T x C lk
R ext
R e fA G N D
T R in g
M T IP
M R in g
X R T 75L00D
T P D a ta
T N D a ta
T x C lk
M T IP
M R in g
T T IP
3 7 .4 Ω + 1 %
3 7 .4 Ω + 1 %
R4 270Ω
R5 270Ω
3 7 .4 Ω + 1 %
R ext
R e fA G N D
T R in g
3 7 .4 Ω + 1 %
REV. 1.0.2
R3
75Ω
1 :1
1 :1
R3
75Ω
When the MTIP and MRing are connected to the TTIP and TRing lines, the drive monitor circuit monitors the
line for transitions. The DMO (Drive Monitor Output) will be asserted “Low” as long as the transitions on the line
are detected via MTIP and MRing.
If no transitions on the line are detected for 128 ± 32 TxClk periods, the DMO output toggles “High” and when
the transitions are detected again, DMO toggles “Low”.
NOTE: The Drive Monitor Circuit is only for diagnostic purposes and does not have to be used to operate the transmitter.
4.5 Transmitter Section On/Off:
The transmitter section can be turned on or off. To turn on the transmitter in the Hardware mode, pull TxON pin
“High”. In the Host mode, write a “1” to the TxON control bit AND pull the TxON pin “High” to turn on the
transmitter.
When the transmitter is turned off, the TTIP and TRing are tri-stated.
NOTES:
1. This feature provides support for Redundancy.
2. If the XRT75L00D is configured in Host mode, to permit a system designed for redundancy to quickly shut-off the
defective line card and turn on the back-up line card, writing a “1” to the TxON control bit transfers the control to
TxON pin.
5.0 THE RECEIVER SECTION:
This section describes the detailed operation of the various blocks in the receiver. The receiver recovers the
TTL/CMOS level data from the incoming bipolar B3ZS or HDB3 encoded input pulses.
5.1 AGC/Equalizer:
The Adaptive Gain Control circuit amplifies the incoming analog signal and compensates for the various flat
losses and also for the loss at one-half symbol rate. The AGC has a dynamic range of 30 dB.
The Equalizer restores the integrity of the signal and compensates for the frequency dependent attenuation of
up to 900 feet of coaxial cable (1300 feet for E3). The Equalizer also boosts the high frequency content of the
signal to reduce the Inter-Symbol Interference (ISI) so that, the slicer slices the signal at 50% of peak voltage
to generate Positive and Negative data.
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