XRT75R03D_06 Datasheet, PDF (48/135 Pages) Exar Corporation – EXAR DATA SHEET FORMAT TEMPLATES

XRT75R03D
THREE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCRONIZER REV. 1.0.4
5.4 Transmit Drive Monitor:
This feature is used for monitoring the transmit line for occurrence of fault conditions such as a short circuit on
the line or a defective line driver.
To activate this function, connect MTIP_n pins to the TTIP_n lines via a 270 Ω resistor and MRing_n pins to
TRing_n lines via 270 Ω resistor as shown in Figure 16.
FIGURE 17. TRANSMIT DRIVER MONITOR SET-UP.
TTIP(n)
R1
31.6Ω +1%
TxPOS(n)
TxNEG(n)
TxLineClk(n)
TPData(n)
TNData(n)
TxClk(n) _TRing(n)
MTIP(n)
R4 270Ω
MRing(n)
R5 270Ω
XRT75R03D (0nly one channel shown)
31.6Ω + 1%
R2
R3
75Ω
1:1
When the MTIP_n and MRing_n are connected to the TTIP_n and TRing_n lines, the drive monitor circuit
monitors the line for transitions. The DMO_n (Drive Monitor Output) will be asserted “Low” as long as the
transitions on the line are detected via MTIP_n and MRing_n.
If no transitions on the line are detected for 128 ± 32 TxClk_n periods, the DMO_n output toggles “High” and
when the transitions are detected again, DMO_n toggles “Low”.
NOTE: The Drive Monitor Circuit is only for diagnostic purpose and does not have to be used to operate the transmitter.
5.5 Transmitter Section On/Off:
The transmitter section of each channel can either be turned on or off. To turn on the transmitter, set the input
pin TxON_n to “High” (in Hardware Mode) or write a “1” to the TxON_n control bits (in Host Mode) and TxON_n
pins tied “High”.
When the transmitter is turned off, TTIP_n and TRing_n are tri-stated.
NOTES:
1. This feature provides support for Redundancy.
2. If the XRT75R03D 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_n control bits transfers the control
to TxON_n pins.
6.0 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.
6.1 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.
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