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XRT73R06 Datasheet, PDF (25/68 Pages) Exar Corporation – SIX CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT | |||
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SIX CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT
FIGURE 12. HDB3 ENCODING FORMAT
XRT73R06
REV. 1.0.0
TClk
TPDATA 1 0 1 1 0 0 0 0 1 0 0 0 0 0 0 0 0
Line
Signal
10
1000V
000
B00V
1
1
V
3.4 TRANSMIT PULSE SHAPER
The Transmit Pulse Shaper converts the B3ZS encoded digital pulses into a single analog Alternate Mark
Inversion (AMI) pulse that meets the industry standard mask template requirements for STS-1 and DS3. For
E3 mode, the pulse shaper converts the HDB3 encoded pulses into a single full amplitude square shaped
pulse with very little slope. The Pulse Shaper Block also includes a Transmit Build Out Circuit, which can
either be disabled or enabled by setting the TxLEV_n bit to â1â or â0â in the control register. For DS3/STS-1
rates, the Transmit Build Out Circuit is used to shape the transmit waveform that ensures that transmit pulse
template requirements are met at the Cross-Connect system. The distance between the transmitter output and
the Cross-Connect system can be between 0 to 450 feet. For E3 rate, since the output pulse template is
measured at the secondary of the transformer and since there is no Cross-Connect system pulse template
requirements, the Transmit Build Out Circuit is always disabled. The differential line driver increases the
transmit waveform to appropriate level and drives into the 75⦠load as shown in Figure 13.
FIGURE 13. TRANSMIT PULSE SHAPE TEST CIRCUIT
TxPOS(n)
TxNEG(n)
TxLineClk(n)
TPData(n) TTIP(n)
TNData(n)
TxClk(n) TRing(n)
R1
31.6⦠+1%
R2
31.6⦠+ 1%
R3
75â¦
1:1
3.4.1 Guidelines for using Transmit Build Out Circuit
If the distance between the transmitter and the DSX3 or STSX-1, Cross-Connect system, is less than 225 feet,
enable the Transmit Build Out Circuit by setting the TxLEV_n control bit to â0â. If the distance between the
transmitter and the DSX3 or STSX-1 is greater than 225 feet, disable the Transmit Build Out Circuit.
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