xrt75r03 Exar Corporation, xrt75r03 Datasheet - Page 45

• Manufacturer Part Number: xrt75r03
• Description: Xrt75r03 -multi-channel Line Interface Unit Liu Family Desynchronizer And Jitter Attenuator With R3 Technologytm
• Manufacturer: Exar Corporation

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THREE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR
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The Transmit Pulse Shaper converts the B3ZS encoded digital pulses into a single analog Alternate Mark
Inversion (AMI) pulse that meet the industry standard mask template requirements for STS-1 and DS3. See
Figures 8 and 9.
For E3 mode, the pulse shaper converts the HDB3 encoded pulses into a single full amplitude square shaped
pulse with very little slope. This is illustrated in Figure 7.
The Pulse Shaper Block also includes a Transmit Build Out Circuit, which can either be disabled or enabled by
setting the TxLEV_n input pin “High” or “Low” (in Hardware Mode) or setting the TxLEV_n bit to “1” or “0” in the
control register (in Host Mode).
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.
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 input pin “Low” (in Hardware Mode) or setting the
TxLEV_n control bit to “0” (in Host Mode).
If the distance between the transmitter and the DSX3 or STSX-1 is greater than 225 feet, disable the Transmit
Build Out Circuit.
The differential line driver increases the transmit waveform to appropriate level and drives into the 75 load as
shown in Figure 6.
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5.3
5.3.1
5.3.2
OTES
1. When Dual-Rail data format is selected, the B3ZS/HDB3 Encoder is automatically disabled.
2. In Single-Rail format, the Bipolar Violations in the incoming data stream is converted to valid data pulses.
3. Encoder and Decoder is enabled only in Single-Rail mode.
:
T
RANSMIT
Guidelines for using Transmit Build Out Circuit:
Interfacing to the line:
P
ULSE
S
HAPER
:
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XRT75R03
REV. 1.0.8