XRT75VL00D datasheet(29/92 Pages) EXAR

29 / 92 page

XRT75VL00D

REV. 1.0.3

E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

4.0

THE TRANSMITTER SECTION:

The Transmitter Section accepts TTL/CMOS level signals from the Terminal Equipment in the selectable data

formats.

• In Single-Rail or un-encoded Non-Return-to-Zero (NRZ) input data via TPData pin while the TNData pin

must be grounded. The NRZ or Single-Rail mode is selected when the SR/DR input pin is “High” (in

Hardware Mode) or bit 0 of the control register is “1” (in Host Mode). Figure 12 illustrates the Single-Rail or

NRZ format.

• In Dual-Rail mode, data is input via TPData and TNData pins. TPData contains positive data and TNData

contains negative data. The SR/DR input pin = “Low” (in Hardware Mode) or bit 0 of the control register = “0”

(in Host Mode) enables the Dual-Rail mode. Figure 13 illustrates the Dual-Rail data format.

• Convert the CMOS level B3ZS or HDB3 encoded data into pulses with shapes that are compliant with the

various industry standard pulse template requirements. Figure 7, Figure 8 and Figure 9 illustrate the pulse

template requirements.

• Encode the un-encoded NRZ data into either B3ZS format (for DS3 or STS-1) or HDB3 format (for E3) and

convert to pulses with shapes and width that are compliant with industry standard pulse template

requirements. Figure 7,Figure 8 and Figure 9 illustrate the pulse template requirements.

4.1

TRANSMIT CLOCK:

The Transmit Clock applied via TxClk pin, for the selected data rate (for E3 = 34.368 MHz, DS3 = 44.736 MHz

or STS-1 = 51.84 MHz), is duty cycle corrected by the internal PLL circuit to provide a 50% duty cycle clock to

the pulse shaping circuit. This allows a 30% to 70% duty cycle Transmit Clock be supplied and thus eliminates

the need to use an expensive oscillator.

4.2

B3ZS/HDB3 ENCODER:

When the Single-Rail (NRZ) data format is selected, the Encoder Block encodes the data into either B3ZS

format (for either DS3 or STS-1) or HDB3 format (for E3).

4.2.1

B3ZS Encoding:

FIGURE 12. SINGLE-RAIL OR NRZ DATA FORMAT (ENCODER AND DECODER ARE ENABLED)

FIGURE 13. DUAL-RAIL DATA FORMAT (ENCODER AND DECODER ARE DISABLED)

TxClk

TPData

Data

TxClk

TPData

TNData

Data

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