XRT75L00D Datasheet, PDF (29/92 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

REV. 1.0.2
XRT75L00D
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.
FIGURE 12. SINGLE-RAIL OR NRZ DATA FORMAT (ENCODER AND DECODER ARE ENABLED)
Data
TPData
TxClk
1
1
0
• 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.
FIGURE 13. DUAL-RAIL DATA FORMAT (ENCODER AND DECODER ARE DISABLED)
Data
TPData
TNData
TxClk
1
1
0
• 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:
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