XRT75L02 View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT75L02' PDF : 50 Pages View PDF
xr
REV. 1.0.3
XRT75L02
TWO CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER
4.0 THE TRANSMITTER SECTION:
The Transmitter Section, within each Channel, accepts TTL/CMOS level signals from the Terminal Equipment
in selectable data formats.
• Convert the CMOS level B3ZS or HDB3 encoded data into pulses with shapes that are compliant with the
various industry standard pulse template requirements. Figures 7, 8 and 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. Figures 7, 8 and 9 illustrate the pulse template requirements.
• In Single-Rail or un-encoded Non-Return-to-Zero (NRZ) mode, data is input via TPOS_n pins while TNEG_n
pins 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 channel 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
0
TPData
TxClk
1
1
0
• In Dual-Rail mode, data is input via TPOS_n and TNEG_n pins. TPOS_n contains positive data and
TNEG_n contains negative data. The SR/DR input pin = “Low” (in Hardware Mode) or bit 0 of channel
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
0
TPData
TNData
TxClk
1
1
0
4.1 TRANSMIT CLOCK:
The Transmit Clock applied via TxClk_n pins, 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 to be supplied.
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:
An example of B3ZS encoding is shown in Figure 14. If the encoder detects an occurrence of three
consecutive zeros in the data stream, it is replaced with either B0V or 00V, where ‘B’ refers to Bipolar pulse
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