XRT83L314 Datasheet, PDF (34/84 Pages) Exar Corporation – 14-CHANNEL T1/E1/J1 LONG-HAUL/SHORT-HAUL LINE INTERFACE UNIT

XRT83L314
14-CHANNEL T1/E1/J1 LONG-HAUL/SHORT-HAUL LINE INTERFACE UNIT
REV. 1.0.0
3.5.4 QRSS Generation
The XRT83L314 can transmit a QRSS random sequence to a remote location from TTIP/TRING. The
polynomial is shown in Table 11.
TABLE 11: RANDOM BIT SEQUENCE POLYNOMIALS
RANDOM PATTERN
T1
E1
QRSS
2²⁰ - 1
2¹⁵ - 1
3.6 Transmit Pulse Shaper and Filter
If TCLK is not present, pulled "Low", or pulled "High" the transmitter outputs at TTIP/TRING will automatically
send an all ones or an all zero signal to the line by programming the appropriate global register. By default, the
transmitters will send all zeros. To send all ones, the TCLKCNL bit must be set "High".
3.6.1 T1 Long Haul Line Build Out (LBO)
The long haul transmitter output pulses are generated using a 7-Bit internal DAC (6-Bits plus the MSB sign bit).
The line build out can be set to -7.5dB, -15dB, or -22dB cable attenuation by programming the appropriate
channel register. The long haul LBO consist of 32 discrete time segments extending over four consecutive
periods of TCLK. As the LBO attenuation is increased, the pulse amplitude is reduced so that the waveform
complies with ANSI T1.403 specifications. A long haul pulse with -7.5dB attenuation is shown in Figure 26, a
pulse with -15dB attenuation is shown in Figure 27, and a pulse with -22.5dB attenuation is shown in
Figure 28.
FIGURE 26. LONG HAUL LINE BUILD OUT WITH -7.5DB ATTENUATION
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