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Advance Data Sheet
T7633 Dual T1/E1 3.3 V Short-Haul Terminator
May 1998
34
Lucent Technologies Inc.
Line Interface Unit: Transmit
Output Pulse Generation
The line interface transmitter accepts a line rate clock and NRZ data in single-rail mode (DUAL = 0) or positive and
negative NRZ data in dual-rail mode (DUAL = 1) from the transmit framer unit or, optionally, the system interface.
The line interface transmitter converts this data to a balanced bipolar signal (AMI format) with optional B8ZS(DS1)/
HDB3(E1) encoding and optional jitter attenuation. Low-impedance output drivers produce the line transmit pulses.
Positive 1s are output as positive pulses on TTIP, and negative 1s are output as positive pulses on TRING. Binary
0s are converted to null pulses.
In DSX-1 applications, transmit pulse shaping is controlled by the on-chip pulse-width controller and pulse equal-
izer. The pulse-width controller produces high-speed timing signals to accurately control the transmit pulse widths.
This eliminates the need for a tightly controlled transmit clock duty cycle that is usually required in discrete imple-
mentations. The pulse equalizer controls the amplitudes and shapes of the pulses. Different pulse equalizations
are selected through settings of EQ2, EQ1, and EQ0 bits (register LIU_REG6, bits 0 to 2) as described in Table 6,
Transmit Line Interface Short-Haul Equalizer/Rate Control, below.
The reset default state of the equalization bits EQ2, EQ1, and EQ0 can be predetermined by setting the
DS1_CEPT pin. The default transmit equalization is EQ2, EQ1, and EQ0 = 000 (0 dB T1/DS1) when DS1_CEPT =
1; EQ2, EQ1, and EQ0 = 110 (CEPT 120
/75
) when DS1_CEPT = 0. This feature aids in transmitting AIS at the
correct rate upon completion of hardware reset; see LIU Transmitter Alarm Indication Signal Generator (XLAIS)
section on page 35.
1.In DS1 mode, the distance to the DSX for 22-Gauge PIC (ABAM) cable is specified. Use the maximum cable loss figures for other cable types.
In CEPT mode, equalization is specified for coaxial or twisted-pair cable.
2.Reset default state is EQ2, EQ1, and EQ0 = 000 when pin DS1_CEPT = 1 and EQ2, EQ1, and EQ0 = 110 when pin DS1_CEPT = 0.
3.Loss measured at 772 kHz.
4.In 75
applications, Option 1 is recommended over Option 2 for lower LIU power dissipation. Option 2 allows for the use of the same trans-
former as in CEPT 120
applications (see the Line Interface Unit: Line Interface Networks section on page 48).
Table 6. Transmit Line Interface Short-Haul Equalizer/Rate Control
Short-Haul Applications
EQ2
EQ1
EQ0
Service
Clock Rate
Transmitter Equalization
1,2
Maximum
Cable Loss
to DSX
3
Feet
Meters
dB
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
DSX-1
1.544 MHz
0 to 131
131 to 262
262 to 393
393 to 524
524 to 655
0 to 40
40 to 80
80 to 120
120 to 160
160 to 200
0.6
1.2
1.8
2.4
3.0
CEPT
4
2.048 MHz
75
(Option 2)
120
or 75
(Option 1)
Not Used
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