XRT86L30
REV. 1.0.1
IGURE 54. LONG
SINGLE T1/E1/J1 FRAMER/LIU COMBO
F
HAUL LINE BUILD OUT WITH -22.5DB ATTENUATION
8.3
T1 Short Haul Line Build Out (LBO)
The short haul transmitter output pulses are generated using a 7-Bit internal DAC (6-Bit plus the MSB sign bit).
The line build out can be set to interface to five different ranges of cable attenuation by programming the
appropriate channel register. The pulse shape is divided into eight discrete time segments which are set to
fixed values to comply with the pulse template. To program the eight segments individually to optimize a
special line build out, see the arbitrary pulse section of this datasheet. The short haul LBO settings are shown
in Table 171
T
ABLE 171: SHORT
H
AUL
L
INE
B
UILD
O
UT
TTENUATION
LBO SETTING EQC[4:0]
08h (01000)
R
ANGE OF
C
ABLE A
0 - 133 Feet
133 - 266 Feet
266 - 399 Feet
399 - 533 Feet
533 - 655 Feet
09h (01001)
0Ah (01010)
0Bh (01011)
0Ch (01100)
8.3.1
Arbitrary Pulse Generator
In T1 mode only, the arbitrary pulse generator divides the pulse into eight individual segments. Each segment
is set by a 7-Bit binary word by programming the appropriate channel register. This allows the system
designer to set the overshoot, amplitude, and undershoot for a unique line build out. The MSB (bit 7) is a sign-
bit. If the sign-bit is set to "0", the segment will move in a positive direction relative to a flat line (zero)
condition. If this sign-bit is set to "1", the segment will move in a negative direction relative to a flat line
condition. The resolution of the DAC is typically 60mV per LSB. Thus, writing 7-bit = 1111111 will clamp the
output at either voltage rail corresponding to a maximum amplitude. A pulse with numbered segments is
shown in Figure 55.
186
EXAR [ EXAR CORPORATION ]
