XRT83L314 Datasheet, PDF (36/84 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
3.6.2 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 12
TABLE 12: SHORT HAUL LINE BUILD OUT
LBO SETTING EQC[4:0]
RANGE OF CABLE ATTENUATION
08h (01000)
0 - 133 Feet
09h (01001)
133 - 266 Feet
0Ah (01010)
266 - 399 Feet
0Bh (01011)
399 - 533 Feet
0Ch (01100)
533 - 655 Feet
3.6.3 Arbitrary Pulse Generator For T1 and E1
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 29.
FIGURE 29. ARBITRARY PULSE SEGMENT ASSIGNMENT
Segment
1
2
3
4
5
6
7
8
Register
0xn8
0xn9
0xna
0xnb
0xnc
0xnd
0xne
0xnf
1
2
3
4
8
7
6
5
NOTE: By default, the arbitrary segments are programmed to 0x00h. The transmitter outputs will result in an all zero
pattern to the line interface.
3.7 DMO (Digital Monitor Output)
The driver monitor circuit is used to detect transmit driver failures by monitoring the activities at TTIP/TRING
outputs. Driver failure may be caused by a short circuit in the primary transformer or system problems at the
transmit inputs. If the transmitter of a channel has no output for more than 128 clock cycles, DMO goes "High"
until a valid transmit pulse is detected. If the DMO interrupt is enabled, the change in status of DMO will cause
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