XRT83SL314IB datasheet(43/83 Pages) EXAR

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XRT83SL314

14-CHANNEL T1/E1/J1 SHORT-HAUL LINE INTERFACE UNIT

REV. 1.0.1

4.6.1

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 13.

4.6.2

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 36.

FIGURE 36. ARBITRARY PULSE SEGMENT ASSIGNMENT

NOTE: By default, the arbitrary segments are programmed to 0x00h. The transmitter outputs will result in an all zero

pattern to the line interface.

4.7

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

TABLE 13: 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

Segment

0xn8

0xn9

0xna

0xnb

0xnc

0xnd

0xne

0xnf

XRT83SL314IB Datasheet(PDF) 43 Page - Exar Corporation

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