XRT7250 datasheet(130/463 Pages) EXAR

130 / 463 page

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

111

Transmit Line Build-Out circuitry, and will transmit un-

shaped (square-wave) pulses onto the line. If the us-

er commands this signal to toggle "Low", then the

XRT7300 DS3/E3 LIU IC will enable the Transmit

Line Build-Out circuitry, and will transmit shaped puls-

es onto the line.

In order to insure that the transmit output pulses of

the XRT7300 device meet the DSX-3 Isolated Pulse

Template Requirements (per Bellcore GR-499-

CORE), the user is advised to set this bit-field to "0", if

the length of cable (between the XRT7300 transmit

output and the DSX-3 Cross Connect System) is

greater than 225 feet.

Conversely, the user is advised to set this bit-field to

"1", if the length of cable (between the XRT7300

transmit output and the DSX-3 Cross Connect sys-

tem) is less than 225 feet.

Writing a "1" to this bit-field commands the Framer to

toggle the TxLev output "High". Writing a "0" to this

bit-field commands the Framer to toggle this output

signal "Low".

NOTES:

1. The TxLEV function is only applicable to DS3 appli-

cations. E3 LIUs do not support this kind of Line

Build out feature.

2. If the customer is not using the XRT7300 or the

(XRT7296 DS3 Line Transmitter) IC, then this bit-

field and the TxLev output pin can be used for other

purposes.

Bit 1 - RLOOP - (Remote Loopback)

This Read/Write bit-field allows the user to control the

state of the RLOOP output pin of the Framer device.

This output pin is intended to be connected to the

RLOOP input pin of the XRT7300 DS3/E3 LIU IC.

In the XRT7300 DS3/E3 LIU IC, the state of the

RLOOP and the LLOOP pins are used to dictate

which loop-back mode the XRT7300 device will oper-

ate in. The following table presents the relationship

between the state of these two input pins (or bit-

fields) and the resulting loop-back modes.

Writing a "1" into this bit-field commands the Framer

IC to toggle the RLOOP output signal "High". Writing

a "0" into this bit-field commands the Framer IC to

toggle this output signal "Low".

For a detailed description of the XRT7300 DS3/E3

LIU's operation, during each of these above-men-

tioned loop-back modes, please consult the XRT7300

DS3/E3/STS-1 LIU IC Data Sheet.

NOTE: If the customer is not using the XRT7300 DS3/E3/

STS-1 LIU IC, then this bit-field and the RLOOP output pin

can be used for other purposes.

Bit 0 - LLOOP - (Local Loop-back)

This Read/Write bit-field allows the user to control the

state of the LLOOP output pin of the Framer device.

This output pin is intended to be connected to the

LLOOP input pin of the XRT7300 DS3/E3 LIU IC.

In the XRT7300 DS3/E3 LIU IC, the state of the

RLOOP and the LLOOP pins are used to dictate

which loop-back mode the XRT7300 device will oper-

ate in. The following table presents the relationship

between the state of these two input pins (or bit-

fields) and the resulting loop-back modes.

Writing a "1" into this bit-field commands the UNI to

toggle the LLOOP output signal "High". Writing a "0"

into this bit-field commands the Framer to toggle this

output signal "Low".

RLOOP

LLOOP

RESULTING LOOP-BACK MODE OF THE XRT7300 DEVICE

Normal Operation (No Loop-back Mode)

Analog Local Loop-back Mode

Remote Loop-back Mode

Digital Local Loop-back Mode

RLOOP

LLOOP

RESULTING LOOP-BACK MODE OF THE XRT7300 DEVICE

Normal Operation (No Loop-back Mode)

Analog Local Loop-back Mode

Remote Loop-back Mode

Digital Local Loop-back Mode

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