XRT7250 datasheet(30/463 Pages) EXAR

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

TxLEV

Transmit Line Build-Out Enable/Disable Select Output (to be con-

nected to the XRT7300 DS3/E3 Line Interface Unit IC).

This output pin is intended to be connected to the TxLev input pin of the

XRT7300 DS3/E3 Line Interface Unit IC. The user can control the state of this

output pin by writing a "0" or a "1" to Bit 2 (TxLev) within the Line Interface

Driver Register (Address = 0x80).

Writing a "1" to Bit 2 of the Line Interface Drive Register (Address = 0x80) will

cause this output pin to toggle "high". Writing a "0" to this bit-field will cause

this output pin to toggle "low".

For DS3 Application

If the user commands this signal to toggle "high" then the "Transmit Line Build-

Out" circuit (within the XRT7300 device) will be disabled. In this mode, the

XRT7300 device will output unshaped (e.g., square) pulses onto the line (via

the TTIP and TRING output pins).

Conversely, if the user commands this signal to toggle "low" then the "Transmit

Line Build-Out" circuit (within the XRT7300 device) will be disabled. In this

mode, the XRT7300 device will output shaped (e.g., more rounded) pulses

onto the line (via the TTIP and TRING output pins).

In order to comply with the "DSX-3 Isolated Pulse Template Requirement" (per

Bellcore GR-499-CORE), the user is advised to command this output pin to be

"high" if the cable length (between the transmit output of the XRT7300 device

and the DSX-3 Cross-Connect System) is greater than 225 feet. Conversely,

the user is advised to command this output pin to be "low" if the cable length

(between the transmit output of the XRT7300 device and the DSX-3Cross Con-

nect System) is less than 225 feet.

For E3 Applications

This pin can be used as a General Purpose Output pin. The Transmit Line

Build-Out circuitry (within the XRT7300 device) is not active for E3 applications.

NOTE: If the customer is not using the XRT7300 DS3/E3 Line Interface Unit IC,

then he/she can use this output pin for a variety of other purposes.

TAOS

Transmit All Ones Signal" (TAOS) Command (for the XR-T7300

Line Interface Unit IC).

This output pin is intended to be connected to the TAOS input pin of the XR-

T7300 DS3/E3 Line Interface Unit IC. The user can control the state of this out-

put pin by writing a '0' or '1' to Bit 4 (TAOS) of the Line Interface Drive Register

(Address = 0x80). If the user commands this signal to toggle "high" then it will

force the XRT7300 Line Interface Unit IC to transmit an "All Ones" pattern onto

the line. Conversely, if the user commands this output signal to toggle "low"

then the XR-T7300 DS3/E3 Line Interface Unit IC will proceed to transmit data

based upon the pattern that it receives via the TxPOS and TxNEG output pins.

Writing a "1" to Bit 4 of the Line Interface Drive Register (Address = 0x80) will

cause this output pin to toggle "high". Writing a "0" to this bit-field will cause

this output pin to toggle "low".

If the customer is not using the XR-T7300 DS3/E3 Line Transceiver IC, then

he/she can use this output pin for a variety of other purposes.

PIN DESCRIPTION

PIN #NAME

TYPE

DESCRIPTION

XRT7250 데이터시트(PDF) 30 Page - Exar Corporation

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