XRT7250 datasheet(31/463 Pages) EXAR

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XRT7250

DS3/E3 FRAMER IC

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REV. 1.1.1

LLOOP

Local Loopback Output Pin (to the XRT7300 DS3/E3 Line Interface

Unit IC).

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

XRT7300 LIU IC. The user can command this signal to toggle "high" and, in

turn, force the LIU into the "Local Loopback" mode. (For a detailed description

of the XRT7300 DS3/E3 Line Interface Unit IC's operation during Local Loop-

back, please see the XRT7300 DS3/STS-1/E3 Line Interface Unit IC's Data

Sheet).

Writing a "1" to bit 1 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 the

RLOOP output to toggle "low".

NOTE: If the user 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.

RLOOP

Remote Loopback Output Pin (to the XRT7300 DS3/E3 Line Interface Unit

IC).

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

XRT7300 DS3/E3 Line Interface Unit IC. The user can command this signal to

toggle "high" and, in turn, force the XRT7300 DS3/E3 Line Interface Unit IC

into the "Remote Loopback" mode. Conversely, the user can command this sig-

nal to toggle "low" and allow the XRT7300 device to operate in the normal

mode. (For a detailed description of the XR-T7300 DS3/E3 Line Interface Unit

IC's operation during Remote Loopback, please see the XR-T7300 DS3/STS-

1/ E3 Line Interface Unit IC's Data Sheet).

Writing a "1" to bit 1 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 the

RLOOP output to toggle "low".

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.

REQB

Receive Equalization Enable/Disable Select output pin - (to be

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

This output pin is intended to be connected to the REQB 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 '1' to Bit 5 (REQB) within the Line Interface Driver

then the internal Receive Equalizer (within the XRT7300 Device) will be dis-

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

the internal Receive Equalizer (within the XRT7300 Device) will be enabled.

For information on the criteria that should be used when deciding whether to

bypass the equalization circuitry or not, please consult the "XRT7300 DS3/E3

Line Interface Unit" data sheet.

Writing a "1" to Bit 5 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 XRT7300 DS3/E3 Line Interface Unit IC, then

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

GND

****

Ground Pin

Not Bonded Out

PIN DESCRIPTION

PIN #NAME

TYPE

DESCRIPTION

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