XRT79L71IB datasheet(47/441 Pages) EXAR

47 / 441 page

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PRELIMINARY

XRT79L71

1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC

REV. P1.0.3

PIN #NAME

TYPE

DESCRIPTION

TRANSMIT LINE SIDE SIGNALS

R15

TxON

Transmit Driver ON - Channel n:

This input pin is used to either enable or disable the Transmit Output Driver of the

XRT79L71.

"Low" - Disables the XRT79L71 Transmit Output Driver. In this setting, the TTIP

and TRING output pins will be tri-stated.

"High" - Enables the XRT79L71 Transmit Output Driver. In this setting, the TTIP

and TRING output pins will be enabled.

NOTES:

Whenever the transmitters are turned off , the TTIP and TRING output

pins will be tri-stated.

These pins are internally pulled high.

P16

M16

DS3CLK

E3CLK

Transmit Clock Input:

These input pins function as the timing source for the XRT79L71 Transmit Section.

NOTE: The user is expected to supply a 44.736MHz ± 20ppm clock signal (for

DS3 applications) or a 34.368MHz ± 20 ppm clock signal (for E3

applications).

T11

TTIP

Transmit Output - Positive Polarity Signal:

This output pin, along with the TRING output pin, function as the Transmit DS3/E3

output signal drivers for the XRT79L71.

The user is expected to connect this signal and the TRING output signal to a 1:1

transformer.

Whenever the Transmit Section of the XRT79L71 generates and transmits a posi-

tive-polarity pulse onto the line, this output pin will be pulsed to a "higher-voltage"

than the TRING output pin.

Conversely, whenever the Transmit Section of the XRT79L71 generates and trans-

mit a negative-polarity pulse onto the line, this output pin will be pulsed to a "lower-

voltage" than the TRING output pin.

NOTE: This output pin will be tri-stated whenever the user sets the TxON input pin

(or bit-field) to "0".

T10

TRING

Transmit Output - Negative Polarity Signal:

This output pin along with the TTIP output pin, functions as the Transmit DS3/E3

output signal drivers for the XRT79L71.

The user is expected to connect this signal and the TTIP output signal to a 1:1

transformer.

Whenever the Transmit Section of the XRT79L71 generates and transmits a posi-

tive-polarity pulse onto the line, this output pin will be pulsed to a "lower-voltage"

than the TTIP output pin.

Conversely, whenever the Transmit Section of the XRT79L71 generates and trans-

mit a negative-polarity pulse onto the line, this output pin will be pulsed to a

"higher-voltage" than the TTIP output pin.

NOTE: This output pin will be tri-stated whenever the user sets the TxON input pin

(or bit-field) to "0".

XRT79L71IB Datasheet(PDF) 47 Page - Exar Corporation

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