XRT79L71 Datasheet, PDF (47/441 Pages) Exar Corporation – 1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC

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PRELIMINARY
1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC
XRT79L71
REV. P1.0.3
PIN #
NAME
TYPE
TRANSMIT LINE SIDE SIGNALS
DESCRIPTION
R15
TxON
I 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:
1. Whenever the transmitters are turned off , the TTIP and TRING output
pins will be tri-stated.
2. These pins are internally pulled high.
P16
DS3CLK
M16
E3CLK
I 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
O 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
O 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".
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