XR72L52 Datasheet, PDF (130/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L52
REV. 1.0.1
xr
TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
Conversely, the user is advised to set this bit-field to "1", if the length of cable (between the LIU transmit output
and the DSX-3 Cross Connect system) 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 applications. E3 LIUs do not support this kind of Line Build out fea-
ture.
2. If the customer is not using an Exar XRT73L0X DS3/E3 LIU IC, then this bit-field and the TxLev output pin can be
used for other purposes.
Bit 1 - RLOOP - (Remote Loop-back)
This Read/Write bit-field permits the user to control the state of the RLOOP[n] output pin of the Framer device.
This output pin is intended to be connected to the RLOOP input pin of the DS3/E3 LIU IC.
When using Exar’s family of XRT73L0X DS3/E3 LIU devices, the state of the RLOOP and the LLOOP pins are
used to dictate which loop-back mode the LIU device will operate in. The following table presents the relation-
ship between the state of these two input pins (or bit-fields) and the resulting loop-back modes.
RLOOP
LLOOP
RESULTING LOOP-BACK MODE OF THE DS3/E3 LIU DEVICE
0
0
Normal Operation (No Loop-back Mode)
0
1
Analog Local Loop-back Mode
1
0
Remote Loop-back Mode
1
1
Digital Local Loop-back Mode
Writing a "1" into this bit-field commands the Framer IC to toggle the RLOOP[n] output signal "High". Writing a
"0" into this bit-field commands the Framer IC to toggle this output signal "Low".
For a detailed description on the operation of a particular Exar XRT73L0X DS3/E3 LIU, while configured into
each of these above-mentioned loop-back modes, please consult the appropriate LIU Data Sheet.
NOTE: If the customer is not using an Exar XRT73L0X DS3/E3/STS-1 LIU IC, then this bit-field and the RLOOP[n] output
pin can be used for other purposes.
Bit 0 - LLOOP - (Local Loop-back)
This Read/Write bit-field permits the user to control the state of the LLOOP[n] output pin of the Framer device.
This output pin is intended to be connected to the LLOOP input pin of the DS3/E3 LIU IC.
When using Exar’s family of XRT73L0X DS3/E3 LIU devices, the state of the RLOOP and the LLOOP pins are
used to dictate which loop-back mode the LIU device will operate in. The following table presents the relation-
ship between the state of these two input pins (or bit-fields) and the resulting loop-back modes.
RLOOP
LLOOP
RESULTING LOOP-BACK MODE OF THE DS3/E3 LIU DEVICE
0
0
Normal Operation (No Loop-back Mode)
0
1
Analog Local Loop-back Mode
1
0
Remote Loop-back Mode
1
1
Digital Local Loop-back Mode
Writing a "1" into this bit-field commands the Framer to toggle the LLOOP[n] output signal "High". Writing a "0"
into this bit-field commands the Framer to toggle this output signal "Low".
For a detailed description of the operation of a particular Exar XRT73L0X DS3/E3 LIU, while configured into
each of these above-mentioned loop-back modes, please consult the appropriate LIU IC Data Sheet.
NOTE: If the customer is not using an Exar XRT73L0X DS3/E3/STS-1 LIU IC, then this bit-field and the LLOOP[n] output
pin can be used for other purposes.
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