XRT72L53 Datasheet, PDF (129/467 Pages) Exar Corporation – THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L53
REV. P1.1.7
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
ENCODIS or the ENDECDIS input pin of the DS3/E3
LIU IC. If the user forces this signal to toggle "High",
then the internal B3ZS/HDB3 encoder (within the
LIU) will be disabled. Conversely, if the user com-
mand this output signal to toggle "Low", then the in-
ternal B3ZS/HDB3 encoder (within the LIU) will be
enabled.
Writing a "1" to this bit-field causes the Channel to
toggle the Encodis[n] output pin "High". Writing a "0"
to this bit-field will cause the Channel to toggle this
output pin "Low".
NOTES:
1. The B3ZS/HDB3 encoder, within the DS3/E3 LIU,
is not to be confused with the B3ZS/HDB3 encod-
ing capable that exists within the Transmit Section
of the Framer IC.
2. The user is advised to disabled the B3ZS/HDB3
encoder (within the LIU IC) if the channel is config-
ured to operate in the B3ZS/HDB3 line code.
3. If the customer is not using an Exar XRT73L0X
DS3/E3/STS-1 LIU IC, then this bit-field and the
Encodis[n] output pin can be used for other pur-
poses.
Bit 2 - TxLev - (Transmit Output Line Build-Out
Select Output)
This Read/Write bit-field is used to control the state of
the TxLev[n] output pin of the Framer. This output pin
is intended to be connected to the TxLev input pin of
the DS3/E3 LIU IC. If the user commands this signal
to toggle High, then the DS3/E3 LIU IC will disable
the Transmit Line Build-Out circuitry, and will transmit
unshaped (square-wave) pulses onto the line. If the
user commands this signal to toggle "Low", then the
DS3/E3 LIU IC will enable the Transmit Line Build-Out
circuitry, and will transmit shaped pulses onto the line.
In order to insure that the transmit output pulses of
the LIU meet the DSX-3 Isolated Pulse Template Re-
quirements (per Bellcore GR-499-CORE), the user is
advised to set this bit-field to "0", if the length of cable
(between the LIU transmit output and the DSX-3
Cross Connect System) is greater than 225 feet.
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 appli-
cations. E3 LIU’s do not support this kind of Line
Build out feature.
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 Loopback)
This Read/Write bit-field is used to control the state of
the RLOOP[n] output pin of the Framer. 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’s, the state of the RLOOP and the LLOOP pins
are used to dictate which loop-back mode the LIU 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
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". Writ-
ing 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 partic-
ular Exar XRT73L0X DS3/E3 LIU, while configured
into each of these above-mentioned loop-back
modes, please consult the appropriate LIU Data
Sheet.
Currently the following XRT73L0X Family of DS3/E3/
STS-1 LIU IC Data Sheets are now available:
• XRT7300 1-Channel DS3/E3/STS-1 LIU IC (5V)
• XRT73L00 1-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT7302 2-Channel DS3/E3/STS-1 LIU IC (5V)
• XRT73L03 3-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT73L04 4-Channel DS3/E3/STS-1 LIU IC (3.3V)
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