XRT72L56 Datasheet, PDF (147/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
XRT72L56
REV. P1.1.2
2.4.8.19 Line Interface Drive Register
LINE INTERFACE DRIVE REGISTER (ADDRESS = 0X80)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
REQB
TAOS
ENCODIS
TxLEV
RLOOP
LLOOP
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
1
0
0
0
Bit 5 - REQB - (Receive Equalization Bypass Con-
trol)
This Read/Write bit-field permits the user to control
the state of the REQB output pin of the Framer de-
vice. This output pin is intended to be connected to
either the REQB or the REQEN input pin of the DS3/
E3 LIU IC.
If the user connects the “REQB” output pin of the
Framer to either the “REQDIS” or the “REQEN” input
pin of the DS3/E3 LIU IC, then the user will have “Mi-
croprocessor Control” over the state of the “Receive
Equalizer” within the DS3/E3 LIU IC.
Writing a "1" to this bit-field causes the Channel to
toggle the REQB output pin "High". Writing a "0" to
this bit-field causes the Channel to toggle the REQB
output pin "Low".
NOTE: If the customer is not using an Exar XRT73L0X
DS3/E3/STS-1 LIU IC, then this bit-field and the REQB out-
put pin can be used for other purposes.
Bit 4 - TAOS - (Transmit All Ones Signal)
This Read/Write bit-field permits the user to control
the state of the TAOS output pin of the Framer device.
This output pin is intended to be connected to the
TAOS input pin of the DS3/E3 LIU IC. If the user forc-
es this signal to toggle "High", then the LIU device will
transmit an "All Ones" pattern onto the line. Con-
versely, if the user commands this output signal to
toggle "Low" then the LIU IC will proceed to transmit
data based upon the pattern that it receives via the
TxPOS[n] and TxNEG[n] output pins (of the Framer
IC).
Writing a "1" to this bit-field will cause the TAOS[n]
output pin to toggle "High". Writing a "0" to this bit-
field will cause this output pin to toggle "Low".
NOTE: If the customer is not using an Exar XRT73L0X
DS3/E3/STS-1 LIU IC, then this bit-field, and the TAOS out-
put pin can be used for other purposes.
Bit 3 - Encodis - (B3ZS Encoder Disable)
This Read/Write bit-field allows the user to control the
state of the Encodis output pin of the Framer device.
This output pin is intended to be connected to either
the 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 device) will be disabled. Conversely, if the us-
er command this output signal to toggle "Low", then
the internal B3ZS/HDB3 encoder (within the LIU de-
vice) 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
device, is not to be confused with the B3ZS/HDB3
encoding 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 permits the user to control
the state of the TxLev[n] output pin of the Framer de-
vice. 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 cir-
cuitry, and will transmit unshaped (square-wave) puls-
es 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 device meet the DSX-3 Isolated Pulse Tem-
plate Requirements (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.
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