XR72L52 Datasheet, PDF (129/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L52
REV. 1.0.1
Bit 5 - REQB - (Receive Equalization Enable/Disable Select)
This Read/Write bit-field allows the user to control the state of the REQB output pin of the Framer device. This
output pin is intended to be connected to the REQB input pin of the XRT73L02A DS3/E3/STS-1 LIU IC. If the
user forces this signal to toggle "High”, then the internal Receive Equalizer (within the XRT73L02A) will be dis-
abled for using short cable length. Conversely, if the user forces this signal to toggle "Low”, then the Receive
Equalizer (within the XRT73L02A) will be enabled for short cable length.
The purpose of the internal Receive Equalizer (within the XRT73L02A) is to compensate for the Frequency-
Dependent attenuation (e.g., cable loss), that a line signal will experience as it travels through coaxial cable,
from the transmitting to the receiving terminal.
Writing a “1” to this bit-field causes the Framer device to toggle the REQB output pin "High”. Writing a “0” to
this bit-field causes the Framer device to toggle the REQB output pin "Low”.
For information on the criteria that should be used when deciding whether to enable or disable the Receive
Equalizer, please consult the XRT73L02A DS3/E3/STS-1 LIU IC Data Sheet.
NOTE: If the customer is not using the XRT73L02A DS3/E3/STS-1 IC, then this bit-field and the REQB output 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 forces this sig-
nal to toggle "High", then the LIU device will transmit an "All Ones" pattern onto the line. Conversely, if the user
commands this output signal to toggle "Low" then the LIU IC will proceed to transmit data based upon the pat-
tern 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 output 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 de-
vice) will be disabled. Conversely, if the user command this output signal to toggle "Low", then the internal
B3ZS/HDB3 encoder (within the LIU device) 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
capability that exists within the Transmit Section of the Framer IC.
2. The user is advised to disable the B3ZS/HDB3 encoder (within the LIU IC) if the channel is configured 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 purposes.
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 device.
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 device meet the DSX-3 Isolated Pulse Template
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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