XR72L52 Datasheet, PDF (141/480 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
Writing a “0” to this bit-field commands the Framer to drive this output signal "Low”.
If the user commands this signal to toggle "High”, then the Transmit Line Build-Out circuitry, within the
XRT73L02A will be disabled. In this mode, the XRT73L02A LIU IC will generate unshaped (e.g., square) puls-
es out onto the line, via the TTIP and TRING output pins.
Conversely, if the user commands this signal to toggle "Low”, then the Transmit Line Build-Out circuitry, within
the XRT73L02A will be enabled. In this mode, the XRT73L02A will generate shaped pulses onto the line, via
the TTIP and TRING output pins.
In order to comply with the Isolated DSX-3 Pulse Template requirements (per Bellcore GR-499-CORE), the us-
er is advised to set this bit-field to “0” if the cable length (between the transmit output of the XRT73L02A and
the DSX-3 Cross Connect System) is less than 225 feet. Conversely, the user is advised to set this bit-field to
“1” if the cable length (between the transmit output of the XRT73L02A and the DSX-3 Cross Connect System)
is greater than 225 feet.
NOTE: If the customer is not using the XRT73L02A DS3/E3/STS-1 IC, then this bit-field and the TxLEV output pin can be
used for other purposes.
Bit 1 - RLOOP (Remote Loop-Back Select)
This Read/Write bit-field permits the user to control the state of the RLOOP output pin of the Framer device.
This output pin is intended to be connected to the RLOOP input pin of the XRT73L02A LIU IC.
The state of this bit-field (or pin) along with LLOOP are used to configure the XRT73L02A into one of four (4)
loop-back modes. The relationship of the values of RLOOP, LLOOP and the resulting loop-back mode (within
the XRT73L02A) is tabulated below.
TABLE 12: THE RELATIONSHIP BETWEEN THE STATES OF RLOOP, LLOOP AND THE RESULTING LOOP-BACK MODE
WITH THE XRT73L02A
RLOOP
0
0
1
1
LLOOP
0
1
0
1
RESULTING LOOP-BACK MODE (WITHIN THE XRT73L02A DS3/E3/STS-1 LIU IC)
Normal Mode (No Loop-back)
Analog Local Loop-back Mode
Remote Loop-back Mode
Digital Local Loop-back Mode
Writing a “1” into this bit-field commands the Framer to drive the RLOOP output signal "High”. Writing a “0” into
this bit-field commands the Framer to drive this output signal "Low”.
For a detailed description of the XRT73L02A LIU’s operation during each of these loop-back modes, refer to
the XRT73L02A DS3/E3/STS-1 LIU IC data sheet.
NOTE: If the customer is not using the XRT73L02A DS3/E3/STS-1 LIU IC, then this bit-field and the RLOOP output pin can
be used for other purposes.
Bit 0 - LLOOP (Local Loop-back Select)
This Read/Write bit-field allows the user to control the state of the LLOOP output pin of the Framer device.
This output pin is intended to be connected to the LLOOP input pin of the XRT73L02A DS3/E3/STS-1 LIU IC.
The state of this bit-field (or pin) along with RLOOP are used to configure the XRT73L02A into one of four (4)
loop-back modes. The relationship of the values of RLOOP, LLOOP and the resulting loop-back modes (within
the XRT73L02A) are presented in Table 12.
Writing a “1” into this bit-field commands the Framer to toggle the LLOOP output pin "High”. Writing a “0” into
this bit-field commands the Framer to toggle this output signal "Low”.
For a detailed description of the XRT73L02A LIU’s operation during each of these loop-back modes, refer to
the XRT73L02A DS3/E3/STS-1 LIU IC Data Sheet.
NOTE: If the customer is not using the XRT73L02A DS3/E3/STS-1 LIU IC, then this bit-field and the LLOOP output pin can
be used for other purposes.
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