XRT72L50 Datasheet, PDF (139/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

áç
XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
If the user commands this signal to toggle "High”, then the Transmit Line Build-Out circuitry, within the
XRT73L0x will be disabled. In this mode, the XRT73L0x LIU IC will generate unshaped (e.g., square) pulses
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 XRT73L0x will be enabled. In this mode, the XRT73L0x 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
user is advised to set this bit-field to “0” if the cable length (between the transmit output of the XRT73L0x 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 XRT73L0x and the DSX-3 Cross Connect System) is
greater than 225 feet.
NOTE: If the customer is not using the XRT73L0x 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. This
output pin is intended to be connected to the RLOOP input pin of the XRT73L0x LIU IC.
The state of this bit-field (or pin) along with LLOOP are used to configure the XRT73L0x into one of four (4)
loop-back modes. The relationship of the values of RLOOP, LLOOP and the resulting loop-back mode (within
the XRT73L0x) is tabulated below.
TABLE 12: THE RELATIONSHIP BETWEEN THE STATES OF RLOOP, LLOOP AND THE RESULTING LOOP-BACK MODE
WITH THE XRT73L0X
RLOOP
0
0
1
1
LLOOP
0
1
0
1
RESULTING LOOP-BACK MODE (WITHIN THE XRT73L0X 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 XRT73L0x LIU’s operation during each of these loop-back modes, refer to the
XRT73L0x DS3/E3/STS-1 LIU IC data sheet.
NOTE: If the customer is not using the XRT73L0x 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. This output
pin is intended to be connected to the LLOOP input pin of the XRT73L0x DS3/E3/STS-1 LIU IC.
The state of this bit-field (or pin) along with RLOOP are used to configure the XRT73L0x into one of four (4)
loop-back modes. The relationship of the values of RLOOP, LLOOP and the resulting loop-back modes (within
the XRT73L0x) 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 XRT73L0x LIU’s operation during each of these loop-back modes, refer to the
XRT73L0x DS3/E3/STS-1 LIU IC Data Sheet.
NOTE: If the customer is not using the XRT73L0x DS3/E3/STS-1 LIU IC, then this bit-field and the LLOOP output pin can
be used for other purposes.
126