XRT72L58 Datasheet, PDF (163/486 Pages) Exar Corporation – EIGHT CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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EIGHT CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
XRT72L58
REV. P1.1.2
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
XRT7300 device and the DSX-3 Cross Connect Sys-
tem) is less than 225 feet. Conversely, the user is ad-
vised to set this bit-field to “1” if the cable length (be-
tween the transmit output of the XRT7300 device and
the DSX-3 Cross Connect System) is greater than
225 feet.
NOTE: If the customer is not using the XRT7300 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 de-
vice. This output pin is intended to be connected to
the RLOOP input pin of the XRT73001 LIU IC.
The state of this bit-field (or pin) along with LLOOP
are used to configure the XRT7300 device into one of
four (4) loop-back modes. The relationship of the val-
ues of RLOOP, LLOOP and the resulting loop-back
mode (within the XRT7300 device) is tabulated below.
TABLE 16: THE RELATIONSHIP BETWEEN THE STATES OF RLOOP, LLOOP AND THE RESULTING LOOP-BACK MODE
WITH THE XRT7300 DEVICE
RLOOP LLOOP
RESULTING LOOP-BACK MODE (WITHIN THE XRT7300 DS3/E3/STS-1 LIU IC)
0
0
Normal Mode (No Loop-back)
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
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 XRT7300 LIU’s oper-
ation during each of these loop-back modes, please
see the XRT7300 DS3/E3/STS-1 LIU IC data sheet.
NOTE: If the customer is not using the XRT7300 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 XRT7300 DS3/E3/STS-1 LIU
IC.
The state of this bit-field (or pin) along with RLOOP
are used to configure the XRT7300 into one of four
(4) loop-back modes. The relationship of the values
of RLOOP, LLOOP and the resulting loop-back
modes (within the XRT7300 device) are presented in
Table 16.
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 XRT7300 LIU’s oper-
ation during each of these loop-back modes, please
see the XRT7300 DS3/E3/STS-1 LIU IC Data Sheet.
NOTE: If the customer is not using the XRT7300 DS3/E3/
STS-1 LIU IC, then this bit-field and the LLOOP output pin
can be used for other purposes.
3.2 BIT-FIELDS WITHIN THE LINE INTERFACE SCAN
REGISTER
The XRT7300 device contains three output pins
which can be made accessible to the Microprocessor
Interface, via the Line Interface Scan register. These
three output pins are listed below.
• DMO - Drive Monitor Output
• RLOL - Receive Loss of Lock Indicator
• RLOS - Receive Loss of Signal Indicator.
The logic state of each of these input pins (or output
pins from the LIU) can be monitored by reading the
contents of the Line Interface Scan register, as de-
picted below.
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