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XRT72L52
TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.3
22
155
RLOOP[0]
O
Remote Loopback Output Pin (to the XRT7300 DS3/E3 Line Inter-
face Unit IC):
This output pin is intended to be connected to the RLOOP input pin of
the XRT7300 DS3/E3 Line Interface Unit IC. The user can command
this signal to toggle "high" and, in turn, force the XRT7300 DS3/E3 Line
Interface Unit IC into the "Remote Loopback" mode. Conversely, the
user can command this signal to toggle "low" and allow the XRT7300
device to operate in the normal mode. (For a detailed description of the
XR-T7300 DS3/E3 Line Interface Unit IC's operation during Remote
Loopback, please see the XR-T7300 DS3/STS-1/ E3 Line Interface Unit
IC's Data Sheet).
Writing a "1" to bit 1 of the "Line Interface Drive Register (Address =
0x80) will cause this output pin to toggle "high". Writing a "0" to this bit-
field will cause the RLOOP output to toggle "low".
N
OTE
:
If the customer is not using the XRT7300 DS3/E3 Line Interface
Unit IC, then he/she can use this output pin for a variety of other pur-
poses.
156
LLOOP[0]
O
Local Loopback Output Pin (to the XRT7300 DS3/E3 Line Interface
Unit IC):
This output pin is intended to be connected to the LLOOP input pin of
the XRT7300 LIU IC. The user can command this signal to toggle "high"
and, in turn, force the LIU into the "Local Loopback" mode. (For a
detailed description of the XRT7300 DS3/E3 Line Interface Unit IC's
operation during Local Loopback, please see the XRT7300 DS3/STS-1/
E3 Line Interface Unit IC's Data Sheet).
Writing a "1" to bit 1 of the "Line Interface Drive Register (Address =
0x80) will cause this output pin to toggle "high". Writing a "0" to this bit-
field will cause the RLOOP output to toggle "low".
N
OTE
:
If the user is not using the XRT7300 DS3/E3 Line Interface Unit
IC, then he/she can use this output pin for a variety of other purposes.
157
Req[0]
O
Receive Equalization Enable/Disable Select output pin - (to be con-
nected to the XRT7300 DS3/E3 Line Interface Unit IC):
This output pin is intended to be connected to the REQ input pin of the
XRT7300 DS3/E3 (REQDIS or REQEN of the XRT73L03 or XRT
73L04) Line Interface Unit IC. The user can control the state of this out-
put pin by writing a '0' or '1' to Bit 5 (REQ) within the Line Interface
Driver Register (Address = 0x80). If the user commands this signal to
toggle "high" then the internal Receive Equalizer (within the XRT7300
Device) will be disabled. Conversely, if the user commands this output
signal to toggle "low", then the internal Receive Equalizer (within the
XRT7300 Device) will be enabled.
For information on the criteria that should be used when deciding
whether to bypass the equalization circuitry or not, please consult the
"XRT7300 DS3/E3 Line Interface Unit" data sheet.
Writing a "1" to Bit 5 of the Line Interface Drive Register (Address =
0x80) will cause this output pin to toggle "high". Writing a "0" to this bit-
field will cause this output pin to toggle "low".
If the Exar XRT7300 DS3/E3 family of Line Interface Unit IC’s are not
used, then this output pin can be used for other purposes.
PIN DESCRIPTION
P
IN
#
P
IN
N
AME
T
YPE
D
ESCRIPTION