XRT7250 Datasheet, PDF (31/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250 DS3/E3 FRAMER IC
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REV. 1.1.1
PIN DESCRIPTION
PIN #
69
NAME
LLOOP
70
RLOOP
71
REQB
72
GND
73
NC
TYPE
DESCRIPTION
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 Loop-
back, 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".
NOTE: 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.
O Remote Loopback Output Pin (to the XRT7300 DS3/E3 Line Interface 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 sig-
nal 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".
NOTE: 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 purposes.
O Receive Equalization Enable/Disable Select output pin - (to be
connected to the XRT7300 DS3/E3 Line Interface Unit IC).
This output pin is intended to be connected to the REQB input pin of the
XRT7300 DS3/E3 Line Interface Unit IC. The user can control the state of this
output pin by writing a '0' or '1' to Bit 5 (REQB) 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 dis-
abled. 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 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 purposes.
**** Ground Pin
Not Bonded Out
12