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XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.3
12
67
TxLev
O
Transmit Line Build-Out Enable/Disable Select Output (to be connected
to the XRT7300 DS3/E3 Line Interface Unit IC):
This output pin is intended to be connected to the TxLev 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 a "1" to Bit 2 (TxLev) within the Line Interface
Driver Register (Address = 0x80).
Writing a "1" to Bit 2 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".
For DS3 Application:
If the user commands this signal to toggle "high" then the "Transmit Line
Build-Out" circuit (within the XRT7300 device) will be disabled. In this mode,
the XRT7300 device will output unshaped (e.g., square) pulses onto the line
(via the TTIP and TRING output pins).
Conversely, if the user commands this signal to toggle "low" then the "Trans-
mit Line Build-Out" circuit (within the XRT7300 device) will be disabled. In this
mode, the XRT7300 device will output shaped (e.g., more rounded) pulses
onto the line (via the TTIP and TRING output pins).
In order to comply with the "DSX-3 Isolated Pulse Template Requirement"
(per Bellcore GR-499-CORE), the user is advised to command this output pin
to be "high" if the cable length (between the transmit output of the XRT7300
device and the DSX-3 Cross-Connect System) is greater than 225 feet. Con-
versely, the user is advised to command this output pin to be "low" if the cable
length (between the transmit output of the XRT7300 device and the DSX-
3Cross Connect System) is less than 225 feet.
For E3 Applications:
This pin can be used as a General Purpose Output pin. The Transmit Line
Build-Out circuitry (within the XRT7300 device) is not active for E3 applica-
tions.
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 purposes.
68
TAOS
O
Transmit All Ones Signal" (TAOS) Command (for the XR-T7300 Line
Interface Unit IC):
This output pin is intended to be connected to the TAOS input pin of the XR-
T7300 DS3/E3 Line Interface Unit IC. The user can control the state of this
output pin by writing a '0' or '1' to Bit 4 (TAOS) of the Line Interface Drive Reg-
ister (Address = 0x80). If the user commands this signal to toggle "high" then
it will force the XRT7300 Line Interface Unit IC to transmit an "All Ones" pat-
tern onto the line. Conversely, if the user commands this output signal to tog-
gle "low" then the XR-T7300 DS3/E3 Line Interface Unit IC will proceed to
transmit data based upon the pattern that it receives via the TxPOS and
TxNEG output pins.
Writing a "1" to Bit 4 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 XR-T7300 DS3/E3 Line Transceiver IC, then
he/she can use this output pin for a variety of other purposes.
PIN DESCRIPTION
P
IN
#
P
IN
N
AME
T
YPE
D
ESCRIPTION