XRT7250 Datasheet, PDF (30/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

áç
PIN DESCRIPTION
PIN #
67
NAME
TxLEV
68
TAOS
DS3/E3 FRAMER IC
XRT7250
REV. 1.1.1
TYPE
DESCRIPTION
O Transmit Line Build-Out Enable/Disable Select Output (to be con-
nected 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 "Transmit
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. Conversely,
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 Con-
nect 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 applications.
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 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 out-
put pin by writing a '0' or '1' to Bit 4 (TAOS) of the Line Interface Drive Register
(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" pattern onto
the line. Conversely, if the user commands this output signal to toggle "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.
11