XRT72L53 Datasheet, PDF (10/467 Pages) Exar Corporation – THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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PRELIMINARY
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
C3
PIN NAME
TxLev[0]
C4
RxLOS[0]
C5
RxAIS[0]
TYPE
O
O
O
DESCRIPTION
Transmit Line Build-Out Enable/Disable Select Output - Channel 0
(to be connected to the DS3/E3 Line Interface Unit IC):
This output pin is intended to be connected to the TxLev input pin of the
DS3/E3 Line Interface Unit IC. The user can control the state of this out-
put 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 DS3/E3 LIU device) will be disabled. In this
mode, the LIU 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 DS3/E3 LIU device) will be
disabled. In this mode, the LIU 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 out-
put 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 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
applications.
Receive Loss of Signal Output Indicator - Channel 0:
This pin is asserted when the Receive Section of Channel 0 encounters
a string of 180 consecutive 0's (for DS3 operation) or 32 consecutive 0's
(for E3 operation) via the RxPOS[0] and RxNEG[0] pins.
This pin will be negated once the Receive Section has detected at least
60 pulses within 180 bit-periods (for DS3 operation); or the Receive
Section has detected a string of 32 consecutive bits, that does not con-
tain a string of 4 consecutive "0s" (for E3 operation).
Receive Alarm Indication Signal Output pin - Channel 0:
Channel 0 will assert this pin to indicate that the Alarm Indication Signal
(AIS) has been identified in the Receive DS3 or E3 data stream.
For DS3 Applications:
Channel 0 will assert this pin to indicate that the Alarm Indication Signal
(AIS) has been identified in the Receive DS3 data stream. An AIS is
detected if the payload consists of the recurring pattern of 1010... and
this pattern persists for 63 M-frames. An additional requirement for AIS
indication is that the C-bits are set to 0, and the X-bits are set to 1. This
pin will be negated when a sufficient number of frames, not exhibiting
the "1010..." pattern in the payload has been detected.
For E3 Applications:
Channel 0 will declare an AIS condition, if it detects two consecutive E3
frames, each containing 7 or less "0s".
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