XRT72L54 Datasheet, PDF (28/484 Pages) Exar Corporation – FOUR CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L54
FOUR CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
PIN DESCRIPTION
PIN #
C5
PIN NAME
RxAIS[0]
C6
TAOS[0]
C7
LLOOP[0]
C8
RLOL[1]
TYPE
O
O
O
I
DESCRIPTION
Receive "Alarm Indication Signal" Output pin:
The Framer will assert this pin to indicate that the Alarm Indication Sig-
nal (AIS) has been identified in the Receive DS3 or E3 data stream.
For DS3 Applications:
The Framer will assert this pin to indicate that the Alarm Indication Sig-
nal (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:
The Receive Section will declare an AIS condition, if it detects two con-
secutive E3 frames, each containing 7 or less "0s".
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 Inter-
face 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 com-
mands this output signal to toggle "low" then the XR-T7300 DS3/E3
Line Interface Unit IC will proceed to transmit data based upon the pat-
tern 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.
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".
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.
See Description for Pin B8
9