
XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.3
á
PRELIMINARY
17
86
RxAIS
O
Receive "Alarm Indication Signal" Output pin:
The Framer 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:
The Framer 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..." pat-
tern in the payload has been detected.
For E3 Applications:
The Receive Section will declare an AIS condition, if it detects two consecu-
tive E3 frames, each containing 7 or less "0s".
87
RxClk
O
Receive Clock Output Signal for Serial and Nibble/Parallel Data Inter-
face:
The exact behavior of this signal depends upon whether the XRT72L50 is
operating in the "Serial" or in the "Nibble-Parallel-Mode".
Serial Mode Operation:
In the "serial" mode, this signal is a 44.736MHz clock output signal (for DS3
applications) or 34.368MHz clock output signal (for E3 applications). The
Receive Payload Data Output Interface will update the data via the RxSer out-
put pin, upon the rising edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to sam-
ple the data on the "RxSer" pin, upon the falling edge of this clock signal.
Nibble-Parallel Mode Operation:
In this Nibble-Parallel Mode, the XRT72L50 will derive this clock signal, from
the RxLineClk signal. The XRT72L50 will pulse this clock signal 1176 times
for each "inbound" DS3 frame (or 1074 times for each inbound “E3/ITU-T
G.832” frame, or 384 times for each inbound “E3/ITU-T G.751 frame). The
Receive Payload Data Output Interface will update the data, on the
"RxNib[3:0]" output pins upon the falling edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to sam-
ple the data on the "RxNib[3:0] output pins, upon the rising edge of this clock
signal
88
GND
****
Ground
89
RxFrame
O
Receive Boundary of DS3 or E3 Frame Output Indicator:
The exact functionality of this output pin depends upon whether the
XRT72L50 Framer IC is operating in the “Serial” or “Nibble-Parallel” Mode.
Serial Mode Operation:
The Receive Section of the XRT72L50 will pulse this output pin “high” (for one
bit-period) when the “Receive Payload Data Output Interface” block is driving
the very first bit of a given DS3 or E3 frame, onto the “RxSer” output pin.
Nibble-Parallel Operation:
The Receive Section of the XRT72L50 will pulse this output pin “high” (for one
nibble-period), when the “Receive Payload Data Output Interface” block is
driving the very first nibble of a given DS3 or E3 frame, onto the “RxNib[3:0]
output pins.
90
VDD
****
Power Supply 3.3V + 5%
PIN DESCRIPTION
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