XRT7250 Datasheet, PDF (35/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250 DS3/E3 FRAMER IC
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REV. 1.1.1
PIN DESCRIPTION
PIN #
90
NAME
RxFrame
91
VDD
92
RxOutClk
93
RxRED
94
RxOOF
95
RxLOS
96
RxOHClk
TYPE
DESCRIPTION
o Receive Boundary of DS3 or E3 Frame Output Indicator:
The exact functionality of this output pin depends upon whether the XRT7250
Framer IC is operating in the “Serial” or “Nibble-Parallel” Mode.
Serial Mode Operation
The Receive Section of the XRT7250 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 XRT7250 will pulse this output pin “high” (for one
nibble-period), when the “Receive Payload Data Output Interface” block is driv-
ing the very first nibble of a given DS3 or E3 frame, onto the “RxNib[3:0] output
pins.
**** Power Supply Pin
O Receive Out Clock - Transmit Terminal Interface Clock for Loop-
Timing.
This clock signal functions as the "Terminal Interface" clock source, if the
XRT7250 Framer IC is operating in the "loop-timing" mode.
In this mode, the Transmitting Terminal Equipment is expected to input data to
the Framer IC, via the “TxSer” input pin, upon the rising edge of this clock sig-
nal. The XRT7250 will use the rising edge of this clock signal to sample the
data at the TxSer input.
This clock signal is a buffered version of the RxLineClk signal.
O Receiver Red Alarm Indicator - Receive Framer:
The Framer asserts this output pin to denote that one of the following events
has been detected by the Receive Framer:
LOS - Loss of Signal Condition
OOF - Out of Frame Condition
AIS - Alarm Indication Signal Detection
O Receiver "Out of Frame" Indicator:
The Receive Section of the XRT7250 Framer IC will assert this output signal
whenever it has declared an "Out of Frame" (OOF) condition with the incoming
DS3 or E3 frames. This signal is negated when the framer correctly locates the
framing alignment bits or bytes and correctly aligns itself with the incoming
DS3 or E3 frames.
O _{Receive Section - Loss of Signal Output Indicator:}
This pin is asserted when the Receive Section encounters a string of 180 con-
secutive 0's (for DS3 operation) or 32 consecutive 0's (for E3 operation) via the
RxPOS and RxNEG 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 contain a string of 4 con-
secutive "0s" (for E3 operation).
O _{Receive Overhead Output Clock Signal}
The XRT7250 will output the Overhead bits (within the incoming DS3 or E3
frames), via the "RxOH" output pin, upon the falling edge of this clock signal.
As a consequence, the "user's data link equipment" should use the rising edge
of this clock signal to sample the data on both the "RxOH" and "RxOHFrame"
output pins.
NOTE: This clock signal is always active.
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