XRT72L13 Datasheet, PDF (335/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

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PRELIMINARY
XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
TABLE 39: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE PAYLOAD DATA OUTPUT
INTERFACE BLOCK
SIGNAL NAME TYPE
DESCRIPTION
RxSer
Output Receive Serial Payload Data Output pin:
If the user opts to operate the XRT72L13 in the "serial" mode, then the chip will output the pay-
load data, of the incoming DS3 frames, via this pin. The XRT72L13 will output this data upon the
rising edge of RxClk.
The user is advised to design the Terminal Equipment such that it will sample this data on the
falling edge of RxClk.
This signal is only active if the "NibInt" input pin is pulled "low".
RxNib[3:0]
Output Receive Nibble-Parallel Payload Data Output pins:
If the user opts to operate the XRT72L13 in the "nibble-parallel" mode, then the chip will output
the payload data, of the incoming DS3 frames, via these pins. The XRT72L13 will output data
via these pins, upon the falling edge of the RxClk output pin.
The user is advised to design the Terminal Equipment such that it will sample this data upon the
rising edge of RxClk.
These pins are only active if the "NibInt" input pin is pulled "high".
RxClk
Output Receive Payload Data Output Clock pin:
The exact behavior of this signal depends upon whether the XRT72L13 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. The Receive Payload Data
Output Interface will update the data via the RxSer output pin, upon the rising edge of this clock
signal.
The user is advised to design (or configure) the Terminal Equipment to sample the data on the
"RxSer" pin, upon the falling edge of this clock signal.
Nibble-Parallel Mode Operation
In this Nibble-Parallel Mode, the XRT72L13 will derive this clock signal, from the RxLineClk sig-
nal. The XRT72L13 will pulse this clock 1176 times for each "inbound" DS3 frame. The Receive
Payload Data Output Interface will update the data, on the "RxNib[3:0]" output pins upon the fall-
ing edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to sample the data on the
"RxNib[3:0] output pins, upon the rising edge of this clock signal
RxOHInd
Output Receive Overhead Bit Indicator Output:
This output pin will pulse "high" whenever the "Receive Payload Data Output Interface" outputs
an "overhead" bit via the "RxSer" output pin. The purpose of this output pin is to alert the Termi-
nal Equipment that the current bit, (which is now residing on the RxSer output pin), is an over-
head bit and should not be processed by the Terminal Equipment.
The XRT72L13 will update this signal, upon the rising edge of the “RxClk" signal.
The user is advised to design (or configure) the Terminal Equipment to sample this signal (along
with the data on the "RxSer" output pin) on the falling edge of the RxClk signal.
For DS3 applications, this output pin is only active if the XRT72L13 is operating in the "Serial
Mode". This output pin will be "low" if the device is operating in the "Nibble-Parallel" Mode.
RxFrame
Output Receive "Start of Frame" Output Indicator:
The exact behavior of this pin, depends upon whether the XRT72L13 has been configured to
operate in the "Serial" Mode or the "Nibble-Parallel" Mode.
Serial Mode Operation:
The Receive Section of the XRT72L13 will pulse this output pin "high" (for one bit period) when
the "Receive Payload Data Output Interface" block is driving the very first bit (or "Nibble") of a
given DS3 frame, onto the RxSer output pin.
Nibble-Parallel Mode Operation:
The "Receive Section" of the XRT72L13 will pulse this output pin "high" (for one nibble period),
when the "Receive Payload Data Output Interface" is driving the very first nibble of a given DS3
frame, onto the "RxNib[3:0] output pins.
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