XRT72L13 Datasheet, PDF (329/370 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 37: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE" BLOCK (METHOD 2)
SIGNAL NAME TYPE
DESCRIPTION
RxOH
Output
Receive Overhead Data Output pin:
The XRT72L13 will output the overhead bits, within the incoming DS3 frames, via this pin.
The Receive Overhead Output Interface will pulse the “RxOHEnable” output pin (for one
“RxOutClk” period) at approximately the middle of the “RxOH” bit period. The user is advised
to design the Terminal Equipment to latch the contents of the “RxOH” output pin, whenever the
“RxOHEnable” output pin is sampled “high” on the falling edge of “RxOutClk”.
RxOHEnable
Output Receive Overhead Data Output Enable - Output pin:
The XRT72L13 will assert this output signal for one “RxOutClk” period when it is safe for the
Terminal Equipment to sample the data on the “RxOH” output pin.
RxOHFrame
Output Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L13 will drive this output pin “high” (for one period of the “RxOH” signal), whenever
the first overhead bit, within a given DS3 frame is being driven onto the “RxOH” output pin.
RxOutClk
Output
Receive Section Output Clock Signal:
This clock signal is derived from the “RxLineClk” signal (from the LIU) for loop-timing applica-
tions, and the “TxInClk” signal (from a local oscillator) for local-timing applications. For DS3
applications, this clock signal will operate at 44.736MHz.
The user is advised to design the Terminal Equipment to latch the contents of the “RxOH” pin,
anytime the “RxOHEnable” output signal is sampled “high” on the falling edge of this clock sig-
nal.
Interfacing the “Receive Overhead Data Output
Interface” block to the Terminal Equipment (Meth-
od 2)
Figure 109 illustrates how one should interface the
“Receive Overhead Data Output Interface” block to
the Terminal Equipment, when using “Method 2” to
sample and process the overhead bits from the “in-
bound” DS3 data stream.
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