XRT72L13 Datasheet, PDF (336/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
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PRELIMINARY
Operation of the Receive Payload Data Output In-
terface block
The Receive Payload Data Output Interface permits
the user to read out the payload data of "inbound"
DS3 frames, via either of the following modes.
• Serial Mode
• Nibble-Parallel Mode
Each of these modes are described in detail, below.
4.3.5.1 Serial Mode Operation
Behavior of the XRT72L13
If the XRT72L13 has been configured to operate in
the “Serial” mode, then the XRT72L13 will behave as
follows.
Payload Data Output
The XRT72L13 will output the payload data, of the in-
coming DS3 frames via the “RxSer” output, upon the
rising edge of RxClk.
Delineation of "inbound" DS3 Frames
The XRT72L13 will pulse the "RxFrame" output pin
"high" for one bit-period; coincident with it driving the
first bit within a given DS3 frame, via the "RxSer" out-
put pin.
Interfacing the XRT72L13 to the "Receive Termi-
nal Equipment"
Figure 112 presents a simple illustration as how the
user should interface the XRT72L13 to that terminal
equipment which processes "Receive Direction" pay-
load data.
FIGURE 112. ILLUSTRATION OF THE XRT72L13 DS3/E3 FRAMER IC BEING INTERFACED TO THE "RECEIVE" TERMI-
NAL EQUIPMENT (SERIAL MODE OPERATION)
Rx_DS3_Clock_In
DS3_Data_In
Rx_Start_of_Frame
Rx_DS3_OH_Ind
44.736 MHz Clock Signal
RxClk
RxSer
RxFrame
RxOHIns
44.736 MHz
Clock Source
RxLineClk
Terminal Equipment
(Receive Payload Section)
XRT72L13 DS3 Framer
Required Operation of the Terminal Equipment
The XRT72L13 will update the data on the RxSer out-
put pin, upon the rising edge of "RxClk". However,
because the “rising edge” of “RxClk” to data delay is
between 14ns to 16ns; the Terminal Equipment
should sample the data on the "RxSer" output pin (or
the "DS3_Data_In" pin at the Terminal Equipment)
upon the rising edge of RxClk. This will still permit
the Terminal Equipment with a “RxSer” to “RxClk” set-
up time of approximately 6ns; and a hold time fo 14 to
16ns. As the Terminal Equipment samples "RxSer"
with each rising edge of "RxClk" it should also be
sampling the following signals.
• RxFrame
• RxOHInd
The Need for sampling "RxFrame"
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