XRT72L13 Datasheet, PDF (338/370 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
The XRT72L13 will pulse the "RxFrame" output pin
"high" for one "nibble-period" coincident with it driving
the very first nibble, within a given "inbound" DS3
frame, via the "RxNib[3:0] output pins.
Interfacing the XRT72L13 the Terminal Equip-
ment.
Figure 114 presents a simple illustration as how the
user should interface the XRT72L13 to that terminal
equipment which processes "Receive Direction" pay-
load data.
FIGURE 114. ILLUSTRATION OF THE XRT72L13 DS3/E3 FRAMER IC BEING INTERFACED TO THE RECEIVE SECTION
OF THE TERMINAL EQUIPMENT (NIBBLE-MODE OPERATION)
Rx_DS3_Clock_In
DS3_Data_In[3:0]
Rx_Start_of_Frame
11.184 MHz Clock Signal
RxClk
RxNib[3:0]
RxFrame
RxLineClk
44.736 MHz
Clock Source
Terminal Equipment
(Receive Payload Section)
XRT72L13 DS3 Framer
Required Operation of the Terminal Equipment
The XRT72L13 will update the data on the "Rx-
Nib[3:0]" line, upon the falling edge of "RxClk".
Hence, the Terminal Equipment should sample the
data on the "RxNib[3:0]" output pins (or the
"DS3_Data_In[3:0]" input pins at the Terminal Equip-
ment) upon the rising edge of "RxClk". As the Termi-
nal Equipment samples "RxSer" with each rising
edge of "RxClk" it should also be sampling the "Rx-
Frame" signal.
The Need for Sampling "RxFrame"
The XRT72L13 will pulse the "RxFrame" output pin
"high" coincident with it driving the very first nibble of
a given DS3 frame, onto the "RxNib[3:0]" output pins.
If knowledge of the "DS3 Frame Boundaries" is im-
portant for the operation of the Terminal Equipment,
then this is a very important signal for it to sample.
NOTE: For DS3/Nibble-Parallel Mode Operation, none of
the Overhead bits will be output via the “RxNib[3:0]” output
pins. Hence, the “RxOH_Ind” output pin will be in-active in
this mode.
The Behavior of the Signals between the "Receive
Payload Data Output Interface" block and the
"Terminal Equipment"
The behavior of the signals between the XRT72L13
and the Terminal Equipment for "DS3 Nibble-Mode"
operation is illustrated in Figure 115 .
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