XRT72L13 Datasheet, PDF (261/370 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
FIGURE 73. ILLUSTRATION OF THE "TERMINAL EQUIPMENT" BEING INTERFACED TO THE "TRANSMIT PAYLOAD DATA
INPUT INTERFACE" BLOCK (OF THE XRT72L13) FOR MODE 6 (NIBBLE-PARALLEL/LOCAL-TIMED/FRAME-MASTER)
OPERATION
44.736MHz Clock Source
DS3_Nib_Clock_In
DS3_Data_Out[3:0]
Tx_Start_of_Frame
11.184MHz
4
VCC
TxInClk
TxNibClk
TxNib[3:0]
TxNibFrame
Terminal Equipment
NibInt
XRT72L13 DS3 Framer
Mode 6, Operation of the Terminal Equipment
In Figure 73 both the Terminal Equipment and the
XRT72L13 will be driven by an external 11.184MHz
clock signal. The Teriminal Equipment will receive
the 11.184MHz clock signal via the
"DS3_Nib_Clock_In" input pin. The XRT72L13 will
output the 11.184MHz clock signal via the "TxNibClk"
output pin.
The Terminal Equipment will serially output the data
on the "DS3_Data_Out[3:0]" pins upon the rising
edge of the signal at the "DS3_Clock_In" input pin.
The XRT72L13 will latch the data, residing on the
"TxNib[3:0] input pins, on the rising edge of the "Tx-
NibClk" signal.
In this case the XRT72L13 has the responsibility of
providing the "framing reference" signal by pulsing
the "TxFrame" output pin (and in turn the
"Tx_Start_of_Frame" input pin of the Terminal Equip-
ment) "high" for one bit-period, coincident with the
last bit within a given DS3 frame.
Finally, the XRT72L13 will always internally generate
the "Overhead" bits, when it is operating in both the
"DS3" and "Nibble-parallel" modes. The XRT72L13
will pull the "TxOHInd" input pin "low".
The behavior of the signals between the XRT72L13
and the Terminal Equipment for "DS3 Mode 6" Opera-
tion is illustrated in Figure 74 .
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