XRT72L13 Datasheet, PDF (250/370 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
If the XRT72L13 has been configured to operate in
this mode, then the XRT72L13 will function as fol-
lows.
A. Local-Timing - Uses the "TxInClk" signal as the
Timing Reference
In this mode, the Transmit Section of the XRT72L13
will use the TxInClk signal as its timing reference.
B. Serial Mode
The XRT72L13 will receive the DS3 payload data, in
a serial manner, via the "TxSer" input pin. The
"Transmit Payload Data Input Interface" (within the
XRT72L13) will latch this data into its circuitry, on the
rising edge of the "TxInClk" input clock signal.
C. Delineation of "outbound" DS3 frames (Frame
Slave Mode)
The Transmit Section (of the XRT72L13) will use the
"TxInClk" input as its timing reference, and will use
the "TxFrameRef" input signal as its "framing refer-
ence". In other words, the Transmit Section of the
XRT72L13 will initiate frame generation upon the ris-
ing edge of the "TxFrameRef" input signal).
D. Sampling of payload data, from the Terminal
Equipment
In Mode 2, the XRT72L13 will sample the data, at the
"TxSer" input pin, on the rising edge of "TxInClk".
Interfacing the "Transmit Payload Data Input In-
terface" block (of the XRT72L13) to the Terminal
Equipment for Mode 2 Operation
Figure 65 presents an illustration of the "Transmit
Payload Data Input Interface" block (within the
XRT72L13) being interfaced to the Terminal Equip-
ment, for "Mode 2" operation.
FIGURE 65. ILLUSTRATION OF THE "TERMINAL EQUIPMENT" BEING INTERFACED TO THE "TRANSMIT PAYLOAD DATA
INPUT INTERFACE" BLOCK (OF THE XRT72L13) FOR MODE 2 (SERIAL/LOCAL-TIMED/FRAME-SLAVE) OPERATION
44.736 MHz Clock
Source
DS3_Clock_In
DS3_Data_Out
Tx_Start_of_Frame
DS3_Overhead_Ind
Terminal Equipment
TxInClk
TxSer
TxFrameRef
TxOH_Ind
NibInt
XRT72L13 DS3 Framer
Mode 2, Operation of the Terminal Equipment
As shown in Figure 65 , both the Terminal Equipment
and the XRT72L13 will be driven by an external
44.736MHz clock signal. The Terminal Equipment
will receive the 44.736MHz clock signal via its
"DS3_Clock_In" input pin, and the XRT72L13 Framer
IC will receive the 44.736MHz clock signal via the
"TxInClk" input pin.
The Terminal Equipment will serially output the "pay-
load data" of the "outbound" DS3 data stream, via the
"DS3_Data_Out" output pin, upon the rising edge of
the signal at the "DS3_Clock_In" input pin. (Note:
The "DS3_Data_Out" output pin of the Terminal
Equipment is electrically connected to the "TxSer" in-
put pin). The XRT72L13 Framer IC will latch the data,
residing on the "TxSer" input line, on the rising edge
of the "TxInClk" signal.
In this case, the Terminal Equipment has the respon-
sibility of providing the "framing reference" signal by
pulsing its "Tx_Start_of_Frame" output signal (and in
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