XRT72L13 Datasheet, PDF (258/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
áç
PRELIMINARY
FIGURE 71. ILLUSTRATION OF THE "TERMINAL EQUIPMENT" BEING INTERFACED TO THE "TRANSMIT PAYLOAD DATA
INPUT INTERFACE" BLOCK (OF THE XRT72L13) FOR MODE 5 (NIBBLE-PARALLEL/LOCAL-TIMED/FRAME-SLAVE)
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]
TxFrameRef
Terminal Equipment
NibInt
XRT72L13 DS3 Framer
Mode 5 Operation of the Terminal Equipment
In Figure 71 both the Terminal Equipment and the
XRT72L13 will be driven by an external 11.184MHz
clock signal. The Terminal 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.
(Note: The "DS3_Data_Out[3:0]" output pins of the
Terminal Equipment is electrically connected to the
"TxNib[3:0] input pins.). The XRT72L13 will latch the
data, residing on the "TxNib[3:0] input pins, on the ris-
ing edge of the "TxNibClk" signal.
In this case, the Terminal Equipment has the respon-
sibility of providing the "framing reference" signal by
pulsing the "Tx_Start_of_Frame" output pin (and in
turn, the "TxFrameRef" input pin of the XRT72L13)
"high" for one bit-period, coincident with the first nib-
ble of a new DS3 frame. Once the XRT72L13 detects
the rising edge of the input at its "TxFrameRef" input
pin; it will begin generation of a new 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 5 Opera-
tion is illustrated in Figure 72 .
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