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PRELIMINARY
XRT79L71
152
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
Requirements Associated with the "Local-Timing/Asynchronous" Mode
If the XRT79L71 is configured to operate in the "Local-Timing/TxFrameRef" Mode, then the following must be
done.
Apply a 44.736MHz clock signal to the TxInClk input pin (Ball C10).
Apply a 9.398kHz clock signal to the TxFrameRef input pin (Ball A11).
This 9.398kHz clock signal (that is being applied to the TxFrameRef input pin) must be synchronous with the
44.736MHz clock signal (that is being applied to the TxInClk input pin).
NOTE: Configuring the XRT79L71 to operate in the "Local-Timing/TxFrameRef" Mode, is synonymous with configuring the
Transmit Payload Data Input Interface block into "Mode 2" (for Serial-Mode Applications - see
Section 4.2.1.2) or
4.2.5.7.3
Loop-Timing Mode
If the XRT79L71 is configured to operate in the "Loop-Timing Mode, then all of the following is true.
The Transmit DS3 Framer block will use the "Recovered" clock signal (from the Receive DS3/E3 LIU Block)
as its timing source, for generating and transmitting the outbound DS3 traffic to the remote terminal
equipment.
DS3 Frame Generation (e.g., the instant whenever the Transmit DS3 Framer block begins to generate and
transmit a new DS3 frame) is asynchronous with respect to any externally supplied clock signal to the
XRT79L71.
Configuring the XRT79L71 to operate in the Loop-Timing Mode
To XRT79L71 to operate in the "Local-Timing/TxFrameRef" Mode set Bits 1 and 0 (TimRefSel[1:0]) within the
Framer Operating Mode Register to "[0, 0]" as depicted below.
Framer Operating Mode Register (Address = 0x1100)
Requirements Associated with the "Loop-Timing" Mode
If the XRT79L71 is configured to operate in the "Loop-Timing" Mode, then the following must be done.
Framer Operating Mode Register (Address = 0x1100)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framer
Local Loop
Back
IsDS3
Internal
LOS
Enable
RESET
Direct
Map
ATM
Frame
Format
TimRefSel[1:0]
R/W
0
1
0
1
0
1
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framer
Local Loop
Back
IsDS3
Internal
LOS
Enable
RESET
Direct
Map
ATM
Frame
Format
TimRefSel[1:0]
R/W
0
1
0
1
0