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PRELIMINARY
XRT79L71
582
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
The Framer/Internal Remote Loop-back Mode
7.1.1
The LIU Analog Local Loop-back Mode
If the XRT79L71 has been configured to operate in the "LIU Analog Local Loop-back" Mode, then (in essence)
the signal that is being output via the "TTIP/TRING" output pads will be internally looped-back to the "RTIP/
RRING" input pads. This type of Loop-back is referred to as the "LIU Analog Local-Loop-back" Mode, because
it is the "analog" signal (that is output via the TTIP/TRING output pads) that is being looped back into the RTIP/
RRING input pads.
Figure 267 presents an illustration of the Functional Block Diagram of the XRT79L71, when it is configured to
operate in the "LIU Analog Local-Loop-back" Mode.
SOME THINGS TO NOTE ABOUT THE LIU ANALOG LOCAL LOOP-BACK MODE:
1.
Whenever the XRT79L71 is configured to operate in the "LIU Analog Local Loop-back" Mode, the
"Transmit Output" line signal will still be output to the remote terminal equipment. A replica of this
"Transmit Output" line signal will also be routed to the "RTIP/RRING" input pads of the device.
2.
Whenever the XRT79L71 is configured to operate in the "LIU Analog Local Loop-back" Mode, then it will
ignore any data that is being applied to the RTIP/RRING input pins.
3.
The LIU Analog Local Loop-back will be broken (e.g., this loop-back mode will NOT function) if the user
sets Bit 0 (TxON), within the "LIU Transmit APS/Redundancy Control" Register to "0" as depicted below.
FIGURE 267. ILLUSTRATION OF THE FUNCTIONAL BLOCK DIAGRAM OF THE XRT79L71 (WHEN CONFIGURED TO
OPERATE IN THE
CLEAR-CHANNEL FRAMER" MODE) WITH THE "LIU ANALOG LOCAL LOOP-BACK" PATH INDICATED
Transmit Payload
Data Input
Interface Block
Transmit DS3/E3
Framer Block
DS3/E3
Jitter
Attenuator
Block
DS3/E3
Jitter
Attenuator
Block
DS3/E3
Jitter
Attenuator
Block
DS3/E3
Jitter
Attenuator
Block
Receive DS3/E3
Framer Block
Receive Payload
Data Output
Interface Block
Microprocessor
Interface
TxSer
TxNib[3:0]
TxInClk
MOTO
D[7:0]
A[8:0]
IntB*
CSB*
RdB_DS
WrB_RW
Rdy_Dtck
Reset*
ALE_AS
RxSer
RxNib[3:0]
RxOutClk
Tx LAPD Buffer/
Controller
Rx LAPD Buffer/
Controller
Transmit Overhead
Input
Interface Block
Receive Overhead
Output
Interface Block
TxOHClk
TxOHIns
TxOHInd
TxOH
TxOHEnable
TxOHFrame
TxNibClk
TxFrame
RxNibClk
RxFrame
RxOHFrame
RxOH
RxOHClk
RxOHEnable
RxOHInd
Transmit
DS3/E3
LIU Block
Transmit
DS3/E3
LIU Block
Receive
DS3/E3
LIU Block
Receive
DS3/E3
LIU Block
TTIP
TRING
RTIP
RRING
Only one JA exists.
Can be configured in
Tx or Rx Path
LIU Analog Local
Loop-back Path