![](http://datasheet.mmic.net.cn/Exar-Corporation/XRT79L71IB-F_datasheet_100145/XRT79L71IB-F_601.png)
PRELIMINARY
XRT79L71
586
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
If the XRT79L71 has been configured to operate in the "LIU Remote Loop-back" Mode, then the output of the
"Clock and Data Recovery" block (within the Receive DS3/E3 LIU Block) will be internally routed to the input of
the "Timing Control" block (within the Transmit DS3/E3 LIU Block).
Figure 269 presents an illustration of the Functional Block Diagram of the XRT79L71, when it is configured to
operate in the "LIU Remote Loop-back" Mode.
SOME THINGS TO NOTE ABOUT THE LIU REMOTE LOOP-BACK MODE:
1.
Whenever the XRT79L71 is configured to operate in the "LIU Remote Loop-back" Mode, the "Receive
signal will still be routed to all down-stream circuitry (e.g., such as the Receive DS3/E3 Framer block,
etc.). A replica of this "Receive Input" signal will also be routed to the "Transmit Direction" within the
device.
2.
Whenever the XRT79L71 is configured to operate in the "LIU Remote Loop-back" Mode, then the
Transmit DS3/E3 LIU Block will ignore any data that is being generated by the Transmit DS3/E3 Framer
block.
3.
The LIU Remote 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 269. ILLUSTRATION OF THE FUNCTIONAL BLOCK DIAGRAM OF THE XRT79L71 (WHEN CONFIGURED TO
OPERATE IN THE
"CLEAR-CHANNEL FRAMER" MODE) WITH THE "LIU REMOTE 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 Remote Loop-back
Path