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PRELIMINARY
XRT79L71
372
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
The purpose of the Receive E3 Framer block (within the XRT79L71) is to accomplish the following.
To acquire and maintain frame synchronization with the incoming E3 data-stream.
To detect and declare all of the following defect/error conditions
a. LOS (Loss of Signal)
b. AIS (Alarm Indication Signal)
c. LOF (Loss of Frame)
d. FERF/RDI (Far-End Receive Failure or Remote Defect Indicator)
e. FEBE/REI (Far-End Block Error or Remote Error Indicator) Events (if configured to support BIP-4
verification)
f. BIP-4 Nibble Errors (if configured to support BIP-4 verification)
At any given time, the Receive E3 Framer block will be operating in one of two modes.
The Frame Acquisition Mode: In this mode, the Receive E3 Framer block is trying to acquire synchronization
with the incoming E3 frame, or
The Frame Maintenance Mode: In this mode, the Receive E3 Framer block is trying to maintain frame
synchronization with the incoming E3 frames.
The operation of the Receive E3 Framer block, in both the Frame Acquisition and the Frame Maintenance
Modes will be discussed, in considerable detail below.
FIGURE 173. ILLUSTRATION OF THE FUNCTIONAL BLOCK DIAGRAM OF THE RECEIVE DIRECTION CIRCUITRY, WHEN-
EVER THE
XRT79L71 HAS BEEN CONFIGURED TO OPERATE IN THE E3, ITU-T G.751 CLEAR-CHANNEL FRAMER
MODE (WITH THE "RECEIVE DS3/E3 FRAMER" BLOCK HIGHLIGHTED).
Receive
Payload Data
Input
Interface
Block
Receive
Payload Data
Input
Interface
Block
Receive
DS3/E3
Framer
Block
Receive
DS3/E3
Framer
Block
Receive
DS3/E3
LIU Block
Receive
DS3/E3
LIU Block
RxSer
RxNib[3:0]
RxClk
RRING
RTIP
Receive
Overhead Data
Input Interface
Block
Receive
Overhead Data
Input Interface
Block
RxOHClk
RxOHInd
RxOH
RxOHEnable
RxOHFrame
RxNibClk
RxFrame
Rx LAPD
Controller
Block
Rx LAPD
Controller
Block
From Microprocessor
Interface Block
Rx LAPD
Buffer
(90 Bytes)
Rx LAPD
Buffer
(90 Bytes)