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PRELIMINARY
XRT79L71
378
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
Transitioning into the "LOF State"
However, if the Receive E3 Framer block resides in the "OOF State" for more than the "User-Selectable"
number of E3 frame periods (without being able to locate the FAS Pattern), then it (the Receive E3 Framer
block) will automatically transition into the "LOF State".
Selecting the number of E3 Frame Periods, before transitioning into the "LOF State"
The user can configure the Receive E3 Framer block to reside in the "OOF State" and search the incoming E3
data-stream for each 8 or 24 E3 frame periods, prior to transitioning into the "LOF State". The user can
accomplish this configuration setting by writing the appropriate value into Bit 7 (Receive LOF Algo), within the
"Receive E3 Configuration and Status Register # 2" as depicted below.
Setting this bit-field to "0" configures the Receive E3 Framer block to reside within the "OOF State" for up to 24
E3 frame periods before transitioning into the "LOF State". Conversely, setting this bit-field to "1" configures
the Receive E3 Framer block to reside within the "OOF State" for up to 8 E3 frame periods before transitioning
into the "LOF State".
The "LOF" (Loss of Frame) State
If the Receive E3 Framer block enters the "LOF Condition" state, then the following things will happen.
The Receive E3 Framer block will discardc the most recent frame synchronization that it had, and
The Receive E3 Framer block will make an unconditional transition to the "FAS Pattern Search" state, within
the "Receive E3 Framer Block's - Frame Acquisition/Maintenance Algorithm".
Additionally, the Receive E3 Framer block will notify the Microprocessor/Microcontroller of this transition into
the "LOF State", by doing the following.
Declaring the "LOF Defect Condition"
The Receive E3 Framer block will indicate that it is declaring the "LOF Defect Condition" by setting Bit 6 (LOF
Defect Condition Declared), within the "Receive E3 Configuration and Status Register # 2" to "1", as depicted
below.
Receive E3 Interrupt Status Register # 1 - G.751 (Address = 0x1114)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
COFA
Interrupt
Status
Change in
OOF Defect
Condition
Interrupt
Status
Change in
LOF Defect
Condition
Interrupt
Status
Change in
LOS Defect
Condition
Interrupt
Status
Change in
AIS Defect
Condition
Interrupt
Status
R/O
RUR
0
1
0
Receive E3 Configuration and Status Register # 2 - G.751 (Address = 0x1111)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxLOF
Algo
LOF
Defect
Condition
Declared
OOF
Defect
Condition
Declared
LOS
Defect
Condition
Declared
AIS
Defect
Condition
Declared
Unused
FERF/RDI
Defect
Condition
Declared
R/W
R/O
X
1
0
1