XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
345
Writing a “0” into this bit-field causes the Receive E3
Framer block to reside in the OOF Condition state for
at most 24 E3 frame periods. Writing a “1” into this
bit-field causes the Receive E3 Framer block to re-
side in the OOF Condition state for at most 8 E3
frame periods.
LOF (Loss of Framing) Condition State
If the Receive E3 Framer block enters the LOF Con-
dition state, then the following things will happen.
The Receive E3 Framer block will discard the most
recent frame synchronization and,
The Receive E3 Framer block will make an uncon-
ditional transition to the FAS Pattern Search state.
The Receive E3 Framer block will notify the Micro-
processor/Microcontroller of its transition to the
LOF Condition state, by generating the Change in
LOF Condition interrupt. When this occurs, Bit 2
(LOF Interrupt Status), within the Rx E3 Interrupt
Status Register - 1 will be set to “1”, as depicted
below.
Finally, the Receive E3 Framer block will also inform
the external circuitry of this transition to the LOF Con-
dition state by toggling the RxLOF output pin "High”.
5.3.2.2
The Framing Maintenance Mode
Once the Receive E3 Framer block enters the In-
Frame state, then it will notify the Microprocessor/Mi-
crocontroller of this fact by generating both the
Change in OOF Condition and Change in LOF Condi-
tion Interrupts. When this happens, bits 2 and 3 (LOF
Interrupt Status and OOF Interrupt Status) will be set
to “1”, as depicted below.
Additionally, the Receive E3 Framer block will inform
the external circuitry of its transition to the In-Frame
state by toggling both the RxOOF and RxLOF output
pins "Low”.
Finally, the Receive E3 Framer block will negate both
the RxOOF and the RxLOF bit-fields within the Rx E3
Configuration & Status Register, as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
Not Used
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Not Used
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
1
0
0
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Not Used
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
1
1
0
0