
XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
PRELIMINARY
REV. P1.0.1
348
Asserting the RxLOS output pin (e.g., toggling it
"High”).
Setting Bit 4 (RxLOS) of the Rx E3 Configuration &
Status Register to “1” as depicted below.
The Receive E3 Framer block will generate a
Change in LOS Condition interrupt request. Upon
generating this interrupt request, the Receive E3
Framer block will assert Bit 1 (LOS Interrupt Status
within the Rx E3 Framer Interrupt Status Register -
1, as depicted below.
Clearing the LOS Condition
The Receive E3 Framer block will clear the LOS con-
dition when it encounters a stream of 32 bits that
does not contain a string of 4 consecutive zeros.
When the Receive E3 Framer block clears the LOS
condition, then it will notify the Microprocessor and
the external circuitry of this occurrence by:
Generating the Change in LOS Condition Interrupt
to the Microprocessor.
Clearing Bit 4 (RxLOS) within the Rx E3 Configura-
tion & Status Register, as depicted below.
Clear the RxLOS output pin (e.g., toggle it "Low”).
5.3.2.8
The AIS (Alarm Indication Status) Con-
dition
Declaring the AIS Condition
The Receive E3 Framer block will identify and de-
clare an AIS condition, if it detects an All Ones” pat-
tern in the incoming E3 data stream. More specifical-
ly, the Receive E3 Framer block will declare an AIS
Condition if 7 or less “0’s” are detected in each of 2
consecutive E3 frames.
If the Receive E3 Framer block declares an AIS Con-
dition, then it will do the following.
Generate the Change in AIS Condition Interrupt to
the Microprocessor. Hence, the Receive E3
Framer block will assert Bit 0 (AIS Interrupt Status)
within the Rx E3 Framer Interrupt Status register -
1, 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
1
0
0
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
0
0
1
0
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