XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
277
ue into Bit 1 (OOF Interrupt Enable) within the RxDS3
Interrupt Enable Register, as illustrated below.
Setting this bit-field to “1” enables this interrupt. Con-
versely, setting this bit-field to “0” disables this inter-
rupt.
Servicing the Change of State on Receive OOF In-
terrupt
Whenever the XRT74L73 Framer IC detects this in-
terrupt, it will do all of the following.
It will assert the Interrupt Request output pin (INT)
by driving this pin "Low".
It will set Bit 1 (OOF Interrupt Status), within the
RxDS3 Interrupt Status Register to “1”, as indicated
below.
Whenever the Terminal Equipment encounters a
Change in OOF on Receive Interrupt, then it should
do the following.
1.
It should determine the current state of the OOF
condition. Recall, that this interrupt can gener-
ated, whenever the XRT74L73 Framer declares
or clears the OOF defects. Hence, the current
state of the OOF defect can be determined by
reading the state of Bit 4 (RxOOF), within the
RxDS3 Configuration & Status Registers, as illus-
trated below.
If OOF is TRUE.
1.
It should transmit a FERF (Far-End Receive Fail-
ure) to the Remote Terminal Equipment. The
XRT74L73 Framer IC automatically supports this
action via the FERF-upon-OOF feature.
2.
It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE), to the Remote Ter-
minal, indicating that a Service Affecting condi-
tion has been detected in the Local Terminal
Equipment.
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
0
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
RxAIS
RxLOS
RxIdle
RxOOF
Reserved
Framing On
Parity
FSync
Algo
MSync
Algo
RO
RO
RO
RO
RO
R/W
R/W
R/W
0
0
0
0
0
0
0
0