XRT72L56 Datasheet, PDF (467/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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PRELIMINARY
XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
the RxE3 Interrupt Enable Register - 1, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
RO
0
BIT 6
Not Used
RO
0
BIT 5
RO
0
BIT 4
COFA
Interrupt
Enable
R/W
0
BIT 3
OOF
Interrupt
Enable
R/W
0
BIT 2
LOF
Interrupt
Enable
R/W
0
BIT 1
LOS
Interrupt
Enable
R/W
X
BIT 0
AIS
Interrupt
Enable
R/W
0
Setting this bit-field to “1” enables this interrupt. Con-
versely, setting this bit-field to “0” disables this inter-
rupt.
Servicing the Change in Receive OOF Condition
Interrupt
Whenever the XRT72L56 Framer IC detects this in-
terrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
• It will set Bit 3 (OOF Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
RO
0
BIT 6
Not Used
RO
0
BIT 5
RO
0
BIT 4
COFA
Interrupt
Status
RUR
0
BIT 3
OOF
Interrupt
Status
RUR
0
BIT 2
LOF
Interrupt
Status
RUR
0
BIT 1
LOS
Interrupt
Status
RUR
1
BIT 0
AIS
Interrupt
Status
RUR
0
Whenever the user’s system encounters the Change
in Receive OOF Condition Interrupt, then it should do
the following.
1. It should determine the current state of the OOF
condition. Recall, that this interrupt can be gen-
erated, whenever the XRT72L56 Framer IC
declares or clears the OOF defect. Hence, the
user can determine the current state of the LOS
defect by reading the state of Bit 5 (RxOOF)
within the Rx E3 Configuration and Status Regis-
ter - 2, as illustrated below.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
Rx LOF Algo
R/W
X
BIT 6
RxLOF
RO
X
BIT 5
RxOOF
RO
X
BIT 4
RxLOS
RO
X
BIT 3
RxAIS
RO
X
BIT 2
RxPld Unstab
RO
X
BIT 1
Rx
TMark
RO
X
BIT 0
RxFERF
RO
X
If the OOF state is TRUE
1. It should transmit a FERF (Far-End-Receive Fail-
ure) indicator to the Remote Terminal Equipment.
The XRT72L56 Framer IC automatically supports
this action via the FERF-upon-OOF feature.
If the OOF state is FALSE
1. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. The
XRT72L56 Framer IC automatically supports this
action via the FERF-upon-OOF feature.
6.3.6.2.3 The Change in Receive LOF Condi-
tion Interrupt
If the Change in Receive LOF Condition Interrupt is
enabled, then the XRT72L56 Framer IC will generate
an interrupt in response to either of the following con-
ditions.
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