XRT74L73 Datasheet, PDF (476/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
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 LOS Condition Interrupt, then it should do
the following.
1. It should determine the current state of the LOS
condition. Recall, that this interrupt can be gen-
erated, whenever the XRT74L73 Framer IC
declares or clears the LOS defect. Hence, the
user can determine the current state of the LOS
defect by reading the state of Bit 4 (RxLOS)
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
BIT 6
RxLOF
R/W
RO
X
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 LOS state is TRUE
1. It should transmit a FERF (Far-End-Receive Fail-
ure) indicator to the Remote Terminal Equipment.
The XRT74L73 Framer IC automatically supports
this action via the FERF-upon-LOS feature.
If the LOS state is FALSE
1. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. The
XRT74L73 Framer IC automatically supports this
action via the FERF-upon-LOS feature.
6.3.6.2.2 The Change in Receive OOF Condi-
tion Interrupt
If the Change in Receive OOF Condition Interrupt is
enabled, then the XRT74L73 Framer IC will generate
an interrupt in response to either of the following con-
ditions.
1. When the XRT74L73 Framer IC declares an
OOF (Out of Frame) Condition, and
2. When the XRT74L73 Framer IC clears the OOF
condition.
Conditions causing the XRT74L73 Framer IC to
declare an OOF Condition.
• If the Receive E3 Framer block (within the
XRT74L73 Framer IC) detects Framing Byte errors,
within four consecutive incoming E3 frames.
Conditions causing the XRT74L73 Framer IC to
clear the OOF Condition.
• If the Receive E3 Framer block (within the
XRT74L73 Framer IC) transitions from the FA1,
FA2 Octet Verification state to the In-Frame state
(see Figure 175).
• If the Receive E3 Framer block transitions from the
OOF Condition state to the In-Frame state (see Fig-
ure 175).
Enabling and Disabling the Change in Receive
OOF Condition Interrupt
The user can enable or disable the Change in Re-
ceive OOF Condition Interrupt, by writing the appro-
priate value into Bit 3 (OOF Interrupt Enable), within
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