XRT74L73 Datasheet, PDF (372/488 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
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
COFA
OOF
LOF
LOS
AIS
Interrupt Status Interrupt Status Interrupt Status Interrupt Status Interrupt Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
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
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 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
If the LOS state is TRUE
1. It should transmit a FERF (Far-End-Receive Fail-
ure) indicator to the Remote Terminal Equipment.
Please see Section 4.2.4.2.1.3 on how to config-
ure the XRT74L73 to transmit a FERF indicator to
the Remote Terminal Equipment.
If the LOS state is FALSE
1. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. Please see
Section 4.2.4.2.1.3 on how to control the state of
the “A” bit, which is transmitted on each outbound
E3 frame.
5.3.6.2.2 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 bit 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 FAS
Pattern Verification state to the In-Frame state (see
Figure 115).
• If the Receive E3 Framer block transitions from the
OOF Condition state to the In-Frame state (see Fig-
ure 115).
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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