XRT74L73 Datasheet, PDF (275/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

PRELIMINARY
XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
• It will set Bit 6 (LOS Interrupt Status) within the
RxDS3 Interrupt Status register to “1”, as illustrated
below.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
0
1
0
0
0
BIT 2
AIC
Interrupt
Status
RUR
0
BIT 1
OOF
Interrupt
Status
RUR
0
BIT 0
P-Bit Error
Interrupt
Status
RUR
0
Whenever the user’s system encounters the Change
of LOS on Receive Interrupt, then it should do the fol-
lowing.
1. It should determine the current state of the LOS
condition. Recall, that this interrupt can gener-
ated, whenever the XRT74L73 Framer declares
or clears the LOS defects. Hence, the current
state of the LOS defect can be determined by
reading the state of Bit 6 (RxLOS), within the
RxDS3 Configuration & Status Registers, as illus-
trated below.
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 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
1
0
0
0
0
0
0
If the LOS State 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-LOS feature.
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE), to the Remote Ter-
minal, indicating that a Loss of Signal condition
has been declared.
If the LOS State is FALSE
1. It should cease transmitting a FERF indicator to
the Remote Terminal Equipment. The XRT74L73
Framer IC automatically supports this action via
the FERF-upon-LOS feature.
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE), to the Remote Ter-
minal Equipment, indicating that the Loss of Sig-
nal condition has been cleared.
4.3.6.2.2 The Change of State on Receive OOF
Interrupt
If the Change of State on Receive OOF (Out-of-
Frame) Interrupt is enabled, then the XRT74L73
Framer IC will generate an interrupt in response to ei-
ther of the following conditions.
1. When the XRT74L73 Framer IC declares an
OOF (Out of Frame) condition, and
2. When the XRT74L73 Framer IC clears the OOF
(Out of Frame) condition.
Conditions causing the XRT74L73 Framer IC to
declare an OOF condition
• If the Receive DS3 Framer block (within the
XRT74L73 Framer IC) detects at least either 3 or 6
F-bit errors, in the last 16 F-bits.
Conditions causing the XRT74L73 Framer IC to
clear the OOF condition.
• Whenever, the Receive DS3 Framer block transi-
tions from the M-Bit Search into the In-Frame state
(within the Frame Acquisition/Maintenance State
Machine Diagram).
Enabling and Disabling the Change of State on
Receive OOF Interrupt:
The Change of State on Receive OOF Interrupt can
be enabled or disabled by writing the appropriate val-
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