XRT74L73 Datasheet, PDF (278/488 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
or clears the AIS defects. Hence, the current
state of the AIS defect can be determined by
reading the state of Bit 7 (RxAIS), 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
0
0
0
0
0
0
0
If the AIS Condition is TRUE
1. The Local Terminal Equipment should transmit a
FERF (Far-End Receive Failure) to the Remote
Terminal Equipment. The XRT74L73 Framer IC
automatically supports this action via the FERF-
upon-AIS 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.
If the AIS Condition is FALSE
1. The Local Terminal Equipment should cease
transmitting a FERF (Far-End Receive Failure)
indicator to the Remote Terminal Equipment.
The XRT74L73 Framer IC automatically supports
this action via the FERF-upon-AIS feature.
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE) to the Remote Ter-
minal, indicates that the Service Affecting condi-
tion no longer exists.
4.3.6.2.4 The Change of State of Receive Idle
Interrupt
If the Change of State on Receive Idle Interrupt is en-
abled, then the XRT74L73 Framer IC will generate an
interrupt in response to either of the following condi-
tions.
1. When the XRT74L73 Framer IC detects an Idle
pattern, in the incoming DS3 data stream, and
2. When the XRT74L73 Framer IC no longer
detects the Idle pattern in the incoming DS3 data
stream.
Conditions causing the XRT74L73 Framer IC to
declare an Idle condition
• If the Receive DS3 Framer block (within the
XRT74L73 Framer IC) detects at least 63 DS3
frames, which contains the Idle pattern.
Conditions causing the XRT74L73 Framer IC to
clear the Idle condition.
• Whenever, the Receive DS3 Framer block detects
63 DS3 frames, which do not contain the Idle pat-
tern.
Enabling and Disabling the Change of State on
Receive Idle Interrupt:
To enable or disable the Change of State on Receive
Idle Interrupt, write the appropriate value into Bit 4
(Idle Interrupt Enable) within the RxDS3 Interrupt En-
able Register, as illustrated below.
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 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
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 Idle In-
terrupt
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