XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
PRELIMINARY
REV. P1.0.1
280
Whenever the XRT74L73 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 4 (Idle Interrupt Status), within the Rx
DS3 Interrupt Status Register to “1”, as indicated
below.
Whenever the Terminal Equipment encounters the
Change in Idle Condition Receive Interrupt, it should
do the following.
1.
It should determine the current state of the Idle
condition. Recall, that this interrupt can gener-
ated, whenever the XRT74L73 Framer declares
or clears the Idle condition. Hence, the current
state of the Idle condition can be determined by
reading the state of Bit 5 (RxIdle), within the
RxDS3 Configuration & Status Registers, as illus-
trated below
4.3.6.2.5
Interrupt
If the Change of State on Receive FERF 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 detects the
FERF indicator, in the incoming DS3 data stream,
and
2.
When the XRT74L73 Framer IC no longer
detects the FERF indicator, in the incoming DS3
data stream.
The Change of State of Receive FERF
Conditions causing the XRT74L73 Framer IC to
declare an FERF (Far-End-Receive Failure) condi-
tion
If the Receive DS3 Framer block (within the
XRT74L73 Framer IC) detects some incoming DS3
frames with both of the “X” bits set to “0”.
Conditions causing the XRT74L73 Framer IC to
clear the FERF condition.
Whenever, the Receive DS3 Framer block starts to
detect some incoming DS3 frames, in which the “X”
bits are not set to “0”.
Enabling and Disabling the Change of State on
Receive FERF Interrupt:
To enable or disable the Change of State on Receive
FERF Interrupt, write the appropriate value into Bit 3
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
0
0
0
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
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