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PRELIMINARY
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L56
REV. P1.1.2
246
Servicing the Change of State on Receive FERF
Interrupt
Whenever the XRT72L56 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 "High".
It will set Bit 3 (FERF Interrupt Status), within the
Rx DS3 Interrupt Status Register, to “1”, as indi-
cated below.
Whenever the Terminal Equipment encounters a
Change in FERF Condition on Receive Interrupt, it
should do the following.
1.
It should determine the current state of the FERF
condition. Recall, that this interrupt can gener-
ated, whenever the XRT72L56 Framer declares
or clears the FERF condition. Hence, the user
can determine the current state of the FERF con-
dition by reading the state of Bit 5 (RxIdle), within
the RxDS3 Configuration & Status Registers, as
illustrated below
4.3.6.2.6
Interrupt
If the Change of State of Receive AIC Interrupt is en-
abled, then the XRT72L56 Framer IC will generate an
interrupt, anytime the Receive DS3 Framer block has
detected a change in the value of the AIC bit, within
the incoming DS3 data stream.
The Change of State of Receive AIC
Enabling and Disabling the Change of State of
Receive AIC Interrupt:
The user can enable or disable the Change of State
on Receive AIC Interrupt, by writing the appropriate
value into Bit 2 (AIC Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
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 AIC In-
terrupt
Whenever the XRT72L56 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 "High".
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
RUR
0
LOS
Interrupt
Status
RUR
0
AIS
Interrupt
Status
RUR
0
Idle Interrupt
Status
FERF
Interrupt
Status
RUR
1
AIC
Interrupt
Status
RUR
0
OOF
Interrupt
Status
RUR
0
P-Bit Error
Interrupt
Status
RUR
0
RUR
0
RXDS3 STATUS REGISTER (ADDRESS = 0X11)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Reserved
RO
0
RxFERF
RO
0
RxAIC
RO
0
RxFEBE[2:0]
RO
0
RO
0
RO
0
RO
0
RO
0
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
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
Enable
R/W
0
LOS
Interrupt
Enable
R/W
0
AIS
Interrupt
Enable
R/W
0
Idle Interrupt
Enable
FERF
Interrupt
Enable
R/W
0
AIC
Interrupt
Enable
R/W
0
OOF
Interrupt
Enable
R/W
0
P-Bit Error
Interrupt
Enable
R/W
0
R/W
0