
XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
PRELIMINARY
REV. P1.0.1
246
2.
Generate a Change in Idle Status Interrupt
Request to the local μP/μC.
The Receive DS3 Framer block will clear the Idle
Condition if it has detected a sufficient number of
Non-Idle M-frames, such that this Up/Down Counter
reaches the value 0.
4.3.2.5.4
The Detection of (FERF) or Yellow
Alarm Condition
The Receive DS3 Framer block will identify and de-
clare a Yellow Alarm condition or a Far-End Receive
Failure (FERF) condition, if it starts to receive DS3
frames with both of its X-bits set to 0.
When the Receive DS3 Framer block detects a FERF
condition in the incoming DS3 frames, then it will then
do the following.
1.
It will assert the RxFERF (bit-field 4) within the Rx
DS3 Status Register, as depicted below.
This bit-field will remain asserted for the duration that
the Yellow Alarm condition exists.
2.
The Receive DS3 Framer block will also generate
a Change in FERF Status interrupt to the μP/μC.
Consequently, the Receive DS3 Framer block will
also assert the FERF Interrupt Status bit, within
the Rx DS3 Interrupt Status Register, as depicted
below.
The Receive DS3 Framer block will clear the FERF
condition, when it starts to receive Receive DS3
Frames that have its X bits set to 1.
N
OTE
:
The FERF indicator is frequently referred to as the
Yellow Alarm.
4.3.2.5.5
The Detection of the FEBE Events
As described in Section
4.2.4.2.1.9
, a given Terminal
Equipment will set the three FEBE (Far-End Block Er-
ror) bit-fields to the value [1, 1, 1] (e.g., all of the
FEBE bits are set to “1”) within the outbound DS3
frames if, all of the following conditions are true about
the incoming DS3 line signal.
The Receive Circuitry (within the Terminal Equip-
ment) detects no P-Bit Errors.
The Receive Circuitry (within the Terminal Equip-
ment) detects no CP-Bit Errors.
If the Receive Section of the Terminal Equipment de-
tects any P or CP bit errors, then the Transmit Sec-
tion of the Terminal Equipment will set the three
RX DS3 CONFIGURATION AND 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
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
R/O
R/O
R/O
R/O
R/W
R/W
R/W
R/W
X
X
1
X
X
X
X
X
RX DS3 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
Not Used
Rx FERF
RxAIC
RxFEBE [2]
RxFEBE [1]
RxFEBE [0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
1
X
X
X
X
RX DS3 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 Inter-
rupt Status
FERF Inter-
rupt Status
AIC Interrupt
Status
OOF Inter-
rupt Status
P-Bit Inter-
rupt Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
X
X
X
1
X
X
X