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XRT79L71
PRELIMINARY
193
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
The LOS Defect Clearance Criteria
Once the Digital LOS Detector (within the Receive DS3/E3 LIU Block) declares the LOS Defect condition it will
proceed to search the incoming DS3 data-stream for DS3 pulses. In short, the Digital LOS Detector will clear
the LOS Defect Condition, if it detects at least a 33% pulse density within the DS3 data-stream.
However, more specifically, the Digital LOS Defect will only clear the LOS Defect condition if it detects at least
10 pulses within each of 5 consecutive 32-bit period blocks (thereby resulting in a pulse density of 33%).
The Receive DS3/E3 LIU Block will indicate (to the outside world) that the Digital LOS Detector is clearing the
LOS defect condition, by doing all of the following.
It will set Bit 5 (Digital LOS Defect Declared), within the LIU Alarm Status Register to "1" as depicted below.
NOTE: The state of Bit 1 (Receive LOS Defect Declared - Receive DS3/E3 LIU Block) within the LIU Alarm Status Register
(at this point) will depend upon the state of Bit 4 (Analog LOS Defect Declared).
It MAY generate the Change of LOS Condition Interrupt.
NOTES:
1.
The XRT79L71 will indicate that it is generating this interrupt by (1) asserting the Interrupt Request output pin, and
(2) by setting Bit 1 (Change of LOS Condition Interrupt), within the LIU Interrupt Status Register to "1" as depicted
below.
2.
The XRT79L71 will only generate this Change of LOS Condition Interrupt if the Digital LOS Detector is also NOT
currently declaring the LOS defect condition.
Disabling the Digital LOS Detector
By default, both the Analog and Digital LOS detectors will be enabled. However, if (for some reason) the user
wishes to disable the Digital LOS Detector, then the user can accomplish this by setting Bit 5 (Disable DLOS
Detector), within the LIU Receive Control Register to "1" as depicted below.
LIU Alarm Status Register (Address = 0x1303)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Digital LOS
Defect
Declared
Analog LOS
Defect
Declared
FL (FIFO
Limit) Alarm
Declared
Receive LOL
Defect
Declared
Receive LOS
Defect
Declared -
Receive
DS3/E3 LIU
Block
Transmit
DMO Condi-
tion
R/O
0
1
0
X
0
LIU Interrupt Status Register (Address = 0x1302)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Change of
FL
Condition
Interrupt
Status
Change of
LOL
Condition
Interrupt
Status
Change of
LOS
Condition
Interrupt
Status
Change of
DMO
Condition
Interrupt
Status
R/O
RUR
0
1
0