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PRELIMINARY
XRT79L71
192
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
4.3.1.6
The LOS Declaration and Clearance Criteria for DS3 Applications
The Receive DS3/E3 LIU Block consists of two different types of LOS (Loss of Signal) Detectors.
An Analog LOS Detector, and
A Digital LOS Detector
The Receive DS3/E3 LIU Block will declare an LOS defect condition, anytime either one of these LOS
Detectors is declaring the LOS defect condition. Therefore, the overall LOS State of the Receive DS3/E3 LIU
Block is simply the Wired-OR of the LOS States of both the Analog and Digital LOS Detectors.
Each of these LOS detectors will be discussed in detail below.
4.3.1.6.1
The Digital LOS Detector
The Digital LOS Detector functions by checking for the occurrence of pulses (which are derived from the
incoming DS3 line signal) from the Slicer Block. The LOS Defect Declaration and Clearance criteria for the
Digital LOS Detector are described below.
The LOS Defect Declaration Criteria
The Digital LOS Detector (within the Receive DS3/E3 LIU Block) will declare the LOS Defect condition anytime
it detects an absence of DS3 Pulses for 160 consecutive bit-periods. The Receive DS3/E3 LIU Block will
indicate (to the outside world) that the Digital LOS Detector is declaring the LOS defect condition, by doing all
of the following.
It will set Bits 5 (Digital LOS Defect Declared) and 1 (Receive LOS Defect Declared - Receive DS3/E3 LIU
Block), within the LIU Alarm Status Register, to "1" as depicted below.
It will generate the Change of LOS Condition Interrupt.
NOTE: 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.
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
Condition
R/O
0
1
0
1
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