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PRELIMINARY
XRT79L71
212
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
To configure the Receive DS3/E3 Framer block to declare the AIS defect condition whenever it detects the
Unframed, All Ones pattern then make sure that Bit 7 (DS3 AIS - Unframed All Ones) within the Receive DS3
Pattern Register is set to "1" as depicted below.
The Receive DS3 Framer block contains, within its circuitry, an Up/Down Counter that supports the declaration
and clearance of the AIS defect condition. The contents within this counter is initially of the value 0x00 upon
power up or reset. The counter is then incremented anytime the Receive DS3 Framer block detects an AIS
Type M-frame. This counter is decremented, or kept at zero value, whenever the Receive DS3 Framer block
detects a non-AIS type M-frame. The Receive DS3 Framer block will declare the AIS Defect Condition if this
counter reaches the value of 63 M-frames or greater. Explained another way, the AIS defect condition is
declared if the number of AIS-type M-frames is detected, such that it meets the following conditions:
(NAIS - NVALID)
63
where:
NAIS = the number of M-frames containing the AIS pattern.
NVALID = the number of M-frames not containing the AIS pattern
If at anytime, the contents of this Up/Down counter reaches the number 63, then the Receive DS3 Framer
block will do all of the following:
It will set Bit 7 (AIS Defect Declared) within the Receive DS3 Configuration and Status Register to "1", as
depicted below.
The Receive DS3 Framer block will also generate a Change in the AIS Defect Condition interrupt request, by
asserting the Interrupt Output pin (e.g., by pulling it "Low"), and setting Bit 5 (Change of AIS Defect Condition
Interrupt Status), within the Receive DS3 Interrupt Status Register to "1", as illustrated below.
Receive DS3 Pattern Register (Address = 0x112F)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
DS3 AIS
- Unframed
All Ones
DS3 AIS
-Non Stuck
Stuff
Unused
Receive LOS
Pattern
Receive DS3 Idle Pattern[3:0]
R/W
R/O
R/W
0
1
0
Receive DS3 Configuration and Status Register (Address = 0x1110)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
AIS Defect
Declared
LOS Defect
Declared
Idle Condi-
tion Detected
OOF Defect
Detected
Unused
Framing with
Valid P-Bits
F-Sync Algo
M-Sync Algo
R/O
R/W
1
0
1
0