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XRT79L71
PRELIMINARY
163
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
Setting this bit-field to "0" configures the Jitter Attenuator to operate in the Receive Path. Conversely, setting
this bit-field to "1" configures the Jitter Attenuator to operate in the Transmit Path.
4.2.6.2.4
Alarm Conditiions occurring within the Jitter Attenuator Block
As mentioned in
Section 4.2.6.2.1.2, the FIFO Under-run and Overflow conditions occur if the distance
between the FIFO_READ and FIFO_WRITE pointers reach 0 bits. In either of these conditions an error-
condition is said to have occurred. The XRT79L71 contains some circuitry to alert the system that the distance
between the FIFO_WRITE and FIFO_READ pointers has fallen to at least two (2) bit-positions. If this condition
were to occur, then Jitter Attenuator FIFO is on the verge of experiencing either a FIFO Under-run or Overflow
condition. In response to this condition, the XRT79L71 will notify the Line Card circuitry of this phenomenon by
declaring a FIFO Limit Alarm condition. The XRT79L71 will indicate that it is declaring a FIFO Limit Alarm
condition by doing all of the following.
a. It will set Bit 3 (FIFO Limit Alarm Declared), within the LIU Alarm Status Register, to "1" as depicted
below.
b. It will also generate the Change of FL Condition Interrupt.
The XRT79L71 will indicate that it is
generating this interrupt by
a.
Asserting the Interrupt Request output pin (e.g., by toggling it "Low")
b. Setting Bit 3 (Change of FL Condition Interrupt Status) within the LIU Interrupt Status Register to
"1" as depicted below.
Jitter Attenuator Control Register (Address = 0x1307)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
DFL
Jitter
Attenuator
FIFO Pointer
RESET
Jitter
Attenuator
PLL/FIFO
Operating
Mode - Bit 1
Jitter
Attenuator
in
Transmit
Path
Jitter
Attenuator
PLL/FIFO
Operating
Mode - Bit 0
R/O
R/W
0
X
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