XRT72L50 Datasheet, PDF (454/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
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• It will set Bit 6 (LOF Interrupt Status), within the Rx E3 Interrupt Status Register - 1 to “1”, as indicated below.
RxE3 Configuration & Status Register 2 (Address = 0x11)
BIT 7
Rx LOF Algo
BIT 6
RxLOF
R/W
RO
X
1
BIT 5
RxOOF
RO
X
BIT 4
RxLOS
RO
X
BIT 3
RxAIS
RO
X
BIT 2
RxPld Unstab
RO
X
BIT 1
Rx
TMark
RO
X
BIT 0
RxFERF
RO
X
6.3.6.2.4
The Change of Framing Alignment (COFA) Interrupt
If the Change of Framing Alignment Interrupt is enabled then the XRT72L50 Framer IC will generate an
interrupt any time the Receive E3 Framer block detects an abrupt change of framing alignment.
NOTE: This interrupt is typically accompanied with the Change in Receive OOF Condition interrupt as well.
Conditions causing the XRT72L50 Framer IC to generate this interrupt.
If the XRT72L50 Framer detects receives at least four consecutive E3 frames, within its Framing Alignment
bytes in Error, then the XRT72L50 Framer IC will declare an OOF condition. However, while the XRT72L50
Framer IC is operating in the OOF condition, it will still rely on the old framing alignment for E3 payload data
extraction, etc.
However, if the Receive E3 Framer had to change alignment, in order to re-acquire frame synchronization, then
this interrupt will occur.
Enabling and Disabling the Change of Framing Alignment Interrupt
The user can enable or disable the Change of Framing Alignment Interrupt by writing the appropriate value into
Bit 4 (COFA InterruptEnable).
RxE3 Interrupt ENABLE Register - 1 (Address = 0x12)
BIT 7
BIT 6
Not Used
BIT 5
RO
RO
RO
0
0
0
BIT 4
COFA
Interrupt
Enable
R/W
X
BIT 3
OOF
Interrupt
Enable
R/W
0
BIT 2
LOF
Interrupt
Enable
R/W
0
BIT 1
LOS
Interrupt
Enable
R/W
0
BIT 0
AIS
Interrupt
Enable
R/W
0
Writing a “1” into this bit-field enables the Change of Framing Alignment Interrupt. Conversely, writing a “0” into
this bit-field disables the Change of Framing Alignment Interrupt.
Servicing the Change of Framing Alignment Interrupt
Whenever the XRT72L50 Framer IC generates this interrupt, it will do the following.
• It will assert the Interrupt Request output pin (Int) by driving it "Low".
• It will set Bit 4 (COFA Interrupt Status), within the Rx E3 Interrupt Status Register -1, to “1”, as indicated
below.
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