XRT72L50 Datasheet, PDF (455/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
RxE3 Interrupt Status Register - 1 (Address = 0x14)
BIT 7
BIT 6
Not Used
BIT 5
RO
RO
RO
0
0
0
BIT 4
COFA
Interrupt
Status
RUR
1
BIT 3
OOF
Interrupt
Status
RUR
0
BIT 2
LOF
Interrupt
Status
RUR
0
BIT 1
LOS
Interrupt
Status
RUR
0
BIT 0
AIS
Interrupt
Status
RUR
0
6.3.6.2.5
The Change in Receive AIS Condition Interrupt
If the Change in Receive AIS Condition Interrupt is enabled, then the XRT72L50 Framer IC will generate an
interrupt in response to either of the following conditions.
1. When the XRT72L50 Framer IC declares an AIS Condition, and
2. When the XRT72L50 Framer IC clears the AIS condition.
Conditions causing the XRT72L50 Framer IC to declare an AIS Condition.
• If the XRT72L50 Framer IC detects 7 or less “0’s” within 2 consecutive E3 frames.
Conditions causing the XRT72L50 Framer IC to clear the AIS Condition.
• If the XRT72L50 Framer IC detects 2 consecutive E3 frames that each contain 8 or more “0’s”.
Enabling and Disabling the Change in Receive AIS Condition Interrupt
The user can enable or disable the AIS Interrupt, by writing the appropriate value into Bit 0 (AIS Interrupt
Enable), within the RxE3 Interrupt Enable Register - 1, as indicated below.
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
0
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
X
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change in Receive AIS Condition Interrupt
Whenever the XRT72L50 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (Int), by driving it "Low".
• It will set Bit 0 (AIS Interrupt Status), within the Rx E3 Interrupt Status Register - 1 to “1”, as indicated below.
RxE3 Interrupt Status Register - 1 (Address = 0x14)
BIT 7
BIT 6
Not Used
BIT 5
RO
RO
RO
0
0
0
BIT 4
COFA
Interrupt
Status
RUR
0
BIT 3
OOF
Interrupt
Status
RUR
0
BIT 2
LOF
Interrupt
Status
RUR
0
BIT 1
LOS
Interrupt
Status
RUR
0
BIT 0
AIS
Interrupt
Status
RUR
1
Whenever the user’s system encounters the Change in Receive AIS Condition Interrupt, then it should do the
following.
442