XRT72L50 Datasheet, PDF (342/471 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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Enabling and Disabling the Change in Receive LOS Condition Interrupt
The user can enable or disable the Change in Receive LOS Condition Interrupt, by writing the appropriate
value into Bit 1 (LOS Interrupt Enable), within the RxE3 Interrupt Enable Register - 1, as indicated below.
RxE3 Interrupt Enable Register - 1 (Address = 0x12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
X
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change in Receive LOS 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 1 (LOS Interrupt Status), within the Rx E3 Interrupt Status Register - 1 to “1”, as indicated below.
RxE3 Interrupt Status Register - 1 (Address = 0x14)
BIT 7
RO
0
BIT 6
Not Used
RO
0
BIT 5
RO
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
OOF
LOF
LOS
AIS
Interrupt Status Interrupt Status Interrupt Status Interrupt Status Interrupt Status
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
Whenever the user’s system encounters the Change in Receive LOS Condition Interrupt, then it should do the
following.
1. It should determine the current state of the LOS condition. Recall, that this interrupt can be generated,
whenever the XRT72L50 Framer IC declares or clears the LOS defect. Hence, the user can determine the
current state of the LOS defect by reading the state of Bit 4 (RxLOS) within the Rx E3 Configuration and
Status Register - 2, as illustrated below.
RxE3 Configuration & Status Register - 2 (Address = 0x11)
BIT 7
RxLOF
Algo
R/W
0
BIT 6
RxLOF
RO
1
BIT 5
RxOOF
RO
1
BIT 4
RxLOS
RO
0
BIT 3
RxAIS
RO
0
BIT 2
BIT 1
Not Used
RO
RO
1
1
BIT 0
RxFERF
RO
1
If the LOS state is TRUE
1. It should transmit a FERF (Far-End-Receive Failure) indicator to the Remote Terminal Equipment. Please
see Section 5.2.4.2.1.3.
If the LOS state is FALSE
1. It should cease transmitting the FERF indication to the Remote Terminal Equipment.
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