XRT7250 datasheet(315/463 Pages) EXAR

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XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

296

• Asserting the RxLOS output pin (e.g., toggling it

"High”).

• Setting Bit 4 (RxLOS) of the Rx E3 Configuration &

Status Register to “1” as depicted below.

• The Receive E3 Framer block will generate a

Change in LOS Condition interrupt request. Upon

generating this interrupt request, the Receive E3

Framer block will assert Bit 1 (LOS Interrupt Status

within the Rx E3 Framer Interrupt Status Register -

1, as depicted below.

Clearing the LOS Condition

The Receive E3 Framer block will clear the LOS con-

dition when it encounters a stream of 32 bits that

does not contain a string of 4 consecutive zeros.

When the Receive E3 Framer block clears the LOS

condition, then it will notify the Microprocessor and

the external circuitry of this occurrence by:

• Generating the Change in LOS Condition Interrupt

to the Microprocessor.

• Clearing Bit 4 (RxLOS) within the Rx E3 Configura-

tion & Status Register, as depicted below.

• Clear the RxLOS output pin (e.g., toggle it "Low”).

5.3.2.8

The AIS (Alarm Indication Status) Con-

dition

Declaring the AIS Condition

The Receive E3 Framer block will identify and declare

an AIS condition, if it detects an All Ones” pattern in

the incoming E3 data stream. More specifically, the

Receive E3 Framer block will declare an AIS Condi-

tion if 7 or less “0’s” are detected in each of 2 consec-

utive E3 frames.

If the Receive E3 Framer block declares an AIS Con-

dition, then it will do the following.

• Generate the Change in AIS Condition Interrupt to

the Microprocessor. Hence, the Receive E3

Framer block will assert Bit 0 (AIS Interrupt Status)

within the Rx E3 Framer Interrupt Status register -

1, as depicted below.

RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0

RxLOF

Algo

RxLOF

RxOOF

RxLOS

RxAIS

Not Used

RxFERF

R/W

RORO

RORORORO

110

000

RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0

Not Used

COFA

Interrupt

Status

OOF

Interrupt

Status

LOF

Interrupt

Status

LOS

Interrupt

Status

AIS

Interrupt

Status

RUR

000

010

RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0

RxLOF

Algo

RxLOF

RxOOF

RxLOS

RxAIS

Not Used

RxFERF

R/W

RORO

RORORORO

100

111

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