XRT7250 datasheet(417/463 Pages) EXAR

417 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

398

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”).

6.3.2.6.2

The AIS (Alarm Indication Status)

Condition

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 “0s” 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 1 (AIS Interrupt Status)

within the Rx E3 Framer Interrupt Status register -

1, as depicted below.

• Assert the RxAIS output pin.

• Set Bit 3 (Rx AIS) within the Rx E3 Configuration &

Status Register, as depicted below.

Clearing the AIS Condition

The Receive E3 Framer block will clear the AIS condi-

tion when it detects two consecutive E3 frames, with

eight or more “zeros” in the incoming data stream.

The Receive E3 Framer block will inform the Micro-

processor that the AIS Condition has been cleared

by:

• Generating the Change in AIS Condition Interrupt

to the Microprocessor. Hence, the Receive E3

Framer block will assert Bit 1 (AIS Interrupt Status)

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

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

Rx LOF Algo

RxLOF

RxOOF

RxLOS

RxAIS

RxPld Unstab

TMark

RxFERF

R/W

RORO

RORORORO

010

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

001

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

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

Rx LOF Algo

RxLOF

RxOOF

RxLOS

RxAIS

RxPld Unstab

TMark

RxFERF

R/W

RORO

RORORORO

001

000

XRT7250 Datasheet(PDF) 417 Page - Exar Corporation

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