XRT7250 datasheet(418/463 Pages) EXAR

418 / 463 page

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

399

within the Rx E3 Framer Interrupt Status Register -

• Clearing the RxAIS output pin (e.g., toggling it

"Low”).

• Setting the RxAIS bit-field, within the Rx E3 Config-

uration & Status Register to “0”, as depicted below.

6.3.2.6.3

The Far-End-Receive Failure (FERF)

Condition

Declaring the FERF Condition

The Receive E3 Framer block will declare a Far-End

Receive Failure (FERF) condition if it detects a user-

selectable number of consecutive incoming E3

frames, with the FERF bit-field (Bit 7, within the MA

Byte) set to “1”. Recall, the bit-format of the MA byte

is presented below.

This User-selectable number of E3 frames is either 3

or 5, depending upon the value that has been written

into Bit 4 (Rx FERF Algo) within the Rx E3 Configura-

tion & Status Register, as depicted below.

Writing a “0” into this bit-field causes the Receive E3

Framer block to declare a FERF condition, if it detects

3 consecutive incoming E3 frames, that have the

FERF bit (within the MA byte) set to “1”.

Writing a “1” into this bit-field causes the Receive E3

Framer block to declare a FERF condition, if it detects

5 consecutive incoming E3 frames, that have the

FERF bit (within the MA byte) set to “1”.

Whenever the Receive E3 Framer block declares a

FERF condition, then it will do the following.

• Generate a Change in FERF Condition interrupt to

the MIcroprocessor. Hence, the Receive E3

Framer block will assert Bit 3 (FERF Interrupt Sta-

tus) within the Rx E3 Framer Interrupt Status regis-

ter - 2, as depicted below.

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

0000

000

THE MAINTENANCE AND ADAPTATION (MA) BYTE FORMAT

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

FERF

FEBE

Payload Type

Payload Dependent

Timing Marker

RXE3 CONFIGURATION & STATUS REGISTER 1 - (E3, ITU-T G.832) (ADDRESS = 0X10)

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

RxPLDType[2:0]

RxFERF

Algo

RxTMark

Algo

RxPLDExp[2:0]

0000

000

XRT7250 Datasheet(PDF) 418 Page - Exar Corporation

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