XRT7250 datasheet(317/463 Pages) EXAR

317 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

298

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 “A”

bit 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 “A”

bit 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.

• Set the RxFERF bit-field, within the Rx E3 Configu-

ration/Status Register to “1”, as depicted below.

Clearing the FERF Condition

The Receive E3 Framer block will clear the FERF

condition once it has received a User-Selectable

number of E3 frames with the “A” bit-field being set to

“0” (e.g., no FERF condition). This User-Selectable

number of E3 frames is either 3 or 5 depending upon

the value that has been written into Bit 4 (RxFERF Al-

go) of the Rx E3 Configuration/Status Register, as

discussed above.

Whenever the Receive E3 Framer clears the FERF

status, then it will do the following:

1. Generate a Change in the FERF Status Interrupt

to the Microprocessor.

2. Clear the Bit 0 (RxFERF) within the Rx E3 Con-

figuration & Status register, as depicted below.

RXE3 CONFIGURATION & STATUS REGISTER - 1 G.751 (ADDRESS = 0X10)

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

Reserved

RxFERF

Algo

Reserved

RxBIP4

R/W

000

RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)

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

Not Used

FERF

Interrupt

Status

BIP-4

Error

Interrupt

Status

Framing

Error

Interrupt

Status

Not Used

RUR

001

000

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

000

XRT7250 Datasheet(PDF) 317 Page - Exar Corporation

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