XRT7250 datasheet(460/463 Pages) EXAR

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

441

7.0

DIAGNOSTIC OPERATION OF THE XRT7250

FRAMER IC

The XRT7250 DS3/E3 Framer IC permits the user to

command it to operate in the Framer Local Loop-back

Mode. When the user does this than the data will be

as follows.

1. Data will enter the XRT7250 Framer IC via both

the Transmit Payload Data Input Interface and the

Transmit Overhead Data Input Interface blocks.

2. This data will be processed through the Transmit

DS3/E3 Framer block and the Transmit DS3/E3

LIU Interface block.

3. This Transmit Output data will be internally

looped-back into the Receive Path via the

Receive LIU Interface block.

4. This data will now be processed through the

Receive DS3/E3 Framer block and will ultimately

arrive at both the Receive Payload Data Output

Interface and Receive Overhead Data Output

Interface blocks, where this data will be output to

the terminal equipment.

The Framer Local Loop-back Path is also illustrated

below in Figure 213 .

The user can configure the XRT7250 into the Framer

Local-Loop-back Mode by writing a “1” into bit-field 7

FIGURE 213. ILLUSTRATION OF THE FRAMER LOCAL LOOP-BACK PATH, WITHIN THE XRT7250 DS3/E3 FRAMER IC

Receive LIU

Interface

Block

Receive DS3/E3

Framer Block

Receive Payload

Data Output

Interface Block

Microprocessor

Interface

MOTO

D[7:0]

A[8:0]

IntB*

CSB*

RdB_DS

WrB_RW

Rdy_Dtck

Reset*

ALE_AS

RxSer

RxNib[3:0]

RxOutClk

RxPOS

RxNEG

RxLineClk

Tx LAPD Buffer/

Controller

Rx LAPD Buffer/

Controller

Receive Overhead

Output

Interface Block

RxNibClk

RxFrame

Transmit

Payload Data

Input

Interface Block

Transmit DS3/E3

Framer Block

Transmit LIU

Interface

Block

TxSer

TxNib[3:0]

TxInClk

TxPOS

TxNEG

TxLineClk

Transmit Overhead

Input

Interface Block

TxOHClk

TxOHIns

TxOHInd

TxOH

TxOHEnable

TxOHFrame

TxNibClk

TxFrame

RxOHFrame

RxOH

RxOHClk

RxOHEnable

Framer Local Loop-back Path

XRT7250 Datasheet(PDF) 460 Page - Exar Corporation

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