XRT7250 datasheet(290/463 Pages) EXAR

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

271

In addition to taking data from multiple sources and

multiplexing them, in appropriate manner, to create

the outbound E3 frames, the Transmit E3 Framer

block has the following roles.

• Generating Alarm Conditions

• Generating Errored Frames (for testing purposes)

• Routing outbound E3 frames to the Transmit E3 LIU

Interface block

Each of these additional roles are discussed below.

5.2.4.2.1

Generating Alarm Conditions

The Transmit E3 Framer block permits the user to, by

writing the appropriate data into the on-chip registers,

to override the data that is being written into the

Transmit Payload Data and Overhead Data Input In-

terfaces and transmit the following alarm conditions.

• Generate the Yellow Alarms (or FERF indicators)

• Manipulate the A-bit, by forcing it to “0”.

• Generate the AIS Pattern

• Generate the LOS pattern

• Generate FERF (Yellow) Alarms, in response to

detection of a Red Alarm condition (via the Receive

Section of the XRT7250).

The procedure and results of generating any of these

alarm conditions is presented below.

The user can exercise each of these options by writ-

ing the appropriate data to the Tx E3 Configuration

ister is presented below.

Bit-fields 1 and 2 permit the user to transmit various

alarm conditions to the remote terminal equipment.

The role/function of each of these two bit-fields within

the register, are discussed below.

5.2.4.2.1.1

Tx AIS Enable - Bit 2

This read/write bit field permits the user to force the

transmission of an AIS (Alarm Indication Signal) pat-

tern to the remote terminal equipment via software

control. If the user opts to transmit an AIS pattern,

then the Transmit Section of the Framer IC will begin

to transmit an unframed all ones pattern to the re-

mote terminal equipment. Table 54 presents the rela-

tionship between the contents of this bit-field, and the

resulting Framer action.

FIGURE 119. A SIMPLE ILLUSTRATION OF THE TRANSMIT E3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO

OTHER

FUNCTIONAL BLOCKS

Transmit

E3 Framer

Block

Transmit

E3 Framer

Block

Transmit HDLC

Controller/Buffer

Transmit Overhead

Data Input Interface

Transmit Payload Data

Input Interface

To Transmit E3 LIU Interface Block

TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)

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

BIP-4

Enable

TxASourceSel[1:0]

TxNSourceSel[1:0]

Tx AIS

Enable

Tx LOS

Enable

Tx FAS

Source

Select

R/W

0000

000

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