XRT7250 datasheet(188/463 Pages) EXAR

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

169

4.2.4.2.1

Generating Alarm Conditions

The Transmit DS3 Framer block permits the user to,

by writing the appropriate data into the on-chip regis-

ters, 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 X-bit (set them to 1)

• Generate the AIS Pattern

• Generate the IDLE 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).

• Generate and transmit a desired value for FEBE

(Far-End-Block Error).

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 DS3 Configuration

ister is presented below.

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

4.2.4.2.1.1

Transmit Yellow Alarm - Bit 7

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

transmission of a Yellow Alarm to the remote terminal

equipment via software control. If the user opts to

transmit a Yellow Alarm then both of the X-bits, within

the outbound DS3 frames will be set to '0'. Table 27

relates the content of this bit field to the Transmit DS3

Framer block's action.

NOTE: This bit is ignored when either the TxIDLE, TxAIS, or

the TxLOS bit-fields are set.

4.2.4.2.1.2

Transmit X-bit - Bit 6

This bit field functions as the logical complement to

Bit 7 (e.g., Tx Yellow Alarm). This read/write bit field

permits the user to force all of the X-bits, in the out-

bound DS3 frames, to "1" and transmit them to the re-

mote terminal equipment. Table 28 relates the con-

tent of this bit field to the Transmit DS3 Framer

Block's action.

TX DS3 CONFIGURATION REGISTER (ADDRESS = 0X30)

BIT 7BIT 6BIT 5BIT 4

BIT 3BIT2BIT 1BIT 0

Yellow Alarm

Tx X-Bit

Tx IDLE

Pattern

Tx AIS

Pattern

Tx LOS

Pattern

FERF on

LOS

FERF on

OOF

FERF on

AIS

R/W

010

011

TABLE 27: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 7 (TX YELLOW ALARM) WITHIN THE TX DS3

CONFIGURATION REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER BLOCK'S ACTION

BIT 7TRANSMIT DS3 FRAMER'S ACTION

Normal Operation:

The X-bits are generated by the Transmit DS3 Framer block based upon Near End Receiving Conditions (as

detected by the Receive Section of the chip)

Transmit Yellow Alarm:

The Transmit DS3 Framer block will overwrite the X-bits by setting them all to 0. The payload information is

not modified and is transmitted as normal.

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