XRT7250 datasheet(292/463 Pages) EXAR

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

273

Hence, if a Yellow Alarm condition needs to be trans-

mitted to the Remote Terminal Equipment, this can

be accomplished by executing the following steps.

STEP 1 - Write a “1” into Bit 1 (A Bit) within the Tx

E3 Service Bits Register, as indicated below.

STEP 2 - Write the value “00” into the TxAS-

ource[1:0] bit-fields within the Tx E3 Configura-

tion Register, as indicated below.

These two steps will cause the Transmit E3 Framer

block to read in the contents of Bit 1 (within the Tx E3

Service Bit register) and insert it into the “A” bit-field

within the outbound E3 data stream. Hence, the “A”

bit will be set to “1”, which will be interpreted as an

Alarm Condition, by the Remote Terminal Equipment.

5.2.4.2.2

Configuring the Transmit E3 Framer

block to insert the BIP-4 nibble into each out-

bound E3 frame.

The XRT7250 Framer IC permits the user to (1) con-

figure the Transmit Section of the device to insert the

BIP-4 value into each outbound E3 frame and (2) to

configure the Receive Section of the device to com-

pute and verify the BIP-4 value, within each inbound’

E3 frame.

These two configurations are accomplished by setting

bit 7 (Tx BIP-4 Enable), within the Tx E3 Configura-

tion Register, to “1”, as indicated below.

TXASOURCESEL[1:0]

SOURCE OF A BIT

TxE3 Service Bits Register (Address = 0x35)

Transmit Overhead Data Input Interface

Transmit Payload Data Input Interface

Functions as a FEBE (Far-End-Block Error) bit-field.

This bit-field is set to "0", if the Near-End Receive Section (within this chip) detects no BIP-4

Errors within the incoming E3 frames.

This bit-field is set to "1", if the Near-End Receive Section (within this chip) detects a BIP-4

Error within the incoming E3 frame.

TXE3 SERVICE BITS REGISTER (ADDRESS = 0X35)

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

Not Used

A Bit

N Bit

R/W

0000

010

TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)

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

Tx BIP-4

Enable

TxASourceSel[1:0]

TxNSourceSel[1:0]

Tx AIS

Enable

Tx LOS

Enable

Tx FAS

Source Select

R/W

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