XRT7250 datasheet(259/463 Pages) EXAR

259 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

240

Configuring the Transmit Payload Data Input Interface

block to accept the “N” Bits from the Terminal Equip-

ment, then the user must write the value “11” into the

TxNSourceSel[1:0] bit-fields. Once the user does

this, then any value, which resides on the TxSer input

pin, when the “N” bit is being processed by the Trans-

mit Section will be inserted into the “N” bit-field within

the very next outbound E3 frame.

For completeness, the relationship between the con-

tents of the TxNSourceSel[1:0] bits and the resulting

source of the “N” bit is listed below.

Bits 4, 3, TxNSourceSel[1:0]

These two Read/Write bit-fields combine to specify

the source of the N-bit, within each outbound E3

frame. The relationship between these two bit-fields

and the resulting source of the N Bit is tabulated be-

low.

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.

TXASOURCESEL[1:0]

SOURCE OF A BIT

TXNSOURCESEL[1:0]

SOURCE OF N BIT

TxE3 Service Bits Register (Address = 0x35)

Transmit Overhead Data Input Interface

Transmit LAPD Controller

Transmit Payload Data Input Interface.

XRT7250 Datasheet(PDF) 259 Page - Exar Corporation