XRT7250 datasheet(273/463 Pages) EXAR

273 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

254

NOTES:

1. The XRT7250 contains mask register bits that per-

mit the user to alter the state of the internally gen-

erated value for these bits.

2. The Transmit LAPD Controller/Buffer can be config-

ured to be the source of the N bits, within the out-

bound E3 data stream.

The Transmit Overhead Data Input Interface permits

the user to insert overhead data into the outbound E3

frames via the following two different methods.

• Method 1 - Using the TxOHClk clock signal

• Method 2 - Using the TxInClk and the TxOHEnable

signals.

Each of these methods are described below.

5.2.2.1

Method 1 - Using the TxOHClk Clock

Signal

The Transmit Overhead Data Input Interface consists

of the five signals. Of these five (5) signals, the fol-

lowing four (4) signals are to be used when imple-

menting Method 1.

• TxOH

• TxOHClk

• TxOHFrame

• TxOHIns

Each of these signals are listed and described below.

Table 48.

TABLE 47: A LISTING OF THE OVERHEAD BITS WITHIN THE E3 FRAME, AND THEIR POTENTIAL SOURCES, WITHIN THE

XRT7250 IC

OVERHEAD BIT

INTERNALLY GENERATED

ACCESSIBLE VIA THE TRANSMIT OVERHEAD

DATA INPUT INTERFACE

BUFFER/REGISTER

ACCESSIBLE

FAS Signal - Bit 9

Yes

Yes*

FAS Signal - Bit 8

Yes

FAS Signal - Bit 7

Yes

Yes*

FAS Signal - Bit 6

Yes

Yes*

FAS Signal - Bit 5

Yes

FAS Signal - Bit 4

Yes

FAS Signal - Bit 3

Yes

FAS Signal - Bit 2

Yes

FAS Signal - Bit 1

Yes

FAS Signal - Bit 0

Yes

A Bit

Yes

N Bit

Yes

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