XRT7250 datasheet(280/463 Pages) EXAR

280 / 463 page

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

261

3. After the Terminal Equipment has waited through

the appropriate number of pulses via the TxO-

HEnable pin, it should then assert the TxOHIns

input signal. Concurrently, the Terminal Equip-

ment should also place the appropriate value (of

the inserted overhead bit) onto the TxOH signal.

4. The Terminal Equipment should hold both the

TxOHIns input pin "High" and the value of the

TxOH signal stable, until the next TxOHEnable

pulse is detected.

Case Study: The Terminal Equipment intends to

insert the appropriate overhead bits into the

Transmit Overhead Data Input Interface (using

Method 2) in order to transmit a Yellow Alarm to

the remote terminal equipment.

In this case, the Terminal Equipment intends to insert

the appropriate overhead bits, into the Transmit Over-

head Data Input Interface such that the XRT7250 will

transmit a Yellow Alarm to the remote terminal equip-

ment. Recall that, for E3, ITU-T G.751 applications, a

Yellow Alarm is transmitted by setting the “A” bit to

“1".

If one assumes that the connection between the Ter-

minal Equipment and the XRT7250 is as illustrated in

Figure 115 then, Figure 116 presents an illustration of

the signaling that must go on between the Terminal

Equipment and the XRT7250.

TABLE 51: THE RELATIONSHIP BETWEEN THE NUMBER OF TXOHENABLE PULSES (SINCE THE LAST OCCURRENCE OF

THE

TXOHFRAME PULSE) TO THE E3 OVERHEAD BIT, THAT IS BEING PROCESSED BY THE XRT7250

NUMBER OF TXOHENABLE PULSES

THE OVERHEAD BIT EXPECTED BY THE

XRT7250

CAN THIS OVERHEAD BIT BE ACCEPTED BY

THE

XRT7250?

0 (Clock edge is coincident with TxO-

HFrame being detected "High”)

FAS Signal - Bit 9

Yes

FAS Signal - Bit 8

Yes

FAS Signal - Bit 7

Yes

FAS Signal - Bit 6

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

XRT7250 Datasheet(PDF) 280 Page - Exar Corporation

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