XRT7250 datasheet(178/463 Pages) EXAR

178 / 463 page

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

159

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 DS3 applications, a Yellow

Alarm is transmitted by setting all of the X bits to 0.

If one assumes that the connection between the Ter-

minal Equipment and the XRT7250 is as illustrated in

Figure 59 then, Figure 60 presents an illustration of

the signaling that must go on between the Terminal

Equipment and the XRT7250.

Yes

UDL

Yes

UDL

Yes

UDL

Yes

UDL

Yes

UDL

Yes

UDL

Yes

TABLE 23: THE RELATIONSHIP BETWEEN THE NUMBER OF TXOHENABLE PULSES (SINCE THE LAST OCCURRENCE OF

THE

TXOHFRAME PULSE) TO THE DS3 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?

XRT7250 Datasheet(PDF) 178 Page - Exar Corporation

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