XRT7250 datasheet(225/463 Pages) EXAR

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XRT7250

DS3/E3 FRAMER IC

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REV. 1.1.1

206

Interfacing the Receive Overhead Data Output In-

terface block to the Terminal Equipment (Method

Figure 88 illustrates how one should interface the Re-

ceive Overhead Data Output Interface block to the

Terminal Equipment when using Method 1 to sample

and process the overhead bits from the inbound DS3

data stream.

TABLE 41: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT

INTERFACE BLOCK

SIGNAL NAME

TYPE

DESCRIPTION

RxOH

Output

Receive Overhead Data Output pin:

The XRT7250 will output the overhead bits, within the incoming DS3 frames, via this pin.

The Receive Overhead Data Output Interface block will output a given overhead bit, upon the

falling edge of RxOHClk. Hence, the external data link equipment should sample the data, at

this pin, upon the rising edge of RxOHClk.

The XRT7250 will always output the DS3 Overhead bits via this output pin. There are no

external input pins or register bit settings available that will disable this output pin.

RxOHClk

Output

Receive Overhead Data Output Interface Clock Signal:

The XRT7250 will output the Overhead bits (within the incoming DS3 frames), via the RxOH

output pin, upon the falling edge of this clock signal.

As a consequence, the user's data link equipment should use the rising edge of this clock sig-

nal to sample the data on both the RxOH and RxOHFrame output pins.

This clock signal is always active.

RxOHFrame

Output

Receive Overhead Data Output Interface - Start of Frame Indicator:

The XRT7250 will drive this output pin "High" (for one period of the RxOHClk signal), when-

ever the first overhead bit within a given DS3 frame is being driven onto the RxOH output pin.

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