XRT7250 datasheet(202/463 Pages) EXAR

202 / 463 page

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

183

1. To receive encoded digital data from the DS3 LIU

IC.

2. To decode this data, convert it into a binary data

stream and to route this data to the Receive DS3

Framer block.

Figure 73 presents a simple illustration of the Receive

DS3 LIU Interface block.

The Receive Section of the XRT7250 will via the Re-

ceive DS3 LIU Interface Block receive timing and data

information from the incoming DS3 data stream. The

DS3 Timing information will be received via the RxLi-

neClk input pin and the DS3 data information will be

received via the RxPOS and RxNEG input pins. The

Receive DS3 LIU Interface block is capable of receiv-

ing DS3 data pulses in unipolar or bipolar format. If

the Receive DS3 framer is operating in the bipolar for-

mat, then it can be configured to decode either AMI or

B3ZS line code data. Each of these input formats

and line codes will be discussed in detail, below.

4.3.1.1

Unipolar Decoding

If the Receive DS3 LIU Interface block is operating in

the Unipolar (single-rail) mode, then it will receive the

Single Rail NRZ DS3 data pulses via the RxPOS in-

put pin. The Receive DS3 LIU Interface block will al-

so receive its timing signal via the RxLineClk signal.

NOTE: The RxLineClk signal will function as the timing

source for the entire Receive Section of the XRT7250.

No data pulses will be applied to the RxNEG input

pin. The Receive DS3 LIU Interface block receives a

logic "1" when a logic "1" level signal is present at the

RxPOS pin, during the sampling edge of the RxLi-

neClk signal. Likewise, a logic "0" is received when a

logic "0" level signal is applied to the RxPOS pin.

Figure 74 presents an illustration of the behavior of

the RxPOS, RxNEG and RxLineClk input pins when

the Receive DS3 LIU Interface block is operating in

the Unipolar mode.

FIGURE 73. A SIMPLE ILLUSTRATION OF THE RECEIVE DS3 LIU INTERFACE BLOCK

RxPOS

RxNEG

RxLineClk

To Receive DS3

Framer Block

Receive DS3

LIU Interface

Block

XRT7250 Datasheet(PDF) 202 Page - Exar Corporation

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