XRT7250 datasheet(404/463 Pages) EXAR

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XRT7250

DS3/E3 FRAMER IC

REV. 1.1.1

385

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

stream and to route this data to the Receive E3

Framer block.

Figure 186 presents a simple illustration of the Re-

ceive E3 LIU Interface block.

The Receive Section of the XRT7250 will via the Re-

ceive E3 LIU Interface Block receive timing and data

information from the incoming E3 data stream. The

E3 Timing information will be received via the RxLi-

neClk input pin and the E3 data information will be re-

ceived via the RxPOS and RxNEG input pins. The

Receive E3 LIU Interface block is capable of receiving

E3 data pulses in unipolar or bipolar format. If the

Receive E3 framer is operating in the bipolar format,

then it can be configured to decode either AMI or

HDB3 line code data. Each of these input formats

and line codes will be discussed in detail, below.

6.3.1.1

Unipolar Decoding

If the Receive E3 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 E3 LIU Interface block will also

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 E3 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 187 presents an illustration of the behavior of

the RxPOS, RxNEG and RxLineClk input pins when

the Receive E3 LIU Interface block is operating in the

Unipolar mode.

FIGURE 186. A SIMPLE ILLUSTRATION OF THE RECEIVE E3 LIU INTERFACE BLOCK

RxPOS

RxNEG

RxLineClk

To Receive DS3

Framer Block

Receive DS3

LIU Interface

Block

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