XRT74L73 Datasheet, PDF (335/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

PRELIMINARY
XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
2. To decode this data, convert it into a binary data
stream and to route this data to the Receive E3
Framer block.
FIGURE 135. THE RECEIVE E3 LIU INTERFACE BLOCK
Figure 135 presents a simple illustration of the Re-
ceive E3 LIU Interface block.
To Receive E3
Framer Block
Receive
E3 LIU Interface
Block
RxPOS
RxNEG
RxLineClk
The Receive Section of the XRT74L73 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 receiv-
ing 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.
5.3.1.1 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 XRT74L73.
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 136 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 136. BEHAVIOR OF THE RXPOS, RXNEG AND RXLINECLK SIGNALS DURING DATA RECEPTION OF UNIPO-
LAR DATA
Data _{1 0 1 1 0 0 1 0 0 1 1 1 0 1 0 1 0 0 1}
RxPOS
1 10
01
RxNEG
RxLineClk
The user can configure the Receive E3 LIU Interface Mode by writing the appropriate data to the I/O Con-
block to operate in either the Unipolar or the Bipolar trol Register, as depicted below.
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