XRT72L13 Datasheet, PDF (290/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
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PRELIMINARY
FIGURE 85. A SIMPLE ILLUSTRATION OF THE "TRANSMIT DS3 LIU INTERFACE" BLOCK
From Transmit DS3
Framer Block
Transmit DS3
LIU Interface
Block
TxPOS
TxNEG
TxLineClk
The "Transmit DS3 LIU Interface" block can transmit
data to the LIU IC or other external circuitry via two
different output modes: Unipolar or Bipolar. If the us-
er selects Unipolar (or Single Rail) mode, then the
contents of the DS3 Frame is output, in a binary (NRZ
manner) data stream via the TxPOS pin to the LIU IC.
The TxNEG pin will only be used to denote the frame
boundaries. TxNEG will pulse "high" for one bit peri-
od, at the start of each new DS3 frame, and will re-
main "low" for the remainder of the frame. Figure 86
presents an illustration of the TxPOS and TxNEG sig-
nals during data transmission while the "Transmit
DS3 LIU Interface" block is operating in the "Unipolar"
mode. This mode is sometimes referred to as "Single
Rail" mode because the data pulses only exist in one
polarity: positive.
FIGURE 86. THE BEHAVIOR OF TXPOS AND TXNEG SIGNALS DURING DATA TRANSMISSION WHILE THE TRANSMIT
DS3 LIU INTERFACE IS OPERATING IN THE UNIPOLAR MODE
Data _{1 0 1 1 0 0 1 0 0 1 1 1 0 1 0 1 0 0 1}
TxPOS
1 10
01
TxNEG
TxLineClk
Frame Boundary
When the "Transmit DS3 LIU Interface" block is oper-
ating in the "Bipolar" (or "Dual Rail") mode, then the
contents of the DS3 Frame is output via both the “Tx-
POS” and “TxNEG” pins. If the user chooses the Bi-
polar mode, then he/she can transmit the DS3 data to
the LIU via one of two different line codes: Alternate
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