XRT73L03 Datasheet, PDF (32/62 Pages) Exar Corporation – 3 CHANNEL E3/DS3/STS-1 LINE INTERFCE UNIT

XRT73L03 3 CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT
REV. P1.0.13
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PRELIMINARY
FIGURE 12. AN EXAMPLE OF B3ZS ENCODING
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 1
TPData
TNData
TxClk
Line Signal
00V
B0V
2.3.2 HDB3 Encoding
If the XRT73L03 has been configured to operate in
the E3 Mode, the HDB3/B3ZS Encoder blocks oper-
ate in the HDB3 Mode. When the Encoder is operat-
ing in this mode it parses through and searches the
Transmit Data Stream from the Transmit Logic Block
for the occurrence of four (4) consecutive zeros
("0000"). If the HDB3 Encoder finds an occurrence of
four consecutive zeros then it substitutes these four
FIGURE 13. AN EXAMPLE OF HDB3 ENCODING
"0’s" with either a "000V" or a "B00V" pattern. The
HDB3 Encoder decides whether to substitute with ei-
ther the "000V" or the "B00V" pattern in order to in-
sure that an odd number of Bipolar pulses exist be-
tween any two consecutive violation pulses.
Figure 13 illustrates the HDB3 Encoder at work with
two separate strings of four or more consecutive ze-
ros.
Data 1 0 1 1 0 0 0 0 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
TPData
TNData
TxClk
Line Signal
000 V
B 0 0V
2.3.3 Disabling the HDB3/B3ZS Encoder
The XRT73L03 HDB3/B3ZS Encoder can be disabled
by two methods.
a. Operating in the Hardware Mode.
The HBD3/B3ZS Encoder blocks of all channels
are disabled by setting the ENDECDIS (Encoder/
Decoder Disable) input pin (pin 25) to “0".
NOTE: By executing this step the HDB3/B3ZS Encoder and
Decoder blocks in all channels of the XRT73L03 are glo-
bally disabled.
b. Operating in the HOST Mode.
When the XRT73L03 is operating in the HOST
Mode the HDB3/B3ZS Encoders in each channel
can be individually enabled or disabled. Disable
the HDB3/B3ZS Encoder block in Channel(n) by
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