XRT7302IV View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT7302IV' PDF : 62 Pages View PDF
XRT7302 2 CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT
REV. 1.1.6
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PRELIMINARY
FIGURE 10. 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 XRT7302 has been configured to operate in the
E3 Mode, the HDB3/B3ZS Encoder blocks operate in
the HDB3 Mode. When the Encoder is operating in
this mode it parses through and searches the Trans-
mit 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 con-
secutive zeros then it substitutes these four "0’s" with
FIGURE 11. AN EXAMPLE OF HDB3 ENCODING
either a "000V" or a "B00V" pattern. The HDB3 En-
coder decides whether to substitute with either the
"000V" or the "B00V" pattern in order to insure that an
odd number of Bipolar pulses exist between any two
consecutive violation pulses.
Figure 11 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 XRT7302 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 to “0".
NOTE: By executing this step the HDB3/B3ZS Encoder and
Decoder blocks in all channels of the XRT7302 are globally
disabled.
b. Operating in the HOST Mode.
When the XRT7302 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 setting
28
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