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Unformatted text preview: duce the seven parity bits:
g(x) = x7 + x6 + x2 + 1 CCSDS 201.0-B-3 Page 3-4 June 2000 CCSDS RECOMMENDATION FOR TELECOMMAND: CHANNEL SERVICE The code generator implementation is shown in Figure 3-4. Note that the shift registers are
initialized to zero. The ganged switch is in position 1 while the 56 TC data bits are being
transmitted, in position 2 for the seven parity bits, and in position 3 for the appended fill bit.
INFORMATION BITS I 0 • • • I 55 (1) (1) (2) (2) CODED
OUTPUT (3) (3) ZERO
0 X0 X1 X2 X3 X4 X5 X6 ZERO
I PARITY BITS Figure 3-4: (63,56) Modified BCH Code Generator
3.3.3 FILL BITS If the Input Data do not fit exactly within an integral number of TC Codeblocks, the last
octet(s) and ONLY the last octet(s) of the information field of the last Codeblock within the
CLTU may contain “Fill” bits. The pattern of the Fill shall consist of a sequence of
alternating “ones” and “zeros” starting with a “zero”.
The Coding layer may require the introduction of these fill bits in th...
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