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<p class="MsoNormal"><span style="font-size:11.0pt">Ken,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> Maximal pattern shift registers. LFSR<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> CCSDS is not supposed to make recommendations about implementation. For implementing I understand that the Galois shift register is sometimes preferred over the Fibonacci form. However, for
understanding and for setting an initial seed, Fibonacci has tremendous advantage because WYSIWYG, if you remember that phrase from the early Apple computers, what you see is what you get.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> You might also remember that we had a recent go-around in the code and synch WG about how to show these shift registers and we (GSFC) were recommending Fibonacci with particular labeling of the
cells so that the polynomial is directly related to the cells that are tapped. Yes, I realize that this can also be done for the Galois form. Another value of the Fibonacci with the particular cell numbering is that it is what MatLab uses. So when people
are doing simulations, no conversion is needed. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> As you might remember there is an ambiguity between the associated polynomial and the shift register labeling. A particular pattern can be generated in one direction or the reverse. We had
a particular proposal and it turned out that MatLab used the same convention. Our proposal was discarded since it would be too much editing to get all the books to follow the same convention, and maybe other reasons. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> But in any case, seems better from an understanding point of view to use Fibonacci.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Victor<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:11.0pt">From:</span></b><span style="font-size:11.0pt"> Kazz, Greg J (US 312B) <greg.j.kazz@jpl.nasa.gov>
<br>
<b>Sent:</b> Monday, May 17, 2021 12:31 PM<br>
<b>To:</b> Andrews, Kenneth S (JPL-332B)[JPL Employee] <kenneth.s.andrews@jpl.nasa.gov><br>
<b>Cc:</b> Sank, Victor J. (GSFC-567.0)[SCIENCE SYSTEMS AND APPLICATIONS INC] <victor.j.sank@nasa.gov>; Kazz, Greg J (US 312B) via SLS-SLP <sls-slp@mailman.ccsds.org><br>
<b>Subject:</b> Your LFSR OID frame RIDs affecting USLP, TM, AOS SDLPs<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi Ken,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The SLP WG decided to put both of your diagrams into a new non-normative annex in USLP, TM, and AOS.<o:p></o:p></p>
<p class="MsoNormal">The text in the normative part of the link layer books will state:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="Paragraph5" style="mso-list:none">The TFDZ of an OID Transfer Frame shall be generated by use of a 32-cell Linear Feedback Shift Register (LFSR) with polynomial 1 + D + D<sup>2</sup> + D<sup>22</sup> +D<sup>32</sup><span style="font-family:"Courier New"">,
see Annex X.</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Where Annex X is TBD and will be added by me to the document.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We have some questions and requests for you:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<ol style="margin-top:0in" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo5"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Why does the initialization data differ from one figure to the other one?</span><span style="font-size:13.5pt;font-family:-webkit-standard;color:black"> </span><span style="font-size:11.0pt"><o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo5">The ‘1’ in the figures are misleading to some WG members, please replace ‘1’ with D sub zero i.e., D<sup>0</sup> in the figures.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo5">Consensus of WG was to specify the initialization vector
<o:p></o:p></li></ol>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks!<o:p></o:p></p>
<p class="MsoNormal">Greg<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Greg Kazz<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Principal Engineer<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Technical Group Supervisor,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">PSSE/EEISE/PPSE (312B)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Jet Propulsion Laboratory<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">4800 Oak Grove Dr., M/S 301-490<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="ES-MX" style="font-size:11.0pt">Pasadena, CA 91109</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="ES-MX" style="font-size:11.0pt">1+(818)393 6529(voice)</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">1</span><span lang="ES-MX" style="font-size:11.0pt">+(818)393 6871(fax)</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="ES-MX" style="font-size:11.0pt">email: <a href="mailto:greg.j.kazz@jpl.nasa.gov">
greg.j.kazz@jpl.nasa.gov</a> </span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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