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Hi, Nick, Dewi,
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<div> As a new engineer I was told by more experienced engineers (way back in the early ‘80s) that the 3 rules of (parts and other) vendors is:</div>
<div> 1. the vendor lies</div>
<div> 2. the vendor lies</div>
<div> 3. the vendor lies</div>
<div><br>
</div>
<div> For bespoke fpga work, the effort is a cycle of fpga delivery to board, test by hardware and or software engineers, followed</div>
<div> by reprogramming up until either “good enough” or end of project/delivery. Correctness was a judgement call.</div>
<div><br>
</div>
<div> I have online access Rierson’s book and at first glance it significantly overlaps mil-std-2167a, I’ve yet to google both DO-178C</div>
<div> and the mill std with the 2 terns as keywords in the search, but consider this a reminder for me to go do that.</div>
<div><br>
</div>
<div>bob s<br id="lineBreakAtBeginningOfMessage">
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<blockquote type="cite">
<div>On Feb 28, 2025, at 2:39 AM, Nick Tudor <njt@tudorassoc.com> wrote:</div>
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<div dir="auto">Re Hardware</div>
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What I found in practice was hardware faults that were never going to be resolved or were resolved in closed door meetings that I was not allowed</div>
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to attend, because the hardware were signed off as working, or the politics of billion dollar procurement and need to keep the money</div>
</div>
<div dir="auto">>></div>
I understand from studies undertaken with people on this list, that some companies make available firmware for their processors. They may make little or no claims for the correctness of that very low level code and in assessing the repositories for some of
this it has been found to have little evidence to support making claims for correctness. The disclaimer (if there is one), is that this is supplied as examples and it is for the user to build their own or/and verify themselves. However, on checking, quite
often these are used ‘out of the box’.</div>
<div dir="auto"><br>
</div>
<div dir="auto">This might give the illusion to some that software (applications) therefore can have a ‘reliability’ attributed to it/them. </div>
<div dir="auto"><br>
</div>
<div dir="auto">In other quiet conversations with hardware developers, it seems that even the publicly declared hardware behaviour might not actually be the behaviour, even accounting for manufacturing variability (that is, known variability, which is often
accounted for in avionics applications; it gets a bit ‘Rumfeldian’ from here on!)</div>
<div dir="auto"><br>
</div>
<div dir="auto">Avionics hardware typically has to be ‘qualified’ for use and this involves a lot of effort to ensure that it behaves as needed prior to entering certification. <br clear="all">
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<div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><span></span><span></span>Nick Tudor
<div>Tudor Associates Ltd</div>
<div>Mobile: +44(0)7412 074654</div>
<div><a href="http://www.tudorassoc.com/" target="_blank">www.tudorassoc.com</a></div>
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<div class="gmail_quote gmail_quote_container">
<div dir="ltr" class="gmail_attr">On Thu, 27 Feb 2025 at 16:57, Dewi Daniels <<a href="mailto:dewi.daniels@software-safety.com">dewi.daniels@software-safety.com</a>> wrote:<br>
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<div dir="ltr" class="gmail_attr">On Mon, 24 Feb 2025 at 19:07, Prof. Dr. Peter Bernard Ladkin <<a href="mailto:ladkin@causalis.com" target="_blank">ladkin@causalis.com</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
On 2025-02-24 19:55 , Robert P Schaefer wrote:<br>
> hi,<br>
><br>
> You have me there, I can’t speak to DAL A and would like to know more.<br>
><br>
> Could you reference a software engineering or computer science textbook that covers the topic?<br>
<br>
I can't, but others here (such as Dewi Daniels) maybe can. The relevant standards are RTCA DO-178C<br>
and RTCA DO-333. They of course cost money, but NASA has oodles of tech reports on the topic.There<br>
are NASA experts on this list who could say more.</blockquote>
<div><br>
</div>
<div>The best book I have read on DO-178C is Developing Safety-Critical Software: A Practical Guide for Aviation Software and DO-178C Compliance by Leanna Rierson. Leanna is a former Chief Scientific and Technical Advisor for airborne software at the FAA and
she was a member of the committee that wrote DO-178C.</div>
<div><br>
</div>
<div><a href="https://www.routledge.com/Developing-Safety-Critical-Software-A-Practical-Guide-for-Aviation-Software-and-DO-178C-Compliance/Rierson/p/book/9781439813683" target="_blank">https://www.routledge.com/Developing-Safety-Critical-Software-A-Practical-Guide-for-Aviation-Software-and-DO-178C-Compliance/Rierson/p/book/9781439813683</a></div>
<div><a href="https://books.google.co.uk/books?id=R0vRBQAAQBAJ&printsec=frontcover&redir_esc=y#v=onepage&q&f=false" target="_blank">https://books.google.co.uk/books?id=R0vRBQAAQBAJ&printsec=frontcover&redir_esc=y#v=onepage&q&f=false</a></div>
</div>
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<div style="color:rgb(34,34,34)"><a name="m_7242547633244158580_SignatureSanitizer_m_-5798674576462993830_SignatureSanitizer_SafeHtmlFilter_UNIQUE_ID_SafeHtmlFilter__MailAutoSig"><span style="font-size:10pt;font-family:Arial,sans-serif"><br>
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<p><span style="font-family:Arial,sans-serif;font-size:10pt">Dewi Daniels | Director | Software Safety Limited</span><br>
</p>
<p><span lang="FR" style="font-size:10pt;font-family:Arial,sans-serif">Telephone +44 7968 837742 | Email
<a href="mailto:dewi.daniels@software-safety.com" target="_blank">dewi.daniels@software-safety.com</a></span></p>
<p><font face="Arial, sans-serif">Software Safety Limited is a company registered in England and Wales. Company number: </font><font face="Arial, sans-serif">9390590</font><font face="Arial, sans-serif">. Registered office: Fairfield,
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