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From: antispam@fricas.org (Waldek Hebisch)
Newsgroups: comp.arch.embedded
Subject: Re: Diagnostics
Date: Fri, 18 Oct 2024 20:30:06 -0000 (UTC)
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Don Y <blockedofcourse@foo.invalid> wrote:
> Typically, one performs some limited "confidence tests"
> at POST to catch gross failures.  As this activity is
> "in series" with normal operation, it tends to be brief
> and not very thorough.
> 
> Many products offer a BIST capability that the user can invoke
> for more thorough testing.  This allows the user to decide
> when he can afford to live without the normal functioning of the
> device.
> 
> And, if you are a "robust" designer, you often include invariants
> that verify hardware operations (esp to I/Os) are actually doing
> what they should -- e.g., verifying battery voltage increases
> when you activate the charging circuit, loopbacks on DIOs, etc.
> 
> But, for 24/7/365 boxes, POST is a "once-in-a-lifetime" activity.
> And, BIST might not always be convenient (as well as requiring the
> user's consent and participation).
> 
> There, runtime diagnostics are the only alternative for hardware
> revalidation, PFA and diagnostics.
> 
> How commonly are such mechanisms implemented?  And, how thoroughly?

This is strange question.  AFAIK automatically run diagnostics/checks
are part of safety regulations.  Even if some safety critical software
does not contain them, nobody is going to admit violationg regulations.  
And things like PLC-s are "dual use", they may be used in non-safety
role, but vendors claim compliance to safety standards.

-- 
                              Waldek Hebisch