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'Human Safety'
1997\09\16@080352 by Miller, Steve

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The new Scenix chips are supposed to comply with some UL 98 standard that
requires the microcontroller to verify the integrity of the code.  Does anyone
have the details of this standard?  Several microcontrollers allow access to the
ROM code, so a checksum is possible.  However, how do I know an ROM error does
not exist in the code that I wrote to check the ROM?  Will the new Scenix chip
have a hardware checksum circuit?
How important is this checksum?
The new AVR does not allow user access to the ROM, is it unusable in safety
circuits?

Thanks.

----- Steve


>Don't use a 16CXXX PIC. If you cannot verify program integrity at
>startup, you shouldn't use it in medical applications.

>You can, however, calculate some sort of a checksum on the 17CXXX's.

>--
>Friendly Regards
>
>Tjaart van der Walt
>spam_OUTtjaartTakeThisOuTspamwasp.co.za

1997\09\16@083204 by Antti Lukats

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At 07:00 AM 16/9/97 -0600, you wrote:
>The new Scenix chips are supposed to comply with some UL 98 standard that
>requires the microcontroller to verify the integrity of the code.  Does anyone
>have the details of this standard?  Several microcontrollers allow access
to the
>ROM code, so a checksum is possible.  However, how do I know an ROM error does
>not exist in the code that I wrote to check the ROM?  Will the new Scenix chip
>have a hardware checksum circuit?
>How important is this checksum?
>The new AVR does not allow user access to the ROM, is it unusable in safety
>circuits?

only AT90S1200 does not have access to ROM, all other AVR variants
can read their ROM contents.

antti

AVR Basic Light NOW Available - Look for September Specials
http://avrbasic.com    Free AVR Basic Compiler Demo Edition

1997\09\16@092617 by Keith Dowsett

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Someone asked earlier about verifying programs before execution. If I were
designing for an application of this sort I guess I'd pay the extra few
dollars for the 17C4x series chips. These have a TABLRD instruction which
can be used to read the program memory for testing.

Hmm, now I think about it I might have an application for one.....

Keith.
------------------------------------------------------------
Keith Dowsett         "Variables won't; constants aren't."

E-mail: .....kdowsettKILLspamspam@spam@rpms.ac.uk  or kdowsettspamKILLspamgeocities.com

WWW: http://kd.rpms.ac.uk/index.htm
    www.geocities.com/CapeCanaveral/Lab/8979

1997\09\17@025752 by mikesmith_oz.nosp*m

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On 16 Sep 97 at 1:24, Antti Lukats wrote:

> At 07:00 AM 16/9/97 -0600, you wrote:
> >The new Scenix chips are supposed to comply with some UL 98 standard that

I've done a bit of a search for this, or similar standards, on the
web.  Anyone got a url for it?

> >requires the microcontroller to verify the integrity of the code.  Does
anyone
> >have the details of this standard?  Several microcontrollers allow access
> to the
> >ROM code, so a checksum is possible.  However, how do I know an ROM error
does
> >not exist in the code that I wrote to check the ROM?  Will the new Scenix
chip

To make it truly safe, it should be in real rom, that just runs thru
the eeprom and compares it with a crc in a known site.

> >have a hardware checksum circuit?
> >How important is this checksum?

Question is - Would working in a faulty manner be better or worse
than not working at all?  Follow up question - how is the 'not
working at all' implemented?
examples-
       Space probe - better to work faulty - or - request a d/l to ram
       Pacemaker - better to fall back to a 'metronome' cct.
       ABS - disable - go to normal braking - warning light
       Traffic lights - disable
MikeS
<mikesmith_oz@nosp*m.relaymail.net>
(remove the you know what before replying)

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