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Discussion Groups | | Re: Watchdogs and safety (was Thinking...)

Re: Watchdogs and safety (was Thinking...) - Oliver Betz - Jun 7 6:44:00 2002

"Michael Pont" <> wrote:

[you mentioned PC/IP corruption by EMI]

> We've done some work on this, but none of it is specific to HC11.
>
> You'll find a copy of one of our papers:

Thanks. One of the most interesting statements in this document is
this one:

"The Instruction Pointer is only one of many registers in an embedded
processor and there is no evidence to suggest that this particular
register is any more or less susceptible to EMI than the others."

Did your experiments include tests for the probability of corruption
of different registers?

Although I don't _know_ the mechanism, I doubt that registers are
influenced directly. There is no direct connection between the outer
world and the register, therefore it's well protected.

But the PC/IP has such a "connection": the clock input. I suspect
that illegal (e.g. too short) clock pulses can influence the PC/IP
logic. When I ran the HC12D60 with the PLL activated, there was no
more "code runaway". Well, that's no "evidence" but a suspicion. I
did not yet investigate the topic in detail.

IMO it would be interesting: to

- check the susceptibility of different registers
- look at the susceptibility of the clock input of the DUT

to search for "evidence to suggest that this particular register is
any more or less susceptible to EMI than the others."

At the moment I'm not able to do it, but maybe in the future.

Oliver





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