Re: AVR Flash EMI Susceptibility?

From: Jim Granville (no.spam_at_designtools.co.nz)
Date: 11/17/04

  • Next message: Gerhard Hempl: "Re: Bootloader - erase flash memory" 
    Date: Thu, 18 Nov 2004 07:56:04 +1300

    jetmarc wrote:
    >>susceptibility (Murphy says we can't), I guess I'll be forced to forgo the
    >>flexibility of in-the-field serial reprogramming and disable
    >>self-programming via the fuse bits. I *think* self programming via the SPM
    >>instruction is the only way to do a page erase.
    >
    >
    > I dont want to scare you, but a fuse-bit is a only a flash cell, too.
    > If the EMI conditions are such that the chip does an SPM to the wrong
    > page or where no SPM instruction actually was, it can just as well do
    > an SPM where the fuse-bit said "NO".
    >
    > As long as the voltage pumps are on-chip, things can go wrong. Less
    > logic to operate them can make it less probable (eg chip without SPM
    > funcionality), but only removing them completely will make the chip
    > safe (eg external VPP like in the old days).
    >
    > Thats my opinion only, certainly flash mcu manufacturers have a different
    > one.

      I think this is a key reason we see a re-emergence of ROM flow
    variants of FLASH uC. These days, it is very unlikely they are
    completely different die/mask flows, most efficent is to disable the
    voltage pumps, and skip the FLASH cycle testing = lower outgoing price,
    AND the highest field reliability.
      I believe some Automotive customers demand high voltage PGM enable, for
    similar reasons.
    -jg

  • Next message: Gerhard Hempl: "Re: Bootloader - erase flash memory"

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