Em 20/2/2011 18:44, IB Peter Feucht escreveu:
> =20
> Hi, all,
>
> I designed a small device about 2 years ago, which can be operated in two
> different modes. Switching to mode 2 is only done here at the factory by
> pressing a key in a specific pattern (Press 10 seconds, then wait until
> light is off, then release key between 2 and 4 seconds, wait until light =
is
> on again, then press 4 times within 3 seconds, someting like that). The
> state of mode is stored in eeprom address 00, 0x00 for mode 1, 0x80 for m=
ode
> 2.
>
> Now during the last 3 weeks about 10 customers called to tell, that the
> device is suddenly operating in mode 2, even if it was shipped in mode 1.
> The procedure to change mode was never made available to the public and
> futhermore there is no advantage at all for most customers to change mode=
..
>
> Question: Does anybody have information about the reliability of eeprom
> content?
> How is it possible that eeprom content changes (electric field, magnetic
> fields or or or)
>
> Thanks for hlep.
>
> Peter


Are the affected equipments old or are of a new batch?

1) If the devices are new:
    a) You may have received a lot of bad MCUs
    b) You may have received a compatible device with different
electrical characteristics (die revision, etc.)
    c) Your programmer or programming procedure may have been broken/wrong

2) If the devices are old:
    a) The EEPROM was marginally programmed and the charge leaked away
    b) Your firmware is over-stressing neighboring EEPROM addresses and
never refresh the affected address
    c) You firmware may have some hidden bug that got activated just now
(very unlikely)


Best regards,

Isaac

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