> Hi, Bob,
>
> well, now that's very interesting!
>
> By the way: I heart in a seminar, that MC invented a new storage cell
> (years
> ago) which allows making the chip smaller and cheaper. Do we have to live
> with unreliable PROGRAM storage space also?

Knock on wood... I have not noticed any problems with the PGM storage cells=
..
>
> I'll make an analysis first before we go into deeper discussion. I want t=
o
> know, from which batch the failing devices are, then I let you know.
>
> Very interesting was the hint about brown out, because my customers alway=
s
> use the device until battery is dead. And the 12F519 has no brown out
> detection...

I think if you switched to PIC12f629 FROM pic12f519 you can be brownout
protected.

Be aware that two years ago there was a problem with several chips,
including the PIC12F629 and PIC12F675, in which the EEPROM timer status
bit dropped back too early. This problem occurred in MANY nanowatt
devices, but Microchip was VERY slow to admit it and issue a workaround
(which was to time the EEPROM Cell charger externally)
>
> Regards
>
> Peter
>
>
>> 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 mode 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)
>>
>
> I spend several weeks on this, finally pinning the problem on our Blessed
> Microchip (sigh).
>
> First: carefully search the archives for ANY EEPROM failures before the
> PIC12F/16F/18Fxxxx series devices were released. I can count on less than
> one finger's worth. And I designed the EEPROM into everything, making
> configuration storage, calibration tables, everything.
>
> Second: Microchip releases many PIC12F/PIC16F/PIC18F devices, and then
> begins to make excuses for EEPROM failures. What happened was that when
> Microchip reduced the die size on the PIC12/PIC16F/PIC18F devices, the
> cell
> size was reduced to an almost unworkable size.
>
> Having gone to an unworkable cell size, they can't go back and fix it. If
> you search carefully, you will notice that Microchip recommends rewriting
> (refreshing) the EEPROM cell array periodically. But I uncovered a BETTER
> way:
>
> Write 5 copies of your variables into the cell array. When you read them,
> read all 5 copies into a buffer. (1) IF ALL ARE IDENTICAL, use the copy
> and
> you are done; (2) if 3 or more of the 5 sets are identical, use one of th=
e
> 3
> same copies as "good" as data, then rewrite all 5 copies of the array. If
> less than 3 are identical, you are screwed... but guess what, I NEVER saw
> that happen. What seems to happen is that one or more bits are changed
> over
> a year's period, and this corrects them.
>
> The advantage over Microchip's method is that there is a MAX rewrite
> limit.
> My method only rewrites when there is a true error, so the limit is very
> unlikely to be reached.
>
> This method, that I call "Best of 5", always works for me.
>
> Otherwise, drop the internal PIC EEPROM and use an external EEPROM, which
> does not have super small cells.
>
> --Bob A
>
>
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>
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