Re: [EE] High reliability store and recall of data in EEPROM

Consider using an 8-bit CRC three or four times in a row.
One byte of the original value,
byte two is your CRC function called on the value once in a row
byte three is your CRC function called on the value twice in a row
byte four is your CRC function called on the value thrice in a row

On Fri, Dec 6, 2024 at 4:51 PM David VanHorn <[email protected]> wrote:

> I have a need to store some data in non-volatile memory, with the caveat
> that corrupt data MUST NOT occur.  Things go "big badda boom" otherwise.
>
> Offhand, I came up with storing each byte as a four byte array (I have TONS
> of space available)
> If I'm storing 0x01 then it would look like this:
>
> 1       2        3       4
> 0x01, 0xFE, 0x01, 0x55
>
> Xor 1 and 2, result must be zero.
> Xor 3 and 2, result must be zero.
> compare 1 and 3 result must be zero (not sure this is needed)
> check 4, must be 0x55 otherwise a wild write has happened in EE.
> Finally the values allowed will be sparse, and likely only a single bit
> will be set, so I will check that the value I read is one of the allowable
> values.
>
> If any of those checks fails, we render safe and halt.
>
> Is there a more "rock solid" method?    What would be done in an automotive
> environment for something like throttle position?   What would be best
> practice for medical life safety?
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-- 
Jason White
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