Cool, I'll give it a try.  My bad assumption seems to be that there 
"must" be an erase to the page to write a single location.  As long as 
what's currently there is all ones, new data can be written without an 
erase - very interesting.

Thanks,

Tony


Vitaliy wrote:
> "Tony Vandiver"
>   
>>    I'm aware of a 1000 write limit on the flash of a lot of the pic
>> micros, and considering that flash is written in pages (512 bytes I
>> think for the PIC24 I'm using on a project, but principle is the same
>> regardless), does anyone know if the limit applies if the bytes are not
>> changed?
>>     
>
> Yes, for the reason you list below.
>
>   
>>  I know that the flash has to be erased first so I would assume
>> that it wouldn't matter if you wrote the same data to the flash 1000
>> times, it would still count against the lifetime of the flash.  I was
>> considering some onboard storage in a project where I've already got the
>> boards in (i.e. no hardware fixes like just add an eeprom), and
>> wondering if a round-robin approach might work in the same page.
>>     
>
> Microchip has an app note which describes a good way to emulate EEPROM in 
> Flash:
>
> http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en530593
>
> Credit goes to my colleague who sent me this link three weeks ago.
>
> Vitaliy 
>
>   
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