[sdiy] dsPIC fun board

[Eric Brombaugh]

On Jan 18, 2009, at 4:27 AM, Ingo Debus wrote:

> Oops. Finally I found that parameter in the data sheet of the  
> dsPIC33. It's on page 272, called Cell Endurance. 1000 is the  
> typical number, the minimum is only 100! (I hope I got this right, I  
> have no idea what the unit E/W means)
>
> I had Atmel processors on my mind, where 100k Write Cycles are  
> specified for the Flash memory (AT89C51RD2/ED2).
> Funny that there's such a big difference.

Yes - that was a rude surprise for me when I first started working  
with the dsPIC33 series parts since the 5V dsPIC30 parts I used prior  
had more common 10^4/10^5 endurance range. I believe that the low  
write endurance values come about because of some compromises that  
MCHP had to make in their 3.3V flash process. Fortunately, I've never  
actually run into the limit despite using the same part for some  
intensive prototype development.

>>> Also, in my experience, EEPROMs are unreliable.
>>
>> This interests me. What specifically were the pitfalls you  
>> experienced in using EEPROM?
>
> It happened very rarely, but sometimes stored data were corrupted. I  
> don't know why. The EEPROM wasn't written very often. There was  
> additional circuitry that prevented unallowed states of the chip  
> enable line during power-up/down.
> Of course you can always add redundancy in software since EEPROM are  
> often much larger than needed (store the data twice, use checksums  
> etc). But this means additional programming effort.

That's good to know. I'll look into some additional protection logic  
for my application as well.

Eric