So, this thread has been alive for long enough to capture my interest 
even though I do not need the solution myself. Here's how I would get 
67M counts ot of 1024 bytes of EEPROM without exceeding 100K writes per 
cell (in fact, keeping about 30% lower than the limit).

Keep two EEPROM bytes for a pointer to EEPROM, these will be the last 
two bytes in EEPROM. Initially pointer is set at 0x0000

Use a 2 byte counter at the pointer position. Increment that counter at 
each event.
At the 2 byte overflow, increment the pointer. This will be at 256^2 
counts (65536).
What was the low byte of the 2-byte counter now becomes the high byte of 
the next pointer.
EEPROM now looks like:
0x00 0x00, 0x00, ..., ... ......., ..., 0x00, 0x01

Byte 1 (the second byte) has been written 65K times.

With the current pointer, Byte 1 will be written another 256 times as 
the High byte of the next pointed value, giving a total of
65792 writes.

To calculate the count it is a simple case of 65536 * Pointer + 2byte 
value at pointer

My math indicates with 1024 bytes EEPROM the numbers are:

Max value: 1021 * 65536 + 65535 = 66,977,791

byte 0 of EEPROM gets 256 writes.
byte 1-1020 get 65792 writes.
byte 1021 gets 65536 writes.
byte 1022 gets 3 writes
byte 1023 gets 768 writes

With some more thought, and a more complicated count mechanism, I am 
sure I could get close to 100M count in 1024 bytes, but would be much 
more complex (I think).

with 256 bytes EEPROM I could get: 16.5M count

Rolf

Gerhard Fiedler wrote:
> Shawn Wilton wrote:
>
>   
>> There is no array to speak of.
>>
>> To answer both you and Gerhard:
>> http://atmel.com/dyn/resources/prod_documents/doc2526.pdf
>>     
>
> Sorry, but that doesn't answer my question; it's too generic and allows all
> kinds of strategies. How exactly do you get your 50M counts out of 1024
> bytes of EEPROM storage when writing to each cell max. 100k times? How do
> you structure the buffer? How do you increment the count? How do you
> calculate the current count?
>
> Gerhard
>
>   

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist