>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 31 May 2006 08:07
>To: Microcontroller discussion list - Public.
>Subject: Re: [PIC] operation time counter
>
>
>Hi Peter, some comments
>
>> The total time to be checked is 5 years and the resolution 
>has to be 1 
>> minute.
>
>You simply won't get that accuracy over 5 years with a PIC's 
>TMR. An external timing source is needed
>

AFAICT the OP only requires a resolution of 1 minute, not an accuracy of 1 minute in 5 years which would be pretty much impossible to achieve with a normal quartz crystal.

There was a fairly recent thread on spreading out writes over the EEPROM to maximise endurance, a search of the archives should find it.

Regards

Mike

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