At 21:04 01/25/99 +1000, Clyde Smith-Stubbs wrote:
>On Mon, Jan 18, 1999 at 06:27:07AM +0100, Gianni wrote:
>> Unfortunately I haven't considered the necessary time to serve int. and
>> reload TMR0 . So I lose 10usec. every 8msec. = 4.5sec/h (a poor clock!!)
>
>The general solution to this is to add the time constant to TMRO in the
>interrupt
>routine, rather than storing the value. E.g.
>
>void interrupt tmr0()
>{
>        TMR0 += -125;
>}
>
>Because at the time of overflow, TMR0 has a value of 0, then however many
>counts
>elapse between then and when your interrupt routine runs will be the same as
>the value of TMR0 at that time, so adding the reload value will automatically
>compensate for the (variable) interrupt service time.

isn't it that since every write to timer 0 clears the prescaler, and your
addition will write to it (after reading it), you still loose on average
half the increment time per write?

ge