> Try again.

Definitely better.

> I am generating 46.25 us interrupt and this is how I calculated.
> Using 16 mhz crystal with 8 bit timer 256(8 bit timer)-185(the value I
> use)=71 so if I put 71 in timer0 I should get 185/4=46.25 us interrupt.
> Now since there are timer0  (2 cycle) latency + interrupt (5 cycle)
> latency now real number should be 71-2-5=64 so if I put 64 in timer0 I
> should be able to get 46us but I am not getting 46us. By adjusting the
> number to 119

Don't try to account for the interrupt latency.  It is much better to add
a fixed value into timer 0 each interrupt.  16MHz clock means 4MHz timer 0
increment rate (assuming prescaler of 1).  1 / 4MHz = 250nS, which is the
timer 0 tick period.  46.25uS / 250nS = 185 timer 0 increments in your
desired interrupt period.

Left alone, timer 0 will cause an interrupt ever 256 ticks.  If you add
into TMR0, it misses 2 ticks, effectively making it 256 + 2 = 258 ticks
per interrupt.  258 - 185 = 73 too many ticks per interrupt period.
Therefore, you will achieve a 46.25uS interrupt period by adding 73 into
TMR0 each interrupt.

This assumes the prescaler is set to 1:1, meaning it must be assigned to
the watchdog timer instead of timer 0.  Of course the accuracy is
proportional to the accuracy of the CPU oscillator.


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