> Hello everybody,
> I am having deficalty in getting the right dely to the clock i am using
for my pic16f877.  which i am using 20MHz clock.  I have calculated a 1msec
as follows:

The problem is: it takes 4 cycles of the 20MHz clock for each instruction
(and 8 for branches and skips 'taken').  So your results are off by a factor
of 3. (note: I didn't actually verify your code, just your comments).

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

> I have a clock of 20MHz that meens 50nsec
> then I have three instructions for each function so what i did is
> 50nsec X 3inst X (how many time to be multiplied (n))= 1msec
> so,
> n = (1m X 20MHz) / 3inst = 6666.66666
> then,
> I devided that number by 100 to split it into two equations,  so I got 67
and 100.
>
> the following is my iomplemented function,  however,  i am not getting the
right delay.  I am geting larger delay
>
>
>
> Wait1ms
>         movlw   .67
>         movwf   temp11
> Wait1msB1
>         movlw   .100
>         movwf   temp12
> Wait1msB2
>         decfsz  temp12,1         ; this is one instruction
>         goto    Wait1msB2       ; this is two instructions which make 3
total
>         decfsz  temp11,1         ; the same here
>         goto    Wait1msB1
>         return
>
> can any body help
> Thank you
>
> regards,
> Paul
>
>
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