Jinx <joecolquitt <at> clear.net.nz> writes:
> > Assembly users whole day keep searching how to create 1 us delay
> > using 6.167MHz crystal and C users do it in 1 minute just specify the
> > clock and ask 1 us delay all done

:)

> Andre, I don't use C, so what's the solution to making a 1us delay
> with 649ns instruction times ?

T ~= 648.613588455
pll x8 -> 81.076698556875 nsec
1000 nsec / 81.076698556875 ~= 12.333999999993

divider is 12.333999999993 rounded up to 12.334

as sum of fractions ~= 12 + 1/3 + 1/1000

so, pll x8, divide by 12 (in software), counting loops (of 12). Every 3rd loop
of 12 divide by 12+1 and every 1000th loop of 12 divide by 12+1 (but by 12+2 if
the 3-s loop count coincides with the 1000-s loop), for a divider error of ~
2x10-12. If ~ 1x10-5 is enough forget the 1/1000 part. Other dividers and pll
settings are also possible.

:) except you likely don't want to do it this way. Doing it in hardware (MSI) is
left as an exercise >;-)~

Peter


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