> Using your formula and simulating in Excel I always get an offset
dependant
> on FF  i.e. if using 1/16 then error is -15 counts and if 1/32 then error
> is -31 counts.  Should this be added on at the end if using integer maths?

The formula was not intended for just integers.  It is usually a good idea
to have enough fraction bits for the bits of shifting implied by FF.  So if
FF is 1/16, then there should be 4 fraction bits.  Of course the formula
works with more too.  Sometimes is is convenient to use 8 fraction bits even
when fewer are needed.  The result can be read by picking off the approriate
bytes instead of having to shift to get rid of the fraction bits.


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