>
Yes this is an expensive operation if you consider this is just one
single addition operation when calculating Bresenham.  I also have in
the background, packets coming in from the parrallel port from a PC,
which have to arrive within a reasonable time.  I think it make take 100
instruction cycles or more to get a single byte from the parrallel port.
I did however calculate my worst case timing senerio of 100micoseconds
max,  and that didn't take into account parrallel loading.  If I can
calculate my next position in less than that, my linear motion can
achieve 10inchs per second or 600 inches per minute.  This is a key
factor in the whole mess of things.
<

The Bresenham algorithm only requires a single add operation per cycle.
This sounds like a small fraction of your overall 100uS requirement.  With a
16xxx PIC running at 20MHz you get 500 instruction in 100uS, which sounds
like enough.  With an 18xxx you get twice that many.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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