hi,
thx for the insight fedia.i shall look more deeply into it.
anyway, i am considering an optical sensor
using reflected red laser light, much like a commercially available tachometer.any help or ideas on the same are welcome.i am basically looking at sticking a paper disc with black background and a plain white strip to reflect red laser onto a photodiode/phototransistor which will be the interrupt source.
does anyone have an idea what is the maximum rate at which i can interrupt the ds5000. i mean, there is a minimum time the interrupt has to be high to be registered (1 clk cycle?).
anyway, thanks guys for the informative feedback.am looking forward to more.

-Vinod