it depends on what you're using as a clock source. if you're using a high-grade crystal with some bullet-proof wiring, the spec sheets for the part can be extremely accurate (i know that the higher-end pics can meausre down to 10 nanoseconds or so..) nick David Knaack wrote: > If I have my AT90S1200 running at 12Mhz, how accurately can I measure time, > and to what resolution? > > Thanks, > DK