Going back to Ger21's post, I fully understand that the pulses will probably not be 'clean' pulses, but as you say, the pulse width can be set in Mach3. So, assuming that a 20 uS pulse is selected, that 'dirty' pulse may consist of several square wave oscillations followed by a low voltage level before the next pulse is sent? Also, assuming that the pulse is read only on the first rising wave form, would it be advantageous that the first rising pulse as well as incrementing the count also initiates a 'wait' sequence of, say 18 uS before it attempts to read the next pulse?