Please suggest a method to generate a 1ns pulse. with 680MHz frequency. i.e ton: 1ns. the pin should also be able to generate pulses with pulse width anything from 1ns to 4s with 1ns step, i.e the pulse can take any value b/n 1 ns and 4s with 1ns step. This pulse is used to trigger a laser. Thanks, Prathap Chandra Edit1: The pulse should be well shaped square wave.