Gil, You ask for code lines, I avoid them, since I want to be global, not specific. as for state machines, I did a google (google also searches .pdf) websearch on | "state machine" design | and found among many others http://www.cs.byu.edu/courses/c...esign.html. You will find that much state machine discussion is on PLD's, however the theory and application is the same. A characteristic of a typical state machine in a '51 will be a subroutine, almost immediately having a jmp @a+dptr or a function that almost immediately has a switch statement.