Yeah I very familiary with PLCs and ladder logic, statement list, etc... I would like mine to be interfaced with a PC so that once the ladder program is finished it can be send to the micro. After which the micro will handle everything by itself. It would be nice if i could send some data back to the PC so that if a swicth is closed I can see the switched closed on thh monitor.

I'm not going to creat timer for now, I wanted to start with something basic first. So that I know that the my communication is correct, and the micro is doing what I want.

Back to the Control block, a was thinking about creating a program in C for the micro in which it accept a variable such as IF (Serial.in = AB) then do this or else do that. Whilst AB is a variable whos value is 101. That is why I wanted to send a byte or more through serial. So that when it get to the micro the micro will sort of luck it up and figure out what i want it to do.