Uh, stopping the clock might do it, but I don't think there's an instruction for that. And if there were, you'd never be able to execute the next instruction under program control.
By way of illumination, let me ask you this: Why would you want to 'not affect' the program counter?
I suspect that you are perhaps new to embedded system programming, and are asking a perfectly logical, classical 'noob' question, "How do I get my program to stop, and wait for an input, and then start up again?" "When I program in a 'stop' command, it just stops, and never restarts."
The answer is, you write the program so it never, never, ever stops running, it just stops _appearing_ to do anything, but it really runs in a loop, constantly polling the input, i.e., asking the same switch, over and over, "Did the idiot out front do anything?", and repeating until it gets an answer different from "no".
I hope that helped, or at least didn't insult you.
you're right, i just started doing this about 2 months by myself, i bought few book and learn at home when i have time, i also bought some equipments to practice at home, thanks for the answer
