I'm not sure I understand your question, but maybe I can answer it anyway. First of all, please read this:

http://www.8052.com/faqs.phtml?FAQ=143904

As the FAQ says, if you want your program to "stop", you must put intentionally put it into an infinie loop. by putting at the end something like this:

stop: sjmp stop         ; Loop here forever

if you are writing in assembly language, or this:

while (1) ;             /* Loop here forever */

if you are writing in C.

However, most microcontroller programs are not supposed to stop. They are supposed to run forever until the power is removed. To make that work, you run the entire program inside an infinite loop, like this:

top:
; Do everyting here
     jmp top            ; Go do everything again

if you are writing in assembly language, or this:

while (1) {             /* Loop forever */
    /* Do everything here */
    }                   /* End 'loop forever' */

if you are writing in C.

If you do not intentionally put your program into an infinite loop, then when it "runs off the end", the processor will try to execute whatever is in the code space immediately after your program. If that memory contains all 0xFFs, as it would in an unprogrammed flash device or EPROM, the processor will execute to the end of the memory. At that point it may wrap back around to address zero and start your program over again (sort of) as though a reset had occurred. Or it may not!

In any case, you should never let your program "run off the end". You should always code an explicit infinite loop to make it behave the way you want it to.

-- Russ