I have problem, I have to find a way to update code to my arm device without removing it, for that purpose I'll use serial communication. Does anyone have idea how to do it?
I agree. And there's not much distance between making an update directly and making the update via a UART cable.
It's basically just to place the part that needs updating in SRAM before starting. One thing that's very important, is to check if the final update is OK (by verification, such as a kind of checksum/CRC), so that if the update code is not valid, it will not be executed. -But jacobbeningo covers these things completely. It's an excellent and well-written document, which can be read more than once.