Say I have a very simple program that functions perfectly fine on a ARM Cortex M0+ processor. How much will I need to change in order for it to work on an ARM Cortex M4 processor, assuming they are both made by the same company and I have imported the new cores header.
I just can't think of any reason it wouldn't work. They use a similar instruction set. I mean the M4 has a much more expanded Thumb-2 instruction set over the M0+. In my experience, companies keep the same naming scheme when they make their ARM device headers.