In LPC21xx ARM7 MCUs, when the MEMMAP[1:0]register=00 ,ie in bootloader mode,the interrupts are mapped from on chip flash to a new location at 0x7FFF E008.But this address is somewhere near 2GB in addres space and the MCU has 16kb ram and 256 kb flash, all of which end at 0x4000 3FFF. Then where is this 'mapped copy' actually copied? Surely, there is no physical storage element present at 0x7FFF E008.
Thanks in advance.
(I don't know much about this, but I would like to answer this question from my understanding, and hope that my answer can be verified and corrected.)
en.wikipedia.org/.../Address_space [start] In computing, an address space defines a range of discrete addresses, each of which may correspond to a physical or virtual memory register, a network host, peripheral device, disk sector or other logical or physical entity.
In general, things in one address space are physically in a different location than things in another address space. However, sometimes different address spaces overlap (some physical location exists in both address spaces). [end]
There are 4G address/memory space there, but the physically memory is much less than 4G. So some of them must be virtual. For myself, I prefer to treat them as, all of the 4G address/memory space are virtual. As I am a software guy, don't know anything about hardware, physically memory address is not important to me.
The memory remapping is just like some kind of creating a "shortcut" or creating a "symbolic link", The data copy is unnecessary.
[start] UM10114 LPC21xx and LPC22xx User manual Rev. 03 â€" 2 April 2008 User manual
Chapter 2: LPC21xx/22xx Memory map
3.1 Memory map concepts and operating modes
The basic concept on the LPC21xx and LPC22xx is that each memory area has a "natural" location in the memory map. This is the address range for which code residing in that area is written. The bulk of each memory space remains permanently fixed in the same location, eliminating the need to have portions of the code designed to run in different address ranges. [end]
ARM7 processor always gets its ARM exception vectors from the virtual memory addresses 0x0000 0000 through 0x0000 001C, no matter where the virtual memory addresses point to. So, if you need different ARM exception vectors, then remap your virtual memory addresses. (And I remember that some expert emphasizes that, An ARM exception vector is an instruction for execution, not an address for goto.)