Hello all, What is the need for memory remapping in ARM?What are the pros and cons? Will there be a time difference in time while fetching a data from a on chip ROM and an off chip flash memory?
What is the need for memory remapping in ARM?What are the pros and cons? One basic reason is that an ARM starts execution from address 0. So, this address must be non-volatile. On the other hand, all the interrupt vectors are located from 0 up. You often want these to be rewritable. So, address 0 must be non-volatile and contain a valid instruction. One common solution to this conundrum is to boot from flash mapped to address 0, jump to a higher, aliased address in that flash, and then remap RAM to address 0. You also might map from an on-chip boot ROM to a reprogrammable off-chip application flash, even with hardwired interrupt vectors. The address space of the ARM is large enough that it's normally just the special addresses that are of interest. Will there be a time difference in time while fetching a data from a on chip ROM and an off chip flash memory? Check your data sheets. ROM/flash is typically significantly slower than RAM. Whether one flash is slower than another will depend on the specific parts. Delay due to external location of the bits is neglible in comparison to their access time.