Hi experts!
I want to use ldr/str or ldm/stm to copy memory not aligned 4bytes.
I know their input address should be aligned by 4 bytes.
but is there any solution to use ldr/str or ldm/stm though src or dst isn't aliged 4byte by modifing following code?
void wordcopy(unsigned char *dst, unsigned char *src, int num) {loop: LDR r3,[r1]; STR r3,[r0]; SUBS r2,r2,#1; BNE loop; BX lr;}
LDM/STM only support aligned addresses.
LDR/STR can be used with unaligned addresses, as long as the target addresses are marked as Normal and that alignment checking isn't enabled.
You didn't mention which processor/architecture you are targeting. For A class, the translation tables that define whether an address is Normal or Device. For R and M class, it's the MPU (if present).
The other option is to test in the passed in pointers. Do a number of byte load/stores until you get an aligned address, then do LDM/STM, and finish with more byte load/stores if needed.
EDIT: Typo