@Toble_Miner that's the point I haven't quite understood yet. The datasheet says the vector table is in ROM (actual ROM, not User Flash) at 0x00000000 but is remapped to the start of SRAM, except the stack pointer and reset vector, which are at the start of User Flash. So I guess at the very start it starts off in user flash and the reset vector points to the startup code that copies the vector table to SRAM. Not quite sure how the ROM plays into this