Hi All, I am new to u-boot and ARM. I am trying to understand uboot thtough start.S file. I have few questions about it. 1) What is the deifference between ARM Supervisior and User mode. why uboot is not running in user mode? 2) At the start of startup file I found below code.
.globl _start _start: b start_code ldr pc, _undefined_instruction ldr pc, _software_interrupt ldr pc, _prefetch_abort ldr pc, _data_abort ldr pc, _not_used ldr pc, _irq ldr pc, _fiq _undefined_instruction: .word undefined_instruction _software_interrupt: .word software_interrupt _prefetch_abort: .word prefetch_abort _data_abort: .word data_abort _not_used: .word not_used _irq: .word irq _fiq: .word fiq .balignl 16,0xdeadbeef What is this code will do? as i believe the instruction "b start_code" will branch it to start_code then how does the other code below branch instruction will work? 3) where does exception vector table located during power on? on boot rom or at any other place? Thanks & Regards, Asmit Patel"
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