> Hi ppl,
> Am a newbie to u-boot as well as arm
> assembly.
> wanted to know about the startup code. Below is the
> vector table pasted from the code. What i dont
> understand is why only the reset vector is PC
> relative
> and all others have memory allocated to hold the
> addresses. I mean all other vectors also could be
> branch instructions.Any reason ?
>
> .globl _start
> _start: b reset
> 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
> Thanks and Regards,
> Srinivas Bakki
Hi,
I have thought of an explanation can anyone please
rectify if am wrong.
the load to PC instruction allows utilizing the full
32-bit address space for placement of the exception
handlers, whereas the relative branch instruction is
limited to +/- 25 bits relative to the current PC.
is that right ?
Regards,
Srinivas Bakki
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