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Stuck at Startup code

Vectors LDR PC, Reset_Addr LDR PC, Undef_Addr LDR PC, SWI_Addr LDR PC, PAbt_Addr LDR PC, DAbt_Addr NOP ; Reserved Vector LDR PC, IRQ_Addr

LDR PC, [PC, #-0x0120] ; Vector

from VicVectAddr

LDR PC, FIQ_Addr

Reset_Addr DCD Reset_Handler

Undef_Addr DCD Undef_Handler

SWI_Addr DCD 0
PAbt_Addr DCD PAbt_Handler

DAbt_Addr DCD DAbt_Handler

DCD 0 ; Reserved Address

IRQ_Addr DCD 0

FIQ_Addr DCD FIQ_Handler

Undef_Handler B Undef_Handler

SWI_Handler B SWI_Handler

PAbt_Handler B PAbt_Handler

DAbt_Handler B DAbt_Handler

;IRQ_Handler B IRQ_Handler

FIQ_Handler B FIQ_Handler

; Reset Handler

EXPORT Reset_Handler

Reset_Handler

; Setup Stack for each mode

LDR R0, =Stack_Top

; Enter Undefined Instruction Mode and set its Stack

Pointer

MSR CPSR_c,

#Mode_UND:OR:I_Bit:OR:F_Bit

MOV SP, R0

SUB R0, R0, #UND_Stack_Size

; Enter Abort Mode and set its Stack Pointer

MSR CPSR_c,

#Mode_ABT:OR:I_Bit:OR:F_Bit

MOV SP, R0

SUB R0, R0, #ABT_Stack_Size

; Enter FIQ Mode and set its Stack Pointer

MSR CPSR_c,

#Mode_FIQ:OR:I_Bit:OR:F_Bit

MOV SP, R0

SUB R0, R0, #FIQ_Stack_Size

; Enter IRQ Mode and set its Stack Pointer

MSR CPSR_c,

#Mode_IRQ:OR:I_Bit:OR:F_Bit

MOV SP, R0

SUB R0, R0, #IRQ_Stack_Size

; Enter Supervisor Mode and set its Stack Pointer

MSR CPSR_c,

#Mode_SVC:OR:I_Bit:OR:F_Bit

MOV SP, R0

SUB R0, R0, #SVC_Stack_Size

; Enter User Mode and set its Stack Pointer

MSR CPSR_c, #Mode_USR

MOV SP, R0

SUB SL, SP, #USR_Stack_Size

; IMPORT TargetResetInit

; BL TargetResetInit

; Enter the C code

IMPORT __main

LDR R0, =__main

BX R0

; User Initial Stack & Heap

AREA |.text|, CODE, READONLY

IMPORT __use_two_region_memory

EXPORT __user_initial_stackheap
__user_initial_stackheap

LDR R0, = Heap_Mem

LDR R1, =(Stack_Mem +

USR_Stack_Size)

LDR R2, = (Heap_Mem +

Heap_Size)

LDR R3, = Stack_Mem

BX LR

END

This is my Startup code.
While debugging the execution stuck at "Enter the C Code part"
Instead of jump to main,program execution enter to below loop

0x0000012C E2522010 SUBS R2,R2,#0x00000010
0x00000130 28A10078 STMCSIA R1!,{R3-R6}
0x00000134 8AFFFFFC BHI 0x0000012C

I cant see the corresponding C code of this loop.
Plz give some suggestions or solution to this problem

Parents
  • While debugging the execution stuck at "BX R0"
    and instead of jump to main,program execution enter to below loop.
    ...
    What will be the problem.

    Why do you think there is a problem? Did you expected that the instruction "BX R0" would jump to main()? Actually, this instruction jumps into standard library initialization code which initializes static variables, stack and heap, and then jumps to main(). The loop you are referring to is zeroing code: uninitialized static variables are filled with zeros prior to main().
    If program flow doesn't reach main() eventually, then you have a problem...

Reply
  • While debugging the execution stuck at "BX R0"
    and instead of jump to main,program execution enter to below loop.
    ...
    What will be the problem.

    Why do you think there is a problem? Did you expected that the instruction "BX R0" would jump to main()? Actually, this instruction jumps into standard library initialization code which initializes static variables, stack and heap, and then jumps to main(). The loop you are referring to is zeroing code: uninitialized static variables are filled with zeros prior to main().
    If program flow doesn't reach main() eventually, then you have a problem...

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