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SAM7.s branch to main() causes SWI. Why ?

Terje Bohler

Hello.

In my SAM7.s startup file for AT91SAM7X256, the following instructions are executed:

. . .
; Enter the C code
       IMPORT  __main
       LDR     R0, =__main
      BX      R0


. . . Disassembled as follows:
0x0010011C  E24DAB01  SUB       R10,R13,#0x00000400
0x00100120  E59F0024  LDR       R0,[PC,#0x0024]
0x00100124  E12FFF10  BX        R0
0x00100128  FFFFFD00  (???)
0x0010012C  A5000401  STRGE     R0,[R0,#-0x0401]
0x00100130  FFFFFF00  (???)

This BX instruction should cause my main() to be executed next.
Instead, the PC executes/enters the SWI_Handler immediately after the BX instruction.
Is there a fundamental issue I have overseen ?
I appreciate your answers/comments to this issue.

Regards Terje Bøhler

Parents
  • 0 in reply to ImPer Westermark

    Thank you Per for your answer!
    I'm new to ARM and KEIL so excuse me for my silly questions.
    The code is running in the simulator.
    Q1: You say " ...in the CRTL". What does "the CRTL" mean ?
    Q2: You say "You might have configured the memory regions wrong". I assume you are referring to the IROM1 and IRAM1 settings done in the "TargetOption Target"? (which is IROM1:100.000 (size=0x40.000) IRAM:0x200.000 (size:0x10.000), generated automatically)
    Regards Terje

Reply
  • 0 in reply to ImPer Westermark

    Thank you Per for your answer!
    I'm new to ARM and KEIL so excuse me for my silly questions.
    The code is running in the simulator.
    Q1: You say " ...in the CRTL". What does "the CRTL" mean ?
    Q2: You say "You might have configured the memory regions wrong". I assume you are referring to the IROM1 and IRAM1 settings done in the "TargetOption Target"? (which is IROM1:100.000 (size=0x40.000) IRAM:0x200.000 (size:0x10.000), generated automatically)
    Regards Terje

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