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KEIL long jump

niekiran

Hello
How can i instruct keil to use BLX instruction instead of BL.W while calling functions ?

any compiler settings ?

I need to call a function which is there in flash from ram code. Thanks.

  • 0

    Call it thru a function pointer.

  • 0 

    ; Reset handler
Reset_Handler    PROC
                 EXPORT  Reset_Handler             [WEAK]
        IMPORT  SystemInit
        IMPORT  __main

                 BL.W    SystemInit ; Relative

                 LDR     R0, =SystemInit
                 BLX     R0 ; Anywhere in 4GB space
                 LDR     R0, =__main
                 BX      R0
                 ENDP

        Reset_Handler
        0x00000000:    f7fffffe    ....    BL       SystemInit
        0x00000004:    4806        .H      LDR      r0,[pc,#24] ; [SystemInit = 0x20] = 0
        0x00000006:    4780        .G      BLX      r0
        0x00000008:    4806        .H      LDR      r0,[pc,#24] ; [__main = 0x24] = 0
        0x0000000a:    4700        .G      BX       r0

    Fixup the relative form based on the address you use, or use a PC relative form to load a literal into a register and use that. Use a jump table with absolute addresses.

    Generally best to keep all the code you want in RAM so as not to touch FLASH. Or use an attribute/pragma to push the functions you want in RAM into a section your describe in RAM via the scatter file load region.