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ISRs vector table on GNU asm

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I have problem with nvic vector table for stellaris lm4f120.


here is my little asm code:


asm file:


.equ STACK_START,  0x20001000
.section .vectors
.align 4
.word _start + 1 // add 1 for thumb mode
linker script:
    FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x00040000
    SRAM (rwx) : ORIGIN = 0x20000000, LENGTH = 0x00008000
    .text :
        _text = .;
        _etext = .;
    } > FLASH
    .data : AT(ADDR(.text) + SIZEOF(.text))
        _data = .;
        _edata = .;
    } > SRAM
    .bss :
        _bss = .;
        _ebss = .;
    } > SRAM
compile options:
arm-none-eabi-as -mthumb -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=softfp -o main.o main.s
arm-none-eabi-as -mthumb -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=softfp -o nvic.o nvic.s
arm-none-eabi-ld -T make.ld  --entry _start  --gc-sections -nostdlib -Map main.map -o main.elf main.o nvic.o
arm-none-eabi-objcopy -O binary main.elf main.bin
but, when i flashing my test application to flash rom, I see that programm counter is not correct and it = 0
please, help me write correct gcc assembler code for vector table.
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On reset, VTABLE equals 0. This means the processor looks for the vector table beginning at memory address 0. You need a valid table there, so on powerup the processor knows where to go.


Put the address of a reset handler in flash address 4. It can load your new table on RAM and point VTABLE there. Any exceptions after that will look at your RAM table for handlers.

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eternauta3k, thanks for your reply.

for example, I want to blink RGB diode, ie just enable RED( on LM4F120 LaunchPad Evaluation Board  pin  PIN_29 ( PF1 ) I want set to low ).


I do:


.global _blink_rgb_red

.type _blink_rgb_red, %function



/* set PF1 as output */
mov r0, #0x02
ldr r1, =0x40025400
str r0,[r1]
/* set  PF1 data to 0 */
mov r0, #0
ldr r1, =0x40025000
str r0,[r1]
but it not working, because after boot program counter in not valid and it = 0 on startup while in flash address 4 offset is valid address.
here is my source code(attached).
Help me please, what am I doing wrong?
gdb session:
(gdb) target remote localhost:7777
Remote debugging using localhost:7777
0x00000000 in ?? ()
(gdb) x/xw 0
0x0: 0x20007fff
(gdb) x/xw 4
0x4: 0x000000e6
(gdb) info reg
r0             0x0 0
r1             0x0 0
r2             0x0 0
r3             0x0 0
r4             0x0 0
r5             0x0 0
r6             0x0 0
r7             0x0 0
r8             0x0 0
r9             0x0 0
r10            0x0 0
r11            0x0 0
r12            0x0 0
sp             0x20007fd8 0x20007fd8
lr             0xfffffff9 4294967289
pc             0x0 0x0
cpsr           0x20007fd8 536903640


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