Reset_Handler:
/*     Loop to copy data from read only memory to RAM. The ranges
 *      of copy from/to are specified by following symbols evaluated in
 *      linker script.
 *      __etext: End of code section, i.e., begin of data sections to copy from.
 *      __data_start__/__data_end__: RAM address range that data should be
 *      copied to. Both must be aligned to 4 bytes boundary.  */

    ldr    r1, =__etext
    ldr    r2, =__data_start__
    ldr    r3, =__data_end__

    subs    r3, r2
    ble    .flash_to_ram_loop_end

    movs    r4, 0
.flash_to_ram_loop:
    ldr    r0, [r1,r4]
    str    r0, [r2,r4]
    adds    r4, 4
    cmp    r4, r3
    blt    .flash_to_ram_loop
.flash_to_ram_loop_end:

#ifndef __NO_SYSTEM_INIT
    ldr    r0, =SystemInit
    blx    r0
#endif

    ldr    r0, =_start
    bx    r0
    .pool
    .size Reset_Handler, . - Reset_Handler

/* Our weak _start alternative if we don't use the library _start
 * The zero init section must be cleared, otherwise the librtary is
 * doing that */
    .align 1
    .thumb_func
    .weak _start
    .type _start, %function
_start:

    /* Zero fill the bss segment. */
    ldr   r1, = __bss_start__
    ldr   r2, = __bss_end__
    movs  r3, #0
    b  .fill_zero_bss
.loop_zero_bss:
    str  r3, [r1]
   adds r1, 4

.fill_zero_bss:
    cmp  r1, r2
    bcc  .loop_zero_bss

    /* Jump to our main */
    bl main
    b .
    .size    _start, . - _start

   /* .stack_dummy section doesn't contains any symbols. It is only
    * used for linker to calculate size of stack sections, and assign
    * values to stack symbols later */
   .stack_dummy (NOLOAD):
   {
      *(.stack)
   } > RAM

   /* Set stack top to end of RAM, and stack limit move down by
    * size of stack_dummy section */
   __StackTop = ORIGIN(RAM) + LENGTH(RAM);
   __StackLimit = __StackTop - SIZEOF(.stack_dummy);
   PROVIDE(__stack = __StackTop);
   
   /* Check if data + heap + stack exceeds RAM limit */
   ASSERT(__StackLimit >= __HeapLimit, "region RAM overflowed with stack")