02-usart/src/init.c


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#include "arch.h"
#include "system.h"

/* Forward-declare the main function. This is implemented in main.c. */
void main();

/* These are defined in the linker script. */
extern uint32_t INIT_DATA_VALUES;
extern uint32_t DATA_SEGMENT_START;
extern uint32_t DATA_SEGMENT_STOP;
extern uint32_t BSS_START;
extern uint32_t BSS_END;

/*
 * Runs before main. Initializes the data and bss segments by loading them
 * into memory.
 */
_Noreturn void on_reset()
{
  uint32_t* src;
  uint32_t* dest;

  src = &INIT_DATA_VALUES;
  dest = &DATA_SEGMENT_START;

  /* Copy the values from flash into the data segment. */
  while (dest != &DATA_SEGMENT_STOP) {
    *(dest++) = *(src++);
  }

  /* Everything in the BSS segment is set to zero. */
  dest = &BSS_START;
  while (dest != &BSS_END) {
    *(dest++) = 0;
  }

  /* Set the vector offset table to be at the start
   * of FLASH memory. */
  SCB.vto_r = 0x08000000;

  /* Jump to main. */
  main();

  for(;;);
}