#include <ST\iostm32f407VG.h> //Это недостающий заголовочник для IAR 6.30, который пришлось добавить самому.

#define COUNT 0x0001A0FF

//////////////////////////////////////////////////////////////////////////////
int main()
{
  RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN; //Enable GPIO A
  RCC->AHB1ENR |= RCC_AHB1ENR_GPIODEN; //Enable GPIO D
 
  //RCC->APB1RSTR |= RCC_AHB1RSTR_GPIOARST; //Reset GPIO A
  //RCC->APB1RSTR |= RCC_AHB1RSTR_GPIODRST; //Reset GPIO D
 
  GPIOD->MODER |= (GPIO_MODER_MODER15_0 |
                   GPIO_MODER_MODER14_0 |
                   GPIO_MODER_MODER13_0 |
                   GPIO_MODER_MODER12_0); // GPIO Mode Port Out
 
  GPIOD->OTYPER = 0x00000000; //Out D type Push-Pull
  GPIOD->OSPEEDR = 0x00000000; //Out Speed Low (2MHz)
  GPIOD->PUPDR = 0x00000000; //Not Pull Up/Down

 
  unsigned char a = 0;
  while(1)
  {
    if((GPIOA->IDR) & (GPIO_IDR_IDR_0) == 1) //if PA0 is set to 1 (button pressed)
    {
      a = ~a;
      while((GPIOA->IDR) & (GPIO_IDR_IDR_0) == 1) //if PA0 is set to 1 (button pressed)
      {
        asm("nop");
      }
    }
   
    if(!a)
    {
      for(int i = 0 ; i < COUNT ; i++){GPIOD->ODR |= GPIO_ODR_ODR_15;} //Set 1 to PD15
      for(int i = 0 ; i < COUNT ; i++){GPIOD->ODR &= ~GPIO_ODR_ODR_15;} //Set 0 to PD15
     
      for(int i = 0 ; i < COUNT ; i++){GPIOD->ODR |= GPIO_ODR_ODR_14;} //Set 1 to PD14
      for(int i = 0 ; i < COUNT ; i++){GPIOD->ODR &= ~GPIO_ODR_ODR_14;} //Set 0 to PD14
     
      for(int i = 0 ; i < COUNT ; i++){GPIOD->ODR |= GPIO_ODR_ODR_13;} //Set 1 to PD13
      for(int i = 0 ; i < COUNT ; i++){GPIOD->ODR &= ~GPIO_ODR_ODR_13;} //Set 0 to PD13
     
      for(int i = 0 ; i < COUNT ; i++){GPIOD->ODR |= GPIO_ODR_ODR_12;} //Set 1 to PD12
      for(int i = 0 ; i < COUNT ; i++){GPIOD->ODR &= ~GPIO_ODR_ODR_12;} //Set 0 to PD12
    }
  }
  //return 0;
}

;;//EXTERN  SystemInit
.....
.......
Reset_Handler

        ;;//LDR     R0, = SystemInit
        ;;//BLX     R0
........
......