#define GPIOB_ODR (*(volatile unsigned int *)0x40020414UL)

GPIOB->ODR

typedef struct
{
    volatile uint32_t MODER;
    volatile uint32_t OTYPER;
    volatile uint32_t OSPEEDR;
    volatile uint32_t PUPDR;
    volatile uint32_t IDR;
    volatile uint32_t ODR;
} GPIO_TypeDef;

RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN;

Ch06_cmsis/
├── Src/
│   └── main.c
├── Startup/
│   └── startup_stm32f439zitx.s
├── STM32F439ZITX_FLASH.ld
└── STM32F439ZITX_RAM.ld

/*
 * Ch06 - The Common Microcontroller Software Interface Standard (CMSIS)
 */
#include "stm32f4xx.h"   /* STM32F439xx 매크로에 따라 stm32f439xx.h를 자동 포함 */
#define LD1_PIN (1UL << 0)   /* PB0 = LD1 (녹색) */
static void delay(volatile unsigned int count)
{
while (count--) { __NOP(); }
}
int main(void)
{
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN;
GPIOB-&gt;MODER &amp;= ~(0x3UL &lt;&lt; (0 * 2));
GPIOB-&gt;MODER |=  (0x1UL &lt;&lt; (0 * 2));

while (1)
{
    GPIOB-&gt;ODR ^= LD1_PIN;
    delay(800000);
}

}

#include "stm32f4xx.h"

RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN;

GPIOB->MODER &= ~(0x3UL << (0 * 2));
GPIOB->MODER |=  (0x1UL << (0 * 2));

GPIOB->ODR ^= LD1_PIN;

Ch02
주소를 직접 계산
↓
volatile pointer 직접 생성
↓
register access
Ch06
CMSIS header
↓
Peripheral structure
↓
register access