C语言中共用体类型和联合体类型以及typedef的用法实例

//定义

typedef union {
  uint32_t val;
  struct {
    uint32_t pa0_fsel :3;
    uint32_t pa1_fsel :3;
    uint32_t          :2;
  } BITS;
} PA_FSEL0;

typedef union {
  uint32_t val;
  struct {
    uint32_t pa0_fsel :3;
    uint32_t pa1_fsel :3;
    uint32_t          :2;
  } BITS;
} PA_FSEL1;

typedef struct {
  PA_FSEL0 pa_fsel0;
  PA_FSEL1 pa_fsel1;
} SYSCTRL_TYPE;

#define SYSCTRL ((volatile SYSCTRL_TYPE *)(0x40001000))

使用：

SYSCTRL->pa_fsel1.val = 0x90;
SYSCTRL->pa_fsel1.BITS.pa11_fsel= 0b010;