AIRCR_VECTKEY_MASK是什么意思

xuchanghe110

AIRCR：配置寄存器分组与自动复位控制


控制中断分组的是第8第9第10位。

如果要改变这三个位，要对16到31位写入0x05FA。#define AIRCR_VECTKEY_MASK 0x05FA0000就是这个意思了，
0x05fa对与AIRCR来说就是一个“入口钥匙”，只有对高16位写对了，才能对低16位写入。所以
AIRCR = AIRCR_VECTKEY_MASK | NVIC_PriorityGroup;
AIRCR = 0x05FA0000 | NVIC_PriorityGroup;
#define NVIC_PriorityGroup_2         ((uint32_t)0x500)
AIRCR = 0x05FA0000 | 0x500;



Access key; 0x05FA must be
written to this field to write to this
register, otherwise the write will
be ignored; the read-back value
of the upper half-word is 0xFA05
Indicates endianness for data: 1
for big endian (BE8) and 0 for little
endian; this can only change after
a reset

xuchanghe110

嵌套向量中断控制初始化，解读。
void NVIC_Init(NVIC_InitTypeDef* NVIC_InitStruct)
{
  uint8_t tmppriority = 0x00, tmppre = 0x00, tmpsub = 0x0F;
  
  /* Check the parameters */
  assert_param(IS_FUNCTIONAL_STATE(NVIC_InitStruct->NVIC_IRQChannelCmd));
  assert_param(IS_NVIC_PREEMPTION_PRIORITY(NVIC_InitStruct->NVIC_IRQChannelPreemptionPriority));  
  assert_param(IS_NVIC_SUB_PRIORITY(NVIC_InitStruct->NVIC_IRQChannelSubPriority));
   
  if (NVIC_InitStruct->NVIC_IRQChannelCmd != DISABLE)//判断是否使能
  {
    /* Compute计算 the Corresponding相应的 IRQ中断清求 Priority优先级 --------------------------------*/   
    tmppriority = (0x700 - ((SCB->AIRCR) & (uint32_t)0x700))>> 0x08;
          //air=0x500&0x700=0x500        0x700-0x500>>8 =0x2
          //这里是算出抢占优先级，所占的位数
    tmppre = (0x4 - tmppriority);//0x4-0x2=2
          //这里是算出抢占优先级后面要左移的次数
    tmpsub = tmpsub >> tmppriority;//0x0f>>2=3
          //这里是把响应优先级的有效位计算出来

    tmppriority = NVIC_InitStruct->NVIC_IRQChannelPreemptionPriority << tmppre;//0x3<<2=0xc
          //抢占优先级向前移一定的位，根据（4－所占的位数）
    tmppriority |=  (uint8_t)(NVIC_InitStruct->NVIC_IRQChannelSubPriority & tmpsub);//0x0c|3=0xf
          //响应优先级与前面算出来的有效位做与，然后与抢占优先级进行组合
    tmppriority = tmppriority << 0x04;//因为IP是使用的高四位，所以左移4次=oxf0
        
    NVIC->IP[NVIC_InitStruct->NVIC_IRQChannel] = tmppriority;//这里是最后配置中断优先级
   
    /* Enable使能 the Selected选择的 IRQ中断请求 Channels通道 --------------------------------------*/
    NVIC->ISER[NVIC_InitStruct->NVIC_IRQChannel >> 0x05] =
      (uint32_t)0x01 << (NVIC_InitStruct->NVIC_IRQChannel & (uint8_t)0x1F);
  }
  else
  {
    /* Disable不使能 the Selected选择的 IRQ中断请求 Channels通道 -------------------------------------*/
    NVIC->ICER[NVIC_InitStruct->NVIC_IRQChannel >> 0x05] =
      (uint32_t)0x01 << (NVIC_InitStruct->NVIC_IRQChannel & (uint8_t)0x1F);
  }
}