Detailed analysis of the 110th blog of the fledgling Xiao Li in stm32__ NVIC_ Setprioritygrouping (uint32_t prioritygroup) function

__NVIC_SetPriorityGrouping(uint32_t PriorityGroup) Introduce

This function is implemented in the kernel file

Code parsing

__STATIC_INLINE void __NVIC_SetPriorityGrouping(uint32_t PriorityGroup)
{
    
  uint32_t reg_value;
  uint32_t PriorityGroupTmp = (PriorityGroup & (uint32_t)0x07UL);            
  reg_value  =  SCB->AIRCR;                                                  
  reg_value &= ~((uint32_t)(SCB_AIRCR_VECTKEY_Msk | SCB_AIRCR_PRIGROUP_Msk));            
  reg_value  =  (reg_value                                   |
                ((uint32_t)0x5FAUL << SCB_AIRCR_VECTKEY_Pos) |
                (PriorityGroupTmp << SCB_AIRCR_PRIGROUP_Pos)  );    
  SCB->AIRCR =  reg_value;
 }

The meaning of the first sentence

uint32_t PriorityGroupTmp = (PriorityGroup & (uint32_t)0x07UL);
 take PriorityGroup This parameter is low 3 position   Use and operate   7 The binary number of is  111

The meaning of the second sentence

reg_value  =  SCB->AIRCR;

// Read the current AIRCR Register value

The meaning of the third sentence

reg_value &= ~((uint32_t)(SCB_AIRCR_VECTKEY_Msk | SCB_AIRCR_PRIGROUP_Msk)); /* clear bits to change /* SCB Application Interrupt and Reset Control Register Definitions */
#define SCB_AIRCR_VECTKEY_Pos 16U /*!< SCB AIRCR: VECTKEY Position */
#define SCB_AIRCR_VECTKEY_Msk (0xFFFFUL << SCB_AIRCR_VECTKEY_Pos) /*!< SCB AIRCR: VECTKEY Mask */

#define SCB_AIRCR_PRIGROUP_Pos 8U /*!< SCB AIRCR: PRIGROUP Position */
#define SCB_AIRCR_PRIGROUP_Msk (7UL << SCB_AIRCR_PRIGROUP_Pos) /*!< SCB AIRCR: PRIGROUP Mask */

//SCB_AIRCR_VECTKEY_Msk Mask 1 Used to clear the high of the register 16 position FFFF<<16
//SCB_AIRCR_PRIGROUP_Msk Mask 2 Used to remove The register of 10 9 8 position 7<<8

The fourth sentence code meaning

reg_value  =  (reg_value                                   |
                ((uint32_t)0x5FAUL << SCB_AIRCR_VECTKEY_Pos) |
                (PriorityGroupTmp << SCB_AIRCR_PRIGROUP_Pos)  );  

Turn the register high 16 The value bit is set to 0x05FA;
Put the register 10 9 8 Set the three digits to PriorityGroupTmp The value taken in the first step .
Finally, assign the result to the register

summary

This function assigns the result of a number to the specified position of a register , The designated position here is high 16 Bit and 8 9 10 position , 8 9 10 Bits affect interrupt priority grouping , By setting the values of these three bits The values of these three bits are 000 001 010 011 100 101 110 111 this 8 In this case , This realizes the grouping of interrupt priority .
The specific grouping is as follows (PriorityGroup Value 0 - 7)

Other related functions and descriptions

• Set priority groups
• Get priority groups
• Coding priority
• Parsing priorities