About STM32 software reset code writing

For STM32, there are two ways to reset the software:

1) Use the official software library

  The system reset function is directly provided in the stm32f10x_nvic.c file of the official software library

/****************************************************** ******************************
* Function Name: NVIC_GenerateSystemReset
* Description: Generates a system reset.
* Input: None
* Output: None
* Return : None
********************************************* **********************************/
void NVIC_GenerateSystemReset(void)
{
  SCB->AIRCR = AIRCR_VECTKEY_MASK | (u32 )0x04;
}

But isn't it OK to just call this function?

There is such a sentence in the Cortex-M3 authoritative guide

There is a point to note here: there is often a delay from the time SYSRESETREQ is asserted to the time the reset generator executes the reset command
. During this delay, the processor can still respond to interrupt requests. But our original intention is often
to stop the execution here and not do anything else. Therefore, it is best to
set FAULTMASK before issuing a reset request.

So it is best to set FAULTMASK to be on the safe side.

The official stm32f10x_nvic.c file also provides this function directly

/****************************************************** ******************************
* Function Name: NVIC_SETFAULTMASK
* Description: Enables the FAULTMASK priority: Raises the execution priority to -1 .
* Input : None
* Output : None
* Return : None
************************************* ******************************************/
void NVIC_SETFAULTMASK(void)
{
  __SETFAULTMASK ();
}

So to reset the system, just call these two functions.

NVIC_SETFAULTMASK();

GenerateSystemReset();

2) Write the corresponding assembly code yourself

In fact, the principle is the same. I didn't see the official function at first, so I wrote it myself. In fact, if you look at the official function, it actually calls the same code as cortexm3_macro.s. Haha.

My code:

/*******************************************************************************
* Function Name : SystemReset
* Description : Configures the port pin connected to the push button. GPIO_D_4
* Input : None
* Output : None
* Return : None
*******************************************************************************/
__asm ​​void SystemReset(void)
{
 MOV R0, #1 //; 
 MSR FAULTMASK, R0 //; Clear FAULTMASK Disable all interrupts
 LDR R0, =0xE000ED0C //;
 LDR R1, =0x05FA0004 //; 
 STR R1, [R0] //; System software reset   

 
deadloop
    B deadloop //; Dead loop prevents the program from running to the following code
}

Then when you need it, just call the function directly in the C program.

SystemReset();

In the MDK environment, when the assembly code is embedded in the C code, writing and calling it is the same as C function.

The above function is defined in misc.c;

The function is declared in misc.h: void SystemReset(void);

Call function in main.c: SystemReset();

Replenish:

Software reset code common to MDK and IAR:

#if defined ( __CC_ARM ) /*------------------RealView Compiler ------------------*/ 
__asm ​​void GenerateSystemReset (void) 
{ 
 MOV R0, #1 //;  
 MSR FAULTMASK, R0 //; FAULTMASK disables all interrupts 
 LDR R0, =0xE000ED0C //; 
 LDR R1, =0x05FA0004 //;  
 STR R1, [R0] //;    
  
deadloop 
    B deadloop //;  
} 
#elif (defined (__ICCARM__)) /*------------------ ICC Compiler -------------- -----*/ 
//#pragma diag_suppress=Pe940 
void GenerateSystemReset(void) 
{ 
  __ASM("MOV R0, #1"); 
  __ASM("MSR FAULTMASK, R0"); 
  SCB->AIRCR = 0x05FA0004; 
  for( ;;); 
}

In the above code, the program can be reset when running in FLASH, but it fails to be debugged in RAM. The reason may be that the boot on the board is loose, resulting in problems with the RAM boot selection.

From the above, we can see that the embedded assembly under IAR is not a simple asm("...");, such as asm("LDR R0, =0xE000ED0C "); will report an error