My simple IWDG dont work - why?

[Terje Bøhler]

Hi.

I downloaded some IWDG example code from Keil because I will use the IWDG-feature of my STM32F107. Configurations/init are located in this procedure:

//__inline static void stm32_IwdgSetup (void) {
static void stm32_IwdgSetup (void) {    
 
  RCC->CSR |= (1<<0);               // LSI (internal low speed oscillator) enable, necessary for IWDG
  while ((RCC->CSR & (1<<1)) == 0); // wait till LSI is ready
 
/*----------------------------------------------------------------------------
Define  IWDG PR and RLR settings
*----------------------------------------------------------------------------*/
  IWDG->KR  = 0x5555;     // enable write to PR, RLR
       IWDG->PR  = 1; 
  IWDG->RLR = 400;
 
  IWDG->KR  = 0xAAAA;           // Reload the watchdog
  IWDG->KR  = 0xCCCC;           // Start the watchdog
} // end of stm32_IwdgSetup

The following is happening when debugging:

1. When I start the debugger, the first breakpoint (at the call to stm32_IwdgSetup) is entered OK (see attached picture).
2. When I single-STEPped the stm32_IwdgSetup to it’s last line, then (at that point) everything “hungs�? (the debugger did not exit the procedure properly, it did not reach/enter the line next to the stm32_IwdgSetup) and it seems like the MCU tries to execute code from memory location 0x21000000 (see attacjed picture).

I very much appreciate some assistance to this issue.

Best regards Terje Bøhler

[Tesla DeLorean]

Is NRST driven HIGH externally? ie not a pull-up, rather some other circuit with a push-pull driver?

The DBGMCU settings can alter some behaviour, executing at 0x21000000 not one I'm familiar with.