STM32L083RBTx unexpected periodic reset

[JJRR]

Hi,

I can see weird behaviour on my STM32L083RBT6. Do not know where to start - I will try:

• When I run my app with Window WD - everything works fine
• When I run my app with Window WD disabled - not every start of my app (power on by inserting battery) starts up corectly - it means the app remains stuck in unknown place (in time < 100 ms after power on)
• When I continue to toogle battery connecting (power on -> power off), so about after 20 cycles the mcu always starts up correctly but after about 500 ms the mcu always resets -> then starts up -> resets and again and again with period about 500 ms - from this moment it looks like the mcu is corrupted - Nothing like reflashing app (with or without WD) can save the mcu. In this state I tried to debug why the mcu resets - by reading the RCC->CSR register - but there is always bunch of set bits (WWDGRSTF, IWDRSTF, PORRSTF, PINRSTF, SFTRSTF) - so this feature probably does not work!

No voltage spikes captured on power pins during connecting and unconnecting battery.

I will be very grateful for any help.

[TDK]

Show a screenshot showing the IWDG is disabled in option bytes in STM32CubeProgrammer.

[JJRR · Accepted solution]

 

So now It is clear. I had unchecked WDG_SW - it means the IWDG was activated by harware and this is why the reset occured.

What I do not understand is why this bit was unchecked.

[TDK]

If IWDG_SW is unchecked, IWDG is enabled automatically by hardware and is causing your reset, as suspected in the very first reply to your post.

[JJRR]

Yes, Thank you very much. Now I understand it. The question fro me is why this bit was unchecked...