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STM32F410 - Freeze after Power Supply Failure of 70 ms? Watch Dog doesn't reset ???

Question asked by Ümit Koyuncu on Jun 1, 2017

Hello world,


i got an STM32F410TB which somehow freezes after a special external failure. In my application the powersupply voltage is gone for about 60-70 ms. The buffer capacitors are discharged and the supply voltage of the µC goes down to 300 mV. At this voltage level the power supply gets back to its normal state and the voltage raises to 3.3V in several ns. So in short there is a power supply break off about 60-70ms. After that i think the µC starts but gets into an error handling. I get not response from the µC. Manually pulling the NRST pin to GND gets the µC back to life.


I have following setup:

PDR_ON Pin is tied to VDD

BOR = Medium

IWDG is ON and it should kick in after 512 ms, but it doesn't.... why??


I modified the startup file before System Init is executed (Reset Handler). I can genereate a continous software reset in the startup file. After that i tried to move it to main. But the reset doesn't work in the main file so the µC doesnt get there.


Somehow i thought that this special case generates a special error which i can solve with a simple reset of the µC. So i looked in the RCC_CSR register for RESET Flags and tried to do a one time Software_Reset  in the Reset Handler (written in Assembler) after the µC is started. I tried to avoid an infinite reset loop by looking for the software_reset flag. If the software reset is not set then i am reseting the µC by software. It works for every power supply failure time except for 60-70 ms. The reset is not executed. I can see this by looking on the potential of the NRST pin...


Somehow i am getting frustrated...

I hope you can help me.


Thank you in advance.