AnsweredAssumed Answered

MKM34 WDOG behaviour after power on reset

Question asked by raul10 on Feb 2, 2017
Latest reply on Feb 8, 2017 by raul10

Dear all,

 

I have an own pcb with the MKM34 on it. My software is running well so now I want to implement the WDOG. However, I found out that after a power on reset the WDOG behaves different to what I expected with the default settings described in the manual.

According to the reset values the WDOG is enabled with the clock source from LPO and a timeout value of 0x4C4B40 which should be a timeout of 83 minutes.

But with this small piece of code which is executed immedeately after reset without any other code in between I found out that the WDOG generates a reset 200 µs after power on reset.

 

void Startup(void)
{
   // configure Port B3 as output
   SIM->SCGC5 |=  SIM_SCGC5_PORTB_MASK;
   PORTB->PCR[3] = 0x100;
   GPIOB->PDDR |= 0x8;

 

   // set Port B3
   GPIOB->PSOR |= 0x8;

 

   while (TRUE) ;
}

 

I confirmed that it is really a WDOG by setting port B3 only if RCM_SSRS0_SWDOG_MASK was set.

 

Does anybody have an explanation for this?

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