Errata 136

[Roei]

Hi,

I have some questions regarding errata 136.

I understand that the workaround is to ignore reset reason bits which are not RESETPIN.

However, I don't understand how ~POWER_RESETREAS_RESETPIN_Msk can help us, as the operation makes pin reset bit 0 and the other bits become 1. Isn't that the opposite from what we want?

In addition, I had some troubles with implementing watchdog, as POWER_RESETREAS_DOG_Msk was always true, until I removed errata 126 fix. Is it possible?

Thanks!

[Håkon Alseth]

Hi,

 

However, I don't understand how ~POWER_RESETREAS_RESETPIN_Msk can help us, as the operation makes pin reset bit 0 and the other bits become 1. Isn't that the opposite from what we want?

The RESETREAS register is cleared by writing '1' to the bit, as shown in the PS:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/power.html?cp=4_2_0_17_8_2#register.RESETREAS

 

This will ensure that the RESETPIN_Msk is still held when the application checks the specific bit after the errata workaround has executed.

  

In addition, I had some troubles with implementing watchdog, as POWER_RESETREAS_DOG_Msk was always true, until I removed errata 126 fix. Is it possible?

Are you clearing the RESETREAS by writing '1' to the source bit? 

Kind regards,.

Håkon 

[Roei]

So the operation  if (NRF_POWER->RESETREAS & POWER_RESETREAS_RESETPIN_Msk) checks if the bit is cleared? And if so, it makes that bit 0 and the others cleared (1)?

I'm using sd_power_reset_reason_get to get the bitmap, and then operating & POWER_RESETREAS_DOG_Msk on the reslt, in order to identify watchdog reset. If watchdog was identified, I'm using sd_power_reset_reason_clr(POWER_RESETREAS_DOG_Msk) to clear the bit.

[Roei]

OK,

So regaring watchdog - your suggestion is to clear whole register bits with 0xFFFFFFFF, in case of watchdog timeout?

[Håkon Alseth]

Roei said:

So regaring watchdog - your suggestion is to clear whole register bits with 0xFFFFFFFF, in case of watchdog timeout?

You can do this if you plan to not check any other sources.

If you check for other RESETREAS sources; you check the certain bit and clear it (by writing '1' to the source bit position) afterwards.

 

Kind regards,

Håkon

[Roei]

The problem is as following:

After MCU watchdog, SystemInit() is called and errata 136 workaround is operated.

After that, when my device is turning of, I'm trying to check the restart reason bit, and I can't indicate that the reason is watchdog, because watchdog bit is reset due to errate 136 workaround.

How can I solve that?

[Roei]

I meant when my device is turning on

[Håkon Alseth]

Hi,

 

The workaround will only be applied if this is true:

if (NRF_POWER->RESETREAS & POWER_RESETREAS_RESETPIN_Msk){
    NRF_POWER->RESETREAS =  ~POWER_RESETREAS_RESETPIN_Msk;
}

 

That should not be true if WDT reset is the only source in RESETREAS. Again, note that this is an accumulate register, meaning that for each reboot, it accumulates and remembers the former reset reason unless the application writes '1' to it.

 

Kind regards,

Håkon

[Roei]

So how can I know that reset pin will not be set the next time WDT occurs? How can I recognize WDT reset if errata 136 clears the bit?

[Håkon Alseth]

reset pin will only be set if the reset pin is pulsed, either by a user, or an external IC.

If watchdog is the only reset source, then you shall be able to detect this in RESETREAS