Can LSI oscillator be disabled once the IWDG has started running on STM32G0 ?

Forum|Forum|3 years ago
July 13, 2022
5 replies
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In my application I have configured IWDG to start running.

I would like to prevent the IWDG from resetting the MCU while in stop 1 mode for extended period of time.

In the reference manual it says: "Once running, the IWDG cannot be stopped."

But in the RCC section of the manual it says

"The LSI RC can be switched on and off using the LSION bit in the Control/status register (RCC_CSR)."

This would lead me to believe that its possible to turn off the LSI clock after the IWDG has been enabled.

If I try to turn off the LSI clock before entering Stop 1 mode, the MCU ends up being reset by the IWDG.

Is it true that LSI cannot be stopped ig IWDG has been engaged?

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Best answer by Piranha

> There is no option byte to disable IWDG in Stop mode.

Bit 17 IWDG_STOP right between your yellow markers is literally that.

Peter BENSCH

ST Technical Moderator

Correct, LSI cannot be stopped when the IWDG has been activated. This is also mentioned in RM0454, section 5.2.13:

If the Independent watchdog (IWDG) is started by either hardware option or software access, the LSI oscillator is forced ON and cannot be disabled.

Regards

/Peter

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Mvill.17

Associate III

Hi Peter

Is there the possibility to freeze the IWDG in STOP clearing the corresponding bit in the option byte?

I cleared it but when in STOP the IWDG is still working and reset my system.

So the question is what's the purpose of these bits in the option byte?

Thanks

Tom MacDonaldAuthor

Associate III

There is no option byte to disable IWDG in Stop mode.

There is, however, and option byte to disable IWDB in Standby mode. I can confirm that in my application when I enter Standby mode that IWDG does not reset the MCU.

See page 65 of RM0454:

PiranhaBest answer

Principal III

> There is no option byte to disable IWDG in Stop mode.

Bit 17 IWDG_STOP right between your yellow markers is literally that.

Tom MacDonaldAuthor

Associate III

You right!

Tom MacDonaldAuthor

Associate III

@Peter BENSCH

Does that mean I can stop the IWDG from restarting my app if I go into stop mode and wait for interrupt (potentially indefinitely?) provided that I set the bit 17 to 0?