Stop mode and peripheral clocks

[DOCon.1]

 Hi. I'm looking for guidance on entering and exiting Stop mode. L4, but probably applies more broadly. The RMs explain how to enter it, but I'm unclear on RCC effects.

PLL oscillators other than HSI or MSI (depending on family) are disabled and deselected. PLL is disabled. These must be manually re-enabled and reselected as PLL source, although I don't think you need to change PLL scalers.

The L4 RM for Stop2 indicates you must disable all periph clocks prior to entering. Is this true? Why? Does it only apply to Stop2?

Various things aren't working normally after exiting Stop. Do I need to do any other steps pre or post Stop? Do I need to re-enable periph clocks (Spi, RTC, GPIO port etc) after exiting Stop? Thank you. I run into problems after Stop mode I don't encounter in Sleep Now.

[Amel NASRI]

Hi @DOCon.1​ ,

Some peripherals can be kept running during Stop2, others are frozen. This is what we see summarized in following table:

This table is extracted from AN4621 STM32L4 and STM32L4+ ultra-low-power features overview.

Please review it in order to understand more about the low power modes for STM32L4 products.

If there is still some troubles, please explain more the problems you are facing. You shouldn't expect the same behavior with Stop & Sleep modes, they are different.

-Amel

[DOCon.1]

Thank you for that info - I appreciate it! That document looks great in general. I haven't solved this one yet, but hope to soon.