exit Standby mode delay with iwdg and rtc.

[GChu]

MCU: STM32H750

exit Standby mode delay with iwdg and rtc.

I find when I enable iwdg it seems will delay 1 second when exit standby mode. After trace code, I find it is hang in HAL_RTC_Init(),

the RTC_EnterInitMode() will check weather the hrtc->Instance->ISR is SET(1) or RESET(0). 

It should be SET(1) because the RTC is enable before enter standby. But when I enable iwdg, it seems will be RESET(0) and cannot be set to SET(1)

after wakeup from standby.

After do some tries, it seems if wait the iwdg count down to zero, will have no problem in RTC (seems hrtc->Instance->ISR is SET(1)).

question:

1. The iwdg should wake up the device but it is not happened. Why?

2. Why the iwdg is running effect the RTC ISR register wrong?

3. How to check the device is wakeup from standby?

[turboscrew]

I have a funny feeling that it's about the write protection of backup domain in reset.

Maybe running init code leaves the backup domain accessible.

[GChu]

When IWDG is enable.

It seems also cannot set the time into RTC when wake up from standby.

also fail in RTC_EnterInitMode().

if IWDG is not enable, it is OK.

How IWDG will effect RTC?