STM32L071CBTx IWDG freeze in Standby mode option byte availability

[isikli]

Hi,

I'm working on a battery-powered sensor with STM32L071CBTx (LQFP48).
The device cycles between Standby mode (~12 µA) and short Run mode (~250 ms).

Reading RM0377 Section 20 (IWDG), I understand that:
1. IWDG cannot be stopped once started (only reset can stop it).
2. IWDG clock (LSI) runs in Standby mode.

I have two specific questions:

Q1: Does STM32L071CB support an IWDG_STDBY option byte bit that freezes
    the IWDG counter in Standby mode (similar to STM32G0/WB/U5 series)?
    If yes, what is the bit name and how to configure it via HAL?

Q2: If Q1 answer is "no", what is the recommended approach to combine
    IWDG-based hang protection with Standby-based ultra-low-power
    operation? Two options I'm considering:
    
    (a) Use LSI manual stop via RCC_CSR.LSION = 0 before entering
        Standby (does IWDG still run if LSI is stopped?)
    
    (b) Software watchdog using a basic timer (TIM6/TIM7) refreshed
        in run mode, NVIC_SystemReset() on timeout.

Best regards,
 

[FBL]

Hi ​@isikli 

There is no option byte that freezes the IWDG in Standby mode on this STM32.

IWDG is not halted by Standby. it is intended to remain active. It cannot be stopped or paused after it has been started. So, if you use IWDG, make sure your standby interval is shorter than the watchdog timeout. Otherwise, consider an external watchdog or a software supervision mechanism.