How can I calculate an approximate IWDG window ?

[mm.51]

Development Board: Nucleo-L476RG.

IDE version: STM Cube IDE 1.11.0

For the system watchdog timer, there's an equation(attached.) Is there an equivalent equation for the IWDG ?

Any suggestions would be appreciated.

Thanks

[Pierre_Paris · Accepted solution]

Hello @Community member​ ,

Thank you for your question. As you may know, the independent watchdog is based on a 12-bit downcounter and 8-bit prescaler.

Indeed, there is an equivalent equation to calculate the refresh interval :In the formula above,

Flsi is equal to an independent 32 kHz internal RC (LSI).

Piwdg_prescaler is the prescaler value.

Niwdg_counterval is the downcounter reload value.

You can configure the two last parameters in STM32CubeMX > Pinout & Configuration > System Core > IWDG > Configuration once the IWDG is activated.

As conclusion, you need to refresh the IWDG before the 12-bit downcounter reaches the zero value. So the Tiwdg time is the maximum delay. 

If you have any other questions or suggestions, don't hesitate to ask.

Pierre