IWDG_STDBY ambiguity

[pretoriandave]

Hi All,

Please could somebody offer some words of wisdom to resolve the apparent ambiguity in the C0 datasheet, which on the one hand states that once IWDG is started it cannot be stopped, yet on the other hand offers a IWDG_STDBY bit in the OPTION registers to allow it to be stopped during Standby. The latter does not appear to work, since my system wakes itself after the prescribed watchdog period, so it seems like the first statement is the correct one.

Since the watchdog definitely CAN be stopped during debug if DBG_IWDG_STOP is set, there is clearly a mechanism by which it can be stopped under certain circumstances, suggesting the first statement is not correct, or at best is not the whole story.

If it can't be stopped in Standby....

a) what's the point of the IWDG_STDBY bit?

b) how can I keep my system in Standby? I must have the watchdog running while awake.

Many thanks

[Andrew Neil]

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@pretoriandave wrote:

the C0 datasheet, which on the one hand states that once IWDG is started it cannot be stopped, yet on the other hand offers a IWDG_STDBY bit in the OPTION registers to allow it to be stopped during Standby. 

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You mean the Reference Manual (RM0490) rather than the Datasheet ?

Please post screenshots of the parts you feel are contradictory.

I couldn't see where it says the IWDG can't be stopped, but that does make sense

My reading is that the IWDG_STDBY bit just pauses the timer during Standby - rather than stopping it altogether?

https://www.st.com/resource/en/reference_manual/rm0490-stm32c0-series-advanced-armbased-32bit-mcus-stmicroelectronics.pdf#page=84

[pretoriandave]

Yes, sorry Andrew, I do. RM0490, 22.3.1....

which contradicts what you just posted from FLASH_OPTR (at 4.7.6 for future readers)

Thank you

[Andrew Neil · Accepted solution]

Again, I take that to mean that the software can't turn the IWDG off - which is common & desirable.

What the IWDG_STDBY bit does is just pause the timer during Standby - rather than turning it off altogether?

As soon as the chip exits Standby, the IWDG will continue counting - it doesn't need the software to restart it.