Contradiction in Reference Manual RM0394

[Stepan Martinek]

There is an inconsistency in RTC shadow register update frequency description. Some places in text mentions that shadow register update happens once every RTCCLK period:

34.3.5, 36.3.4: "Every RTCCLK periods, the current calendar value is copied into the shadow registers..."

34.3.10, 36.3.8: "The copy is performed every RTCCLK cycle."

And other place say that it actually happens every other RTCCLK cycle:

34.6.7, 36.6.3: "Calendar values (when reading from RTC_SSR, RTC_TR, and RTC_DR) are taken from the shadow registers, which are updated once every two RTCCLK cycles."

I assume that "every two RTCCLK cycles" is correct, because some other Reference Manuals state this consistently.

[Imen.D · Accepted solution]

Hello @Stepan Martinek​ and welcome to the Community :)

The shadow registers are updated every ck_rtc cycle on RTC2_v2_0 and all versions after that. 

I think it was "every two cycles" for v1.

So, "every two RTCCLK cycles" is wrong and should be “every RTCCLK cycle�?.

Hope this answer your question.

When your question is answered, please close this topic by choosing Select as Best.

Imen

[waclawek.jan]

Hi Imen,

> So, "every two RTCCLK cycles" is wrong and should be “every RTCCLK cycle�?.

This means to fix virtually every STM32 RM, except RM0008, isn't it?

And also AN4759

(and yes, I still consider "modern feel and look" wrong.)

Also, AN4759 should mention in this very chapter the RTC v2 lock bug.

Jan

@Imen DAHMEN​ 

[Stepan Martinek]

Hello and thank you for clarification.

[Imen.D]

Thanks @[waclawek.jan]​ for your feedback.

I have escalated this issue to the appropriate Owner for further check all impacted docs and take the action for correction.

Imen

[waclawek.jan]

Thanks, Imen!

Jan

[waclawek.jan]

Hi @Imen.D ,

AN4759 has seen rev.8 at 08-Nov-2022, yet the line in question hasn't been corrected.

JW