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Contradiction in Reference Manual RM0394

Stepan Martinek
Associate III

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.

1 ACCEPTED SOLUTION

Accepted Solutions
Imen.D
ST Employee

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

When your question is answered, please close this topic by clicking "Accept as Solution".
Thanks
Imen

View solution in original post

6 REPLIES 6
Imen.D
ST Employee

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

When your question is answered, please close this topic by clicking "Accept as Solution".
Thanks
Imen

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

0693W00000FAZFBQA5.png(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​ 

Hello and thank you for clarification.

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

When your question is answered, please close this topic by clicking "Accept as Solution".
Thanks
Imen

Thanks, Imen!

Jan

Hi @Imen.D ,

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

JW