F0 RTC Alarm matching - documentation typo?

Andrew Neil · ‎2025-01-07

RM0360 (STM32F030x4/x6/x8/xC and STM32F070x6/xB) says:

"The ALRAF is set to 1 if the calendar subseconds, seconds, minutes, hours, date or (sic?) day match the values programmed in the alarm registers RTC_ALRMASSR and RTC_ALRMAR"

But, surely, that should be AND - not or ?

ALRAF is set to 1 if the calendar subseconds, seconds, minutes, hours, date and day match the values programmed in the alarm registers RTC_ALRMASSR and RTC_ALRMAR

https://www.st.com/resource/en/reference_manual/rm0360-stm32f030x4x6x8xc-and-stm32f070x6xb-advanced-armbased-32bit-mcus-stmicroelectronics.pdf#page=490

RM0091 (STM32F0x1/STM32F0x2/STM32F0x8) is the same:

https://www.st.com/resource/en/reference_manual/rm0091-stm32f0x1stm32f0x2stm32f0x8-advanced-armbased-32bit-mcus-stmicroelectronics.pdf#page=596

STTwo-32 · ‎2025-01-07

hello @Andrew Neil

Thank you so much for your feedback. I Will take a look internally and i Will get back to you with an answer ASAP.

Best Regards.

STTwo-32

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waclawek.jan · ‎2025-01-08

"date or day" is correct, as you can select (using RTC_ALRMAR.WDSEL), whether you want to wake up say on 15th of each month, or say Wednesday on each week. In other words, "date" here means "date-of-month", and "day" here means "day-of-week".

But I see where are you coming from: the conditions for seconds, minutes, etc. are indeed ANDed together (after being individually masked) to provide the alarm. This is IMO quite hard to formulate clearly in a narrative; perhaps something such as an equation or a schematics would be more illustrative here.

JW

Andrew Neil · ‎2025-01-08

@waclawek.jan wrote:
"date or day" is correct, as you can select (using RTC_ALRMAR.WDSEL), whether you want to wake up say on 15th of each month, or say Wednesday on each week.

Ah - I hadn't realised that.

So the alarm is actually triggered on:

(subseconds AND seconds AND minutes AND hours) AND (date OR day)

@waclawek.jan wrote:
This is IMO quite hard to formulate clearly in a narrative; perhaps something such as an equation or a schematics would be more illustrative here.

Indeed.

Andrew Neil · ‎2025-01-08

@waclawek.jan wrote:
"date" here means "date-of-month", and "day" here means "day-of-week".

I think those terms are generally used poorly & confusingly throughout.

Good Naming Is Key!