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RTC subseconds count down

KIbra.3
Associate II

I am using the RTC of the STM32L4 Discovery board and have noticed that the sub-seconds are counting down. Is there anyone with an idea on how to resolve this issue?

1 ACCEPTED SOLUTION

Accepted Solutions

Why would that be an issue? It's a documented behaviour. Simply subtract the value read out from the subsecond register from the synchronous prescaler to obtain increasing value.

Note, that consistently reading out subseconds together with time/date may be challenging.

JW

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4 REPLIES 4

Why would that be an issue? It's a documented behaviour. Simply subtract the value read out from the subsecond register from the synchronous prescaler to obtain increasing value.

Note, that consistently reading out subseconds together with time/date may be challenging.

JW

Peter BENSCH
ST Employee

@KIbra.3 You could also take a look at this discussion on subseconds, where the (apparent) mystery is revealed a little.

Good luck
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
KIbra.3
Associate II

Thank you for providing this information. I'd like to know if there is any configuration that may force the RTC to count up instead of subtracting the value.

> I'd like to know if there is any configuration that may force the RTC to count up instead of subtracting the value.

No.

JW