STM32L452 LSE not running if CSS enabled

[Martin Blank]

I have once activated CSS in CubeMX and then the LSE can no longer be started. Even if I change CSS to disabled in CubeMX and recompile this does not change.

I have to say that I have buffered the RTC / LSE with a CAP at VBatt so it does not loose power even at main power down. Only if I remove the CAP I can reactivate the LSE.

So are there any know problems with CSS activated for LSE?

And is there a way do disable CSS after it was once activated even at battery powered systems?

Thanks

MB

[waclawek.jan]

You mean, the LSE CSS?

Have you read and followed the Clock security system on LSE subchapter in RCC, and the procedures related to LSECSSON and LSECSSD as described in description of these bits?

JW

[Martin Blank]

Yes I mean LSE CSS. My main problem was to turn off the LSE CSS while VBatt is connected always. I could not find how to do so.

Also I am wondering why LSE CSS does shut down my LSE clock at startup. Normally it should just work all time because I have it with VBatt connected.

MB

[waclawek.jan]

> My main problem was to turn off the LSE CSS while VBatt is connected always. I could not find how to do so.

Backup domain reset does not clear the LSECSSON bit?

> Also I am wondering why LSE CSS does shut down my LSE clock at startup.

Is LSECSSD set or not?

JW

[waclawek.jan]

Any progress with this?

JW