KL25z Dev kit 8Mhz Clock Selection for RTC

[andrewreilly]

I was wondering if anyone knew the part number of the xtal used in the dev kit design?

Also if anyone could explain why a 8Mhz is used instead of a 32kHz clock would be great!

Thank you!

Andy

[jeremyzhou]

Hi Andy,

After had a brief look through the statement above, I'm not very clear with your questions.

Did you want to input an external 8MHz clock through the RTC_CLKIN pin ad the clock source of the RTC?

And I'll appreciate a lot if you can describe your questions in details.
Have a great day,
Ping

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[andrewreilly]

I have used the Kl43z and it required an external 32kHz clock to operate the RTC.  I can not find a description for if the RTC for the kl25z needs an external 32kHz clock as well and if so does that mean I replace the 8Mhz clock with a 32kHz clock?  What is the 8Mhz used for as the system is internally clocked by 48Mhz, correct?

I plan to use the 32 pin package of the KL25Z and it has an RTC_CLKIN on PTC3. 

Also I was wondering if anyone knew the accuracy of the LPTMR vs the RTC?

Thanks,

Andy

[jeremyzhou]

Hi Andy,

The KL25 is as same as the KL43, and I'd like to suggest that you can follow this thread below to operate the RTC without replacing the external 8MHz clock with a 32KHz clock.

And the accuracy of the timer is mainly up to the clock source.

Using RTC module on FRDM-KL25Z
Have a great day,
Ping

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[mjbcswitzerland · Accepted solution]

Hi

There is also a discussion about the RTC details in the KL devices at µTasker KL RTC Support

Regards

Mark

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