Kl15 RTC pins

[yar]

Hello, I'm a newbie in Kinetis microcontollers. I use KL15 microcontroller and I would use XTAL, EXTAL (PTA18-19) pins for RTC and connect to them 32.768 crystal. And as the system oscillator use internal KL15 osciallator. KL15 support this configuration?

[mjbcswitzerland · Accepted solution]

Hi

If you use a 32.768kHz crystal the oscillator's output OSC32KCLK can be used to drive the RTC.

The OSCCLK (also 32.768kHz output can then be used as reference to the FLL to generate a 47.972352MHz system clock.

You can also use internal oscillators to generate the system clock but the 32768kHz will be more accurate if you have it anyway. The KL15 has also a PLL that could be used instead (with additional flexibility) so you have various options.

Regards

Mark

[yar]

If i use 32.768 crystall on EXTAL0 XTAL0 it will continue to work in sleep mode?

[mjbcswitzerland]

Hi

The KL15 has various low power modes and the SLEEP setting is just one input to the actual low power mode used. Therefore you need to know which one you require to use - check the table 7-2 to see which modules are operational in the various types (eg. RTC and OSC).

I think that the "low frequency range" oscillator will operate in all low power modes and, apart from VLLS0, also the RTC from this clock source.

Regards

Mark