Using both 32 kHz and 8 MHz crystals?

bobpaddock — Wed, 11 Nov 2020 19:01:38 GMT

On the K32L2A4S I am confused by its oscillator set up in regards to external crystals.

The FRDM-K32L2A4S has a 32 kHz crystal on the EXTAL/XTAL pins for the RTC.

The data sheet says that the minimum input to the PLL is 8 MHz.

What do you need to do if you want an accurate RTC, for when the system is sleeping, and a accurate system clock when running, when not connected to USB?

From the data sheet and Reference Manual it looks like you can connect a 32 kHz OR a 8 MHz (or higher) crystal, but not both at the same time as they are both on (E)Xtal.

Is there a way to trim the internal osc. with the 32 kHz crystal, like can be done with the AVR?:

"AVR055: Using a 32kHz XTAL for run-time calibration of the internal RC Osc."

https://www.microchip.com//wwwAppNotes/AppNotes.aspx?appnote=en591195

K32 L Series MicrocontrollersのトピックUsing both 32 kHz and 8 MHz crystals?

Using both 32 kHz and 8 MHz crystals?