Can I use OSC32KCLK(from system oscillator) to run my RTC?

[durgeshtanuku]

Hello,

I am using RTC_LDD component for my board with KL25Z. In component settings I have selected, ERCLK32K as clock source. As I don't have any oscillator to connect to my RTC_CLKIN, In CPU settings I have selected system oscillator 0(I have read in user manual that I can source ERCLK32K from system oscillator) as ERCLK32K source. But I am getting an error that "system oscillator is not in low frequency range"

[adriancano]

Hi Durgesh Tanuku,

The message "system oscillator is not in low frequency range" is because the RTC module needs to work within the Low Frequency Range which is 32 to 40 kHz and as you can see the OSC0ERCLK clock is 8 MHz which is in the high frequency range, if you are going to connect a different Oscillator in the EXTAL0 and XTAL0 pins you need to change the value of  System Oscillator > Clock Source > Clock output pin > Clock Frequency = a value between 32-40 kHz. The problem is that if you change the value of the XTAL to one in the Low Frequency range you will not be able to use the core in external modes to get  it running at 48 Mhz (example FEE, PEE) because the divider and multiplier factors can not reach that frequency with a low range frequency. But you are able to use the internal modes like FEI and run the core at 47.97 MHz.

You can use the MCGIRCLK clock and connect it to the RTC_CLKIN pin. Here is how you can do this: Using RTC module on FRDM-KL25Z.

I hope this information can help you.

Regards,

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