topic Re: K24 rtc_clkout in low power mode ? in Kinetis Microcontrollers

K24 rtc_clkout in low power mode ?

dkh — Fri, 17 Feb 2017 16:26:33 GMT

Hello,

I am using a 32 khz crystal connected to extal32 and xtal32 and running the output to the rtc_clkout pin.

What is the lowest power mode that this function will work ?

The reason I ask is the reference manual says rtc_clkout is disabled in LLS and VLLS2 modes suggesting

VLPS is the lowest power mode at a typical of 57 uA.

The problem we see is that this function is still working in VLLS2 mode. Is the manual wrong ?

If not, why is it still working ?

Regards,

Dennis

Re: K24 rtc_clkout in low power mode ?

jorge_a_vazquez — Tue, 21 Feb 2017 01:43:40 GMT

Hi Denis

Could you clarify what you mean when you see is that this function is still working in VLLS2?

Reference Manual has a note that says:

So, the RTC is Full Functional, but it has a note that mentioned:

8. RTC_CLKOUT is not available.

So the RTC module is still functional but you have not available the RTC_CLKOUT output;

Hope this information helps

Best Regards

Jorge Alcala

Re: K24 rtc_clkout in low power mode ?

dkh — Tue, 21 Feb 2017 13:56:56 GMT

Hello Jorge,

To be clear I am asking about the RTC_CLKOUT. The output

we were able to go down to VLLS2 and still see the 32kHz come out.

From manual:

As you noted above the manual says the rtc_clkout is not available. If this is true why do we see it ?

Are there any configurations that would allow this to happen in a VLLSx mode ?

Regards,

Dennis

Re: K24 rtc_clkout in low power mode ?

jorge_a_vazquez — Wed, 22 Feb 2017 06:15:42 GMT

Hi Dennis

Ok, so you saw the rtc_clkout signal in the pin, right? Are you using SDK drivers?

I will need to verify this in my side I will tell you anything that I find as soon as possible

Regards

Jorge Alcala

Re: K24 rtc_clkout in low power mode ?

jorge_a_vazquez — Thu, 23 Feb 2017 02:44:30 GMT

Hi Dennis

I tested this case scenario in my side and I couldn't replicate your problem. Could you tell me how you test this?

I used the demo code included with SDK drivers, located in the path: {SDK_2.0_TWR-K24F120M}\boards\twrk24f120m\demo_apps\power_manager

This code already set up different power modes. Then I just add the following code to see RTC_CLKOUT:

PORT_SetPinMux(PORTE, 26u, kPORT_MuxAlt6);

/* RTC set up */
rtc_config_t rtcConfig;
RTC_GetDefaultConfig(&rtcConfig);
RTC_Init(RTC, &rtcConfig);
RTC->CR |= RTC_CR_OSCE_MASK; /* Enable the RTC 32KHz oscillator */
RTC_StopTimer(RTC);
CLOCK_SetRtcClkOutClock(0); //Select 1HZ in RTC_CLKOUT
RTC_StartTimer(RTC);‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

I run the code and I saw the signal in my scope, and if I set the MCU to go to LLS or VLLS mode, this signal disappear. Could you try this set up and tell me how it goes?

Hope this information helps you
Best Regards
Jorge Alcala