MQX Software SolutionsのトピックRe: K20 RTC CRYSTAL PINS XTAL32 & EXTAL32 has no voltage

K20 RTC CRYSTAL PINS XTAL32 & EXTAL32 has no voltage

markkalior — Fri, 11 Sep 2015 17:36:34 GMT

I see no voltage on the K20 RTC pins XTAL32 & EXTAL32. The BSP does turn on this External Crystal.

Any have any idea why?

I am expecting about 1/2 voltage.

Re: K20 RTC CRYSTAL PINS XTAL32 & EXTAL32 has no voltage

danielchen — Mon, 14 Sep 2015 07:24:22 GMT

Hi Kalior:

I think first you need to check the register OSC_CR , Bit 7 ERCLKEN , make sure that external reference clock is enabled

Then you can check the MCG control 2 Register, what is the value?

Regards

Daniel

Re: K20 RTC CRYSTAL PINS XTAL32 & EXTAL32 has no voltage

markkalior — Mon, 14 Sep 2015 15:28:44 GMT

If the System Osc isn't being used, still set the OSC_CR, bit 7? I have tried both ways. Currently, I have it set to zero. MCG_C2 = 0, MCG_C7=0x01. Which should select the XTAL32 & EXTAL32, instead of the XTAL0 & EXTAL0.

Will the RTC work at all, if the VBAT is flowing?

Re: K20 RTC CRYSTAL PINS XTAL32 & EXTAL32 has no voltage

danielchen — Tue, 15 Sep 2015 07:01:51 GMT

You are right. If the system OSC isn't being used, you do not need to set the OSC_CR , bit 7.

RTC is powered by VBAT.

MCG_C2 = 0 and MCG_C7 =0x01, that is OK

Please also check the RTC Control Register (RTC_CR)

You need to enable OSCE: Oscillator Enable; configure the CLKO, according to your requirement.

SC20, SC4P, SC8P, SC16P, you need to configure them according to the schematic.

Regards

Daniel

Re: K20 RTC CRYSTAL PINS XTAL32 & EXTAL32 has no voltage

markkalior — Tue, 15 Sep 2015 14:49:59 GMT

I do have RTC_CR, bit OSCE set to a one.

Do you know if the any of the RTC registers will work, if VBAT is flowing?

Re: K20 RTC CRYSTAL PINS XTAL32 & EXTAL32 has no voltage

danielchen — Wed, 16 Sep 2015 05:39:02 GMT

Yes, if VBAT is flowing, the RTC registers can be accessed. But when the chip main power lost, the core doesn't work and couldn't access the RTC registers.