K20 RTC CRYSTAL PINS XTAL32 & EXTAL32 has no voltage

[markkalior]

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.

[danielchen]

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

[markkalior]

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?

[danielchen]

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

[markkalior]

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?

[danielchen]

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.