EK-TM4C123GXL Launchpad HibernateRTCTrimSet

Michael Clarke93

Other Parts Discussed in Thread: EK-TM4C123GXL

Hello TI E2E Community Members,

I am looking for some guidance in understanding the HibernateRTCTrimSet function, the TivaWare Peripheral Driver Lib documentation states that this register value should nominally be 0x7FFF (or 32,767) and that it is applied to the pre-divider once every 64 seconds. I know that the crystal connected to the RTC on my EK-TM4C123GXL launchpad is a 32,768Hz crystal.

So my hypothetical question is if my RTC is one second slow every 64 seconds and the current value of the RTCTrimSet register is 32,767 how do I calculate what the new RTC trim value should be.

over 10 years ago

0 Amit Ashara over 10 years ago

TI__Guru**** 244440 points

Hello Michael

The forumla to correct the same is in the data sheet. And there is a thread on the forum where another member did check the crystal frequency and wanted to confirm the correction (amongst a list of other things).

If the value of the RTC is 32768 Hz, then no correction is to be applied.

Regards
Amit

0 Michael Clarke93 over 10 years ago

Prodigy 140 points

Thank you for your response Amit,

I understand now that the trim value replaces the pre-divider once every 64 seconds. Although I do not have the equipment to verify the actual crystal frequency I can use this information to calculate the approximate trim value given the time difference encountered over a period.

Regards, Michael.

0 Amit Ashara over 10 years ago in reply to Michael Clarke93

TI__Guru**** 244440 points

Hello Michael,

Yes. And you would need some kind of circuit component to make sure that the reference is being maintained and not drifting as well.

And also found the post...

e2e.ti.com/.../1337224

Regards
Amit

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EK-TM4C123GXL Launchpad HibernateRTCTrimSet