HPRTC and SRTC Compensation

[mjbcswitzerland]

Hi All

The HPRTC has a compensation value allowing some calibration in case of drift: HPCALB_VAL in HPCR

However its calibration resolution looks to be extremely course +/-1 count in 32768 ticks of the counter.
If ticks means the 32768Hz oscillator frequency it means a compensation of +/-1s each 9.1hours, or 15.6 minutes a year. Since RTCs are typically accurate to <=5 minutes a year this doesn't seem to be very useful unless there is a big error in the HW design.

There doesn't look to be any calibration for the SRTC, which - if I understand correctly - is used for time keeping when the main power is off. The HP RTC compensation would only be of interest if the processor is powered all the time and not when it spends a lot of time in battery backed up state.

Is this understanding correct and is there any way to achieve fine compensation (as is possible in Kinetis parts, for example, which allows about 37s / year compensation steps)?

Regards

Mark

[Hui_Ma]

Hi Mark,

Sorry for the later reply.

I do not find RT10xx RTC module provided Kinetis RTC module similar extended range compenstation feature/register fields. The HPCALB_VAL could do some compenstation to RTC clock, which is quite limited and like a temperature compensation for external 32KHz crystal.

RT10xx RTC module has another function, which will generate 4ms and 1ms delay during chip POR. More detailed info please refer below picture:

Thanks for the attention.

Mike