RTC in NRF9160

[ibrahem]

Dears,

I used NRF9160 and i have some questions about it: 
1. the internal rtc is accurate or not ? is calibrated or need to be calibrated every time?
2. this rtc is internal in application processor or is internal in lte modem/chip itself ? , so if rtc is internal just in application processor only , how commands like +CCLK which set/read the time works ? or when EMM information get from the MME to set the local time zone , how the lte modem know the time ? is there happen by communicating with the application processer ? or the modem/lte chip has its own internal rtc ?

i get confused !

[Kazi Afroza Sultana]

Hello,

Your case arrived in holiday so a bit late reply. Sorry for that. 

Regarding first question, you can look at  https://infocenter.nordicsemi.com/topic/ps_nrf9160/pmu_oscillators.html?cp=2_0_0_4_3_0#hfclk 

The HFCLK controller will automatically provide the clock(s) requested by the system. If the system does not request any clocks from the HFCLK controller, the controller will switch off all its clock sources and enter a power saving mode.

The HFINT source will be used when HFCLK is requested and HFXO has not been started.

The HFXO is started by triggering the HFCLKSTART task and stopped using the HFCLKSTOP task. A HFCLKSTARTED event will be generated when the HFXO has started and its frequency is stable.

Regarding question 2: I would like to know more. Could you please explain a bit details?

Thanks.

Best Regards,

Kazi Afroza Sultana