RTCv2 coarse calibration remarks

[waclawek.jan]

While the Coarse calibration in RTCv2 is obsolete, in 'L1 and 'F2 it's the only method (and I know 'L1 is NRND, but it's still around and will be for years to come, if ST sticks to its commitment), and as long as it's mentioned in 'F4 it should be properly described there too.

So, my question #1 is, what's the role of RTC_CR.DCE. It's not described in the narrative. I can guess and test, but I don't intend to.

Question #2 is, whether the Coarse calibration is supported in 'F3 (according to AN4759 Rev.9) or not (according to RM0316 Rev 10).

JW

[Sarra.S]

Hello @waclawek.jan 

The AN4759 is not accurate ( I've submitted an internal ticket to be corrected: 196854) 

The DCE bit was the “digital calibration enable” control bit, used to enable the coarse calibration, but Coarse calibration was not fitting customers’ requirements, it was removed from RTC, and the smooth calibration was introduced instead.

So the stm32F3 only support smooth calibration. 

[waclawek.jan]

Hi @Sarra.S ,

Thanks.

Still, I believe, the (relevant)'L1/'F2/'F4 RMs deserve to describe the DCE bits functionality in the "Coarse calibration" subchapter of RTC, as currently it's not mentioned anywhere and the narrative explicitly states that coarse calibration is enabled by clearing the INIT bit. Note, that in 'F2 and 'L1 the Coarse calibration is the only calibration method in RTC.

JW