RTC clock calibration value The value indicates how many clock pulses are ignored or added every 2^20 RTC clock pulses.
(Section 4.4.2, page 59, emphasis mine)
After implementing a calibration procedure I don't think that the second (emphasized) part is true. That means it looks like the RCCV can only be used to ignore clock pulses.
(In which case, when having a clock that is too slow, one would need to decrement the prescaler and calibrate from a (then) too fast clock.)
My tests show that RCCV isn't interpreted as signed (two's complement) value.
And I can't find any other field that would work as a sign bit, either. I mean, e.g. in contrast to the GD32F1x0 where the RTC_HRFC register contains the CMSK (Calibration mask number) and FREQI fields.
The GD32CVF103 User Manual (1.3) specifies the RTC clock calibration value (RCCV) as:
(Section 4.4.2, page 59, emphasis mine)
After implementing a calibration procedure I don't think that the second (emphasized) part is true. That means it looks like the RCCV can only be used to ignore clock pulses.
(In which case, when having a clock that is too slow, one would need to decrement the prescaler and calibrate from a (then) too fast clock.)
My tests show that RCCV isn't interpreted as signed (two's complement) value.
And I can't find any other field that would work as a sign bit, either. I mean, e.g. in contrast to the GD32F1x0 where the RTC_HRFC register contains the CMSK (Calibration mask number) and FREQI fields.
Can you clarify this point?