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NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
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Revision V1.30
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be raised high. Then user can feel free to write data into register. RWENF will keep high for a short
period (about 24ms) and it will be pull low by internal state machine automatically.
Frequency Compensation
5.15.5.3
The RTC_FREQADJ allows software control digital compensation of a 32.768 KHz crystal oscillator.
User can utilize a frequency counter to measure RTC tick output in pin PH.4 and PI.3 during
manufacture, and store the value in Flash memory for retrieval when the product is first power on.
Time and Calendar counter
5.15.5.4
RTC_TIME and RTC_CAL are used to read the time and calendar. RTC_TALM and RTC_CALM are
used as alarm. They are all BCD counters.
12/24 hour Time scale selection
5.15.5.5
The 12/24 hour time scale selection decided by 24HEN (RTC_TIMEFMT[0]).
Day of the week counter
5.15.5.6
Count from Sunday to Saturday
Tick Time interrupt
5.15.5.7
RTC block use a counter to calibrate the tick time count value. When the value in counter reaches
zero, RTC will issue an interrupt.
RTC register property
5.15.5.8
When system power is off but RTC power is on, data stored in RTC registers will not be lost except
RTC_TSSR, RTC_INTEN and RTC_INTSTS. Because of difference between RTC clock and system
clock, every time user write new data to any one register, the register will be updated until 2 RTC clock
later (60us).
In addition, user must be aware that RTC block does not check whether loaded data is out of bounds.
RTC does not check rationality between RTC_WEEKDAY and RTC_CLR either.
Note:
RTC_TALM, RTC_CALM, RTC_TIME and RTC_CAL are all BCD counter, but RTC_FREQADJ is not
a BCD counter.
Programmer must be aware that the RTC block does not check whether the loaded value is
reasonable. For example, Load RTC_CAL as 201a (year), 13 (month), 00 (day), or RTC_CAL does
not match with RTC_WEEKDAY, etc.
In RTC_TIME and RTC_TALM, only 2 BCD digits are used to express
“
year”. We assume 2 BCD
digits of XY denote 20XY, but not 19XY or 21XY.