NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
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Revision V1.30
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Real Time Clock (RTC)
5.15
5.15.1 Overview
The Real Time Clock (RTC) controller provides the real time clock and calendar information. The clock
source of RTC controller is from an external 32.768 kHz low-speed crystal which connected at pins
X32_IN and X32_OUT (refer to pin Description). The RTC controller provides the real time clock (hour,
minute, second) in RTC_TIME (RTC Time Loading Register) as well as calendar information (year,
month, day) in RTC_CAL (RTC Calendar Loading Register). It also offers RTC alarm function that
user can preset the alarm time in RTC_TALM (RTC Time Alarm Register) and alarm calendar in
RTC_CALM (RTC Calendar Alarm Register). The data format of RTC time and calendar message are
all expressed in BCD (Binary Coded Decimal) format.
The RTC controller supports periodic RTC Time Tick and Alarm Match interrupts. The periodic RTC
Time Tick interrupt has 8 period interval options 1/128, 1/64, 1/32, 1/16, 1/8, 1/4, 1/2 and 1 second
which are selected by RTC_TICK (RTC_TICK[2:0] Time Tick Register). When real time and calendar
message in RTC_TIME and RTC_CAL are equal to alarm time and calendar settings in RTC_TALM
and RTC_CALM, the ALMIF (RTC_INTSTS [0] RTC Alarm Interrupt Flag) is set to 1 and the RTC
alarm interrupt signal is generated if the ALMIEN (RTC_INTEN [0] Alarm Interrupt Enable) is enabled.
Both RTC Time Tick and Alarm Match interrupt signal can cause chip to wake-up from Idle or Power-
down mode if the corresponding interrupt enable bit (ALMIEN or TICKIEN) is set to 1 before chip
enters Idle or Power-down mode.
Real Time Clock (RTC) block can operate with independent power supply (RTC_VDD) while the
system power is off.
5.15.2 Features
Supports real time counter and calendar counter for RTC time and calendar check.
Supports time (hour, minute, second) and calendar (year, month, day) alarm and alarm
mask settings.
Selectable 12-hour or 24-hour time scale.
Supports Leap Year indication.
Supports Day of the Week counter.
Supports frequency compensation mechanism for 32.768 kHz clock source.
All time and calendar message expressed in BCD format.
Supports periodic RTC Time Tick interrupt with 8 period interval options 1/128, 1/64, 1/32,
1/16, 1/8, 1/4, 1/2 and 1 second.
Supports RTC Time Tick and Alarm match interrupt.
Supports chip wake-up from Idle or Power-down mode while alarm or relative alarm interrupt
is generated.
Supports 64
bytes spare registers to store user’s important information.
Supports power on/off control mechanism to control system core power.