Realtek Ameba-D RTL872 D Series, User Manual

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Real-time Clock (RTC)
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11.4 Operation Flow
11.4.1 Initialize the Calendar
The initialization calendar configure flow is shown in Table 11-3.
Table 11-3 Initialization calendar configure flow
Step What to do How to do Comments
1 Disable the RTC registers write protection Write ‘0xCA’ and then ‘0x53’
into the RTC_WPR register RTC registers can be modified
2 Enter Initialization mode Set INIT bit to ‘1’ in RTC_ISR
register The calendar counter is stopped to allow update
3 Wait for the confirmation of Initialization
mode (clock synchronization) Poll INITF bit of in RTC_ISR
until it is set It takes approximately 2 RTCCLK clock cycles for
medium density devices
4 Program the prescaler register if needed Configure RTC_PRER register By default, the RTC_PRER prescalers register is
initialized to provide 1Hz to the Calendar unit when
RTCCLK = 32.768kHz
5 Load time value in the shadow registers Set RTC_TR -
6 Configure the time format (12h or 24h) Set FMT bit in RTC_CR register FMT = 0: 24 hour/day format
FMT = 1: AM/PM hour format
7 Exit Initialization mode Clear the INIT bit in RTC_ISR
register The current calendar counter is automatically
loaded and the counting restarts after 4 RTCCLK
cycles
8 Enable the RTC registers Write protection Write ‘0xFF’ into the RTC_WPR
register RTC registers can no longer be modified
11.4.2 Configure Alarm
The alarm configure flow is shown in Table 11-4.
Table 11-4 Alarm configure flow
Step What to do How to do Comments
1 Disable the RTC registers write
protection Write ‘0xCA’ and then ‘0x53’ into the
RTC_WPR register RTC registers can be modified
2 Disable alarm Clear the ALME bit in RTC_CR register -
3 Check that the RTC_ALRMA register
can be accessed Poll the ALMWF bit until it is set in
RTC_ISR register. It takes approximately two RTCCLK clock cycles
(clock synchronization).
4 Configure the alarm Configure RTC_ALMR1L and
RTC_ALMR1H register The alarm hour format must be the same as the
RTC Calendar
5 Re-enable alarm Set the ALME bit in RTC_CR register -
6 Enable the RTC registers write
protection Write "0xFF" into RTC_WPR register RTC registers can no longer be modified
Note
:

The alarm behaviour can be configured using the MSK x bits ( x = {0, 1, 2, 3}) of the RTC_ALMR1L and RTC_ALMR1H registers.

Alarm can also be configured in the initialization mode.
11.4.3 Configure Calibration
The calibration configure flow is shown in Table 11-5.
Table 11-5 Calibration configure flow
Step What to do How to do Comments
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2019-05-15 10:08:03