Maxim Integrated MAX32600, Руководство пользователя

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MAX32600 User’s Guide System Clock, Timers/Counters, Watchdog Timers and Real Time Clock 10.3 Real Time Clock (RTC)
Although the 4kHz clock domain interrupt flag can be set while the main system is powered off (e.g., if a time of day alarm is matched), main power must be present
in order for the system to wake up and service the interrupt. The CPU cannot operate from the V
RTC
backup supply without the main 3V supply (V
DD
and/or V
BUS
)
active.
RTC interrupts to the ARM core are set by the CLKMAN_CLK_CTRL_13_RTC_INT_SYNC.rtc_clk_scale register. By default, RTC interrupts are disabled. To enable
CPU interrupts generated from the RTC block, the register needs to be set to a non-zero number.
rtc_clk_scale write RTC Interrupt Clock Sync Setting
0000b CLK is Disabled (Default)
0001b CLK = (System Clock Source / 1)
0010b CLK = (System Clock Source / 2)
0011b CLK = (System Clock Source / 4)
0100b CLK = (System Clock Source / 8)
0101b CLK = (System Clock Source / 16)
0110b CLK = (System Clock Source / 32)
0111b CLK = (System Clock Source / 64)
1000b CLK = (System Clock Source / 128)
1001b CLK = (System Clock Source / 256)
other CLK = (System Clock Source / 1)
Note
This clock is disabled by default following reset.
10.3.4 RTC Configuration
In order for firmware to configure the RTC for a desired application and start the operation of the RTC, the following operations must be performed:
1. The 32kHz crystal oscillator (which provides the time base for the RTC module) must be started by powering on the RTC block.
2. The clock for the RTC synchronizers (which translate signals between the 4kHz and high-frequency clock domains) must be started for CPU interrupts to
function properly.
3. OPTIONAL : If the RTC digital trim function will be used, the settings for the trim must be loaded with the RTCTMR_TRIM_VALUE register. The RTC prescaler
must be configured to determine the time period represented by the LSB of the RTC timer. The prescaler must be within 0x3 and 0xC.
Rev.1.3 April 2015 Maxim Integrated Page 565