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stm32:peripherals:rtc_wakeup [2017/08/24 12:52] – [Wake Up Timer] ruan | stm32:peripherals:rtc_wakeup [2018/10/10 06:18] – [RTC_ISR] Added WUTF description kjaz | ||
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The wakeup timer can be used to generate a periodic interrupt through the wakeup timer flag (WUTF). Additionally the WUTF flag can be output (through signals WKUP, RTC_ALARM and on to RTC_AF1) to pin PC13. | The wakeup timer can be used to generate a periodic interrupt through the wakeup timer flag (WUTF). Additionally the WUTF flag can be output (through signals WKUP, RTC_ALARM and on to RTC_AF1) to pin PC13. | ||
+ | |||
+ | The wakeup timer clock input can be | ||
+ | * RTCCLK (usually 32.768 kHz) divided by 2, 4, 8 or 16. \\ As a result this allows wakeup interrupt periods from 122 us to 32 s, with a resolution down to 61 us. | ||
+ | * ck_spre (usually 1 Hz internal clock). \\ As a result this allows wakeup interrupt periods from 1 s to around 36 hours. | ||
===== Programming Instructions ===== | ===== Programming Instructions ===== | ||
==== RTC register write protection ==== | ==== RTC register write protection ==== | ||
- | After a reset the backup domain is write protected. \\ | + | After a reset the backup domain is write protected. The backup domain encompasses: |
Unlock access to backup domain: | Unlock access to backup domain: | ||
* Set the '' | * Set the '' | ||
Line 33: | Line 37: | ||
* Disable wakeup timer in '' | * Disable wakeup timer in '' | ||
* Wait until configuration of RTC is allowed. \\ Check corresponding bit in '' | * Wait until configuration of RTC is allowed. \\ Check corresponding bit in '' | ||
- | * Program reload value in '' | ||
* Program prescaler value in '' | * Program prescaler value in '' | ||
+ | * Program reload value in '' | ||
* Enable wakeup interrupt in '' | * Enable wakeup interrupt in '' | ||
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|WUTWF*|0|Wake up timer configuration not allowed| | |WUTWF*|0|Wake up timer configuration not allowed| | ||
|:::|1|Wake up timer configuration allowed| | |:::|1|Wake up timer configuration allowed| | ||
+ | |WUTF||Wake up timer flag is set by hardware when wakeup counter reaches 0 and cleared by software by writing 0.|| | ||
* This bit is set, after the WUTE bit (control register) has been set to 0, and reset by hardware. | * This bit is set, after the WUTE bit (control register) has been set to 0, and reset by hardware. |