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| Both sides previous revision Previous revision Next revision | Previous revision | ||
| stm32:peripherals:rtc_wakeup [2017/08/24 12:52] – [Wake Up Timer] ruan | stm32:peripherals:rtc_wakeup [2022/12/27 18:42] (current) – ruan | ||
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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 '' | ||
| Line 52: | Line 56: | ||
| ===== Configuration Registers ===== | ===== Configuration Registers ===== | ||
| - | ==== RTC_CR ==== | + | ==== RTC_CR |
| - | + | ||
| - | Configuration register | + | |
| \\ {{rtc_reg_cr.svg}} \\ \\ | \\ {{rtc_reg_cr.svg}} \\ \\ | ||
| Line 68: | Line 70: | ||
| |:::|1|Wake up timer interrupt enabled|| | |:::|1|Wake up timer interrupt enabled|| | ||
| - | ==== RTC_WUTR ==== | + | ==== RTC_WUTR |
| - | + | ||
| - | Wakeup timer register | + | |
| \\ {{rtc_reg_wutr.svg}} \\ \\ | \\ {{rtc_reg_wutr.svg}} \\ \\ | ||
| Line 77: | Line 77: | ||
| ===== Status Registers ===== | ===== Status Registers ===== | ||
| - | ==== RTC_ISR | + | ==== RTC_ISR |
| - | + | ||
| - | Initialization and status register | + | |
| \\ {{rtc_reg_isr.svg}} \\ \\ | \\ {{rtc_reg_isr.svg}} \\ \\ | ||
| Line 86: | Line 84: | ||
| |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. | ||
| + | |||
| + | ===== Back domain control register ===== | ||
| + | |||
| + | ==== RCC_BDCR - Back domain control register ==== | ||
| + | |||
| + | \\ {{rcc_reg_bdcr.svg}} \\ \\ | ||
| + | |||
| + | |< 100% 5em 5em >| | ||
| + | |RTCEN*|0|RTC clock disabled| | ||
| + | |:::|1|RTC clock enabled| | ||
| + | |RTCSEL|00|No clock| | ||
| + | |:::|01|LSE oscillator clock used as the RTC clock| | ||
| + | |:::|10|LSI oscillator clock used as the RTC clock| | ||
| + | |:::|11|HSE oscillator clock divided by a programmable prescaler(selection Through RTCPRE[4:0] bits in the RCC clock configuration register (RCC_CFGR)) used as the RTC clock| | ||
| + | |||