Note: When the peripheral clock is not active, the peripheral register values may not be readable
by software and the returned value is always 0x0.
Bits 31:11 Reserved, must be kept at reset value.
Bit 10 SDIOEN: SDIO clock enable
Set and cleared by software.
0: SDIO clock disabled
1: SDIO clock enabled
Bits 9 Reserved, always read as 0.
Bit 8 FSMCEN: FSMC clock enable
Set and cleared by software.
0: FSMC clock disabled
1: FSMC clock enabled
Bit 7 Reserved, always read as 0.
Bit 6 CRCEN: CRC clock enable
Set and cleared by software.
0: CRC clock disabled
1: CRC clock enabled
Bit 5 Reserved, must be kept at reset value.
Bit 4 FLITFEN: FLITF clock enable
Set and cleared by software to disable/enable FLITF clock during Sleep mode.
0: FLITF clock disabled during Sleep mode
1: FLITF clock enabled during Sleep mode
Bit 3 Reserved, must be kept at reset value.
Bit 2 SRAMEN: SRAM interface clock enable
Set and cleared by software to disable/enable SRAM interface clock during Sleep mode.
0: SRAM interface clock disabled during Sleep mode.
1: SRAM interface clock enabled during Sleep mode
Bit 1 DMA2EN: DMA2 clock enable
Set and cleared by software.
0: DMA2 clock disabled
1: DMA2 clock enabled
Bit 0 DMA1EN: DMA1 clock enable
Set and cleared by software.
0: DMA1 clock disabled
1: DMA1 clock enabled
APB2 peripheral clock enable register (RCC_APB2ENR)
Address: 0x18
Reset value: 0x0000 0000
Access: word, half-word and byte access
No wait states, except if the access occurs while an access to a peripheral in the APB2
domain is on going. In this case, wait states are inserted until the access to APB2 peripheral
is finished.
Note: When the peripheral clock is not active, the peripheral register values may not be readable
by software and the returned value is always 0x0.
Bits 31:22 Reserved, must be kept at reset value.
Bit 21 TIM11EN: TIM11 timer clock enable
Set and cleared by software.
0: TIM11 timer clock disabled
1: TIM11 timer clock enabled
Bit 20 TIM10EN: TIM10 timer clock enable
Set and cleared by software.
0: TIM10 timer clock disabled
1: TIM10 timer clock enabled
Bit 19 TIM9EN: TIM9 timer clock enable
Set and cleared by software.
0: TIM9 timer clock disabled
1: TIM9 timer clock enabled
Bits 18:16 Reserved, always read as 0.
Bit 15 ADC3EN: ADC3 interface clock enable
Set and cleared by software.
0: ADC3 interface clock disabled
1: ADC3 interface clock enabled
Bit 14 USART1EN: USART1 clock enable
Set and cleared by software.
0: USART1 clock disabled
1: USART1 clock enabled
Bit 13 TIM8EN: TIM8 Timer clock enable
Set and cleared by software.
0: TIM8 timer clock disabled
1: TIM8 timer clock enabled
Bit 12 SPI1EN: SPI1 clock enable
Set and cleared by software.
0: SPI1 clock disabled
1: SPI1 clock enabled
Bit 11 TIM1EN: TIM1 timer clock enable
Set and cleared by software.
0: TIM1 timer clock disabled
1: TIM1 timer clock enable
Bit 10 ADC2EN: ADC 2 interface clock enable
Set and cleared by software.
0: ADC 2 interface clock disabled
1: ADC 2 interface clock enabled
Bit 9 ADC1EN: ADC 1 interface clock enable
Set and cleared by software.
0: ADC 1 interface disabled
1: ADC 1 interface clock enabled
Bit 8 IOPGEN: IO port G clock enable
Set and cleared by software.
0: IO port G clock disabled
1: IO port G clock enabled
Bit 7 IOPFEN: IO port F clock enable
Set and cleared by software.
0: IO port F clock disabled
1: IO port F clock enabled
Bit 6 IOPEEN: IO port E clock enable
Set and cleared by software.
0: IO port E clock disabled
1: IO port E clock enabled
Bit 5 IOPDEN: IO port D clock enable
Set and cleared by software.
0: IO port D clock disabled
1: IO port D clock enabled
Bit 4 IOPCEN: IO port C clock enable
Set and cleared by software.
0: IO port C clock disabled
1: IO port C clock enabled
Bit 3 IOPBEN: IO port B clock enable
Set and cleared by software.
0: IO port B clock disabled
1: IO port B clock enabled
Bit 2 IOPAEN: IO port A clock enable
Set and cleared by software.
0: IO port A clock disabled
1: IO port A clock enabled
Bit 1 Reserved, must be kept at reset value.
Bit 0 AFIOEN: Alternate function IO clock enable
Set and cleared by software.
0: Alternate Function IO clock disabled
1: Alternate Function IO clock enable
APB1 peripheral clock enable register (RCC_APB1ENR)
Address: 0x1C
Reset value: 0x0000 0000
Access: word, half-word and byte access
No wait state, except if the access occurs while an access to a peripheral on APB1 domain
is on going. In this case, wait states are inserted until this access to APB1 peripheral is
finished.
Note: When the peripheral clock is not active, the peripheral register values may not be readable
by software and the returned value is always 0x0.
Bits 31:30 Reserved, must be kept at reset value.
Bit 29 DACEN: DAC interface clock enable
Set and cleared by software.
0: DAC interface clock disabled
1: DAC interface clock enable
Bit 28 PWREN: Power interface clock enable
Set and cleared by software.
0: Power interface clock disabled
1: Power interface clock enable
Bit 27 BKPEN: Backup interface clock enable
Set and cleared by software.
0: Backup interface clock disabled
1: Backup interface clock enabled
Bit 26 Reserved, must be kept at reset value.
Bit 25 CANEN: CAN clock enable
Set and cleared by software.
0: CAN clock disabled
1: CAN clock enabled
Bit 24 Reserved, always read as 0.
Bit 23 USBEN: USB clock enable
Set and cleared by software.
0: USB clock disabled
1: USB clock enabled
Bit 22 I2C2EN: I2C2 clock enable
Set and cleared by software.
0: I2C2 clock disabled
1: I2C2 clock enabled
Bit 21 I2C1EN: I2C1 clock enable
Set and cleared by software.
0: I2C1 clock disabled
1: I2C1 clock enabled
Bit 20 UART5EN: USART5 clock enable
Set and cleared by software.
0: USART5 clock disabled
1: USART5 clock enabled
Bit 19 UART4EN: USART4 clock enable
Set and cleared by software.
0: USART4 clock disabled
1: USART4 clock enabled
Bit 18 USART3EN: USART3 clock enable
Set and cleared by software.
0: USART3 clock disabled
1: USART3 clock enabled
Bit 17 USART2EN: USART2 clock enable
Set and cleared by software.
0: USART2 clock disabled
1: USART2 clock enabled
Bits 16 Reserved, always read as 0.
Bit 15 SPI3EN: SPI 3 clock enable
Set and cleared by software.
0: SPI 3 clock disabled
1: SPI 3 clock enabled
Bit 14 SPI2EN: SPI2 clock enable
Set and cleared by software.
0: SPI2 clock disabled
1: SPI2 clock enabled
Bits 13:12 Reserved, must be kept at reset value.
Bit 11 WWDGEN: Window watchdog clock enable
Set and cleared by software.
0: Window watchdog clock disabled
1: Window watchdog clock enabled
Bits 10:9 Reserved, must be kept at reset value.
Bit 8 TIM14EN: TIM14 timer clock enable
Set and cleared by software.
0: TIM14 clock disabled
1: TIM14 clock enabled
Bit 7 TIM13EN: TIM13 timer clock enable
Set and cleared by software.
0: TIM13 clock disabled
1: TIM13 clock enabled
Bit 6 TIM12EN: TIM12 timer clock enable
Set and cleared by software.
0: TIM12 clock disabled
1: TIM12 clock enabled
Bit 5 TIM7EN: TIM7 timer clock enable
Set and cleared by software.
0: TIM7 clock disabled
1: TIM7 clock enabled
Bit 4 TIM6EN: TIM6 timer clock enable
Set and cleared by software.
0: TIM6 clock disabled
1: TIM6 clock enabled
Bit 3 TIM5EN: TIM5 timer clock enable
Set and cleared by software.
0: TIM5 clock disabled
1: TIM5 clock enabled
Bit 2 TIM4EN: TIM4 timer clock enable
Set and cleared by software.
0: TIM4 clock disabled
1: TIM4 clock enabled
Bit 1 TIM3EN: TIM3 timer clock enable
Set and cleared by software.
0: TIM3 clock disabled
1: TIM3 clock enabled
Bit 0 TIM2EN: TIM2 timer clock enable
Set and cleared by software.
0: TIM2 clock disabled
1: TIM2 clock enabled
Backup domain control register (RCC_BDCR)
Address offset: 0x20
Reset value: 0x0000 0000, reset by Backup domain Reset.
Access: 0 ≤ wait state ≤ 3, word, half-word and byte access
Wait states are inserted in case of successive accesses to this register.
Note: The LSEON, LSEBYP, RTCSEL and RTCEN bits of the Backup domain control register
(RCC_BDCR) are in the Backup domain. As a result, after Reset, these bits are writeprotected
and the DBP bit in the Power control register (PWR_CR) has to be set before
these can be modified. Refer to Section 5 on page 44 for further information. These bits are
only reset after a Backup domain Reset (see Section 7.1.3: Backup domain reset). Any
internal or external Reset will not have any effect on these bits.
Bits 31:17 Reserved, must be kept at reset value.
Bit 16 BDRST: Backup domain software reset
Set and cleared by software.
0: Reset not activated
1: Resets the entire Backup domain
Bit 15 RTCEN: RTC clock enable
Set and cleared by software.
0: RTC clock disabled
1: RTC clock enabled
Bits 14:10 Reserved, must be kept at reset value.
Bits 9:8 RTCSEL[1:0]: RTC clock source selection
Set by software to select the clock source for the RTC. Once the RTC clock source has been
selected, it cannot be changed anymore unless the Backup domain is reset. The BDRST bit
can be used to reset them.
00: No clock
01: LSE oscillator clock used as RTC clock10: LSI oscillator clock used as RTC clock
11: HSE oscillator clock divided by 128 used as RTC clock
Bits 7:3 Reserved, must be kept at reset value.
Bit 2 LSEBYP: External low-speed oscillator bypass
Set and cleared by software to bypass oscillator in debug mode. This bit can be written only
when the external 32 kHz oscillator is disabled.
0: LSE oscillator not bypassed
1: LSE oscillator bypassed
Bit 1 LSERDY: External low-speed oscillator ready
Set and cleared by hardware to indicate when the external 32 kHz oscillator is stable. After
the LSEON bit is cleared, LSERDY goes low after 6 external low-speed oscillator clock
cycles.
0: External 32 kHz oscillator not ready
1: External 32 kHz oscillator ready
Bit 0 LSEON: External low-speed oscillator enable
Set and cleared by software.
0: External 32 kHz oscillator OFF
1: External 32 kHz oscillator ON
Control/status register (RCC_CSR)
Address: 0x24
Reset value: 0x0C00 0000, reset by system Reset, except reset flags by power Reset only.
Access: 0 ≤ wait state ≤ 3, word, half-word and byte access
Wait states are inserted in case of successive accesses to this register.
Bit 31 LPWRRSTF: Low-power reset flag
Set by hardware when a Low-power management reset occurs.
Cleared by writing to the RMVF bit.
0: No Low-power management reset occurred
1: Low-power management reset occurred
For further information on Low-power management reset, refer to Low-power management
reset.
Bit 30 WWDGRSTF: Window watchdog reset flag
Set by hardware when a window watchdog reset occurs.
Cleared by writing to the RMVF bit.
0: No window watchdog reset occurred
1: Window watchdog reset occurred
Bit 29 IWDGRSTF: Independent watchdog reset flag
Set by hardware when an independent watchdog reset from VDD domain occurs.
Cleared by writing to the RMVF bit.
0: No watchdog reset occurred
1: Watchdog reset occurred
Bit 28 SFTRSTF: Software reset flag
Set by hardware when a software reset occurs.
Cleared by writing to the RMVF bit.
0: No software reset occurred
1: Software reset occurred
Bit 27 PORRSTF: POR/PDR reset flag
Set by hardware when a POR/PDR reset occurs.
Cleared by writing to the RMVF bit.
0: No POR/PDR reset occurred
1: POR/PDR reset occurred
Bit 26 PINRSTF: PIN reset flag
Set by hardware when a reset from the NRST pin occurs.
Cleared by writing to the RMVF bit.
0: No reset from NRST pin occurred
1: Reset from NRST pin occurred
Bit 25 Reserved, must be kept at reset value.
Bit 24 RMVF: Remove reset flag
Set by software to clear the reset flags.
0: No effect
1: Clear the reset flags
Bits 23:2 Reserved, must be kept at reset value.
Bit 1 LSIRDY: Internal low-speed oscillator ready
Set and cleared by hardware to indicate when the internal RC 40 kHz oscillator is stable.
After the LSION bit is cleared, LSIRDY goes low after 3 internal RC 40 kHz oscillator clock
cycles.
0: Internal RC 40 kHz oscillator not ready
1: Internal RC 40 kHz oscillator ready
Bit 0 LSION: Internal low-speed oscillator enable
Set and cleared by software.
0: Internal RC 40 kHz oscillator OFF
1: Internal RC 40 kHz oscillator ON
