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RM0008 Power control (PWR)

Doc ID 13902 Rev 12 73/1096

● real-time clock (RTC): this is configured by the RTCEN bit in the Backup domain control

● Internal RC oscillator (LSI RC): this is configured by the LSION bit in the Control/status

● External 32.768 kHz oscillator (LSE OSC): this is configured by the LSEON bit in the

Backup domain control register (RCC_BDCR).

The ADC or DAC can also consume power during the Stop mode, unless they are disabled

before entering it. To disable them, the ADON bit in the ADC_CR2 register and the ENx bit

in the DAC_CR register must both be written to 0.

Exiting Stop mode

Refer to Ta bl e 1 4 for more details on how to exit Stop mode.

When exiting Stop mode by issuing an interrupt or a wakeup event, the HSI RC oscillator is

selected as system clock.

When the voltage regulator operates in low-power mode, an additional startup delay is

incurred when waking up from Stop mode. By keeping the internal regulator ON during Stop

mode, the consumption is higher although the startup time is reduced.

5.3.5 Standby mode

The Standby mode allows to achieve the lowest power consumption. It is based on the

Cortex-M3 deepsleep mode, with the voltage regulator disabled. The 1.8 V domain is

consequently powered off. The PLL, the HSI oscillator and the HSE oscillator are also

switched off. SRAM and register contents are lost except for registers in the Backup domain

and Standby circuitry (see Figure 4).

Table 14. Stop mode

Stop mode Description

Mode entry

WFI (Wait for Interrupt) or WFE (Wait for Event) while:

– Set SLEEPDEEP bit in Cortex™-M3 System Control register

– Clear PDDS bit in Power Control register (PWR_CR)

– Select the voltage regulator mode by configuring LPDS bit in PWR_CR

Note: To enter Stop mode, all EXTI Line pending bits (in Pending register

(EXTI_PR)) and RTC Alarm flag must be reset. Otherwise, the Stop mode

entry procedure is ignored and program execution continues.

Mode exit

If WFI was used for entry:

Any EXTI Line configured in Interrupt mode (the corresponding EXTI

Interrupt vector must be enabled in the NVIC). Refer to Table 63: Vector

table for other STM32F10xxx devices on page 195.

If WFE was used for entry:

Any EXTI Line configured in event mode. Refer to Section 10.2.3:

Wakeup event management on page 198

Wakeup latency HSI RC wakeup time + regulator wakeup time from Low-power mode

ST STM32F101xx User Manual

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