Power control (PWR) RM0033
70/1381 RM0033 Rev 9
Figure 7. PVD thresholds
4.3 Low-power modes
By default, the microcontroller is in Run mode after a system or a power-on reset. In Run
mode the CPU is clocked by HCLK and the program code is executed. Several low-power
modes are available to save power when the CPU does not need to be kept running, for
example when waiting for an external event. It is up to the user to select the mode that gives
the best compromise between low-power consumption, short startup time and available
wakeup sources.
The devices feature three low-power modes:
• Sleep mode (Cortex
®
-M3 core stopped, peripherals kept running)
• Stop mode (all clocks are stopped)
• Standby mode (1.2 V domain powered off)
In addition, the power consumption in Run mode can be reduce by one of the following
means:
• Slowing down the system clocks
• Gating the clocks to the APBx and AHBx peripherals when they are unused.
Entering low-power mode
Low-power modes are entered by the MCU by executing the WFI (Wait For Interrupt), or
WFE (Wait for Event) instructions, or when the SLEEPONEXIT bit in the Cortex
®
-M3
System Control register is set on Return from ISR.
V
DD
/V
DDA
PVD output
100 mV
hysteresis
PVD threshold
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