GD32F403xx User Manual
63
power domains are active. Users can achieve lower power consumption through slowing
down the system clocks (HCLK, PCLK1, and PCLK2) or gating the clocks of the unused
peripherals or configuring the LDO output voltage by LDOVS bits in PMU_CTL register. The
LDOVS bits should be configured only when the PLL is off, and the programmed value is
selected to drive 1.2V domain after the PLL opened. While the PLL is off, LDO output voltage
low mode is selected to drive 1.2V domain. Besides, three power saving modes are provided
to achieve even lower power consumption, they are Sleep mode, Deep-sleep mode, and
Standby mode.
Sleep mode
The Sleep mode is corresponding to the SLEEPING mode of the Cortex
®
-M4. In Sleep mode,
only clock of Cortex
®
-M4 is off. To enter the Sleep mode, it is only necessary to clear the
SLEEPDEEP bit in the Cortex
®
-M4 System Control Register, and execute a WFI or WFE
instruction. If the Sleep mode is entered by executing a WFI instruction, any interrupt can
wake up the system. If it is entered by executing a WFE instruction, any wakeup event can
wake up the system (If SEVONPEND is 1, any interrupt can wake up the system, refer to
Cortex-M4 Technical Reference Manual). The mode offers the lowest wakeup time as no time
is wasted in interrupt entry or exit.
According to the SLEEPONEXIT bit in the Cortex
®
-M4 System Control Register, there are two
options to select the Sleep mode entry mechanism.
◼
Sleep-now: if the SLEEPONEXIT bit is cleared, the MCU enters Sleep mode as soon as
WFI or WFE instruction is executed.
◼
Sleep-on-exit: if the SLEEPONEXIT bit is set, the MCU enters Sleep mode as soon as it
exits f rom the lowest priority ISR.
Deep-sleep mode
The Deep-sleep mode is based on the SLEEPDEEP mode of the Cortex
®
-M4. In Deep-sleep
mode, all clocks in the 1.2V domain are off, and all of IRC8M, HXTAL and PLLs are disabled.
The contents of SRAM and registers are preserved. The LDO can operate normally or in low
power mode depending on the LDOLP bit in the PMU_CTL register. Before entering the Deep-
sleep mode, it is necessary to set the SLEEPDEEP bit in the Cortex
®
-M4 System Control
Register, and clear the STBMOD bit in the PMU_CTL register. Then, the device enters the
Deep-sleep mode after a WFI or WFE instruction is executed. If the Deep-sleep mode is
entered by executing a WFI instruction, any interrupt from EXTI lines can wake up the system.
If it is entered by executing a WFE instruction, any wakeup event from EXTI lines can wake
up the system (If SEVONPEND is 1, any interrupt from EXTI lines can wake up the system,
refer to Cortex-M4 Technical Reference Manual). When exiting the Deep-sleep mode, the
IRC8M is selected as the system clock. Notice that an additional wakeup delay will be incurred
if the LDO operates in low power mode.
The low-driver mode in Deep-sleep mode can be entered by configuring the LDEN, LDNP,
LDLP, LDOLP bits in the PMU_CTL register. The Low-driver mode provides lower drive
capability, and the Low-power mode take lower power.
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