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GD32E23x User Manual
64
Generally, digital circuits are powered by V
DD
, while most of analog circuits are powered by
V
DDA
. To improve the ADC conversion accuracy, the independent power supply V
DDA
is
implemented to achieve better performance of analog circuits. V
DDA
can be externally
connected to V
DD
through the external filtering circuit that avoids noise on V
DDA
, and V
SSA
should be connected to V
SS
through the specific circuit independently. Otherwise, if V
DDA
is
different from V
DD
, V
DDA
must always be higher, but the voltage difference should not exceed
0.3V.
3.3.3.
1.2V power domain
The main functions that include Cortex
®
-
M23
logic, AHB / APB peripherals, the APB
interfaces for the Backup domain and the
V
DD
/ V
DDA
domain, etc, are located in this power
domain. Once the 1.2V is powered up, the POR will generate a reset sequence on the 1.2V
power domain. If need to enter the expected power saving mode, the associated control bits
must be configured. Then, once a WFI
(Wait for Interrupt)
or WFE
(Wait for Event)
instruction
is executed, the device will enter an expected power saving mode which will be discussed in
the following section.
3.3.4.
Power saving modes
After a system reset or a power reset, the GD32E23x
MCU operates at full function and all
power domains are active. Users can achieve lower power consumption through slowing
down the system clocks (HCLK, PCLK1, 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. 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
®
-M23. In Sleep
mode, only clock of Cortex
®
-M23 is off. To enter the Sleep mode, it is only necessary to clear
the SLEEPDEEP bit in the Cortex
®
-M23 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
®
-M23
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
®
-M23 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