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GD32L23x User Manual
66
RC oscillator (IRC32K) or the Low Speed Crystal oscillator (LXTAL), or HXTAL clock divided
by 32. When V
DD
is shut down, only LXTAL is valid for RTC. Before entering the power saving
mode by executing the WFI/WFE instruction, the Cortex
®
-M23 can setup the RTC register
with an expected alarm time and enable the alarm function and according EXTI lines to
achieve the RTC alarm event. After entering the power saving mode for a certain amount of
time, the RTC alarm will wake up the device when the time match event occurs. The details
of the RTC configuration and operation will be described in the
When the Backup domain is supplied by V
DD
(V
BAK
pin is connected to V
DD
), the following
functions are available:
PC13 can be used as GPIO or RTC function pin described in the
PC14 and PC15 can be used as either GPIO or LXTAL Crystal oscillator pins.
When the Backup domain is supplied by V
BAT
(V
BAK
pin is connected to V
BAT
), the following
functions are available:
PC13 can be used as RTC function pin described in the
PC14 and PC15 can be used as LXTAL Crystal oscillator pins only.
Note
:
Since PC13, PC14, PC15 are supplied through the Power Switch, which can only be
obtained by a small current, the speed of GPIOs PC13 to PC15 should not exceed 2MHz
when they are in output mode(maximum load: 30pF).
The external V
BAT
battery can be charged by the V
DD
through an internal resistor. The charging
resistor can be selected by configuring the VCRSEL bit in PMU_CTL0 register. A 5 kOhms
resistor or a 1.5 kOhms resistor can be selected for external V
BAT
battery charing. The external
V
BAT
battery charing is enabled by setting the VCEN bit in PMU_CTL0 register. When in
BKP_ONLY mode, the V
BAT
battery charing is disabled by hardware.
Note:
DD
is power-off, and the backup domain is power by V
BAT
pin.
3.3.2.
V
DD
/V
DDA
power domain
V
DD
/V
DDA
domain includes two parts: V
DD
domain and V
DDA
domain. V
DD
domain includes
HXTAL (High Speed Crystal oscillator), LDO (Voltage Regulator), POR/PDR (Power On/Down
Reset), FWDGT (Free Watchdog Timer), all pads except PC13/PC14/PC15, etc. V
DDA
domain
includes ADC/DAC (AD/DA Converter), IRC16M (Internal 16MHz RC oscillator), IRC48M
(Internal 48MHz RC oscillator at 48MHz frequency), IRC32K (Internal 32KHz RC oscillator),
PLLs (Phase Locking Loop), LVD (Low Voltage Detector), etc.
V
DD
domain
The LDO, which is implemented to supply power for the 1.1V domain, is always enabled after
reset. It can be configured to operate in different status, including in the Sleep mode (1.1V full
power on, 0.9V full power on, Low power), in the Deep-sleep/Deep-sleep 1/Deep-sleep 2
mode (on or low power), and in the Standby mode (power off).
The POR/PDR circuit is implemented to detect V
DD
/V
DDA
and generate the power reset signal