Datasheet

Description STM32F405xx, STM32F407xx
28/167 Doc ID 022152 Rev 2
Standby mode, the SRAM and register contents are lost except for registers in the
backup domain and the backup SRAM when selected.
The device exits the Standby mode when an external reset (NRST pin), an IWDG reset,
a rising edge on the WKUP pin, or an RTC alarm / wakeup / tamper /time stamp event
occurs.
Note: When in Standby mode, only an RTC alarm/event or an external reset can wake up the
device provided V
DD
is supplied by an external battery.
2.2.19 V
BAT
operation
The V
BAT
pin allows to power the device V
BAT
domain from an external battery, an external
supercapacitor, or from V
DD
when no external battery and an external supercapacitor are
present.
V
BAT
operation is activated when V
DD
is not present.
The V
BAT
pin supplies the RTC, the backup registers and the backup SRAM.
Note: When the microcontroller is supplied from V
BAT
, external interrupts and RTC alarm/events
do not exit it from V
BAT
operation.
2.2.20 Timers and watchdogs
The STM32F405xx and STM32F407xx devices include two advanced-control timers, eight
general-purpose timers, two basic timers and two watchdog timers.
All timer counters can be frozen in debug mode.
Table 3 compares the features of the advanced-control, general-purpose and basic timers.