Reset and clock control for STM32F405xx/07xx and STM32F415xx/17xx(RCC)
RM0090
214/1731
DocID018909 Rev 11
Low-power management reset
There are two ways of generating a low-power management reset:
1.
Reset generated when entering the Standby mode:
This type of reset is enabled by resetting the nRST_STDBY bit in the user option bytes.
In this case, whenever a Standby mode entry sequence is successfully executed, the
device is reset instead of entering the Standby mode.
2. Reset when entering the Stop mode:
This type of reset is enabled by resetting the nRST_STOP bit in the user option bytes.
In this case, whenever a Stop mode entry sequence is successfully executed, the
device is reset instead of entering the Stop mode.
7.1.2 Power
reset
A power reset is generated when one of the following events occurs:
1.
Power-on/power-down reset (POR/PDR reset) or brownout (BOR) reset
2. When exiting the Standby mode
A power reset sets all registers to their reset values except the Backup domain (see
These sources act on the NRST pin and it is always kept low during the delay phase. The
RESET service routine vector is fixed at address
0x0000_0004
in the memory map.
The system reset signal provided to the device is output on the NRST pin. The pulse
generator guarantees a minimum reset pulse duration of 20 µs for each internal reset
source. In case of an external reset, the reset pulse is generated while the NRST pin is
asserted low.
Figure 20. Simplified diagram of the reset circuit
The Backup domain has two specific resets that affect only the Backup domain (see
7.1.3 Backup
domain
reset
The backup domain reset sets all RTC registers and the RCC_BDCR register to their reset
values. The BKPSRAM is not affected by this reset. The only way of resetting the
BKPSRAM is through the Flash interface by requesting a protection level change from 1 to
0.
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