ST STM32G0 1 Series User Manual

Reset and clock control (RCC) RM0444
160/1390 RM0444 Rev 5
5 Reset and clock control (RCC)
5.1 Reset
There are three types of reset, defined as system reset, power reset and RTC domain reset.
5.1.1 Power reset
A power reset is generated when one of the following events occurs:
• power-on reset (POR) or brown-out reset (BOR)
• exit from Standby mode
• exit from Shutdown mode
Power and brown-out reset set all registers to their reset values except the registers of the
RTC domain.
When exiting Standby mode, all registers in the V
CORE
domain are set to their reset value.
Registers outside the V
CORE
domain (RTC, WKUP, IWDG, and Standby/Shutdown mode
control) are not impacted.
When exiting Shutdown mode, the brown-out reset is generated, resetting all registers
except those in the RTC domain.
5.1.2 System reset
System reset sets all registers to their reset values except the reset flags in the clock
control/status register (RCC_CSR) and the registers in the RTC domain.
System reset is generated when one of the following events occurs:
• low level on the NRST pin (external reset)
• window watchdog event (WWDG reset)
• independent watchdog event (IWDG reset)
• software reset (SW reset) (see Software reset)
• low-power mode security reset (see Low-power mode security reset)
• option byte loader reset (see Option byte loader reset)
• power-on reset
The reset source can be identified by checking the reset flags in the RCC_CSR register
(see Section 5.4.24: Control/status register (RCC_CSR)).
NRST pin (external reset):
Through specific option bits, the NRST pin is configurable for operating as:
• Reset input/output (default at device delivery)
Valid reset signal on the pin is propagated to the internal logic, and each internal reset
source is led to a pulse generator the output of which drives this pin. The GPIO
functionality (PF2) is not available. The pulse generator guarantees a minimum reset
pulse duration of 20 µs for each internal reset source to be output on the NRST pin. An
internal reset holder option can be used, if enabled in the option bytes, to ensure that
the pin is pulled low until its voltage meets V
IL
threshold. This function allows the

ST STM32G0 1 Series Specifications

General

Brand	ST
Model	STM32G0 1 Series
Category	Microcontrollers
Language	English