The NRST of the STM32F is an asynchronous reset pin. When NRST goes low, the MCU is reset, resetting all internal registers and the tens of kilobytes of on-chip SRAM. When NRST goes high from low, the PC pointer starts from 0. However, the reset does not reset the STM32’s on-chip RTC registers and back-up memory, as they are powered by the battery via a dedicated VBAT pin. The NRST in the STM32 has a Schmitt function. It resets the chip roughly when the input voltage falls below 1.0V.
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