Some microcontrollers, when they are powered, have all their peripherals powered and enabled, automatically. STM32 MCUs, however, by default have their peripherals disabled in order to save power. In ...

STM32F051 memory map from its datasheet. By default, the Flash memory on STM32F0 MCUs starts at 0x0800 0000, and the starting with 0x0000 0000 is used to map to the boot medium.