The main task of the bootloader is to download the application program into the internal memories through the UART1， UART2， UART3， SPI or CAN peripherals without using the SWIM protocol and dedicated hardware. Data are provided by any device （host） capable of sending information through one of the above serial interfaces. The bootloader permits downloading of application software into the device memories， including the program memory， using standard serial interfaces （UART1， UART2， UART3， SPI and CAN） without dedicated hardware. It is a complementary solution to programming via the SWIM debugging interface. The bootloader code is stored in the internal boot ROM memory. After a reset， the bootloader code checks whether the program memory is virgin or whether a specific option byte is set allowing code modifications. If these conditions are not fulfilled， the bootloader resumes and the user application is started. In case of a successful check the bootloader is executed. When the bootloader procedure starts， the main tasks are： ● Polling all supported serial interfaces to check which peripheral is used. ● Programming code， data， option bytes and/or vector tables at the address（es） received from the host.