An embedded system includes a host controller circuit and a microcontroller circuit. The host controller circuit is configured to access a storage device to obtain an address of a first firmware file in the storage device. The microcontroller circuit is configured to determine whether a memory circuit is being accessed by other circuits, in which the memory circuit includes memory blocks. If the memory circuit is not being accessed by the other circuits, the microcontroller circuit is further to control the host controller circuit to write the first firmware file to a first block of the memory blocks according to the address.