Flash based microcontrollers typically store program code in and execute from one monolithic flash bank. While loading instructions out of the Flash bank it is not possible to update its content. Instead, code needs to be executed from another memory while reprogramming of the Flash occurs. With a dual bank Flash, it is possible to reprogram one bank simultaneous with code being executed from the other bank. The upload of new software can fail for many reasons, especially at a unit power loss or communication link breakdown. In case of single bank Flash, such failure will corrupt the system. Using an external memory enables safe upload but a power outage during the transfer of the new program from external memory to the on-chip Flash can still corrupt the system. Dual bank Flash enables safe upload and dual boot functionality offers a safe transition from the current to the updated software version.