The SPIFI software supports write-while-execute functionality, which means it can program or erase the external memory simply and quickly, even when the processor is executing code from on-chip flash. Since the SPIFI peripheral can run on its own, without interaction from the CPU, the system can perform its functions without interruption while the serial Flash is being reprogrammed. This feature can be used to perform software upgrades in the field, because the system can write to the external memory without interrupting critical application code. The golden copy of the application code can be kept in on-chip Flash while the code updates are loaded into external SPI Flash. Even if there is a power failure or other Flash update interruption, the on-chip Flash remains uncorrupted and the software updates can be written again into the external SPI Flash.