Embedded devices typically have an operating system, one or more file-systems, as well as a bootloader and other data components resident in flash memory. During software development and testing, there is frequently a need to selectively update a combination of such images. The described technique organizes the images in the flash memory such that one can speed up the update process by eliminating relocation of existing images. A command-driven update mechanism provides a flexible process--eg, one can upload the images back to a host, one can update the update code itself, etc. A start handshake is used that enables auto-detection of the embedded serial port that is used for the update.