1. Attempt to detect the USB mass storage device with a FAT32 file system.
2. Verify whether the boot-loader update image name is correct or not.
3. Verify the integrity of the boot-loader update image.
4. Attempt to perform a boot-loader update if the correctly named boot-load update image is located on the USB mass storage device.
5. Write, read an erase the protected region on Flash memory.
转载于:https://www.cnblogs.com/procoder/archive/2010/06/10/Boot-loader-update-sequence.html