This a simple bootloader for AT91SAM7{S,X}{64,128,256} processors. It permits you to download new code to the device over USB. This bootrom is installed at address 0x00000000 in the ARM, which means that it is the first piece of code to execute after reset. At startup, it waits for a few seconds to see if the downloader is trying to connect. If not, then the bootloader gives up control and jumps to your program. If the downloader is trying to connect, then the bootloader receives the new program over USB and writes it into flash.