nuttx/boards/z80/ez80/z20x/configs/sdboot

README.txt
^^^^^^^^^^

sdboot.zdsproj is a simple ZDS-II project that will allow you
  to use the ZDS-II debugger.
sdboot.zfpproj is a simple project that will allow you to use the Smart Flash
  Programming.  NOTE:  As of this writing this project does not work, probably
  due to RAM configuration in the project.  Use ZDS-II instead as is described
  in the upper README.txt file
sdboot_flash.ztgt is the target file that accompanies the project files.  This
  one is identical to boards/scripts/z20x_ram.ztgt.
sdboot_ram.ztgt is the target file that accompanies the project files.  This
  one is identical to boards/scripts/z20x_flash.ztgt.