How do I fill data to unused area in the memory?

There are two methods.

1. Input at the end of a section
   Specify the –padding option.
   Input a value (0x00, the NOP instruction) at the end of a section so that the size of the section is an integer multiple of its alignment. Specifiable file types for output are *.abs, *.hex, *.mot, and *.bin.
   Adjust sections with absolute addresses (sections generated under the “.org” assembler directive) by your own processing, since these are not padded automatically.
2. Input other than at the end of a section
   Specify the –space option and fill the output area with the data (user-specified).
   Specifiable file types for output are *.abs, *.hex, *.mot, and *.bin.