Question: When is it useful to use the ROMS directive ?

Answer:

syntax : ROM { origin=xxx length=yyy width =zzz }

If used, the COFF file code MUST be contained within the range defined by the ROM directive. If not used, it's assumed to cover the entire processor memory map.

It's useful when:
1. You want to use the FILL option but within a certain memory range.

--> origin and length will limit the scope of the FILL command

2. Filter out some specific COFF file sections out of the HEX output file.

--> The Hex utility will complain but still the output file is created.The same can be achieved by adding only the desired sections in the SECTIONS directive.