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.