Richard,

Years ago i wrote an inline assembler for an 8085 monitor program. One of these nice by products of this is that if you do it in reverse you get a dis-assembler as well. The 8051 mnemonics are more regular than the 8085 so the logic could be simpler.

You have to decide if you are going to implement a "get_line" approach or if your going to be interactive at the time of entry.

Another issue is whether you will support the SFRs mnemonically. If you do the resulting disassembler (if implemented) would gain in sophistication.

regards,
p