I've used this one as part of an IDE (http://www.opcube.com/home.html#MIDE51).

http://plit.de/asem-51/

It's a 2-pass macro-assembler, and, since I don't, myself, believe in using HLL's for MCU applications with <<100K lines, I've found it useful over the years. It does provide the OMF's that are sometimes required for debugging. etc. It also has really decent documentation.

A lot of the guys use the KEIL stuff because they prefer 'C' to doing everything in ASM. I, however, have devised macros that make ASM do pretty much everything that one might like a compiler to do, and I can much more easily follow what's more going on, due to my own perhaps limited viewpoint, and not due to any compiler shortcoming, and maybe just because there weren't any compilers for MCU's when I was learning ... <sigh> ... times have changed, I guess.

These macros can be produced such that they're callable or simply linked in whenever they're instantiated so they behave pretty much as a 'C' function would. That way, once you've written your macro and defined the associated hardware locations, it works as it always has, even though it's been unused for a decade, which I find refreshing.

I wouldn't worry about how "professional" your code looks. It's how well it's organized, commented, and maintained that really defines its quality.

RE