Hi Bogdan,

I feel like I'm in a time warp. I still have my CP/M machines. I'm wondering which is older, the 8051 or CP/M. You might try looking for an 8048 assembler in source form, and modify it.

Have you done searches in Google for CP/M and "abandonware" ? I found a number of sites with a lot of links, possibilities. For example, http://www.seasip.demon.co.uk/Cpm/
http://www.retroarchive.org/cpm/

Worse case, you might be able to find an existing DOS assembler source and convert it to run under CP/M. Will you be looking for CP/M-based programmers next? It wouldn't take much to write a CP/M driver for the serial in-circuit programming some newer 8051s support.

Good luck!

Dennis