Thanks, Peter, for your explanation of the memory segmentation issue; the fact that there is no 80C85 Jump Relative opcode and thus no relocation was unknown to me. As you may deduce my depth on the M100 is pretty shallow. Until recently I had only the bar code reader software to play with (other than the ROM suite) and my bar code reader seems to be DOA, so not much familiarity with machine code.
The RS M100 Assembler / Debugger application documentation has a brief appendix of ROM routines, listing purpose, entry and exit conditions and addresses, but unfortunately incomplete. One new objective is to find a complete listing, hopefully commented, such as the one I have for my Model III ROM. Another objective is to develop a reliable method for tape duplication before I damage or wear out the OEM distributions. I am thinking it might be possible to make a digital copy of the OEM tape on my Win10 machine, using a hi-fi tape deck as the playback source and Audacity as the DTR. With luck reversing the roles will yield a functional copy tape. But again, if someone has a better idea... Thanks again for your input. -CH-
