I haven't worked with PLM for a long time by I remember that the underscore in _distance are added by the PLM compiler. So, dont use the underscore in your PLM source file. A tip - Write the asm program first in PLM. Then compile it using the "code" directive in the command line. Now look at the .lst file to see how the compiler created its code. You can now cut and paste this to your asm file, change it and assemble it with asm80.

Regards
Kobus