I need to set the address where the library I've included will reside in the code memory
first, thank you for your replies. That really is a very esoteric system for an 8051! I thought mentioning the tool c51 is enough ... my bad.
Perhaps you can look at the Linker Map file to identify the code sections from the Library, and then use Linker controls to place them...? that works only with the modules included in .c files not for libraries, the linker refuse to define an absolute address for the segments of the code in the library.
I'll try to contact keil support, thanks again.