PL/M codes mixing on single-board systems

For 8-bit microprocessors, there is no immediate software solution to the problem raised by block-structured procedures, ROM implanted and called from a program located in a memory area. What happens with the debugging and evaluation of application software intended for a single-board system is that the modules have to be tested one by one through the target system before they are gradually implemented into ROM. The use of an incircuit emulator prevents this difficulty from occurring but, as most of the time only one emulator is available for a few teams, its use seems to be restricted to integration into the hardware.This paper describes a software interface which allows the ROM-implemented code and the RAM-implemented code to communicate. It is thus possible to allocate the code obtained using a high-level language at two noncontiguous locations, the first in ROM for the procedures already checked and the second in RAM for the procedures to be debugged. The use of a monitor allows the debugging of the critical parts and the evaluation of all the software before burning it permanently into ROM.