MON51 User's Guide

Interrupt Offset

When the Monitor-51 code is installed at ROM address 0, an application would never be able to reach an interrupt vector. Therefore, Monitor-51 diverts all interrupt vectors to a higher (RAM) address, where the application's interrupt vectors can be loaded. The interrupt offset has no meaning when the Monitor-51 code is not located at address 0.

Example: The code of Monitor-51 is installed at address 0. The von Neumann-wired RAM starts at 8000H. The interrupt offset has to be set to 8000H and the application has to be linked to 8000H and above.

INT_ADR_OFF EQU 8000H   ; INTERRUPT VECTOR OFFSET IF MONITOR
                        ; IS INSTALLED AT ADDRESS 0000H