OS-9 Assembly Code Development
From F256 Foenix
Overview
Each process in NitrOS9 is allocated its own 64K address space. When run, the program object code is loaded into one memory space, and the variables and data structures are loaded into the other. This includes separate execution and data directories and std in, std out and std err for each process. In addition, NitrOS9 keeps an separate MMU table (DAT Image) for each process. So it is important to use the OS9 calls F$MapBlk and F$ClrBlk calls to map in memory blocks with the MMU.
When a new process is created, registers U, Y, DP and SP are set with U = start of data area, Y = end of data area, DP = page # of beginning page, SP = end of data area + 1.
