How can I load/store data to the periphery which address is bigger than 216 with IN/OUT instructions.
When I use IN/OUT instruction, lets say OUT DX, AL, I know that the segment register of DX is not used so I can access only the first 216 addresses (because DX is 16 bits wide).
One of my devices is on the address 18000h. How can I reach it? The memory/IO space overlaps (the M/IO pin is not used), so is it ok to say something like
MOV BX, 18000h
MOV [BX], AL
You can't with IN or OUT instruction!
The x86 processor supports an I/O address space that contains up to 65,536 8-bit I/O ports.
From Intel datasheet:
The processor permits applications to access I/O ports in either of two ways:
- Through a separate I/O address space
- Through memory-mapped I/O
Accessing I/O ports through the I/O address space is handled through a set of I/O instructions and a special I/O protection mechanism. Accessing I/O ports through memory-mapped I/O is handled with the processors general-purpose move and string instructions, with protection provided through segmentation or paging. I/O ports can be mapped so that they appear in the I/O address space or the physicalmemory address space (memory mapped I/O) or both.