Memory Mapped I/O vs I/O Mapped I/O

Memory Mapped I/O

•It considers them like any other memory location.

–They are assigned a 16-bit address within the address range of the 8085.

–The exchange of data with these devices follows the transfer of data with memory. The user uses the same instructions used for memory.

I/O Mapped I/O

•It treats them separately from memory. 

–I/O devices are assigned a “port number” within the 8-bit address range of 00H to FFH. 

–The user in this case would access these devices using the IN and OUT instructions only.

Memory Mapped IO	IO Mapped IO
•IO is treated as memory.	•IO is treated IO.
•16-bit addressing.	•8-bit addressing.
•More Decoder Hardware.	•Less Decoder Hardware.
•Can address 216=64k locations.	•Can address 28=256 locations.
•Less memory is available.	•Whole memory address space is available.
•Memory Instructions are used.	•Special Instructions are used like IN, OUT.
•Memory control signals are used.	•Special control signals are used.
•Arithmetic and logic operations can be performed on data.	•Arithmetic and logic operations cannot be performed on data.
•Data transfer between register and I/O.	•Data transfer between accumulator and I/O.