Differentiate between isolated I/O and memory mapped I/O.
The isolated I/O and memory mapped I/O can be differentiated according to device address, control signals, instruction available. The differences are tabulated below:
| Properties | Memory-mapped I/O | Isolated I/O |
| Device register | 16 bit | 8 bit |
| Control signals | MEMR/MEMW | IOR/ IOW |
| Instructions available | Memory related instruction such as STA, LDA, LDAX, STAX | IN/OUT |
| Data transfer | Between any register and I/O | Only between I/O and accumulator |
| Maximum number of I/O possible | The memory map (64k) is shared between I/O and system memory | I/O map is independent of the memory map; 256 i/p devices and 256 o/p devices can be connected |
| Execution speed | 13 T-states (STA, LDA)7 T–states (MOV M , R) | 10 T- states |
| Hardwire requirements | More hardware is needed to decode 16 bit address | Less hardware is needed to decode 8 bit address |
| Other features | Arithmetic or logical operations can be directly performec with i/o data | Not available |