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