The microprocessor cannot do anything by itself therefore, It needs to be linked with memory, extra peripherals, or IO devices. This linking is called Interfacing.
The interfacing of the I/O devices in 8085 can be done in two ways :
1. Memory-Mapped I/O Interfacing :
In this kind of interfacing, we assign a memory address that can be used in the same manner as we use a normal memory location.
2. I/O Mapped I/O Interfacing :
A kind of interfacing in which we assign an 8-bit address value to the input/output devices which can be accessed using IN and OUT instruction is called I/O Mapped I/O Interfacing.
Difference between Memory-Mapped I/O Interfacing and I/O Mapped I/O Interfacing :
|Features||Memory Mapped IO||IO Mapped IO|
|Addressing||IO devices are accessed like any other memory location.||They cannot be accessed like any other memory location.|
|Address Size||They are assigned with 16-bit address values.||They are assigned with 8-bit address values.|
|Instructions Used||The instruction used are LDA and STA, etc.||The instruction used are IN and OUT.|
|Cycles||Cycles involved during operation are Memory Read, Memory Write.||Cycles involved during operation are IO read and IO writes in the case of IO Mapped IO.|
|Registers Communicating||Any register can communicate with the IO device in case of Memory Mapped IO.||Only Accumulator can communicate with IO devices in case of IO Mapped IO.|
|Space Involved||216 IO ports are possible to be used for interfacing in case of Memory Mapped IO.||Only 256 I/O ports are available for interfacing in case of IO Mapped IO.|
|IO/M` signal||During writing or read cycles (IO/M` = 0 ) in case of Memory Mapped IO.||During writing or read cycles (IO/M` = 1) in case of IO Mapped IO.|
|Control Signal||No separate control signal required since we have unified memory space in the case of Memory Mapped IO.||Special control signals are used in the case of IO Mapped IO.|
|Arithmetic and Logical operations||Arithmetic and logical operations are performed directly on the data in the case of Memory Mapped IO.||Arithmetic and logical operations cannot be performed directly on the data in the case of IO Mapped IO.|
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