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why is this difference in memory Mapped and port mapped interafcing

Question asked by Aditya Nagal on Oct 25, 2017
Latest reply on Oct 25, 2017 by igorpadykov

Hi ,

 

In the memory mapped I/O interfacing , peripherals are connected/interfaced over the address bus. If there are 32 address lines , then theoretically we can interface 2 power 32 devices to the CPU. This interfacing also includes MEMR  and MEMW (Memory Read and Memory write signals).

In the Port Mapped I/O interfacing , peripherals are again connected to the same address lines . Just the instructions for reading and writing would be different like inportb  and outportb  and the control signals would be IOR and IOW (IO READ and IO WRITE) . But the number of devices which can be interfaced will probably be less i.e. 2 power 16 . 

Why is this difference between Memory Mapped I/O and Port Mapped I/O. 

 

Regards, 

Aditya Nagal

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