why is this difference in memory Mapped and port mapped interafcing

[adityanagal]

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

[igorpadykov]

Hi Aditya

this depends in internal processor architecture, as memory and port may

use different internal processor buses. Please check processor manual with

description of internal mapping of peripherals.

Best regards
igor
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