Difference between Memory Mapped and IO Mapped ?

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Having an address which is accessable through an instruction to read or write system RAM.

Having an I/O location assigned, accessable though an I/O instruction.

I/O registers that are accessed via normal memory instructions. Some processors have no separate I/O instructions, so all I/O is memory mapped.

Memory accessable by I/O instructions? One example is an external FIFO that you write one byte at a time. Another would be external EEPROM that are accessed serially and used in small systems.

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