I/O devices Interface

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    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.
    interfacing of the I/O devices in 8085 can be done in two ways
    • Memory mapped IO interface:
    • I/O mapped I/O interface

Memory Mapped IO interface:


We assign a memory address that can be used in the same manner as we use a normal memory location.
Let's look into below memory mapped on the STM32L microcontroller.
  • Memory mapping of STM32.
  • The ARM architecture is following the Memory-mapped I/O. 
  • common address space for both I/O and Memory. 
  • Two control signal
    • MEMR
    • MEMW
  • Only Memory related Instruction to communicate I/O address space. 
  • ARM has single address liner for memory and IO. 
  • cat /proc/iomem to see memory address space.  


I/O mapped  I/O interface:

  • also called port mapped IO.
  • example:  Intel
  • Have separate I/o address and Memory address space. 
  • 4 control single 
    • MEMR
    • MEMR
    • IOR
    • IOW
  • IN, OUT Assembly instruction because of separate address lines. 
  • 8085 has 16-bit address line for Memory and 8-bit address lines for I/O
  • cat /proc/ioports command to see the address lines of the ports 
  • 0060 and 0064 are used for the Keyboard.




    

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