13. Input/Output Ports

• Processor and I/O interface points for exchanging data are called I/O ports.

• Two ways of mapping I/O ports:

  1. Memory-mapped I/O:

     • I/O ports are mapped to the memory address space.

     • Reading/writing I/O is similar to reading/writing memory.

     • Can use memory read/write instructions.

     • Motorola 68000 uses memory-mapped I/O.

  2. Isolated I/O:

     • Separate I/O address space.

     • Intel 80x86 processors support isolated I/O.

     • Requires special I/O instructions, like IN and OUT on x86.