Input output interface

Input output interface

• 1.
  DON’T JUST SIT THERE.YOU CAN LEARN INPUT OUTPUT INTERFACE IN QUICK 15 MINUTES.
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  Contents Input Output Interface I/OBus and Interface Modules I/O versus Memory Bus Isolated (Port-Mapped) versus Memory-Mapped I/O Example of I/O Interface
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  Input Output Interface Internalstorage & External I/O Devices Direct Communication is not possible. The major differences are:  Different manner of operation  Data transfer rate  Difference in word format  Difference in operating modes of peripherals
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  I/O Bus &Interface Module Interface Interface Interface Interface Keyboard & Display Terminal Printer Magnetic Disk Magnetic Tape Data Address Control I/O Bus Processor Fig. Connection of I/O Bus to input-output devices
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  IO Commands There arefour types of I/O Command:  Control Command  Status Command  Output Data Command  Input Data Command
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  I/O Versus MemoryBus Like I/O Bus, Memory Bus also contains Data, Address & Control Lines. Three ways to communicate:  Use two separate buses  Use one common bus but separate control lines  Use common bus with common control lines
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  Isolated versus Memory-MappedI/O ISOLATED I/O MEMORY MAPPED I/O Separate read/write control lines A single set of read/write control lines Separate memory and I/O address spaces Common address space Distinct input & output instructions No Specific input or output instructions - Considerable flexibility in handling I/O operations
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  Example of anI/O Interface I/O Data Bus Buffers Status Register Control Register Port B Register Port A Register CS RS1 RS0 RD WR Timing & Control Signal InternalBus Bidirectional Data Bus Chip Select Register Select I/O Read I/O Write To CPU To I/O Device Control I/O Data Status Fig. Example of an I/O Interface Unit