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Chapter 6 Input & Output (I/O Modules (1.Control and Timing the…

- - - - I/O Commands
        
        2.Test
        
        3.Read
        
        1.Control
        
        3.Write
      - I/O Instructions
        
        Memory mapped I/O
        
        Isolated I/O
    - - Software poll
        
        When an interrupt happens, an interrupt service program will poll or ask each I/O module to determine which module caused the interrupt.
      - Multiple interrupt lines
        
        Having multiple interrupt attached to each I/O modules. But this is not practical
      - Daisy chain
        
        ▪ Uses a hardware poll.
        ▪ When the processor gets an interrupt, it sends out an interrupt acknowledgement signal.
        ▪ The signal goes to all the I/O module.
        ▪ The requesting I/O module will respond by placing its address on the data line.
        ▪ So now the processor knows which I/O module interrupted and can proceed with the necessary actions.
      - Bus arbitration
        
        ▪ I/O module must first gain control of the bus before it can issue an interrupt.
        ▪ This way only one module can interrupt at a given time.
    - - External Interface
        
        Parallel Interface
        
        o Multiple lines connect the peripheral and the I/O module. So multiple bits are transferred at once.
        o Used in high speed peripherals such as hard disk, printer and scanner.
        
        Serial Interface
        
        o There is only one line to transmit data and bits are transferred one at a time.
        o Used in slower devices such as mouse and keyboard.
      - Universal Serial Bus (USB)
        
        It supports data transfer rates of 12 Mbps
        
        It can be used to connect up to 127 peripheral devices
        
        USB supports hot-swapping
      - FireWire Serial Bus (USB)
        
        all-digital interface
        
        peer-to-peer interface
        
        It enables multiple computers to share a given peripheral without any special support in the peripheral or the computers.
        
        supports data rates of 100, 200, and 400 Mbps