Input/Output Devices

Input/Output Devices

1. I/O Controllers

   • Electronic circuits that allow input or output devices to communicate with internal hardware components by connecting the device to the system bus. The controller acts as an intermediary for all interactions between the CPU and and the connected I/O devices.
   • Each I/O device has its own type of controller. This includes storage devices such as hard disks or CDs.
   • In the Three Box Model I/O controllers have two-way interaction with the control and data buses and are recipients of information from the address bus.
     • This is because some I/O devices have registers or other memory addresses that may need to be accessed by the computer.
   • Individual controllers may be used to control multiple devices.

2. Some I/O devices may be classified as peripherals - hardware that allows the computer to perform additional functions but that is not an integral part of the computer.

   • Peripherals are kept separate from the CPU by the system bus for several reasons:
     • Each peripheral operates in a different manner.
     • New forms of peripheral would require new CPUs.
     • Peripherals may process at different rates to the CPU.
     • Peripherals might operate at a different voltage to the CPU.

3. I/O Ports

   • In this context, ports are the physical points of interface of I/O devices. They allow the physical exchange of signals between devices and the CPU.
   • The USB (Universal Serial Bus) port system allows all I/O devices to be connected in the same manner, minimising micromanagement for users and manufacturers.
   • Upon power up or connection to the computer, port addresses are assigned to each connected device and their modes of data transfer of ascertained.