Computer architecture/Input Output Organization

This is a lesson in in the course, Computer Architecture, which is a part of The School of Computer Science

Objective edit

Input Output Organization edit

External Devices

I/O operations are accomplished through external devices that provide a means of exchanging data between external environment and computer. An external device attaches to the computer by a link to an I/O module. An external device linked to an I/O module is called peripheral device or peripheral.

External Devices can be categorized as:

  1. Human readable: suitable for communicating with computer user. For example - video display terminals and printers.
  2. Machine readable: suitable for communicating with equipment. For example - sensor, actuators used in robotics application.
  3. Communication: suitable for communicating with remote devices. They may be human readable device such as terminal and machine readable device such as another computer.
  1. The interface to I/O module: The interface to I/O module is in the form of

a) Control Signal – determines the function that the device will perform. E.g. send data to I/O module (READ or INPUT), receive data from I/O module (WRITE or OUTPUT), report status or perform some control function such as position a disk head. b) Data Signal – send or receive the data from I/O module. c) Status Signal – it indicates the status of signal. E.g. READY/NOT READY

  1. Control Logic: associated with the device controls on specific operation as directed from I/O module.
  2. Transducer: converts the data from electrical to other form of energy during output and from other forms of electrical during input.
  3. Buffer register: is associated with transducer to temporarily hold data during data transmission from I/O module and external environment. Buffer size of 8 to 16 bits is common.

It mainly depends on transducer.

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