This is a lesson in in the course, Computer Architecture, which is a part of The School of Computer Science
Input Output Organization
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:
- Human readable: suitable for communicating with computer user. For example - video display terminals and printers.
- Machine readable: suitable for communicating with equipment. For example - sensor, actuators used in robotics application.
- Communication: suitable for communicating with remote devices. They may be human readable device such as terminal and machine readable device such as another computer.
- 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
- Control Logic: associated with the device controls on specific operation as directed from I/O module.
- Transducer: converts the data from electrical to other form of energy during output and from other forms of electrical during input.
- 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.