Introduction to I/O and Peripheral devices

Let me ask you some very basic questions...

  1. What are peripheral devices?
  2. What is an interface?
  3. What is I/O module or I/O interface and why we need it?
  4. Why can't we directly connect I/O devices or peripheral devices to system bus or processor?

let's try to find the answers together..

Peripheral devices:-I/O operations are accomplished through a wide assortment of external devices that provide a means of exchanging data between the external environment and the computer. Example:

Keyboard, Monitor, Disk Drive, Mouse, Printer, etc.

 

Interface:- When we have two devices of different types and we want to connect them we need a place where they can meet or connect, that point is called is Interface.

 

I/O module or I/O interface:-

An I/O interface acts as a point where the processor can communicate with various I/O devices.

Why can't we directly connect I/O devices or peripheral devices to system bus or processor?

  • The data transfer rate of peripherals is often much slower than that of the
  • memory or processor. 
  • The data transfer rate of some peripherals is faster than that of the memory or processor. 
  • Peripherals often use different data formats and word lengths than the computer to which they are attached.
  • Peripherals are electromagnetic or electromechanical but CPU and memory are electronics.

Therefore an I/O module is required. This module has two major functions

  •  Interface to the processor and memory via the system bus or central switch
  •  Interface to one or more peripheral devices by tailored data links

Modes of I/O transfer:

1. Programmed I/O

2. Interrupt driven 

3. DMA

We will discuss all these modes shortly.

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