Let me ask you some very basic questions...
- What are peripheral devices?
- What is an interface?
- What is I/O module or I/O interface and why we need it?
- 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
We will discuss all these modes shortly.