Busses

“In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers.”

       Types:

It has 3 types:

      ·   System bus

      ·   Data bus

      ·   Control bus

1. Data Bus

Data bus is the most common type of bus. It is used to transfer data between different components of computer. The number of lines in data bus affects the speed of data transfer between different components. The data bus consists of 8, 16, 32, or 64 lines. A 64-line data bus can transfer 64 bits of data at one time.

The data bus lines are bi-directional. It means that:

1.  CPU can read data from memory using these lines

2. CPU can write data to memory locations using these lines

2. Address Bus.

Many components are connected to one another through buses. Each component is assigned a unique ID. This ID is called the address of that component. It a component wants to communicate with another component, it uses address bus to specify the address of that component. The address bus is a unidirectional bus. It can carry information only in one direction. It carries address of memory location from microprocessor to the main memory.

3. Control Bus

Control bus is used to transmit different commands or control signals from one component to another component. Suppose CPU wants to read data from main memory. It will use control is also used to transmit control signals like ASKS (Acknowledgement signals).

Command	Purpose
MEMORY WRITE	Write data to a given location in main memory.
MEMORY READ	Read data from a given out put device.
I/O WRITE	Write data to a given output device.
I/O READ	Read data from a given input device.
BUS REQUEST	Request for a control on the bus for transmitting data.
BUS GRANT	Indicate the grant of the bus to a device.