Bus in digital system

 Bus in digital system

A bus is a group of wires of connecting two or more devices and providing a path to perform communication.

A bus that connects major computer components/models (,CPU Memory, I/O ) is called system bus. In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components (wire, optical fiber, etc.) and software, including communication protocols

These system buses are separated into three functional groups:

1.      Data bus

2.      Address bus

3.      Control bus

Data Bus : The  Data bus lines are bidirectional.

It use transfer the data. Data bus carries data from on component to another. It is uni-directional for input and output devices and bi-directional for memory and CPU. The data bus consists of 8, 16, 32 or more parallel lines.

Address Bus : It is unidirectional bus.The address bus consists of 16, 20, 24 or more parallel lines. The  sends out the address of the memory location or I/O port that is to be written or read by using address CPU bus.

Many components are connected to one another though buses. Each components a unique ID. This unique ID is called address of that component. If any component want to communicate with another component it is use address bus. Address bus carries memory address. A memory address is a numerical value used for identifying a memory location. computer performs all its task through the memory address.

Control Bus: control lines regulate the activity on the bus. The CPU sends the signals on the control bus to enable the outputs of addressed memory device or port device. Control bus are used to transmit the different component or control signal from one component to another component.


Functional units of a digital computer

Bus architecture:

Bus in digital system

1.      The computer bus consists of two parts, the address bus and a data bus. The data bus transfer actual data, whereas the address bus transfers address or memory location of where the data should go.

2.      The bus provides physical links and the means of controlling the communication exchange of signals over bus.

3.      The principle use of the system bus is high speed data transfer between the CPU and memory.

4.      Most I/O devices are slower than the CPU or the memory. The I/O devices are attached to the system bus through external interfaces.

5.      The input/output ports are used to connect various devices to the computer and , hence, enable communication between the device and the computer.