Fundamentals of Computer > Central Processing Unit (CPU) > Types of Bus and Their Role

Types of Bus and Their Role

In microcomputer, the term ’bus’ refers to the paths between the components of a computer which carries all information and signals involved in the system operation.

There are three buses used in microcomputer:

1. Address Bus
2. Data Bus
3. Control Bus

Like the processor, the bus’s speed is measured in megahertz (MHz), because it has its own clock speed.

Address Bus:

This is a unidirectional bus that carries binary address outputs from the CPU to the memory or I/O elements. In a computer with 16-bit address bus, there are 2¹⁶=65536 different possible addresses. Each of these addresses corresponds to one memory location or one I/O element. Address bus is important because the number of wires in it determines the maximum number of memory addresses.  The bigger the address bus, the CPU can address more memory and hence the bigger memory size. 

Data Bus:

This is a bi-directional bus that carries data between the CPU and memory or I/O elements.

• An 8-wires (or 8-bit) data bus can move eight bits (1 byte) at a time, a 16-wires (or 16-bit) data bus can transfer 16 bits (2 bytes) at a time, a 32-wires (32-bit) data bus can transfer 32 bits (4 bytes) at a time.
• With a wider data bus, the computer can move more data in the same amount of time.

Therefore, the number of wires in the data bus affects the speed at which data can travel between hardware components. 

Control Bus:

This bus carries control signals from the CPU to the memory or I/O devices.

• The signal of the control bus synchronizes the activities of the separate computer elements.
• The CPU sends some of these control signals (such as Read or Write) to the other elements to tell them what type of operation is currently in process.

 

 

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