System Bus (Control, Data, Address)Architecture

A System bus is a set of wires for moving data, instructions, and control signals from one computer component to another component. It is a high-speed internal connection between the processor and other components.

There are 3 types of system bus, or we can say components of a system bus. They are Address bus, Data bus, and Control bus. We can think bus as a highway on which data travels in a computer and within it.

A bus can be 8 bit, 16 bit, 32 bit, and so on. A 32-bit bus means, it can transmit 32 bits of information at a time. A bus can be internal or external.

System Bus Architecture
System Bus > Data, Control & Address Bus


Functions of system bus


Different types of buses are used in the computer bus scheme. Depending on its purpose, each of these buses is allocated to carry a certain form of signal and data.

Some basic functions carried out by system bus are:

  • Addressing the issue
  • Signals of Control
  • Providing Components with Power
  • Scheduling System Time
  • Data Sharing

Data Bus

A data bus is a computer subsystem that carries the data between the processor and other components. The data bus is bidirectional that allows for the transferring of data from one component to another within a computer system or between two computers.

This can include transferring data to and from the memory, or from the central processing unit (CPU) to other components. Each one is designed to handle so many bits of data at a time. It is the main part of a system bus that allows actual transmission of data.

A typical data bus is 32-bits wide. This means that up to 32 bits of data can travel through a data bus every second. Newer computers are making data buses that can handle 64-bit and even 128-bit data paths. At the same time, they are making data buses to handle more bits and can handle those higher bitrates.

Address Bus

An address bus is a computer bus architecture that carries memory addresses from the processor to other components such as primary storage to input/output devices.

The address bus is unidirectional. It is used to transfer data between devices that are identified by the hardware address of the physical memory (the physical address), which is stored in the form of binary numbers to enable the data bus to access memory storage.

The address bus is used by the CPU or direct memory access (DMA) enabled device to locate the physical address to communicate read/write commands. All address busses are read and written by the CPU or DMA in the form of bits.

Control Bus

A control bus is a computer bus that is used to carries control signals from the processor to other components. It also carries the clock’s pulses which are used by the CPU to communicate with devices that are contained within the computer.

In the computer system, the CPU transmits a variety of control signals to components and devices. This occurs through physical connections such as cables or printed circuits.

The control bus is bidirectional and is comprised of interrupt lines, byte enables lines, read/write signals, and status lines.

After data being processed, the control bus carries commands from the CPU and returns status signals from the devices. For example, if the data is being read or written to the device, the appropriate line (read or write) will be active (i.e. logic one).

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