Buses             

The processor, main memory, and I/O devices can be interconnected through common data communication lines which are termed as common bus.

The primary function of a common bus is to provide a communication path between the devices for the transfer of data. The bus includes the control lines needed to support interrupts and arbitration.

           The bus lines used for transferring data may be grouped into three categories:

• data,
• address
• control lines.

A single line is used to indicate Read or Write operation. When several sizes are possible like byte, word, or long word, control signals are required to indicate the size of data.

The bus control signal also carry timing information to specify the times at which the processor and the I/O devices may place data on the bus or receive data from the bus.