BUS system

Data Bus

• As name tells that it is used to transfer data within Microprocessor and Memory/Input or Output devices. It is bidirectional as Microprocessor requires to send or receive data.
• The data bus also works as address bus when multiplexed with lower order address bus. Data bus is 8 Bits long.
•  The word length of a processor depends on data bus, that why Intel 8085 is called 8 bit Microprocessor because it have an 8 bit data bus.

Address Bus

• It is a group of wires or lines that are used to transfer the addresses of Memory or I/O devices. It is without direction .
• In Intel 8085 microprocessor, Address bus was of 16 bits. This means that Microprocessor 8085 can transfer maximum 16 bit address which means it can address 65,536 different memory locations. 

Control Bus

Microprocessor uses control bus to process data, that is what to do with the selected memory location.

Some control signals are Read, Write and Operation code fetch. Various operations are performed by microprocessor with the help of control bus. This is a dedicated bus, because all timing signals are generated according to control signal.