2. 8085 BUS ORGANISATION

System Bus Bus is a group of communication lines to carry information bits. Different components of a microprocessor system are organised around bus. The 8085 microprocessor has three buses: address bus, data bus and control bus.

Types of Buses ? Address Bus ? Data Bus ? Control Bus

Address Bus A collection of wires used to identify location in main memory is called Address Bus. It is a group of 16 lines generally marked as A0 to A15. It is unidirectional which flow from microprocessor to Input Output devices. The address bus carries address bits. It is used to identify IO peripheral or a memory location.

Data Bus A collection of wires through which data is transmitted from one part of a computer to another is called Data Bus. It is a group of 8 lines used for data flow generally mark as D0 to D7. These lines are bidirectional. This bus connects all the computer components to the CPU and main memory. Data flow in both directions between microprocessor and memory. The data bus is used to transfer binary information.

Control Bus The connections that carry control information between the CPU and other devices within the computer is called Control Bus. This bus provides timing signals. It is compromised of various single lines that carry synchronisation signals. There are three control pins: Input Output/Memory (IO/M'), Read (RD') and Write (WR'). Using these three pins, four different control signals can be generated: Memory Read, Memory Write, Input Read, Output Write.