8085 Bus Organisation

The various units of a microprocessor are connected by three sets of parallel conducting lines called buses.

There are three buses in microprocessor:

• Data bus
• Address bus
• Control bus

8085 Bus Organisation

Data Bus: 

• 8085 microprocessor has 8-bit data bus. This means that it can carry the 8-bit data starting from 00H to FFH.
• It is bidirectional. This means that these lines are used to flow data in both the directions. Data can be transferred or received through these lines.
• It also connects the I/O ports and CPU.
• It has 8 parallel lines of data bus i.e. it can access upto 2^8 = 256 data lines.

Address Bus:

• 8085 microprocessor has 16-bit address bus.
• The CPU sends the address of the memory location over this bus.
• So the address bus carries the address of the memory location on which data is to written or from which data is to read.
• It is unidirectional. This means that these lines are used to flow data only in one direction i.e. from microprocessor to peripheral devices.
• It can access upto 2^16 = 64kB of memory location.

Control Bus:

• Control bus is used for sending control signals from the microprocessor to memory and I/O devices.
• These control signals enable the outputs of addressed memory devices and I/O devices.
• Some important control signals are: memory read, memory write, I/O read, I/O write.