Electronics - Computer Hardware and Software - Discussion

Address Bus, Control Bus and Data Bus.

1) Address bus.

2) Data bus.

3) Control bus.

Address bus-16bits (A0-A15).

Aata bus-8bits (D0-D7).

Control bus-Carrying the control signals such as read /write enable, flag bits.

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 unidirectional. 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. This bus is multiplexed with 8 bit data bus. So the most significant bits (MSB) of address goes through Address bus (A7-A0) and LSB goes through multiplexed data bus (AD0-AD7).

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, thats why Intel 8085 is called 8 bit Microprocessor because it have an 8 bit data bus.

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 Op code fetch etc. 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.

Address bus, data bus, control bus.