The buses of microprocessor.

A bus is a collection of wires used to transmit signals in parallel. According to the purpose, the buses of a microcomputer can be divided into three types: address bus, data bus, and control bus.

1. Address Bus

The unidirectional address bus transmits the address signals emitted from CPU to memory and I/O port.
The address bus consists of 16, 20, 24 or 32 parallel signal lines.On these lines the CPU sends out the address of the memory location that is to be written to or read from. The no of memory location that the CPU can address is determined by the number of address lines. If the CPU has N address lines, then it can directly address 2N memory locations i.e. CPU with 16 address lines can address 216 or 65536 memory locations.

2. Data Bus

The signal on the bidirectional data bus is the data either from CPU to memory and I/O or from memory and I/O to CPU.The data bus consists of 8, 16 or 32 parallel signal lines. The data bus lines are bi-directional. This means that the CPU can read data in from memory or it can send data out to memory

3. Control Bus

The control bus is used to transmit the control signals such as read, write, and interrupt control signal. The control bus consists of 4 to 10 parallel signal lines.The CPU sends out signals on the control bus to enable the output of addressed memory devices or port devices.Typical control bus signals are Memory Read, Memory Write, I/O Read and I/O Write.