1. Microprocessor unit
2. Memory
3. I/O parts
4. Buses
A microprocessor is a simple chip which is capable of processing data and controlling all the microcomputer components.
A typical microprocesor contains are:
1. Temporary Storage: This is a storage in terms of the number of registers which can hold a number of bits of binary information by presenting program instruction or data.
2. ALU: This unit carries out arithmetic and logical operations.
3. Timing and Control Circuits: This unit keeps the other parts of the microcomputer working together in the right time sequence.
Memory: This is the part of the microcomputer that is used to store programs and data, provide data to the microprocessor on request and accept new data from the microprocessor from the storage.
There are two sets of memory which are:
1. ROM
2. RAM
Read Only Memory (ROM): The ROM consists of a firmware which is a software fixed during manufacture and cannot be altered. Data cannot be written into the ROM. Note that ROM is a non volatile memory which means that it does not lose its information when the power is off. ROM is used to install operational software essential to the functioning of the microcomputer.
Random Access Memory (RAM): RAM has read and write capability. Information can be written to and read from the RAM. RAM is volatile which means that data is lost when the power is lost. RAM stores program which the microcomputer user wants to rum correctly.
Input/Output (I/O) Ports: These ports is the link between the microprocessor and the outer world. An input port is a circuit through which an external device can send signals to the microprocessor. An output port is the circuit that allows the microprocessor to output signals to external devices.
BIOS (Basic Input/Output System): This is the program a microcomputer uses to get the microprocessor system started. Once the BIOS is switched on it manages data flow between the microprocessor and the rest of the system.
Buses: These are groups of wires through which binary information is transferred from one part of a microcomputer to another.
There are 3 buses in a microcomputer system:
1. Data Bus
2. Address Bus
3. Control Bus
Address Bus: An address is a binary number that identifies a specific memory location or input/output port involved in a data transfer. The address bus is used to transmit the address of the specific storage location to the memory or the port. An address bus is unidirectional. An 8 - bit microprocessor has 16 address pins.
Data Bus: This bus carries data which has been transferred throughout the system. There are 8 - bit data pins on an 8 - bit microprocessor with a data bus 8 lines one for each pin. Data bus is bidirectional which means that it can travel in both directions. The size or width of a data bus determines how much data can be transferred at one time and what arithmetic can be done.
Control Bus: In the control bus, each line goes only one way. Some control bus signals such as READ and WRITE are output lines while others such as INTERRUPT are input lines. These signals are generated by timing control circuits of the microprocessor whenever it needs to perform a specific function.
Each microprocessor has its unique set of machine instructions called instruction set.
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