In this lecture, we will learn What is a Microprocessor? What are the components of a Microprocessor? System Bus. And Microprocessor System with Bus Organization.

Today because of advances in semiconductor technology, the million-dollar computing capacity of the 1960s is now available for less than five dollars in an integrated circuit called the microprocessor. The microprocessor can be defined as a programmable logic device that can be used to control processes, turn devices on or off, or as a data processing unit of a computer. A computer that is designed using microprocessors is called a microcomputer.

The microprocessor communicates and operates on binary numbers 0 and 1, called bits. Each microprocessor has a fixed set of instructions in the form of binary patterns called a machine language. However, it is difficult for humans to communicate in the language of 0s and 1s. Therefore, the binary instructions are given abbreviated names, called mnemonics, which form the assembly language for a given microprocessor.

In this tutorial, you will learn:

What is Microprocessor?

The microprocessor is a multipurpose, clock-driven, register-based, digital-integrated circuit that accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output. A microprocessor is a computer Central Processing Unit (CPU) on a single chip that contains millions of transistors connected by wires.

A microprocessor is designed to perform arithmetic and logic operations that make use of small number-holding areas called registers. Typical microprocessor operations include adding, subtracting, comparing two numbers, and fetching numbers from one area to another.

In detail, a microprocessor is a multipurpose, programmable logic device that reads binary instructions from a storage device called memory, accepts binary data as input and processes data according to those instructions, and provides results as output. A typical programmable machine can be represented with three components: microprocessor, memory, and I/O device. These three components work together or interact with each other to perform a given task; thus, they comprise a system.

The physical components of this system are called Hardware. A set of instructions is written for the microprocessor to perform a task called a Program, and a group of programs is called Software.

The microprocessor system may be simple or sophisticated, depending on its applications, and it is recognized by various names depending upon the purpose for which it is designed. When the microprocessor system is used for control applications such as turning devices (or machines) on and off, it is generally known as a microcontroller. When it is used for computing or data processing, it is known as Microcomputer.

Components of Microprocessor

A microprocessor is capable of performing various computing functions and making decisions to change the sequence of program execution. The microprocessor can be divided into three segments as shown in the figure, Arithmetic/logic unit (ALU), register array, and control unit. These three segments are responsible for all processing done on a computer.

Components of Microprocessor
Components of Microprocessor

Arithmetic and logic unit (ALU)

It is the unit of microprocessor where various computing functions are performed on the data. It performs arithmetic operations such as addition, subtraction, and logical operations such as OR, AND, and Exclusive-OR. It is also known as the brain of the computer system.

Register array

It is the part of the register in the microprocessor which consists of various registers identified by letters such as B, C, D, E, H, and L. Registers are the small additional memory locations that are used to store and transfer data and programs that are currently being executed.

Control unit

The control unit provides the necessary timing and control signals to all the operations in the microcomputer. It controls and executes the flow of data between the microprocessor, memory, and peripherals. The control bus is bidirectional and assists the CPU in synchronizing control signals to internal devices and external components. This signal permits the CPU to receive or transmit data from the main memory.

System Bus (Data, Address and Control Bus)

This network of wires or electronic pathways is called the ‘Bus’. A system bus is a single computer bus that connects the major components of a computer system. It combines the functions of a data bus to carry information, an address bus to determine where it should be sent, and a control bus to determine its operation. The technique was developed to reduce costs and improve modularity.

System Bus
System Bus

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. The width of the address bus corresponds to the maximum addressing capacity of the bus or the largest address within memory that the bus can work with. The addresses are transferred in binary format, with each line of the address bus carrying a single binary digit. Therefore the maximum address capacity is equal to two to the power of the number of lines present (2^lines).

Data Bus

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. Each wire is used for the transfer of signals corresponding to a single bit of binary data. As such, a greater width allows greater amounts of data to be transferred at the same time.

Control Bus

The microprocessor uses a control bus to process data, i.e. what to do with the selected memory location. Some control signals are Read, Write and Opcode fetch, etc. Various operations are performed by a microprocessor with the help of a control bus. This is a dedicated bus because all timing signals are generated according to the control signal.

Microprocessor Systems with Bus Organization

Microprocessor systems with bus organization
Microprocessor systems with bus organization

To design any meaningful application microprocessor requires the support of other auxiliary devices. In the most simplified form, a microprocessor-based system consists of a microprocessor, I/O (input/output) devices, and memory. These components are interfaced (connected) with microprocessors over a common communication path called a system bus. The typical structure of a microprocessor-based system is shown in Figure. Here, the microprocessor is the master of the system and is responsible for executing the program and coordinating with connected peripherals as required. Memory is responsible for storing programs as well as data. The system generally consists of two types of memory ROM (Read-only and non-volatile) and RAM (Read/Write and volatile). I/O devices are used to communicate with the environment. Keyboards can be examples of input devices and LED, LCD or monitors can be examples of output devices. Depending on the application, the level of sophistication varies in microprocessor-based systems. For example washing machines, computers.