Microprocessor as CPU | Microprocessor Tutorials

Microprocessor as CPU – The microprocessor is a multipurpose, programmable logic device that reads an instruction from a storage device called memory, accepts binary data as input, processes data according to those instructions, and provides results at the output. The CPU is the main element of the Microprocessor as it performs all the operations for the Microprocessor.

In a broad way, a digital circuit that has computing and decision-making capability is structurally designed in such a way that if proper instructions are given to this circuit, it results in the desired output. In other words, we can say that this structured design is the microprocessor architecture.

The microprocessor as CPU

Hardware and software are two principal components of a microcomputer system. The physical devices and circuitry are named hardware, whereas software refers to the program written for the computer. There are four main elements in a microcomputer system:

1. Central Processing Unit
2. Memory
3. Input/ Output Devices
4. The system buses

The block diagram of a microcomputer system is shown in Figure 1. The central processing unit (CPU) is responsible for performing all the numerical processes, logical operations, and timing functions. Semiconductor memories are used to store programs and data. I/O devices, also called peripherals, are the means by which the CPU communicates with the outside world. The CPU is connected to memory and I/O by a set of parallel wires or lines called a system bus.

Here, Figure 1 (a) is the block diagram of a traditional computer system with CPU, and (b) is the block diagram of a Microcomputer with MPU. The CPU operations are controlled by a set of instructions, called a program. The CPU accepts the data and instructions through the input, executes one instruction at a time, and sends the results to the output. A typical CPU consists of the following three units:

1. Register Array
2. Arithmetic and Logic Unit (ALU)
3. Control Unit

Register Array

Register Array provides temporary storage within the CPU for memory addresses, status, and other information. The number of registers and the size of the register array vary in accordance with the different microprocessors.

Arithmetic and Logic Unit (ALU)

The ALU contains an adder. This is responsible for performing binary arithmetic operations on the data obtained from memory, the register array, or other inputs. Boolean logical operations on data are also the responsibility of the ALU. Some ALUs perform more complex operations such as multiplication, division, and data shifting. ALU also contains flag bits that signal the results of arithmetic and logical manipulations.

Control Unit

To complete any task or job, a proper sequence of events is required. The control unit coordinates all the microprocessor activities. A clock input signal is used for the proper sequencing of all activities. The control unit decodes the instructions and issues control and timing signals to units both internal and external to the CPU to perform the proper processing action.