The microprocessor is a multipurpose, programmable logic device that reads an instruction from a storage device called memory accepts binary data as input and processes data according to those instructions and provides results at the output. In a broad way, a digital circuit that has computing and decision-making capability is structurally designed in such a way that if proper instruction is given to this circuit, it results in the desired output. In other words, we can say, this structured design is the microprocessor architecture.
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:
- Central Processing Unit(CPU)
- Input/ Output Devices and
- The system buses
The block diagram of a microcomputer system is shown below figure. The central processing unit (CPU) is responsible to perform 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 in the above image (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 at the output. A typical CPU consists of the following three units:
- Register Array
- Arithmetic and Logic Unit (ALU)
- Control Unit
Register Array provides temporary storage within the CPU for memory addresses, status, and other information. The number of registers and size of the register array varies in accordance with the different microprocessors.
Arithmetic and Logic Unit (ALU)
The ALU contains an adder. This is responsible to perform binary arithmetic operations on the data obtained from memory, the register array varies, or other inputs. Boolean logical operations on data is also the responsibility of 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.
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.