Microprocessor and Microcontroller
Microprocessor and Microcontroller
A microprocessor is an integrated circuit (IC) which incorporates core functions of a computer’s central processing unit (CPU). It is a programmable multipurpose silicon chip, clock driven, register based, accepts binary data as input and provides output after processing it as per the instructions stored in the memory.
How does a Microprocessor work ?
A processor is the brain of a computer which basically consists of Arithmetical and Logical Unit (ALU), Control Unit and Register Array. As the name indicates ALU performs all arithmetic and logical operations on the data received from input devices or memory. Register array consists of a series of registers like accumulator (A), B, C, D etc. which acts as temporary fast access memory locations for processing data. As the name indicates, control unit controls the flow of instructions and data throughout the system.So basically a microprocessor takes input from input devices, process it as per instructions given in the memory and produces output.
Advantages of a Microprocessor
- Low Cost
Microprocessors are available at low cost due to integrated circuit technology. Which will reduce the cost of a computer system. - High Speed
Microprocessor chips can work at very high speed due to the technology involved in it. It is capable of executing millions of instructions per second. - Small Size
Due to very large scale and ultra large scale integration technology, a microprocessor is fabricated in a very less footprint. This will reduce the size of the entire computer system. - Versatile
Microprocessors are very versatile, the same chip can be used for a number of applications by simply changing the program (instructions stored in the memory). - Low Power Consumption
Microprocessors are usually manufactured using metal oxide semiconductor technology, in which MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) are working in saturation and cut off modes. So the power consumption is very low compared to others. - Less Heat Generation
Compared to vacuum tube devices, semiconductor devices won’t emit that much heat. - Reliable
Microprocessors are very reliable, failure rate is very less as semiconductor technology is used. - Portable
Devices or computer system made with microprocessors can be made portable due to the small size and low power consumption.Common Terms used in a Microprocessor
Here are some common terms that we will use in microprocessor field.
Bus
A bus is a set of conductors intended to transmit data, address or control information to different elements in a microprocessor. Usually a microprocessor will have 3 types of buses : Data Bus, Control Bus and Address Bus. An 8-bit processor will be using 8-bit wide bus.Instruction Set
Instruction set is the group of commands that a microprocessor can understand. So instruction set is an interface between hardware and software (program). An instruction commands the processor to switch relevant transistors for doing some processing in data. For eg. ADD A, B; is used to add two numbers stored in the register A and B.Word Length
Word Length is the number of bits in the internal data bus of a processor or it is the number of bits a processor can process at a time. For eg. An 8-bit processor will have an 8-bit data bus, 8-bit registers and will do 8-bit processing at a time. For doing higher bits (32-bit, 16-bit) operations, it will split that into a series of 8-bit operations.Cache Memory
Cache memory is a random access memory that is integrated into the processor. So the processor can access data in the cache memory more quickly than from a regular RAM. It is also known as CPU Memory. Cache memory is used to store data or instructions that are frequently referenced by the software or program during the operation. So it will increase the overall speed of the operation.Clock Speed
Microprocessors uses a clock signal to control the rate at which instructions are executed, synchronize other internal components and to control the data transfer between them. So clock speed refers to the speed at which a microprocessor executes instructions. It is usually measured in Hertz and are expressed in megahertz (MHz), gigahertz (GHz) etc.Classification of Microprocessors
Based on Word Length
Hope you read about word length above. So based on the word length of a processor we can have 8-bit, 16-bit, 32-bit and 64-bit processors.RISC – Reduced Instruction Set Computer
RISC is a type of microprocessor architecture which uses small, general purpose and highly optimized instruction set rather than more specialized set of instructions found in others. RISC offers high performance over its opposing architecture CISC (see below). In a processor, execution of each instruction require a special circuit to load and process the data. So by reducing instructions, the processor will be using simple circuits and faster in operation.
- Simple instruction set
- Larger program
- Consists of large number of registers
- Simple processor circuitry (small number of transistors)
- More RAM usage
- Fixed length instructions
- Simple addressing modes
- Usually fixed number of clock cycles for executing one instruction
CISC – Complex Instruction Set Computer
CISC is the opposing microprocessor architecture for RISC. It is made to reduce the number of instructions per program, ignoring the number of cycles per instruction. So complex instructions are directly made into hardware making the processor complex and slower in operation.This architecture is actually designed to reduce the cost of memory by reducing the program length.
- Complex instruction set
- Smaller program
- Less number of registers
- Complex processor circuitry (more number of transistors)
- Little RAM usage
- Variable length instructions
- Variety of addressing modes
- Variable number of clock cycles for each instructions
Special Purpose Processors
There are some processors which are designed to handle some specific functions.- DSP – Digital Signal Processors
- Coprocessors – processors used along with a main processor (8087 math-coprocessor used with 8086)
- Input/Output processors
- Transputer – Transistor Computer : Microprocessor with its own local memory
Examples
- Intel 4004 – The First Microprocessor
- Intel 8085
- Intel 8086
- Intel Pentium 4
- Intel Core i7
- AMD Athlon
Microcontroller
A microcontroller is a compact integrated circuit designed to govern a specific operation in an embedded system. A typical microcontroller includes a processor, memory and input/output (I/O) peripherals on a single chip.Microcontroller features
A microcontroller's processor will vary by application. Options range from the simple 4-bit, 8-bit or 16-bit processors to more complex 32-bit or 64-bit processors. In terms of memory, microcontrollers can use random access memory (RAM), flash memory, EPROM or EEPROM. Generally, microcontrollers are designed to be readily usable without additional computing components because they are designed with sufficient onboard memory as well as offering pins for general I/O operations, so they can directly interface with sensors and other components.Microcontroller architecture can be based on the Harvard architecture or von Neumann architecture, both offering different methods of exchanging data between the processor and memory. With a Harvard architecture, the data bus and instruction are separate, allowing for simultaneous transfers. With a Von Neumann architecture, one bus is used for both data and instructions.
Microcontroller processors can be based on complex instruction set computing (CISC) or reduced instruction set computing (RISC). CISC generally has around 80 instructions while RISC has about 30, as well as more addressing modes, 12-24 compared to RISC's 3-5. While CISC can be easier to implement and has more efficient memory use, it can have performance degradation due to the higher number of clock cycles needed to execute instructions. RISC, which places more emphasis on software, often provides better performance than CISC processors, which place more emphasis on hardware, due to its simplified instruction set and, therefore, increased design simplicity, but because of the emphasis it places on software, software can be more complex. Which ISC is used varies depending on application.
When they first became available, microcontrollers solely used assembly language. Today, the C programming language is a popular option.
Get an overview of microcontrollers from Microchip Technology.
Types of microcontrollers
Common MCUs include the Intel MCS-51, often referred to as an 8051 microcontroller, which was first developed in 1985; the AVR microcontroller developed by Atmel in 1996; the programmable interface controller (PIC) from Microchip Technology; and various licensed ARM microcontrollers.A number of companies manufacture and sell microcontrollers, including NXP Semiconductor, Renesas Electronics, Silicon Labs and Texas Instruments.
Microcontroller applications
Microcontrollers are used in multiple industries and applications, including in the home and enterprise, building automation, manufacturing, robotics, automotive, lighting, smart energy, industrial automation, communications and internet of things (IoT) deployments.Microcontrollers vs. microprocessors
The distinction between microcontrollers and microprocessors has gotten less clear as chip density and complexity has become relatively cheap to manufacture and microcontrollers have thus integrated more "general computer" types of functionality. On the whole, though, microcontrollers can be said to function usefully on their own, with direct connection to sensors and actuators, where microprocessors are designed to maximize compute power on the chip, with internal bus connections (rather than direct I/O) to supporting hardware such as RAM and serial ports. Simply put, coffee makers use microcontrollers; desktop computers use microprocessors.
Microchip Technology Inc.
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