Microcontrollers – Types & Applications

What is a Microcontroller?

A microcontroller is a small, low-cost and self contained computer-on-a-chip that can be used as an embedded system. A few microcontrollers may utilize four-bit expressions and work at clock rate frequencies, which usually include:

  • An 8 or 16 bit microprocessor.
  • A little measure of RAM.
  • Programmable ROM and flash memory.
  • Parallel and serial I/O.
  • Timers and signal generators.
  • Analog to Digital and Digital to Analog conversion

Microcontrollers usually must have low-power requirements since many devices they control are battery-operated. Microcontrollers are used in many consumer electronics, car engines, computer peripherals and test or measurement equipment. And these are well suited for long lasting battery applications. The dominant part of microcontrollers being used now a days are implanted in other apparatus.

How are Microcontrollers Classified?

The microcontrollers are characterized regarding bus-width, instruction set, and memory structure. For the same family, there may be different forms with different sources. This article is going to describe some of the basic types of the Microcontroller that newer users may not know about.

The types of microcontroller is shown in figure, they are characterized by their bits, memory architecture, memory/devices and instruction set. Let’s discuss briefly about it.

Types of Microcontrollers
Types of Microcontrollers

Classification According to Number of Bits

The bits in microcontroller are 8-bits, 16-bits and 32-bits microcontroller.

In 8-bit microcontroller, the point when the internal bus is 8-bit then the ALU is performs the arithmetic and logic operations. The examples of 8-bit microcontrollers are Intel 8031/8051, PIC1x and Motorola MC68HC11 families.

The 16-bit microcontroller performs greater precision and performance as compared to 8-bit. For example 8 bit microcontrollers can only use 8 bits, resulting in a final range of 0×00 – 0xFF (0-255) for every cycle. In contrast, 16 bit microcontrollers with its 16 bit data width has a range of 0×0000 – 0xFFFF (0-65535) for every cycle. A longer timer most extreme worth can likely prove to be useful in certain applications and circuits. It can automatically operate on two 16 bit numbers. Some examples of 16-bit microcontroller are 16-bit MCUs are extended 8051XA, PIC2x, Intel 8096 and Motorola MC68HC12 families.

The 32-bit microcontroller uses the 32-bit instructions to perform the arithmetic and logic operations. These are used in automatically controlled devices including implantable medical devices, engine control systems, office machines, appliances and other types of embedded systems. Some examples are Intel/Atmel 251 family, PIC3x.

Classification According to Memory Devices

The memory devices are divided into two types, they are

  • Embedded memory microcontroller
  • External memory microcontroller

Embedded memory microcontroller: When an embedded system has a microcontroller unit that has all the functional blocks available on a chip is called an embedded microcontroller. For example, 8051 having program & data memory, I/O ports, serial communication, counters and timers and interrupts on the chip is an embedded microcontroller.

External Memory Microcontroller: When an embedded system has a microcontroller unit that has not all the functional blocks available on a chip is called an external memory microcontroller. For example, 8031 has no program memory on the chip is an external memory microcontroller.

Classification According to Instruction Set

CISC: CISC is a Complex Instruction Set Computer. It allows the programmer to use one instruction in place of many simpler instructions.

RISC: The RISC is stands for Reduced Instruction set Computer, this type of instruction sets reduces the design of microprocessor for industry standards. It allows each instruction to operate on any register or use any addressing mode and simultaneous access of program and data.

Example for CISC and RISC:

CISC: Mov AX, 4         RISC: Mov AX, 0
Mov BX, 2 Mov BX, 4
ADD BX, AX Mov CX, 2
Begin ADD AX, BX
Loop Begin

From above example, RISC systems shorten execution time by reducing the clock cycles per instruction and CISC systems shorten execution time by reducing the number of instructions per program. The RISC gives a better execution than the CISC.

Classification According to Memory Architecture

Memory architecture of microcontroller are two types, they are namely:

  • Harvard memory architecture microcontroller
  • Princeton memory architecture microcontroller

Harvard Memory Architecture Microcontroller: The point when a microcontroller unit has a dissimilar memory address space for the program and data memory, the microcontroller has Harvard memory architecture in the processor.

Princeton Memory Architecture Microcontroller: The point when a microcontroller has a common memory address for the program memory and data memory, the microcontroller has Princeton memory architecture in the processor.

5 Applications of Microcontrollers

Microcontroller has many applications electronic equipment’s

  • Mobile Phones
  • Auto Mobiles
  • Washing Machines
  • Cameras
  • Security Alarms

4 Types of Microcontrollers

Microcontroller 8051

It is a 40pin microcontroller with Vcc of 5V connected to pin 40 and Vss at pin 20 which is kept 0V. And there are input and output ports from P1.0 – P1.7 and which having open drain feature. Port3 has got extra features. Pin36 has open drain condition and pin17 has internally pulled up transistor inside the microcontroller. When we apply logic 1 at port1 then we get logic 1 at port21 and vice versa. The programming of microcontroller is dead complicate. Basically we write a program in C-language which is next converted to machine language understand by the microcontroller. A RESET pin is connected to pin9, connected with a capacitor. When the switch is ON, the capacitor starts charging and RST is high. Applying a high to the reset pin resets the microcontroller. If we apply logic zero to this pin, the program starts execution from the beginning.

Memory Architecture of 8051

The memory of 8051 is divided to two parts.They are Program Memory and Data Memory. Program Memory stores the program being executed whereas Data Memory temporarily stores the data and the results. The 8051 has been in use in a wide number of devices, mainly because it is easy to integrate into a device. Microcontrollers are mainly used in energy management, touch screen, automobiles, and medical devices.

Program Memory of 8051
Program Memory of 8051

And

Data Memory of 8051
Data Memory of 8051

 

Pin Description of 8051 Microcontroller

Pin-40: Vcc is the main power source of +5V DC.
Pin 20: Vss – it represents ground (0 V) connection.
Pins 32-39: Known as Port 0 (P0.0 to P0.7) to serving as I/O ports.
Pin-31: Address Latch Enable (ALE) is used to demultiplex the address-data signal of port 0.
Pin-30: (EA) External Access input is used to enable or disable external memory interfacing. If there is no external memory requirement, this pin is always held high.
Pin- 29: Program Store Enable (PSEN) is used to read signal from external program memory.
Pins- 21-28: Known as Port 2 (P 2.0 to P 2.7) – in addition to serving as I/O port, higher order address bus signals are multiplexed with this quasi bi directional port.
Pins 18 and 19: Used to interfacing an external crystal to provide system clock.
Pins 10 – 17: This port also serves some other functions like interrupts, timer input, control signals for external memory interfacing Read and Write. This is a quasi bidirectional port with internal pull up.
Pin 9: It is a RESET pin, used to set the 8051 microcontroller to its initial values, while the microcontroller is working or at the initial start of application. The RESET pin must be set high for 2 machine cycles.
Pins 1 – 8: This port does not serve any other functions. Port 1 is a quasi bi directional I/O port.

Renesas Microcontroller

Renesas is latest automotive microcontroller family that offers high performance feature with exceptionally low power consumption over a wide and versatile extend of items. This microcontroller offers rich functional security and embedded safety characteristics required for new and advanced automotive applications. The core structure of microcontroller CPU support high reliability and high performance requirements.

The Renesas microcontroller offering low power, high performance, modest packages and the largest range of memory sizes combined together with characteristics rich peripherals.

Renesas
Renesas

Renesas offers the most versatile microcontroller families in the world for example our RX family offers a many types devices with memory variants from 32K flash/4K RAM to an incredible 8M flash/512K RAM.

The RX Family of 32-bit microcontrollers is a feature rich, general purpose MCU covering a wide range of embedded control applications with high speed connectivity, digital signal processing and inverter control.

The RX microcontroller family uses a 32-bit enhanced Harvard CISC architecture to achieve very high performance.

Pin Description:

Pin arrangement of Renesas microcontroller is shown in figure:

Renesas cir

It is a 20 pin microcontroller. The pin 9 is Vss, ground pin and Vdd, power supply pin. It has three different kinds of interrupt, which are normal interrupt, fast interrupt, high speed interrupt.

Normal interrupts store the significant registers on stack by using push and pop instructions. The fast interrupts are automatically store program counter and processor status word in special backup registers, so response time is faster. And high speed interrupts allocate up to four of the general registers for dedicated use by the interrupt to expand speed even further. The internal bus structure gives 5 internal busses to ensure data handling is not slowed down. Instruction fetches occur via a wide 64-bit bus, so that due to the variable length instructions used in CISC architectures.

Features and Benefits of the RX Microcontrollers

  • Low power consumption is realized using multi-core technology
  • Support for 5V operation for industrial and appliance designs
  • Scalability from 48 to 145 pins and from 32KB to 1MB flash memory, with 8KB of data flash memory included
  • Integrated safety feature
  • An integrated rich function set of 7 UART, I2C, 8 SPI, comparators, 12-bit ADC, 10-bit DAC and 24-bit ADC (RX21A), which will reduce system cost by integrating most functions

Application of Renesas Microcontroller:

  • Industrial automation
  • Communication applications
  • Motor control applications
  • Test and measurement
  • Medical applications

AVR Microcontrollers

AVR microcontroller is developed by Alf-Egil Bogen and Vegard Wollan from Atmel Corporation. The AVR microcontrollers are modified harvard RISC architecture with separate memories for data and program and speed of AVR is high when compare to 8051 and PIC. The AVR is stands for Alf-Egil Bogen and Vegard Wollan’s RISC processor.

Difference between 8051 and AVR Controllers:

  • 8051s are 8-bit controllers based on CISC architecture, AVRs are 8-bit controllers based on RISC architecture
  • 8051 consumes more power than AVR microcontroller
  • In 8051, we can program easily than the AVR microcontroller
  • The speed of AVR is more than the 8051 microcontroller

Classification of AVR Controllers:

AVR Microcontrollers are classified into three types:

  • TinyAVR – Less memory, small size, suitable only for simpler applications
  • MegaAVR – These are the most popular ones having good amount of memory (up to 256 KB), higher number of inbuilt peripherals and suitable for moderate to complex applications
  • XmegaAVR – Used commercially for complex applications, which require large program memory and high speed

Features of AVR Microcontroller:

  • 16KB of In-System Programmable Flash
  • 512B of In-System Programmable EEPROM
  • 16-bit Timer with extra features
  • Multiple internal oscillators
  • Internal, self-programmable instruction flash memory up to 256K
  • In-system programmable using ISP, JTAG or high voltage methods
  • Optional boot code section with independent lock bits for protection
  • Synchronous/asynchronous serial peripherals (UART/USART)
  • Serial peripheral interface bus (SPI)
  • Universal serial interface (USI) for two/three-wire synchronous data transfer
  • Watchdog timer (WDT)
  • Multiple power-saving sleep modes
  • 10-bit A/D Converters, with multiplex of up to 16 channels
  • CAN and USB controller support
  • Low-voltage devices operating down to 1.8v

There are many AVR family microcontrollers, such as ATmega8, ATmega16 and so on. In this article we discussing about the ATmega328 microcontroller. The ATmega328 and ATmega8 are pin compatible ICs but functionally they are different. The ATmega328 has flash memory of 32kB, where the ATmega8 has 8kB. Other differences are extra SRAM and EEPROM, addition of pin change interrupts and timers. Some of the features of ATmega328 are:

Features of ATmega328:

  • 28-pin AVR microcontroller
  • Flash program memory of 32kbytes
  • EEPROM data memory of 1kbytes
  • SRAM data memory of 2kbytes
  • I/O pins are 23
  • Two 8-bit timers
  • A/D converter
  • Six channel PWM
  • In built USART
  • External Oscillator: up to 20MHz

Pin Description of ATmega328:

It comes in 28 pin DIP, shown in figure below:

AVR
AVR

Vcc: Digital supply voltage.

GND: Ground.

Port B: Port B is an 8-bit bi-directional I/O port. The Port B pins are tri-stated when a reset condition becomes active or one, even if the clock is not running.

Port C: Port C is a 7-bit bi-directional I/O port with internal pull-up resistors.

PC6/RESET

Port D: It is an 8-bit bi-directional I/O port with internal pull-up resistors. The output buffers of the Port D consist symmetrical drive characteristics.

AVcc: AVcc is the supply voltage pin for the ADC.

AREF: AREF is the analog reference pin for the ADC.

Typical Circuit of AVR Microcontroller:

AVR cir

Applications of AVR Microcontroller:

There are many applications of AVR microcontroller; they are used in home automation, touch screen, automobiles, medical devices and defense.

PIC Microcontroller

PIC is a peripheral interface controller, developed by general instrument’s microelectronics, in the year of 1993. It is controlled by the software. They could be programmed to complete many task and control a generation line and many more. PIC microcontrollers are finding their way into new applications like smart phones, audio accessories, video gaming peripherals and advanced medical devices.

There are many PICs, started with PIC16F84 and PIC16C84. But these were the only affordable flash PICs. Microchip has recently introduced flash chips with types that are much more attractive, such as 16F628, 16F877 and 18F452. The 16F877 is around twice the price of the old 16F84, but has eight times the code size, much more RAM, much more I/O pins, a UART, A/D converter and a lot more.

PIC

Features of PIC16F877

Core Features:

  • High-performance RISC CPU
  • Up to 8K x 14 words of FLASH program memory
  • 35 Instructions (fixed length encoding-14-bit)
  • 368×8 static RAM based data memory
  • Up to 256 x 8 bytes of EEPROM data memory
  • Interrupt capability (up to 14 sources)
  • Three addressing modes (direct, indirect, relative)
  • Power-on reset (POR)
  • Harvard architecture memory
  • Power saving SLEEP mode
  • Wide operating voltage range: 2.0V to 5.5V
  • High sink / source current: 25mA
  • Accumulator based machine

Peripheral Features:

  • 3 Timer/counters (programmable pre-scalars)

–        Timer0, Timer2 are 8-bit timer/counter with 8-bit pre-scalar

–        Timer1 is 16-bit, can be incremented during sleep via external crystal/clock

  • Two capture, compare, PWM modules

–        Input capture function records the Timer1 count on a pin transition

–        A PWM function output is a square wave with a programmable period and duty cycle.

  • 10-bit 8 channel analog-to-digital converter
  • USART with 9-bit address detection
  • Synchronous serial port with master mode and I2C Master/Slave
  • 8-bit parallel slave port

Analog Features:

  • 10-bit, up to 8-channel Analog-to-Digital Converter (A/D)
  • Brown-out Reset (BOR)
  • Analog Comparator module (Programmable input multiplexing from device inputs and comparator outputs are externally accessible)

Pin Description of PIC16F877A:

PIC micro

PIC microcon

PIC microcontro

Advantages of PIC:

  • It is a RISC design
  • Its code is extremely efficient, allowing the PIC to run with typically less program memory than its larger competitors
  • It is low cost, high clock speed

A Typical Application Circuit of PIC16F877A:

PIC microcontroller

The circuit below consists of a lamp whose switching is controlled using a PIC microcontroller. The Microcontroller is interfaced with an external crystal which provides clock input. The PIC is also interfaced with a push button and on pressing the push button, the Microcontroller accordingly sends a high signal to the base of the transistor, so as to switch on the transistor and thus give proper connection to the relay to switch it on and allow passage of AC current to the lamp and thus the lamp glows. The status of the operation is displayed on the LCD interfaced to the PIC microcontroller.

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