Microcontroller

Microcontroller
               A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications.
           Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes. Mixed signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems.
              Some microcontrollers may use four-bit words and operate at clock rate frequencies as low as 4 kHz, for low power consumption (single-digit milliwatts or microwatts). They will generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt; power consumption while sleeping (CPU clock and most peripherals off) may be just nanowatts, making many of them well suited for long lasting battery applications. Other microcontrollers may serve performance-critical roles, where they may need to act more like a digital signal processor (DSP), with higher clock speeds and power consumption.
             A microcontroller can be considered a self-contained system with a processor, memory and peripherals and can be used as an embedded system.[6] The majority of microcontrollers in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems. While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relays, solenoids,LEDs, small or custom LCD displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other recognizable I/O devices of a personal computer, and may lack human interaction devices of any kind.

Types :





A Conexant ARM processor used mainly in routers



Atmel ATMEGA32 microcontroller





The die from an Intel 8742, an 8-bit microcontroller that includes a CPU running at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I/O in the same chip.
1.Atmel AVR
                    The AVR is a Modified Harvard architecture 8-bit RISC single chip microcontroller which was developed by Atmel in 1996. The AVR was one of the first microcontroller families to use on-chip flash memory for program storage, as opposed to One-Time Programmable ROM, EPROM, or EEPROM used by other microcontrollers at the time. Atmel's low power, high performance AVR microcontrollers handle demanding 8 and 16-bit applications. With a single cycle instruction RISC CPU, innovative Pico Power® technology, and a rich feature set, the AVR architecture ensures fast code execution combined with the lowest possible power consumption. Whether you program in C or assembly, the tuned AVR instructions decrease program size and development time. The well-defined I/O structure limits the need for external components and reduces development cost. A variety of internal oscillators, timers, UARTs, SPIs, Pulse Width Modulation, pull-up resistors, ADCs, Analog Comparators and Watch-Dog Timers are some of the features available for creative engineers. The AVR microcontrollers are divided into 4 families tiny AVR, mega AVR, XMEGA and Application specific AVR. 

Basic families

AVRs are generally classified into six broad groups:
  • tinyAVR — the ATtiny series
    • 0.5–16 kB program memory
    • 6–32-pin package
    • Limited peripheral set
  • megaAVR — the ATmega series
    • 4–512 kB program memory
    • 28–100-pin package
    • Extended instruction set (multiply instructions and instructions for handling larger program memories)
    • Extensive peripheral set
  • XMEGA — the ATxmega series
    • 16–384 kB program memory
    • 44–64–100-pin package (A4, A3, A1)
    • Extended performance features, such as DMA, "Event System", and cryptography support.
    • Extensive peripheral set with ADCs
  • Application-specific AVR
    • megaAVRs with special features not found on the other members of the AVR family, such as LCD controller, USB controller, advanced PWM, CAN, etc.
  • FPSLIC (AVR with FPGA)
    • FPGA 5K to 40K gates
    • SRAM for the AVR program code, unlike all other AVRs
    • AVR core can run at up to 50 MHz [5]
  • 32-bit AVRs


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