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• Microcontroller (MCU)


  A single chip, self-contained computer with main components: CPU, RAM, ROM, I/O, Timer, Interrupt circuitry, Buses, Oscillatory circuits, A/D Converters
• Microprocessor (μP)


  A general-purpose processor that needs external components to interact
• Microcontrollers are


  Optimized to control electronic devices
• Microcontrollers are usually used for


  Controlling industrial equipment and machinery
• Microcontrollers


  • Have special instructions like bit manipulation instructions
• Added features of a microcontroller over a microprocessor


  • Nonvolatile Program and Data Memories
  • Internal SRAM
  • A/D
  • Analog Comparator
  • Internal Calibrated RC Oscillator
  • Timers/Counters
  • External and Internal Interrupt Sources
  • Sleep Modes
  • Serial Peripheral Interface (SPI), USART, Two-wire Serial Interface
  • Watchdog
• RISC (Reduced Instruction Set Computer)


  Simple with fixed length instruction set, executes one instruction per clock cycle, requires very fast memory systems
• CISC (Complex Instruction Set Computer)


  Very powerful but complex instruction set, accesses memory less frequently, instructions take more than one cycle to execute, slower speed
• Pipelining in RISC architectures

  1. Allows the processor to work on different steps of instruction like fetch, decode and execute simultaneously

  2. Each instruction is executed in number of stages simultaneously

  3. When the first stage of first instruction is completed, next instruction enters the first stage

  4. This process continues until all instructions are executed
• Embedded system


  A computer system with a dedicated function within a larger mechanical or electrical system, often with real-time computing constraints, embedded as part of a complete device often including hardware and mechanical parts
• Embedded systems


  • Have minimal requirements for memory and program size, need to communicate with simple inputs and outputs, rarely need keyboards, screens, disks, printers but simple displays, microcontrollers are usually dedicated to one task and run one specific program
• Advantages of embedded systems

  • Cheap
  • Very small in size
  • Programming of microcontrollers is simple to learn (C language or Assembly)
  • Ability to simulate project before implementation
• Embedded systems solutions


  • System-on-Chip (SoC)
  • Microcontroller
  • Arduino
  • Raspberry Pi
• AVR microcontroller


  A family of microcontrollers developed by Atmel Corporation, focused on embedded systems, conceived by two students at the Norwegian Institute of Technology
• AVR microcontroller families


  • Tiny AVR (8-32 pin, 16 members)
  • Mega AVR (32-100 pin, 23 members)
  • Xmega AVR (32-100 pin)
  • AVR UC3 (32-bit, DSP support, dual port SRAM)
• ATmega16 microcontroller


  • Harvard architecture, 8-bit, 16MIPS @ 16MHz, EEPROM, Two 8-bit and One 16-bit timer with 4 PWM channels, On-chip 10-bit ADC, 8 channels, UART, I2C, SPI protocol support
• Microcontroller building blocks


  • Processor Core (CPU)
  • Memory (Registers, Data/Instruction Memory)
• AVR


  Alf and Vegard's RISC processor
• AVR families


  • Tiny AVR
  • Mega AVR
  • Xmega AVR
  • AVR UC3
• Tiny AVR family


  • 8 -32 pin
  • 16 family members
• Mega AVR family


  • 32 -100 pin
  • 23 family members
• Xmega AVR family


  • 32 -100 pin
• AVR UC3


  • 32-bit
  • DSP support
  • Dual port SRAM
• ATmega16


  • Harvard architecture
  • 8 bit Microcontroller
  • High performance - 16MIPS @ 16MHz
  • EEPROM – non volatile memory
  • Two 8 bit, One 16 bit timer with total 4 PWM channels
  • On chip 10 bit ADC, 8 channels
  • UART, I2C, SPI protocol support
• Processor Core


  The main part of any microcontroller, often taken from an existing processor
• Microcontroller building blocks


  • Processor Core
  • Memory
  • Buses
• Register


  A temporary (internal) storage element
• Data/Instruction Memory


  External memory to a CPU, different members in a MCU family usually provide different amounts
• Data Bus


  Allows data to be passed from a register or an input to the ALU at one instant and from the ALU to a register or to an output at another instant
• System buses


  • Address bus
  • Data bus
  • Control lines
• Address bus


  Unidirectional, carries Memory and I/O Addresses
• Data bus


  Bidirectional, transfers Binary Data and Instructions
• Control lines


  Carry Read and Write timing signals
• Port


  Group of 8 pins, or set of pins used for exchanging data with external world
• Width of almost all registers : 8 bits (some 16 bits)
• In port related registers, every bit corresponds to one pin of the port. Bit 0 corresponds to Pin 0, Bit 1 corresponds to Pin 1 .. Etc
• There is a direct one to one correspondence between HEX and BINARY numbers.
• Pin types


  • GND
  • VCC
  • AVCC
  • AREF
  • Reset
• Pull Up Resistor


  Used to ensure that tri-stated input always reads HIGH (1) when it is not driven by any external entity
• General Purpose IO


  Data Direction Input or Output, Internal Pullup can be used for Input Pins, Output driver can source 20mA current