Microcontrollers and Microcomputers

Microcontrollers

• Microcomputers consist of a microprocessor (CPU) chip, input and output chips, and memory chips for storing programs and data.
• Microprocessors are the CPU of a microcomputer contained in a single chip that interfaces with memory and I/O chips.
• Microcontrollers are implemented in a single chip, containing a CPU, memory, and I/O peripherals, with typical IOPs including I/O units, timers, and AD converters.

Basic Blocks of a Microcomputer

• Central Processing Unit (CPU) executes instructions and performs arithmetic and logic operations.
• Memory stores both instructions and data.
• Read-Only Memory (ROM) retains its content when powered off and is used for instructions and data that do not change.
• Random Access Memory (RAM) loses its content when powered off and is used for programs and data that are temporary and change during execution.
• Input/output (I/O) transfers data between the microcomputer and external devices via I/O ports involving data, status, and control signals.

System Bus

• The system bus contains three buses for address, data, and control information.
  • The address bus transfers information in one direction, from the microprocessor to memory or I/O elements.
  • The data bus allows data flow in both directions, to and from the CPU.
  • The control bus synchronizes the operation of microcomputer elements.
• Microcontrollers need synchronization from a clock or timing circuit.
• System clock signals generate clock periods for instruction executions.

CPU Architectures

• Two types of CPU architectures are used for designing microcontrollers:
  • Von Neumann architecture uses a single memory system with shared buses for programs and data, meaning programs and data cannot be accessed simultaneously.
  • Harvard Architecture uses separate program and data memory units with separate buses, allowing simultaneous instruction execution and data access.

Main Functional Elements of a CPU

• Registers are volatile storage for bits entered simultaneously or sequentially.
  • Instruction Register (IR) stores instructions, with its size determined by the CPU's word size.
  • Program Counter contains the address of the instruction or operation code.
  • Memory Address Register (MAR) contains the address of data to be transferred.
  • Accumulator stores the results of most arithmetic and logic operations.
• Arithmetic and Logic Unit (ALU) performs data manipulations, its size conforms to the word length of the microcontroller.
• The control unit translates or decodes instructions and generates enable signals.

Program Execution Steps

• Fetch: The CPU fetches the instruction from program memory into the instruction register.
• Decode: The CPU decodes the instruction using the control unit to determine its type.
• Execute: The CPU executes the instruction, generating enable signals via the control unit.

RISC vs CISC

• Reduced Instruction Set Computer (RISC) emphasizes software, uses single-clock, instruction and register to register operations, with low cycles per second and larger code sizes.
• Complex Instruction Set Computer (CISC) emphasizes hardware, includes multi-clock operations, and memory-to-memory operations with smaller code sizes and higher cycles per second.

Arduino

• Arduino is an open-source electronics platform with hardware, software/IDE, and a programming language.

Advantages of Arduino

• Inexpensive: Arduino boards are relatively inexpensive.
• Cross-platform: The Arduino IDE runs on Windows, Macintosh OSX, and Linux.
• Simple: Arduino IDE is beginner-friendly and flexible for advanced users.
• Open source: Arduino software and hardware are open-source for extensions.

Basic Arduino Boards

• Arduino Uno has 14 digital I/O pins (6 PWM), 6 analog inputs, USB connection, and power jack.
• Arduino Nano is a compact board that uses a Mini-B USB cable.
• Arduino Leonardo has 20 digital I/O pins (7 PWM, 12 analog), a micro USB connection, and a power jack.
• Arduino Micro is the smallest board similar to the Leonardo.

Parts of an Arduino Board

• Digital pins are used as input or output.
• Pin 13 LED is the only built-in actuator
• Power LED indicates that the board is receiving power.
• ATmega microcontroller is the programmable part of the board.
• Analog in pins read from an analog sensor and converts it to a value to read.
• GND and 5V pins provide +5V power and ground.
• Power connector powers the board using an external supply.
• TX and RX LEDs indicate transmitting or receiving data.
• USB port powers the board and uploads sketches/programs.
• Reset button restarts the program.

Arduino Software (IDE)

• The open-source IDE simplifies coding and uploading, written in Java and based on Processing.
• The Arduino Web Editor allows writing code and uploading to official Arduino boards from a web browser.