Microcontrollers are the brains of embedded systems. They pack a CPU, memory, and peripherals into a tiny chip. This section breaks down the key parts that make them tick, from the central processing unit to the power management system.

Understanding microcontroller architecture is crucial for embedded systems design. We'll explore how these components work together, enabling microcontrollers to process data, interact with the world, and manage power efficiently. This knowledge forms the foundation for programming and optimizing embedded systems.

Core Components

Central Processing Unit and Arithmetic Logic Unit

• CPU acts as the brain of the microcontroller, executing instructions and controlling other components
• Fetches instructions from memory, decodes them, and executes them sequentially
• ALU performs arithmetic and logical operations on data (addition, subtraction, AND, OR, etc.)
• ALU is a fundamental building block of the CPU, allowing it to perform complex calculations and decision-making

Registers and Memory

• Registers are high-speed storage locations within the CPU used for temporary data storage and quick access
• Registers hold operands for ALU operations, store intermediate results, and keep track of the program counter and stack pointer
• Memory stores program instructions and data for long-term access
  • RAM (Random Access Memory) is volatile and used for temporary data storage during program execution
  • ROM (Read-Only Memory) is non-volatile and stores permanent data, such as bootloader code or device-specific information
  • Flash memory is non-volatile and can be erased and reprogrammed, making it suitable for storing application code and updatable firmware

Bus Architecture and Data Transfer

• Bus architecture facilitates communication and data transfer between different components of the microcontroller
• Consists of address bus, data bus, and control bus
  • Address bus carries the memory addresses for read and write operations
  • Data bus transfers data between the CPU, memory, and peripherals
  • Control bus carries control signals, such as read/write enable and clock signals
• Bus width (8-bit, 16-bit, 32-bit) determines the amount of data that can be transferred in a single cycle, affecting performance and memory addressing capabilities

Peripheral Interfaces

Input/Output Ports and Timers

• I/O ports allow the microcontroller to interface with external devices, such as sensors, actuators, and displays
• Ports can be configured as inputs or outputs and are controlled by setting registers
• Timers generate precise time intervals and can be used for tasks like generating PWM signals, measuring pulse widths, and triggering events
  • Timers can be configured to count up or down and can generate interrupts upon reaching a specific value
  • Multiple timers with different resolutions and capabilities are often available (8-bit, 16-bit, 32-bit timers)

Interrupt Controller and Event Handling

• Interrupt controller manages and prioritizes interrupt requests from various sources (timers, I/O pins, communication interfaces)
• Interrupts allow the CPU to respond to external events or specific conditions without constantly polling for changes
• When an interrupt occurs, the CPU suspends its current task, saves the context, and executes the corresponding interrupt service routine (ISR)
• ISRs are special functions that handle the interrupt event and perform the necessary actions before returning control to the main program
• Interrupt-driven programming enables efficient resource utilization and real-time responsiveness in embedded systems

System Management

Clock System and Timing Control

• Clock system generates and distributes the clock signals required for synchronizing the microcontroller's operations
• Consists of oscillators (crystal, RC, or external) and clock generation circuits (PLLs, dividers)
• Different clock sources can be selected based on the desired frequency, accuracy, and power consumption
• Clock gating and scaling techniques are used to optimize power consumption by disabling unused peripherals and adjusting clock frequencies dynamically

Power Management Unit and Low-Power Modes

• Power management unit controls the power supply and monitors the system's power consumption
• Provides features like voltage regulation, brownout detection, and battery management
• Microcontrollers often have multiple low-power modes to reduce power consumption during periods of inactivity
  • Sleep mode: CPU is halted, but peripherals continue to operate
  • Deep sleep mode: Most peripherals are disabled, and the system operates on a low-frequency clock
  • Hibernate mode: All components are powered down, and the system state is saved in non-volatile memory for later restoration
• Low-power modes are essential for battery-powered applications and energy-efficient designs, extending battery life and minimizing heat generation