03. Module1_AnatomyOfAMicrocontroller

PART 2: Anatomy of a Microcontroller

Before we can program a microcontroller at the register level, we need to understand how it's internally organised. This section breaks down a typical MCU block diagram and explains the essential building blocks you'll encounter across most platforms (like STM32, AVR, MSP430, etc.).

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Typical Microcontroller Block Diagram

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What are the Key Components?

1. CPU Core

• The brain of the MCU. Executes instructions from your program.
• Common cores: ARM Cortex-M0/M3/M4, AVR, RISC-V, etc.
• Handles interrupts, arithmetic, logic, and program flow.

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2. Flash Memory

• Stores your compiled program (non-volatile).
• You flash your binary here via a programmer/debugger.

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3. SRAM (Static RAM)

• Stores variables, stack, and runtime data.
• Volatile—cleared when the device resets or powers off.

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4. Clock System

• Provides timing signals to the entire chip.
• Sources: internal RC oscillator, external crystal, PLL (Phase Locked Loop).
• Critical for setting up peripherals and processor speed.

Common terms:

Term	Description
HSI	High-Speed Internal Oscillator
HSE	High-Speed External crystal
SYSCLK	System Clock
AHB/APB	Clock buses for peripherals

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5. GPIO (General Purpose I/O)

• Digital input/output pins.

• Can be configured for:

  • Input (buttons)
  • Output (LEDs)
  • Alternate Function (UART, SPI, etc.)

• Each GPIO port is usually connected to:

  • A MODER register (mode: input/output/alternate)
  • An ODR register (output data)
  • An IDR register (input data)

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6. Timers & Counters

• Measure time, generate delays, create PWM signals.

Common features:

• One-shot or periodic timing
• Compare & capture modes
• Input edge detection

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7. Interrupt Controller (NVIC)

• Handles interrupts from peripherals.
• Lets you pause main code to respond to events (like button press or UART input).
• Essential for low-latency systems.

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8. Communication Interfaces

Peripheral	Use Case
UART	Serial communication (e.g., with PC, sensors)
SPI	Fast synchronous data transfer (e.g., displays, sensors)
I²C	Communicates with multiple devices on a shared bus
CAN	Used in automotive and industrial control systems

These interfaces often share pins via pin multiplexing (more below).

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9. ADC (Analogue-to-Digital Converter)

• Converts analogue voltages (like from sensors) into digital numbers.

Key settings:

• Resolution (e.g., 10-bit, 12-bit)
• Sampling time
• Input channel

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10. Pin Multiplexing

• Most MCU pins have multiple possible functions.
• Example: Pin A2 might be GPIO, UART TX, or ADC input.
• Function is selected using AF (Alternate Function) registers.

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Bus Architecture

• AHB/APB buses connect the CPU with peripherals.
• Each peripheral lives at a fixed address in the memory map.
• Think of your MCU as a mini city with memory and peripherals wired together on a bus grid.

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Recap

Block	Description
CPU Core	Executes your code
Flash	Stores program
SRAM	Runtime memory
GPIO	Talk to external devices
Timers	Create delays, PWM
Clocks	Control timing for everything
Peripherals	UART, SPI, ADC, etc.

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Practice: Spot the Blocks

Take a datasheet for your microcontroller (e.g., STM32F103C8) and identify:

• Clock sources
• Flash/SRAM size
• Number of GPIOs
• Available peripherals
• Pin multiplexing options

Next Up: Module 1 - Part 3 | Registers and the Memory Map

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