Basic microcontroller concepts

Content aligned with Topic 1 — Basic concepts from the Microcontrollers course (UNEXPO · Mechatronics), based on Prof. Ing. Yoel Pire’s material.

What is a microcontroller

A microcontroller (μC) is a programmable integrated circuit that puts the basic blocks of a tiny computer on one chip:

CPU — executes program instructions step by step.
Memories — store the program and working data.
Input/output lines — connect the chip to LEDs, buttons, sensors, etc.
Peripherals — internal or external modules that extend what the device can do.

To use it you write firmware: the CPU reads instructions stored in memory and runs them. There is no operating system like on a PC; control is direct.

Microprocessor vs microcontroller

	Microcontroller (μC)	Microprocessor (μP)
What it integrates	CPU, memory, buses, and peripherals in one chip	Only the CPU (processor)
System type	Closed — complete computer with fixed capability	Open — you attach external memory, I/O, and peripherals
External pins	Lines that drive peripherals and ports	Address, data, and control buses to build a PC
Programming	You focus on the application	You must also manage external devices
Academic example	PIC18F4550 (single chip)	Classic PC CPU in a socket (RAM, chipset, and storage live on the motherboard, not inside the processor chip)

Comparison of architectures and embedded computing systems — The μC integrates CPU, memory, and peripherals in one chip; the μP is only the processor and the rest of the system is built separately. — Based on Topic 1 — Basic concepts · UNEXPO

Raspberry Pi and similar boards: not the same thing

A Raspberry Pi is not a microcontroller or a bare microprocessor. It is a single-board computer (SBC) — a mini PC already assembled on the board:

An SoC (System-on-Chip): application ARM cores, GPU, and other blocks in one integrated circuit.
RAM included on the board (soldered or in the SoC package, depending on model).
USB, HDMI, network, power, and GPIO connectors.
microSD (or internal storage) for the operating system and your programs.

You do not start from an empty chip and add RAM like in an academic μP-only design: the board is already a complete computer. It runs Linux (a full OS), not direct firmware burned to Flash like on the PIC.

	PIC18F4550	Raspberry Pi
What it is	Microcontroller (μC)	Single-board computer (SBC)
Program	Firmware in chip Flash	OS + apps on SD card / Linux
Memory	Flash, RAM, and EEPROM inside the chip	RAM on the board + storage on SD
Study level	Registers, bits, assembly	Python, Linux, high-level drivers

Internal and external peripherals

Peripherals let the μC interact with the world. They can be inside the chip or wired outside.

Internal peripherals (on-chip)

Modules the manufacturer builds into the microcontroller. On the PIC18F4550 you will find, among others:

Timers / counters (Timer0, Timer1, Timer2)
A/D converter (ADC)
UART / USART (serial communication)
PWM / CCP module
SPI and I2C interfaces
USB (on the 4550)
Internal EEPROM memory

External peripherals (wired to the μC)

Devices not inside the chip, connected to pins:

Sensors (temperature, pressure, distance…)
Communication modules (Bluetooth, Wi-Fi, GPS…)
External memories
LCD or OLED displays
7-segment displays
Matrix keyboards
Motors, relays, drivers

In the lab you use both: the PIC’s internal ADC and, for example, an external LCD wired to GPIO ports.

Memory types

Program memory (fabrication technology)

By how firmware is stored, the course distinguishes:

Type	What it is	Reprogrammable
ROM	Program burned at the factory	No
OTP	One-Time Programmable — written once	No
EPROM	Electrically programmed; erased with UV light	Yes (UV erase)
EEPROM	Electrically programmed and erased	Yes
Flash	Electrically programmed; PIC18F4550 stores your `.hex` here	Yes

On the PIC18F4550 the program lives in Flash (non-volatile: kept when power is off). Data you want to keep between power cycles can go in internal EEPROM.

Data memory (at runtime)

Type	Role in the μC
RAM	Temporary variables, counters, flags while the program runs. Lost on power-off unless saved elsewhere.
Special registers (SFR)	Control ports, timers, ADC, etc. (covered in Foundations).

Typical applications

A microcontroller can be used in:

Sensor and actuator control
Industrial process control
Medical equipment and robotics
Appliances and human-machine interfaces (keyboard, display)
Motor control (PWM)
Communication (SPI, I2C, UART, USB)
Clocks, alarms, calculators, and many more

Next step

You now know the general Topic 1 concepts. Continue with What is the PIC18F4550 to see how these blocks apply to the chip you will use in the lab.