What Is MCU in Electronics? The Brains Behind Embedded Systems

What is MCU in electronics?

Most modern electronic gadgets, systems, sensors, and appliances run on the processing power provided by microcontroller systems. 

Abbreviated as MCU, microcontroller units have become synonymous with electronics.

And the trend won’t stop anytime soon because the chips are tiny, programmable, versatile, and inexpensive.

But what is it? And how does it work? Let’s find out!

What Is an MCU?

An MCU is a tiny, self-contained computer mounted in a single integrated circuit.

The keyword here is self-contained. So the chip features memory, processing power, and peripherals.

These features make microcontrollers programmable to handle only single functions.

So you’ll most likely find these computers in embedded systems, such as home appliances and individual car systems.

How Microcontrollers Work

MCUs are like simplified versions of SoCs (System on Chip). So they can detect and interpret (react) to data received from the I/O peripherals via different communication protocols.

These can be sensors, USB, or touch events.

But to get a clear picture of how these chips work, let’s look at the internal elements first.

What Are the Elements of an MCU?

Microcontrollers have four components.

Central Processing Unit

The CPU is the primary element in an MCU because it is the computer’s brain.

It handles logical & arithmetic functions, generates control signals, manages data flow, and monitors all processes taking place in the MCU.

High-level programming languages like C and C++ have simplified the task of writing code for these CPUs.

Previously, you had to write code in assembly language for the processors to generate control signals.

An Arduino UNO board with an 8-bit ATmega328P microcontroller

An Arduino UNO board with an 8-bit ATmega328P microcontroller

What Is MCU in Electronics: Memory

MCUs house volatile and non-volatile memory.

  • Volatile Memory (RAM): This temporary storage can only store data when powered. It holds this data to help the CPU run calculations based on user instructions (code). And it gets overwritten continuously when the computer is running.
  • Non-Volatile Memory (ROM): ROM is permanent memory that persists even when the power goes off. So it holds the data and instructions that tell the CPU how to process programs from user inputs. For instance, the chip’s firmware gets stored in the ROM to initialize the computer when booting.

What Is MCU in Electronics: Peripherals

Peripherals are hardware components that enable the MCU to communicate with external systems. They include the following.

  • Data converters: analog-to-digital converters, reference voltage generators, and digital-to-analog converters
Analog-to-digital converter integrated circuits

Analog-to-digital converter integrated circuits

  • Timers: real-time clock, pulse-width modulation, and general-purpose timers
  • Analog signal processors: analog comparators, operational amplifiers
  • Serial communication: I2C, UART, USB, SPI
  • I/O: parallel memory interface and general-purpose digital I/O circuitry
  • Clock generators: crystal drive circuitry, oscillators, phase-locked loop

What Is MCU in Electronics: Support Circuitry

These components don’t fall under the peripherals category because they don’t monitor, control, or communicate with external devices. But they simplify the microcontroller operations and enhance the development process. They include the following.

  • Interrupts: Generated by internal or external hardware-based events, interrupts halt program execution, causing the processor to respond to these events first. After executing these instructions, the CPU can resume running the primary program.
  • Debug circuitry: This circuit allows you to monitor the microcontroller to identify bugs and optimize performance.
  • Power supply circuitry: Microcontrollers have multiple power supply circuits. They include power management modules, integrated voltage regulators, and supervisor modules.
  • Clock generation modules: MCUs have peripheral clock modules to generate clock signals for coordinating the CPU and its peripherals. But this clock is usually a low-precision device. So you can have a high-precision clock module to support the circuitry.

Microcontroller Architectures

MCUs can have either a Harvard or von Neumann architecture. The difference is the methods of exchanging data between the CPU and memory.

With the latter, the data and address buses are the same. So one connection handles both.

But in the newer Harvard architecture, these buses are separate. This separation enables quick, simultaneous transfers, resulting in faster data flow and instruction processing.

MCUs with the von Neumann architecture are known as CISC (Complex Instruction Set Computer) microcontrollers. On the other hand, those with the Harvard architecture are known as RISC (Reduced Instruction Set Computer).

CISC microcontrollers usually have more instructions (80) than their RISC counterparts (30). Also, they have more addressing modes (12-24) compared to 3-5 for RISC.

A RISC-based microcontroller chip

A RISC-based microcontroller chip

CISC emphasizes more on hardware optimization because it is easier to implement and utilizes memory more efficiently.

But it requires higher clock cycles to execute its instructions because they are many.

Higher clock cycles degrade performance.

But RISC emphasizes more on software. It hosts a simplified instruction set that reduces the clock cycles, resulting in better performance than CISC.

And the chips are also more versatile because you can vary the instruction complexity depending on the application.

Types of Microcontrollers Based on Bits

You can have various microcontroller types based on different categories. And it is worth visiting the classification by bits.


These microcontrollers have the narrowest bus widths. This limited data pipe affects the microcontroller CPU’s speed and precision when dealing with arithmetic and logic operations.

The final range for every cycle in these controllers is 0-255 (0x00 – 0xFF).

An 8-bit ATmega128 microcontroller

An 8-bit ATmega128 microcontroller

What Is MCU in Electronics: 16-bit

16-bit microcontrollers offer better speed and precision than their 8-bit counterparts when handling mathematical and logical operations.

They achieve this performance because their bus is broader (0-65535) for each cycle. However, they are costlier.

What Is MCU in Electronics: 32-bit

These MCUs are the most expensive of the three because they are the fastest.

They have the broadest data pipe (0-4294967295), making them ideal for processing data in these devices.

  • Appliances
  • Office machines
  • Engine control systems
  • Implantable medical devices
Microcontrollers with a TQPF-32 package

Microcontrollers with a TQPF-32 package

Microcontroller Unit vs. Microprocessor

The distinction between these two is becoming less defined each day because it has become cheap to increase chip density. But the terms don’t refer to the same thing.

Microcontroller units emphasize more on the additional hardware modules that enable them to function as self-contained computers.

For instance, they have internal RAM and ROM plus other components, making them capable of running systems.

A microcontroller mounted on a PCB

A microcontroller mounted on a PCB

So they are ideal for functioning independently with direct connections to actuators, sensors, etc.

On the other hand, microprocessors emphasize more on instruction execution or computing power.

So they contain powerful, dense chips with internal bus connections to external supporting hardware, such as serial ports and RAM.

A microprocessor

A microprocessor

Remember, microcontrollers have direct I/O to these parts because they are internal components.

An easier way to contextualize the two is by comparing PCs to home appliances like coffee makers.

Computers use microprocessors, while coffee makers run on microcontrollers.

Here is a detailed comparison.

Low power drawHigh power draw
Built for specific applications (performs one task repeatedly)Built to handle various complex tasks (picture how many applications you can run on your computer)
Slower clock speeds (usually in the MHz range)High clock speeds (Usually in the GHz range)
Easy and inexpensive to buildChallenging and expensive to manufacture
Complete, self-contained unitsRequire more external components (RAM. ROM, flash memory, I/O ports, etc.)

Microcontroller vs. Digital Signal Processor

A digital signal processor is an optimized microprocessor that can handle demanding computational functions.

These include data compression, real-time signal mathematical analysis, and digital filtering.

It is possible to replace a DSP with a powerful, sophisticated microcontroller.

Microcontroller vs. System on Chip (SoC)

A System on Chip is a single chip that contains one or more of the following.

  • Central processing units
  • DSPs
  • Memory components
  • Microcontrollers
  • Accelerators
  • Supporting hardware

But unlike microcontrollers, it does not adhere to any circuitry standards.

So it is like a more powerful version of a microcontroller that can handle complex tasks. And its data pipe is usually broader, ranging from 16-64 bits.

In other words, it is a more-complete computer mounted on a single chip. A typical example is the Qualcomm Snapdragon chip.

MCU Applications

  • Robotics
  • Automotive systems (fuel injection system, suspension control, anti-lock braking systems, etc.)
A car ABS unit module

A car ABS unit module

  • IoT
  • Consumer electronics
  • Home appliances
  • Medical and laboratory equipment
  • Smart energy systems

Wrap Up

In conclusion, microcontrollers are the brains used in embedded systems because they are affordable and consume little power. 

So they are critical in our everyday lives because we have embedded systems everywhere.

Think of your home appliances or car’s intelligent systems. And they are not the same as microprocessors. 

That’s it for this article. Share your thoughts and sentiments in the comments below to keep the conversation going. Cheers!