What is a microcontroller?

These compact integrated circuits (ICs) contain a processor core (or cores), random-access memory (RAM) and electrically erasable programmable read-only memory (EEPROM) for storing the custom programs that run on the microcontroller, even when the unit is disconnected from a power supply.

Unlike general-purpose microprocessors, microcontrollers integrate processing, memory and input/output (I/O) peripherals—including timers, counters and analog-to-digital converters (ADCs)—into one efficient and cost-effective standalone unit. By combining multiple components into a single system, microcontrollers are well-suited for applications requiring real-time signal processing, such as controlling motors and servos and interfacing with various types of sensors and communications.

The following are key components of a microcontroller:

• Central processing unit (CPU): Colloquially referred to as the “brain” of the computer, the CPU serves as the core component responsible for executing instructions and controlling operations.

• Memory: Microcontrollers contain both volatile memory (RAM)—which, unlike program memory, stores temporary data that may be lost if the system loses power—and non-volatile flash memory for storing the microcontroller’s programming instruction set (firmware).
  
  
• Peripherals: Depending on the intended application, a microcontroller might contain various auxiliary components, such as input/output (I/O) interfaces—including timers, counters, analog-to-digital (ADC) and digital-to-analog (DAC) signal converters (ADCs)—and communication protocols (UART, SPI, I2C). Auxiliaries might also include components like LCD screens, ethernet connectivity ports or interfaces for such types of modules.

Microcontrollers are ideal for battery-operated consumer electronics, such as smartphones, smartwatches and other wearables, because they are lightweight, small and require comparatively low power.

A favorite among open-source hobbyists, low-cost microcontrollers and microcontroller development boards, such as those made by Arduino and Adafruit, can be easily configured within an integrated development environment (IDE) using common programming languages like C, C++ and Python. Although readily accessible to even beginner developers, microcontrollers are also frequently used to control systems in a wide range of professional applications, including prototyping, robotics, automotive systems, industrial automation and Internet of Things (IoT) applications.

Microcontrollers and microprocessors share many similarities. Both can be described as single-chip processors capable of executing computing logic, and both are highly valuable in the development and proliferation of general computing technology. However, the two components differ in both hardware architecture and application.

The defining characteristic of a microcontroller is the combination of all necessary computing elements into a single chip—microcontrollers do not require any additional external circuits to operate. Conversely, microprocessors consist of a CPU and several supporting chips providing memory, serial interface, I/O and other necessary features.

While the terms microprocessor and CPU are sometimes used interchangeably, it’s more accurate to describe microprocessor semiconductors as single integrated circuits that contain a CPU and can be connected to other external auxiliaries, such as input/output devices.

The main difference between these two types of microchips is that microcontrollers are self-contained, whereas microprocessors are designed to interface with external auxiliaries.

As a result, generalized and demanding tasks that might require specialized hardware with increased processing power are better suited for microprocessors. Specific tasks within embedded systems, such as sensor or motor control, are good examples of suitable microcontroller applications.

When comparing microcontrollers and microprocessors, it's helpful to consider four key features:

1. Integrations:
   • Microcontrollers integrate CPU, memory and I/O auxiliaries onto a single chip.
   • Microprocessors require external memory and additional auxiliaries.
2. Applications:
   • Microcontrollers are better suited for specific, low-power or ultra-low power applications within embedded systems, such as home appliances or IoT devices.
   • Microprocessors are more suitable for general-purpose and high-performance applications requiring more processing power, such as personal computers or the data centers' servers.
3. Performance:
   • Microcontrollers are optimized for efficiency and real-time processing and operate at lower clock speeds up to 200MHz.
   • Microprocessors are built for more demanding and complicated computations and can operate at clock speeds above 1 GHz.
4. Operational costs:
   • Microcontroller hardware is inexpensive, and because they do not require specialized programming knowledge, they add little to overall project budgets.
   • Microprocessors are more expensive and more complex. Configuring an advanced microprocessor-based system might require specialized skills.

The first types of microcontrollers grew out of advancements made in microprocessor manufacturing as researchers developed techniques to integrate CPU, memory and peripheral components into single chips.

Texas Instruments engineers Gary Boone and Michael Cochran are credited with creating the first microcontroller in 1971. Manufacturers like Intel and various Japanese electronics vendors followed quickly.

Today, dozens of different microcontroller manufacturers—such as Intel, NXP and Arm—offer hundreds of varieties, ranging from general-purpose options for hobbyists and amateurs to highly specialized solutions for professional technologists and all manner of industries.

Here are some of the more common types of microcontrollers: