Last revised: November 21, 2024

Reviewed by: Scott Orlosky, consulting engineer

A microcontroller (MCU) is a full computer built on a chip. They are used for a specific application and are normally found as part of embedded systems. MCUs execute the commands of the program by storing values in memory, by fetching values from memory and storage, and by controlling peripherals according to the statements of the program.

MCUs are employed in devices that need human interaction or human control. Evolution of computer technology is closely tied to the development of MCUs. Two main reasons for their development include improvements in integrated circuit (IC) design and fabrication, such as complimentary metal-oxide semiconductor (CMOS) and very large scale integration (VLSI) technology, and improvements in memory technologies. Modern semiconductors have revolutionized computing; large amounts of memory, fast operating speeds, and reduced power, size, and cost with a small chip are now possible.

Examples of common MCUs are the clock in a kitchen oven, and the IC that signals to open a car door when the handle is touched. MCUs are used in devices that need human interaction or human control.

Components

The accompanying figure shows the main components of an MCU and their interrelations. The most important components are the central processing unit (CPU), memory unit, mass storage, and input and output ports. Other important components for the operation of MCU include the program counter, clock oscillator, power supply circuitry, and program and source code.

CPU: The CPU is the brain of the microcontroller and its most important component. It is an extremely useful digital electronic circuit. If the CPU is entirely contained in an IC package it is also called a microprocessor (MPU).

Memory unit: In an MCU, memory stores data and code instructions. Mainly, there are two types of memory in a typical MCU: ROM and RAM memory. Other types of memory such as Flash or EEPROM memory is used in some MCUs.

Mass storage: All MCUs need to have access to electronics hardware to store information. The information includes program instructions (source code), executables, images, documents, numbers, strings, and other data.

I/O ports: The input/output ports are electronic connectors (pins) that connect with peripherals outside the MCU. Peripherals include devices such as keyboards, monitors, serial communication devices, printers, and all type of devices. To enhance the storage and memory capabilities of the MCU it is possible to add extra external storage or extra external memory using the I/O ports.

Manufacture

All MCUs are electronic devices built in a chip with standard fabrication techniques used in the manufacturing of all ICs. An MCU is a computer in a chip, and its form factor is an IC.

Specifications

MCU Family (Width of Data Bus)

MCU family refers to the size of the data bus. The data bus is the number of bits that can transferred at the same time. Based on this specification, there are families known as 8-bit, 16-bit, 32-bit, 64-bit, and so on. The higher the size of the bus, the faster data transfer is for the MCU.

Clock Rate

 All MCUs need a clock (oscillator) to operate. At intervals the MCU performs an operation or executes a command. Faster devices have higher clock rates. Clock rate is measured in megahertz (MHz) or "tics" per second.

Memory

 The installed memory is important because it will hold the source code of the operating program and will store temporary instructions and data. An MCU with big memory can perform faster. This is similar to a personal computer, where more memory means faster operations.

Supply Voltage

 This parameter is important when the MCU is part of an embedded system. A low power requirement means that system energy can be used to drive more devices.

Types and Number of Ports 

The number of input and output ports is important if you plan to drive many devices with the MCU. Also, the type of port is essential, because this will allow you to drive specific devices. Some of the port types include:

• CAN, controlled area network
• SPI, serial peripheral interface
• I2C, inter-integrated circuits
• USB, universal serial ports

Microcontrollers (MCU) FAQs

How do different types of microcontrollers vary in terms of features and applications?

Microcontrollers (MCUs) vary significantly in terms of their architecture and intended use. Here is a structured overview of some variations.

Bit Width and Processing Power

8-bit Microcontrollers: These are suitable for smaller applications with lower processing power requirements. They are often used in devices that perform a single task with limited data processing and user interface needs. Examples include toys, games, and simple domestic appliances.

16-bit Microcontrollers: These offer more processing power and features compared to 8-bit MCUs. They are faster, have more flash and SRAM, and often include additional hardware like ADCs, DACs, and Ethernet capabilities. They are used in mid-range applications such as automotive systems and technical equipment.

32-bit Microcontrollers: These are used for high-end applications requiring significant processing power and multitasking capabilities. They support real-time operating systems and are suitable for complex applications like industrial automation and advanced consumer electronics.

Note: Although 64-bit architectures do exist, they are not commonly used.  32-Bits strike the better balance between cost and performance.

Integration and Features

Microcontrollers integrate a CPU, memory, and I/O units on a single chip, which reduces the cost and complexity of embedded systems.

They often include features like flash memory, SRAM, EEPROM, timers, and I/O ports. Some advanced MCUs also have encryption engines, DMA controllers, and operational amplifiers.

Applications

Low-Cost Applications: 4/8-bit microcontrollers are used in high-volume, cost-sensitive applications like domestic appliances and simple electronic devices.

General Purpose Applications: 8/16-bit microcontrollers are used in technical equipment and automotive applications, where moderate processing power and flexibility are needed.

Specialized Applications: Some microcontrollers are designed for specific applications, such as the MSP430 series, which are ideal for metering, building automation, and portable health devices due to their low power consumption and fast processing capabilities.

Power Consumption

Microcontrollers are generally low-power devices, making them suitable for battery-powered applications. They are designed to perform specific tasks efficiently, often with power consumption as low as 0.05 watts.

Environmental Durability:

Some microcontrollers are designed to operate in extreme environmental conditions, such as automotive applications where they must withstand high temperatures and vibrations.

How do microcontrollers manage power consumption in battery-operated devices?

Low Power Modes

Microcontrollers often include various low power modes, such as sleep or standby modes, which significantly reduce power consumption when the device is idle or not performing critical tasks. These modes can be activated automatically or through software control to conserve energy.

Efficient Processing

Some microcontrollers, like the MSP430 series, incorporate features such as low-energy accelerators (LEA) for digital signal processing, which allow them to perform complex calculations more efficiently and quickly, thus spending less time in active mode and more time in low power states.

Integrated Features

By integrating multiple functions on a single chip, microcontrollers reduce the need for additional components, which can lower overall power consumption. This integration includes features like timers, counters, and communication interfaces that are optimized for low power operation.

Power Management Techniques

Microcontrollers can use dynamic voltage and frequency scaling (DVFS) to adjust the power supply and clock frequency according to the processing demands, thereby reducing power usage during less demanding tasks.

Peripheral Control

Many microcontrollers allow selective enabling and disabling of peripherals. By turning off unused peripherals, the microcontroller can save power.

Optimized Code Execution

Efficient coding practices and the use of power-aware programming techniques can help minimize the active time of the microcontroller, thus conserving battery life.

What are the advantages of using 32-bit microcontrollers in industrial applications?

32-bit microcontrollers are suitable for high-end applications that require significant processing power and multitasking capabilities. They can support real-time operating systems (RTOSs), which are essential for complex industrial applications that demand precise timing and control.

These microcontrollers integrate a CPU, memory, and I/O units on a single chip, which reduces the cost and complexity of embedded systems. This integration is particularly beneficial in industrial settings where space and cost efficiency are critical.

32-bit microcontrollers often come with advanced features such as encryption engines, DMA controllers, and operational amplifiers. These features enhance the microcontroller's ability to handle complex tasks and improve the overall system performance.

They offer expanded application code and can address applications with large RAM requirements. This is crucial for industrial applications that involve extensive data processing and storage.

Microcontrollers used in industrial applications are designed to operate in extreme environmental conditions, such as high temperatures and vibrations, ensuring reliability and durability in harsh industrial environments.

What are the integration features of microcontrollers?

Microcontrollers are highly integrated devices that combine several components on a single chip, which makes them efficient and cost-effective for embedded systems. Here is more about these features.

CPU, Memory, and I/O Integration

Microcontrollers integrate a CPU, memory (such as flash memory, SRAM, and EEPROM), and input/output (I/O) units onto a single chip. This integration reduces the need for additional components and simplifies the design of embedded systems.

Clock Sources

They often include an internal resistance capacitance (RC) oscillator to provide a clock source. For applications requiring precise timing, an external crystal can be used.

Peripheral Integration

Microcontrollers come with integrated peripherals such as timers, counters, and communication interfaces (e.g., UART, SPI, I2C) that are optimized for low power operation.

Advanced Hardware Blocks

Some microcontrollers, especially 16-bit and 32-bit ones, include advanced hardware blocks like encryption engines, Direct Memory Access (DMA) controllers, and operational amplifiers. These features enhance the microcontroller's ability to handle complex tasks and improve system performance.

On-Chip Debugging

Many microcontrollers offer on-board debugging capabilities, allowing developers to peek into registers and other system areas to facilitate application code debugging.

Low Power Features

Integration of low-energy accelerators (LEA) for digital signal processing allows microcontrollers to perform complex calculations efficiently, spending more time in low power states.

What are the differences between microcontrollers and microprocessors?

Microcontrollers and microprocessors are both integral components in computing and electronics, but they serve different purposes and have distinct characteristics. between them.

Microprocessor: A microprocessor is essentially a single-chip CPU. It requires additional components like memory, input/output interfaces, and other peripherals to function as a complete system. It is designed for general-purpose computing tasks and is typically used in personal computers and servers.

Microcontroller: A microcontroller integrates a CPU, memory (RAM and ROM), and input/output peripherals on a single chip. This integration makes it a complete system on a chip, suitable for embedded applications where space and cost efficiency are crucial.

Microprocessor: Primarily used in applications that require high processing power and flexibility, such as personal computers, servers, and workstations. They are designed to handle complex computations and run multiple applications simultaneously.

Microcontroller: Used in control-oriented applications where the system is designed to perform specific tasks. Commonly found in embedded systems like automotive controls, home appliances, and industrial automation.

Microprocessor: The instruction set is designed to enhance processing capabilities, with powerful addressing modes and instructions suitable for handling large-scale data. It can operate on various data sizes, including bytes, words, and double words.

Microcontroller: The instruction set is optimized for input/output control, often including bit manipulation instructions for controlling devices. It is streamlined to fit within the limited resources of the microcontroller chip.

Microprocessor: Requires external components for memory and I/O operations, which can increase the complexity and cost of the system.

Microcontroller: Offers built-in peripherals and features like timers, serial communication interfaces, and interrupt handling, making it ideal for embedded applications where minimal external components are desired.

What is the role of microcontrollers in embedded systems?

Microcontrollers provide a compact, efficient, and cost-effective solution for controlling and managing various electronic devices.

Microcontrollers typically integrate a CPU, memory (such as RAM and ROM), and input/output peripherals on a single chip, making them a complete system on a chip. This integration reduces the need for additional components and simplifies the design of embedded systems, leading to cost and space efficiency.

In industrial applications, microcontrollers are responsible for controlling and coordinating the activities of the entire device. They manage tasks such as fetching and executing instructions, providing control signals, and handling interrupts, which are essential for real-time operations.

Unlike general-purpose computers, microcontrollers are designed for specific tasks. They are embedded in devices to control their functions and operations, running dedicated programs stored in ROM. This makes them ideal for applications like automotive controls, home appliances, and industrial automation.

Microcontrollers are typically low-power devices, making them suitable for battery-operated applications. They incorporate features like low power modes and efficient processing techniques to conserve energy, which is critical in embedded systems where power efficiency is a priority.

Microcontrollers are used in a wide range of applications, from simple consumer electronics to complex industrial systems. They can be found in devices such as toys, games, automotive systems, and technical equipment, where they perform control-oriented tasks efficiently.

Microcontrollers (MCU) Media Gallery

References

Electronics360—Texas Instruments Expands Portfolio of MSP430 MCUs Available from Mouser

GlobalSpec—Real-Time Systems Development

Image credit:

Texas Instruments