Field programmable gate arrays (FPGAs) vs. microcontrollers: What’s the difference?

Field programmable gate arrays (FPGAs) and microcontroller units (MCUs) are two types of commonly compared integrated circuits (ICs) that are typically used in embedded systems and digital design. Both FPGAs and microcontrollers can be thought of as “small computers” that can be integrated into devices and larger systems.

As processors, the primary difference between FPGAs and microcontrollers comes down to programmability and processing capabilities. While FPGAs are more powerful and more versatile, they are also more expensive. Microcontrollers are less customizable, but also less costly. In many applications, microcontrollers are exceptionally capable and cost-effective. However, for certain demanding or developing applications, like those requiring parallel processing, FPGAs are necessary.

Unlike microcontrollers, FPGAs offer reprogrammability on the hardware level. Their unique design allows users to configure and reconfigure the chip’s architecture depending on the task. FPGA design can also handle parallel inputs simultaneously, whereas microcontrollers can only read one line of code at a time. An FPGA can be programmed to perform the functions of a microcontroller; however, a microcontroller cannot be reprogrammed to perform as an FPGA.

First introduced by manufacturer Xilinx in 1985, FPGAs are highly valued for their versatility and processing power. As a result, they are a preferred choice in many high-performance computing (HPC), digital signal processing (DSP) and prototyping applications.

Unlike traditional application-specific integrated circuits (ASICs), FPGAs are designed to be configured (and reconfigured) “in the field” after the initial manufacturing process is complete. While customization is the FPGAs greatest value offering, it should be noted that FPGAs not only allow for programmability, they require it. Unlike ASICs, FPGAs are not “out-of-the-box” solutions, and they must be configured prior to use with a hardware description language (HDL), such as verilog or VHDL. Programming an FPGA requires specialized knowledge, which can increase costs and delay deployments. While some FPGAs do offer non-volatile memory that can retain programming instructions when powered off, typically FPGAs must be configured on start-up.

FPGA benefits

Despite these challenges, FPGAs remain useful in applications requiring high-performance, low-latency and real-time flexibility. FPGAs are particularly well suited for applications requiring the following:

• Rapid prototyping: FPGAs can be quickly configured into multiple types of customized digital circuits, allowing for expedited deployments, assessments and modifications without the need for costly and time-consuming fabrication processes. 
• Hardware acceleration: Demanding applications benefit from the FPGA’s parallel-processing capabilities. FPGAs may offer significant performance improvements for computationally intensive tasks, such as signal processing, cryptography, and machine learning algorithms.
• Customization: FPGAs are a flexible hardware solution that can be easily optimized to meet specific project requirements. 
• Longevity: FPGA-based designs may benefit from a longer hardware lifespan as FPGAs can be updated and reconfigured to meet evolving project demands and technology standards. 

FPGA components

To achieve reconfigurability, FPGAs are composed of an array of programmable logic blocks interconnected by a programmable routing fabric. The main components of a typical FPGA are as follows:

• Configurable logic blocks (CLBs): CLBs provide compute functionality and may contain a small number of primitive logic elements, such as logic gates, small look-up tables (LUTs), multiplexors and flip-flops for data storage. 
• Programmable interconnects: Made up of wire segments joined by electrically programmable switches, these linkages provide routing pathways between the various FPGA resources, allowing for different configurations and the creation of custom digital circuits. 
• I/O Blocks (IOBs): The interface between an FPGA and other external devices is enabled by input output (I/O) blocks, which allow the FPGA to receive data from and control peripherals 

FPGA use cases

Versatile by nature, FPGAs are common among a wide variety of industries and applications:

• Aerospace and defense: Offering high-speed parallel processing valuable for data acquisition, FPGAs are a preferred choice for radar systems, image processing and secure communications. 
• Industrial control systems (ICS): Industrial control systems used to monitor infrastructure—like power grids, oil refineries and water treatment plants—use FPGAs that can be easily optimized to meet the unique needs of various industries. In these critical industries, FPGAs can be used to implement various automations and hardware-based encryption features for efficient cybersecurity.
• ASIC development: FPGAs are often used in the prototyping of new ASIC chips. 
• Automotive: Advanced signal processing also makes FPGAs well-suited for automotive applications, including advanced driver assistance systems (ADAS), sensor fusion and GPS.
• Data centers: FPGAs add value to data centers by optimizing high-bandwidth, low-latency servers, networking and storage infrastructure.

FPGA features

• Processing core: Configurable logic blocks
• Memory: External memory interface 
• Peripherals: Configurable I/O blocks
• Programming: Hardware description language (VHDL, Verilog) 
• Reconfigurability: Highly reconfigurable, reprogrammable logic

Microcontrollers are a type of compact, ready-made ASIC containing a processor core (or cores), memory (RAM), and erasable programmable read-only memory (EPROM) for storing the custom programs that run on the microcontroller. Known as a “system-on-a-chip (SoC)” solution, microcontrollers are essentially small computers integrated into a single piece of hardware that can be used independently or in larger embedded systems.

Consumer-grade microcontrollers, such as the Arduino Starter Kit or Microchip Technology PIC, can be configured using assembly language or common programming languages (C, C++), and they are favored by hobbyists and educators for their cost-effective accessibility. Microcontrollers are also capable of handling more complex and critical tasks and are common in industrial applications. However, decreased processing power and memory resources can limit the microcontroller’s efficacy in more demanding applications.

Microcontroller benefits

Despite their limitations, microcontrollers offer many advantages, including the following:

• Compact design: Microcontrollers integrate all necessary components onto a small, single chip offering a small footprint valuable in applications where size and weight are a priority.
• Energy efficiency: Designed to operate on low power, microcontrollers are well suited for battery-powered devices and other applications where power consumption is a concern.
• Cost-effective: Microcontrollers offer a complete SoC solution that reduces the need for additional peripherals and components. Low-cost, general-purpose microcontrollers can greatly reduce overall project expenses.
• Flexibility: Although not as versatile as FPGAs, microcontrollers are programmable for a wide range of various applications. While they cannot be reprogrammed on the hardware level, microcontrollers can be easily reconfigured, updated and optimized on a software level.

Microcontroller components

When reprogrammability is not a priority, self-contained microcontrollers offer a compact and capable alternative. The following are the key components of a microcontroller:

• Central processing unit (CPU): Colloquially referred to as the “brain,” the central processing unit (CPU) serves as the core component responsible for executing instructions and controlling operations.
• Memory: Microcontrollers contain both volatile memory (RAM), which stores temporary data that may be lost if the system loses power, and non-volatile memory (ROM, FLASH) for storing the microcontroller’s programming code.
• Peripherals: Depending on the intended application, a microcontroller may contain various peripheral components, such as input/output (I/O) interfaces like timers, counters, analog-to-digital converters (ADCs) and communication protocols (UART, SPI, I2C).

Microcontroller use cases

Unlike FPGAs, small, affordable, and non-volatile microcontrollers are ubiquitous in modern electronics, frequently deployed for specific tasks, including the following:

• Automotive systems: Microcontrollers are used in engine control, airbag deployment and in-car infotainment systems.
• Consumer electronics: Microcontrollers are critical to smartphones, smart TVs and other home appliances, especially devices that integrate into the Internet of Things (IoT).
• Industrial automation: Microcontrollers are well-suited to industrial applications, such as controlling machinery, monitoring systems and process automation.
• Medical devices: Microcontrollers are often deployed in life-saving devices, such as pacemakers, blood glucose monitors and diagnostic tools.

Microcontroller features

• Processing core: Fixed CPU
• Memory: Integrated RAM and ROM/Flash 
• Peripherals: Built-in I/O interfaces for
• Programming: Software (C, Assembly) 
• Reconfigurability: Limited, firmware updates

When comparing FPGAs and microcontrollers, it is important to consider a number of key differences, including hardware architecture, processing capabilities, power consumption, and developer requirements.

• Hardware structure
  • FPGA: Highly configurable programmable logic blocks and interconnects, allowing for reprogrammable and custom digital circuits.
  • Microcontroller: Fixed architecture with predefined components (CPU, memory, peripherals) integrated into a single chip.
• Processing capabilities
  • FPGA: Advanced parallel processing enables multiple simultaneous operations.
  • Microcontroller: Designed for sequential processing, microcontrollers can only execute instructions one at a time.
• Power consumption
  • FPGA: Typically consumes more power than microcontrollers.
  • Microcontroller: Optimized for low power consumption, suitable for battery-powered applications.
• Programming
  • FPGA: Require specialized knowledge in hardware description languages to configure and debug.
  • Microcontroller: Can be programmed using software development languages including Javascript, Python, C, C++ and assembly languages.
• Cost
  • FPGA: Offering increased power, but requiring advanced skills, FPGA hardware is often more expensive with the additional cost of higher power consumption and specialized programmer talent.
  • Microcontroller: Generally, a more cost-effective solution with off-the-shelf availability, lower power consumption and support for more accessible programming languages.
• Versatility
  • FPGA: The FPGA is far more flexible than the microcontroller, allowing for customization on the hardware level.
  • Microcontroller: While suitable for a broad range of applications, microcontrollers offer only superficial customization compared to FPGAs.

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