How to Choose the Right Instruction Set Architecture for Embedded Systems?

To build an embedded system, the first step is to confirm the desired Instruction Set Architecture (ISA). Each ISA has its advantages and disadvantages, and this article will introduce the concept and scope of embedded systems, as well as the aspects to consider when choosing an ISA.

To meet the diverse application needs of customers, DigiKey’s application and technology webpage provides a variety of application-related resources to assist engineers in designing faster. From the application perspective, DigiKey offers various solutions for automotive, automation and control, IoT solutions, energy harvesting, and more.

Furthermore, this webpage lists various ISAs covered by different embedded systems and microcontroller technologies, evaluation boards, development boards, system-on-modules, expansion boards, real-time operating systems, embedded peripheral components, microprocessors, digital signal processors, single board computers, microcontrollers, and field-programmable gate arrays, for researchers and electronics enthusiasts to further explore according to their needs.

Next, we will introduce various applications and technologies related to embedded systems on the webpage, such as evaluation boards and real-time operating systems (RTOS), microprocessors (MPU), various controllers (DSP, SBC, MCU, FPGA), and various peripherals (memory, clock, communication, I/O, power). Let’s first look at the relevant technologies and applications of embedded systems and microcontrollers.

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Choosing Embedded Systems and Instruction Set Architectures

An embedded system is a special-purpose computer system that is usually embedded in other devices or systems to perform specific tasks or functions. These systems are typically designed for specific applications or products and consist of relatively small, specialized hardware and software. To build an embedded system, the first step is to confirm the desired Instruction Set Architecture (ISA). Each ISA has its advantages and disadvantages, and below we will roughly introduce the concept and scope of embedded systems and the aspects to consider when choosing an ISA.

The Application Fields of Embedded Systems Are Quite Extensive

The application fields of embedded systems are quite extensive, typically designed to perform various specific functions or tasks, existing in areas from household appliances to automotive electronic systems, medical devices, and industrial automation. They play a key role in enhancing product intelligence, efficiency, and functionality. Moreover, many embedded systems require real-time processing and response to commands, meaning they must complete tasks within specific time constraints, which is especially important in applications requiring real-time control and feedback.

On the other hand, since embedded systems are usually configured in resource-limited designs, their hardware resources (such as processors and memory) and power are correspondingly constrained. Therefore, software must be carefully designed to fully match these limited resources, and as the hardware configuration of embedded systems is typically fixed and difficult to upgrade, optimizing the software’s performance is crucial.

Most embedded systems today need to communicate with other devices or systems to perform collaborative tasks or transmit data, requiring support for various communication protocols, which may include wired or wireless communication, such as Bluetooth, Wi-Fi, and CAN (Controller Area Network).

Embedded systems must also be paired with embedded software to perform their specific functions, which is often specifically designed for their hardware platform, including real-time operating systems (RTOS) or software stacks for specific applications.

Choosing an Instruction Set Architecture Is the First Step in Developing Embedded Systems

Embedded systems typically coordinate the electronic systems that receive, interpret, and send signals, with functionality arising from the combination of hardware and software. For those new to embedded systems, programming in C can serve as an ideal starting point for software development. To engage in software development, one must begin with choosing the overall architecture (such as the instruction set architecture) and end with some larger control categories (such as microcontrollers).

The Instruction Set Architecture (ISA), also known as the instruction set or instruction set architecture, is the part of computer architecture related to program design, including basic data types, instruction sets, registers, addressing modes, storage systems, interrupts, exception handling, and external I/O. Typically, ISAs are not cross-compatible, so a system designed for one ISA usually cannot run on another ISA. For example, x86 systems and software cannot run on ARM chips because they handle program code instructions and data sets differently.

Of course, there are several different solutions available on the market to address compatibility issues, including software that simulates different ISA operating conditions or combining different ISAs into a single software toolkit. For example, ARM has created a hybrid architecture called ARM big.LITTLE, which is a heterogeneous multiprocessing architecture that prioritizes high-power processes by combining high-power and low-power processing cores in one system, allowing for greater system flexibility and more precise power management.

ISAs can generally be divided into Reduced Instruction Set Computing (RISC) and Complex Instruction Set Computing (CISC) architectures. The concept of RISC dates back to the 1980s, aiming to execute single-step operations in computations using a simple instruction set, primarily by reducing the number of simple instructions used to load, evaluate, and store data to simplify hardware. Generally, each program code instruction can be seen as performing one action for the computer system; simpler operations can achieve faster completion speeds and reduce power consumption, making them popular in portable devices or other applications driven by power efficiency.

In contrast, CISC allows for multiple instructions and program code operations to occur at each step of the computation process, typically involving complex instructions for loading and storing steps. Generally, CISC can be considered all instruction set architectures other than RISC, as this term was developed in response to the emergence of RISC chips and systems. Although CISC does not have an official definition, they are usually considered to have more complex design systems, thus typically requiring more power to operate.

The purposes of RISC and CISC architectures are actually aimed at making CPU execution faster: RISC achieves faster CPU execution speed by reducing the cycle of each instruction at the cost of reducing the total number of instructions for each application; while CISC aims to achieve the same goal by minimizing the number of instructions for each program at the cost of more complex hardware.

When choosing an instruction set architecture, various factors need to be considered, typically involving hardware, software, and system integration aspects, including performance requirements, power consumption, cost, software ecosystem, compatibility, scalability, and security. Overall, selecting an instruction set architecture is a complex decision-making process that requires comprehensive consideration of multiple factors and making appropriate choices based on specific application scenarios and needs.

Different Instruction Set Architectures Meet Different Application Needs

Currently, there are many mainstream instruction set architectures, each with its characteristics and application fields. Some common major ISAs include RISC-V, x86, ARM, MIPS, and Power. The following will introduce the most common RISC-V, x86, and ARM.

RISC-V

RISC-V is an open standard ISA based on the RISC architecture. Unlike other chip designs, RISC-V is completely open-source and has an open architecture, with scalability and free licensing features, meaning anyone, anywhere can manufacture RISC-V chips without paying any licensing fees. This has attracted wide attention and made RISC-V a popular choice in the open-source community. However, while the RISC-V core is open-source, there may be other additional components and peripheral extensions not considered public. RISC-V has made some achievements in embedded systems, IoT devices, and emerging markets, rapidly rising in certain specific fields. Currently, there are already some RISC-V development boards available on the market, includingSparkfun RED-V and Digilent RVfpga, which can significantly accelerate the research and development process of adopting the RISC-V instruction set for embedded systems.

Sparkfun’s RED-V development board

Digilent’s RVfpga development board

More product models:

114993026	LOFIVE-R1,	110991164
102110647	102991184	110991188
110991190	114992445	102110425
102991310	113991054	DEV-22925
ESP32-C3-DEVKIT-LIPO
MPFS-ICICLE-KIT-ES	MAX78002EVKIT#
ESP32-C3-DEVKIT-LIPO	P0082

x86

CISC processors are one of the oldest instruction set architecture series, with the x86 processor series starting in the late 1970s as an extension of Intel’s 8-bit microprocessor. After continuous adjustments and improvements, it has become one of the most common types of computer processors today. x86 features a rich instruction set and general-purpose cache, originally designed for desktop computers and server applications. x86 chips are typically used in laptops, desktop computers, servers, workstations, and supercomputers, as well as some embedded systems designed for optimal performance. Currently, development boards for x86 architecture includeLattePanda x86 board and Udoo x86 board.

More product models:

DFR0470-ENT	DFR0419	DFR0981
DFR0418	DFR0545	DFR0982
DFR0444	DFR0543	VL-EPM-16F
SB02-3740-0000-C1-V
SB02-4940-0000-C1-V

ARM

ARM originally stood for “Advanced RISC Machines” (Advanced RISC Machines), but is now simply referred to as “ARM,” a series of RISC processors developed and licensed by Arm LTD. ARM adopts a RISC architecture, focusing on simplicity and energy efficiency. Due to its low power consumption and low heat generation, ARM chips are widely used in mobile devices and portable devices, embedded systems, and applications with low power requirements, such as smartphones, tablets, embedded systems, IoT devices, and certain laptops and other low-power devices. Common ARM development boards includeSTMicroelectronics NUCLEO and STMicroelectronics IOT .

STMicroelectronics’ NUCLEO development board

STMicroelectronics’ IOT development board

More product models:

102110420	SC0915	SC0195(9)
SC0919	DEV-16771	DEV-16997
MAKER-PI-RP2040	SC0193(9)	SC0695
SC0194(9)	SC0692	SC0917
102010428	EK-TM4C123GXL	NUCLEO-F103RB
STM32F407G-DISC1	NUCLEO-F446RE	NUCLEO-L476RG
NUCLEO-H743ZI2	DEV-16771	B-U585I-IOT02A
NUCLEO-F401RE	NUCLEO-L053R8	DEV-20359
DEV-21438	SC1146	NUCLEO-F411RE
STM32F429I-DISC1	NUCLEO-F746ZG	NUCLEO-G431KB
A000062	ABX00012	NUCLEO-G431RB
102110646	OM13058UL	NUCLEO-L152RE
NUCLEO-F303K8	STM32H735G-DK	NUCLEO-F303RE
STM32F769I-DISCO	NUCLEO-L432KC	DEV-16402
STM32F072B-DISCO	BBB01-SC-505	ABX00087
ST25R3911B-DISCO,	FRDM-KE06Z	CY8CKIT-043
STM32MP157F-DK2	NUCLEO-U575ZI-Q	102010328

Instruction Set Architecture	Comparison/Summary
RISC-V	Reduced Instruction Set Architecture, open-source and open architecture, with no licensing fees, the most promising instruction set architecture.
x86	Complex instruction set architecture with a long history, widely used in personal computing, the preferred choice for personal computer compatibility.
ARM	Widely used in smartphones, reduced instruction set architecture, low power consumption, low heat generation, but requires licensing fees and has higher development costs.

RISC-V Is Currently the Most Promising Instruction Set Architecture

CPU design and development is a long and costly process. Since suppliers like ARM charge developers patent fees for using their designs to cover development costs, the open-source, royalty-free RISC-V architecture has become the most promising instruction set architecture today.

The distinction of RISC-V from other ISAs is that the standard is open-source and free for personal, academic, and commercial use. Furthermore, it defines the basic core that handles the most important functions in the CPU, which itself is a general-purpose computer capable of simplified functions. This basic core can be extended using extension instructions, which are designated to work with the base core and do not conflict with each other. For example, you can implement a CPU with a 64-bit basic integer instruction set and include an extension that supports single-precision floating-point instructions, as well as another for integer multiplication and division.

Currently, some manufacturers have implemented the RISC-V ISA, and you can choose from various development boards using such CPUs. One of them isLoFive R1, which is an easy and economical start to the RISC-V ecosystem, featuring all the functionalities you would expect from a development board (like Arduino) at a low price.

GroupGets LLC’s LoFive R1 RISC-V evaluation board

SparkFun RED-V is another low-cost entry-level development board, which has the same form factor as the established Arduino Uno R3, making it the best choice for those wanting to replace Arduino in existing designs. Seeed Studio GAPUino is another board fully compatible with the popular Arduino Uno R3 pins. However, its price is less affordable compared to the first two evaluation boards.

Seeed Studio’s GAPUino development board

Conclusion

Embedded systems and microcontrollers are currently hot topics, and choosing an ISA is the first step in embedded system development. DigiKey offers various ISA development boards for customers to choose from and provides corresponding support. Designers can also refer to the application and technology webpage for more detailed introductions to applications and technologies to speed up system development. If there are more needs, you can also contact DigiKey for more detailed information.

More related cutting-edge technologies and selected content:

• RVfpga: Understanding RISC-V Architecture and Implementation on FPGA

• Development Kit Limitations—How to Determine Compatibility

• Expansion Boards/Subcards

• How to Run the Same C Language Code on Chips from Multiple Vendors

• Implementing AI Edge Computing with Asymmetric Multi-core RISC-V SoC FPGA, A Careful Guide!

• First-Word Fall-Through (FWFT) Read Operations

• FPGA Lean University | Introduction and Positioning of FPGA

• FPGA Lean University | Professors Present Three Application Examples to Make You Love FPGA!

• FPGA Lean University | Professors Explain: Detailed Explanation of Development Platform Selection

• Kickstart Your Raspberry Pi – Quick Start

Editor’s Note

Choosing the appropriate instruction set architecture is crucial for solution development, as it determines the system’s performance, compatibility, power consumption, and cost. By making reasonable choices, one can ensure that the solution achieves the best balance in these aspects. Now, you can quickly start your solution design with the rich resources provided by DigiKey. Any questions and experiences, welcome to leave a message and share!

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