As described in the previous post on Embedded System Design, the processor forms the most important of all embedded systems components. Understanding embedded systems architecture is fundamental to making the right processor choice. In this post, we discuss various processor types, their classification, and the key considerations for processor selection in embedded systems architecture design.
While in an embedded system a micro-controller is a more accurate term — as most are highly integrated System-on-Chips — we use the term "Processor" to refer to the processing core throughout this guide.
Processor Classification by Internal Architecture of CPU
The internal architecture of cpu is the primary basis for classifying embedded processors. Understanding the internal architecture of cpu helps design teams align processor choice with application requirements — from real-time control to high-performance computing. The internal architecture of cpu directly influences data throughput, power consumption, and software complexity in embedded systems architecture decisions.
By Data Width
Microprocessors are available in various data width configurations: 8-bit, 16-bit, 32-bit, and 64-bit. A processor with 'n' bit-width can manipulate 'n'-bit data in a single instruction cycle. For example, a 32-bit microprocessor has 32-bit wide registers and performs 32-bit operations in one cycle, compared to an 8-bit controller that may need more than 4 cycles for the same operation.
Higher bit-width processors generally come with larger addressing capability, enabling heavier operating systems to run. Conversely, lower bit-width designs achieve higher code density, enabling more functionality within the same program memory footprint.
By Number of Cores
Modern microprocessors often feature more than one core — typically 2 or 4. Multi-core processors are well-suited for multitasking environments as they offer multiple execution contexts simultaneously. Key factors in multi-core selection include cache availability and power consumption. To use multiple cores effectively, the operating system must support symmetric or asymmetric multiprocessing.
By Type of Cores
In a multi-core processor, the cores may be of the same or different architectures. A Symmetrical multi-core processor has identical cores. An Asymmetrical multi-core processor has cores with different instruction sets, clock speeds, and memory models. ARM's big.LITTLE is a well-known example — each core is specialized for a specific task type, yielding improved performance. The trade-off is higher application development complexity compared to symmetrical designs.
By Architecture
Various vendors have designed processor cores based on different design philosophies and technologies. Understanding the embedded systems architecture of each vendor's offering is key to system design. Notable architectures include ARM, PPC, x86, AVR, SH, and MIPS — each suited to different application scenarios.
Popular Embedded System Architecture Types
Understanding the popular embedded systems architecture types guides system designers in balancing performance, power, and ecosystem maturity. The following embedded system architecture families are most widely used in commercial and industrial embedded designs today.
ARM
ARM is one of the leading suppliers of microprocessor technology, offering the widest range of processor cores for performance, power, and cost requirements. The ARM embedded system architecture delivers arguably the best power-performance ratio and dominates battery-operated embedded segments — particularly with the proliferation of smartphones and IoT devices.
ARM v7 cores are available in application-specific variants: Cortex-A (Applications), Cortex-R (Real Time), and Cortex-M (Microcontroller). ARM also offers technology extensions including:
- Thumb Instruction Set – 16-bit instruction set for higher code density
- Jazelle – Java Byte Code Execution
- VFP – Vector Floating Point Units
- SIMD – Single Instruction Multiple Data
- NEON – Advanced SIMD for media processing
- TrustZone – Security Extension
ARM supports 32-bit and 64-bit cores in single-core and multi-core variants, making the ARM embedded systems architecture highly versatile across product categories.
PowerPC
PowerPC (Performance Optimization With Enhanced RISC – Performance Computing) is a RISC architecture created by the Apple–IBM–Motorola alliance, originally for personal computers. PowerPC CPUs have since become popular as embedded and high-performance processors, particularly in communication and networking segments. Along with i386 and ARM, PowerPC is a well-supported architecture in Linux.
x86
x86 is the generic name for a microprocessor architecture first developed by Intel. While historically dominant in desktops and servers, x86 is increasingly used in embedded designs where software portability and ecosystem maturity are priorities. The embedded system architecture advantage of x86 is software compatibility — any application running on an x86 PC works on the embedded target with minimal effort. The main disadvantages are higher power consumption, limited industrial-grade temperature availability, and higher overall design cost compared to ARM.
AVR
The AVR is a modified Harvard architecture 8-bit RISC single-chip microcontroller developed by Atmel (now Microchip). These cores are popular for low-end application segments, with a wide range of devices supporting multiple peripherals. 32-bit AVR cores are also available for more demanding applications.
PIC
PIC is a family of modified Harvard architecture microcontrollers made by Microchip Technology. They are among the most cost-effective devices and are widely used in both the student community and industrial segments, with a broad range of core and peripheral set options.
For vendor-specific guidance on microcontroller families including STM32 and other ST devices, Embien's ST Micro Device Expertise team provides design support from silicon selection through firmware development. Embien's Digital Transformation Services also help organizations leverage the right embedded systems architecture for their next-generation connected product roadmaps.
Embedded Systems Components and Processor Selection
The processor is the most critical of all embedded systems components, but it does not operate in isolation. Processor selection directly impacts memory architecture, power supply design, IO requirements, and enclosure constraints — all key embedded systems components discussed in subsequent posts in this series.
Embedded Systems Programming Languages by Architecture
The choice of processor architecture shapes your embedded systems programming languages options. ARM supports C, C++, Python, and Rust with mature toolchains. x86 platforms offer the broadest embedded systems programming languages ecosystem due to their PC lineage. PIC and AVR are predominantly C and assembly. Selecting the right architecture early simplifies toolchain, RTOS, and middleware choices downstream.
Now that processor classification within embedded systems architecture is covered, the next article discusses further considerations for processor selection — including performance benchmarking, ecosystem maturity, and long-term availability. Read the next post: Embedded System Design – Processor Selection.