The ARM processor is the first RISC microprocessor designed by Acorn Computers for the low-budget market, earlier known as Acorn RISC Machine. The ARM processor is designed to be 32-bit but also features a 16-bit instruction set, generally saving up to 35% compared to equivalent 32-bit code while retaining all the advantages of a 32-bit system. In the 1990s, ARM 32-bit embedded RISC (Reduced Instruction Set Computer) processors expanded globally, dominating the fields of low-power, low-cost, and high-performance embedded system applications. ARM does not manufacture or sell chips; it only sells chip technology licenses.
An MCU is essentially a microcontroller, which refers to a single chip that integrates a computer’s CPU, RAM, ROM, timer/counter, and various I/O interfaces to form a chip-level computer.
DSP (Digital Signal Processing) is the theory and technology of processing signals using numerical calculations. Additionally, DSP is short for Digital Signal Processor, which is a chip that integrates a specialized computer and is about the size of a coin.
FPGA (Field-Programmable Gate Array) is a product developed further based on programmable devices like PAL, GAL, and CPLD. It emerged as a semi-custom circuit in the field of Application-Specific Integrated Circuits (ASIC), addressing the shortcomings of custom circuits while overcoming the limitations of the number of gates in existing programmable devices.
The definition of SoC varies widely, and due to its rich connotation and broad application range, it is challenging to provide an accurate definition. Generally, SoC refers to a system-on-chip, meaning it is a product, an integrated circuit with a specific purpose that contains a complete system along with all embedded software. At the same time, it is a technology used to implement the entire process from defining system functions to hardware/software partitioning and completing the design.
Comparison of ARM, MCU, DSP, FPGA, and SoC
ARM: The architecture uses a 32-bit Reduced Instruction Set (RISC) processor architecture. From ARM9 onwards, ARM has adopted Harvard architecture, which separates the storage of instructions and data in their respective independent memory structures, significantly improving the processor’s processing capabilities.
ARM often uses pipelining technology, which reduces program execution time by allowing multiple power components to work in parallel, enabling instructions to flow through multiple pipelines, thus improving the efficiency and throughput of the processor. Today, ARM7 uses a typical three-stage pipeline, ARM9 uses a five-stage pipeline technology, while ARM11 employs a seven-stage pipeline, and ARM Cortex-A9 even uses a variable pipeline structure (supporting 8-11 stages). In terms of multi-core support, ARM Cortex-A9 can support up to four cores, marking the first instance of multi-core technology in the ARM series of processors. The following figure represents the NXP ARM architecture processor.
Most are structurally based on the von Neumann architecture, which clearly defines the four essential parts required for embedded systems: a central processing unit core, program memory (ROM or flash memory), data memory (RAM), one or more timers/counters, and input/output ports for communication with peripheral devices and expansion resources—all integrated into a single integrated circuit chip. Early MCUs used CISC instruction sets, which were later replaced by RISC. In terms of bus width, MCUs cover 4-bit, 8-bit, 16-bit, and 32-bit, with extensive applications.
Also known as Digital Signal Processor, it is a microprocessor specialized for real-time digital signal processing. Structurally, it adopts Harvard architecture and also employs pipelining technology. Additionally, when used in a host environment, it can operate as a direct memory access device and supports data acquisition from Analog-to-Digital Converters (ADC), ultimately outputting data converted from digital to analog signals by Digital-to-Analog Converters (DAC), supporting certain parallel processing capabilities.
FPGA stands for Field-Programmable Gate Array, which is a product developed further based on programmable devices like PAL, GAL, and PLD. It is the highest integrated form of Application-Specific Integrated Circuits (ASIC). FPGA introduces the concept of Logic Cell Array (LCA), which includes Configurable Logic Blocks (CLB), Input Output Blocks (IOB), and internal interconnects. Users can reconfigure the internal logic and I/O modules of FPGA to realize user-defined logic. It also features static reprogramming and dynamic in-system reconfiguration capabilities, allowing hardware functionality to be modified through programming like software. FPGA differs from DSP, ARM, and MCU primarily in its parallel processing capability, which significantly enhances the speed of complex computations.
A System-on-Chip (SoC) is an integrated circuit that integrates a computer or other electronic system onto a single chip. SoCs can process digital signals, analog signals, mixed signals, and even higher frequency signals. SoCs are often used in embedded systems. The integration scale of SoCs is large, typically reaching millions to tens of millions of gates. SoCs are relatively flexible, allowing the integration of ARM architecture processors with specialized peripheral chips to form a system. Some ARM processors, such as Hisi-3507, Hisi-3516, are examples of SoC systems, particularly application processors that integrate many peripheral devices to provide strong support for more complex tasks and applications.
It can be said that ARM’s significant success in the mobile market is mainly due to its low power consumption. It is well-known that electronic products in the mobile market are very sensitive to processor power consumption. In the past, processor power consumption on PC platforms ranged from several tens of watts to hundreds of watts, which is unimaginable in the mobile platform. ARM operates at a frequency of 1GHz with only a few hundred mW of power consumption, making it suitable for mobile electronic products.
According to a set of data from a non-profit organization, DSP and FPGA each hold half of the market share in digital signal processing. One advantage of DSP over FPGA is its relatively low power consumption. DSP manufacturers strive to maintain market share by increasing processor frequency and working to reduce power consumption since FPGA seems to have an advantage in the high-performance digital processing market. Among DSP manufacturers, TI’s DSP processors stand out for their lower cost and power consumption compared to others, enhancing TI’s competitiveness in the market.
MCUs have been around the longest, with various manufacturers having their own architectures and instruction sets. In terms of low power consumption, TI’s MSP430 MCU performs relatively well.
Due to its internal structure, FPGA has relatively high power consumption and generates a lot of heat, which is a drawback. However, this is unavoidable, as it supports high-performance concurrent computing digital circuits, and the logic gates mostly adopt standard width-to-length ratios, ultimately leading to power consumption that cannot compete with ASICs and other specialized processors.
Due to the flexibility of SoC, it integrates multiple components onto a very small chip to form a system. Compared to systems composed of MCUs and other processors, SoC systems have an advantage in power consumption. Additionally, SoC chips can optimize system power consumption at the layout level by integrating factors like process and circuit design, resulting in lower power consumption and smaller footprint compared to systems built with current external PCB boards.
With the increasing demand for market applications, ARM manufacturers are optimizing to enhance their frequency and performance. From the initial 100MHz to an astonishing 2.3GHz, ARM’s frequency has progressed at an impressive pace.
Today’s fastest frequency can reach 1.2GHz. However, one cannot simply judge performance based on frequency; DSP can complete a multiplication and an addition in a single clock cycle, a capability that typical ARM processors do not possess. DSP’s advantages in computation are especially prominent, which is why TI combined the strengths of ARM and DSP to produce the Da Vinci heterogeneous chip, which falls under the SoC category.
As a low-end application processor, its frequency ranges from a few MHz to several tens of MHz.
FPGA’s clock frequency can reach several GHz, even exceeding 10GHz, though its cost is also significant. Comparing FPGA with ARM, DSP, etc., based on frequency is not particularly meaningful, as the parallel computing capability far exceeds that of general-purpose processors using serial computation by dozens of times. For instance, implementing the same filtering algorithm on a 100MHz FPGA is faster than on a 1GHz ARM.
ARM processors are currently divided into three series: A series, R series, and M series, with the A series primarily targeting consumer electronics applications and having widespread use.
Computing: Netbooks, smart books, input boards, e-book readers, thin clients
Mobile: Smartphones, feature phones
Digital Appliances: Set-top boxes, digital TVs, Blu-ray players, game consoles
Automobiles: Infotainment, navigation
Enterprises: Laser printers, routers, wireless base stations, VOIP phones and devices
Wireless Infrastructure: Web 2.0, wireless base stations, switches, servers
The R series processors mainly target applications that require high real-time performance, such as aerospace and automotive electronics, offering high reliability, high availability, fault tolerance, and real-time response advantages.
The M series processors primarily target lower-end applications, initially aimed at replacing existing MCUs on the market.
DSP primarily targets applications that require high computational power, such as video image processing, intelligent robotics, digital wireless, broadband access, digital audio, high-resolution imaging, and digital motor control.
MCUs are the most widely used due to their cost control, allowing them to thrive in many applications where computational power is not as critical. It is believed that in the coming years, the key growth drivers for the MCU market will come from green energy, smart electronic devices, smart grids, and upgrades of electronic products like automotive electronics.
SoC applications are also very widespread, primarily because the architecture used by existing mainstream ARM chips is a form of SoC architecture. SoC is a broad concept, and many ARM and DSP systems are starting to adopt SoC methods to combine multiple devices with processors to form complex systems.
ARM is mainly equipped with LINUX, ANDROID, WINCE, etc. In terms of development difficulty, it is relatively more challenging to start compared to MCUs and DSPs, requiring developers to have a deep understanding of operating systems; from a cost perspective, the single-chip cost of ARM is higher than that of MCUs, mainly used in more complex systems to accelerate product launch and reduce hardware design barriers.
The MCU is the easiest to start with, quick to grasp, and has a lower development difficulty, making it widely used in low-end markets due to its low cost.
DSP is relatively easy to start with, but the cost of single chips is higher, mainly used in applications that require high computational power. Of course, DSP can also run operating systems, suitable for multitasking applications.
FPGA has a higher development difficulty and a relatively longer development cycle, in addition to its high single-chip cost.
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