How to select ARM Processors
Introduction
The widest range of microprocessor cores for almost all application markets. Explore ARM. Performance, power & cost requirements for almost all application markets, processors are crucial. The system performance depends heavily on its hardware; this article will guide you through a study of the ARM Processor and be of great assistance in your decision-making.
A Brief Introduction to ARM
Figure 1. ARM Processors Roadmap
Before 2003, there are classic ARM Processors which are including ARM7(ARMv4 Architecture), ARM9(ARMv5 Architecture), ARM11(ARMv6 Architecture). ARM7 has no MMU (memory management unit), cannot run multi-user multi-process system such as Linux and WinCE. Only can run system such as ucOS and ucLinux which do not need MMU. ARM9 and ARM11 are embedded CPUs with MMU, which can run Linux.
After 2003, When it came to the ARMv7 architecture, it was named after Cortex and divided into three series: Cortex-A, Cortex-R, and Cortex-M.
- Cortex-A — application processor cores for a performance-intensive systems
- Cortex-R – high-performance cores for real-time applications
- Cortex-M – microcontroller cores for a wide range of embedded applications
Simply put, Cortex-A series are suitable for applications that have high computing requirements, run rich operating systems, and provide interactive media and graphics experience. Cortex-R are suitable for that require reliability, high availability, fault tolerance, maintainability and real-time response. Cortex-M series are aimed at cost and power-sensitive MCUs and end applications.
Cortex-A VS Cortex-R VS Cortex-M
Cortex-A
The Cortex-A category of processors is dedicated to Linux and Android devices. Any devices – starting from smartwatches and tablets and continuing with networking equipment – can be supported by Cortex-A processors.
- Cortex-A processors (A5, A7, A8, A9, A12, A15 and A17) is based on the ARMv7-A architecture
- The set of common features for A-processors includes a media processing engine (NEON), a tool for security purposes (Trustzone), and various supported instruction sets (ARM, Thumb, DSP etc.)
- The main features of Cortex-A processors are top performance and brilliant power efficiency closely bundled to provide users with the best service possible
The main characteristics of Cortex-A processor:
Cortex-A5: The Cortex A5 is the smallest and lowest power member of the Cortex A series, but it can still demonstrate multicore performance, it is compatible with A9 and A15 processors.
Cortex-A7: The power consumption of A7 is nearly the same as A5, But the performance provided by the A7 is 20% higher than A5 as well as full architectural compatibility with Cortex-A15 and Cortex-A17. The Cortex-A7 is an ideal choice for cost -sensitive smartphone and tablet implementations.
Contrex-A15: The Cortex-A15 is the highest performance member of this series, providing twice the performance than A9. A15 finds its application in high-end devices, low-power servers, and wireless infrastructure. This is the first processor support for data management and virtual environment solutions.
Contrex-A17: The Cortex-A17 demonstrates 60% higher performance than that of the A9. The main aim is satisfying the needs of premium-class devices.
Contrex-A50: Contrex-A50, latest series, are built on the ARMv8 architecture and bring with them support for Arch64-bit an energy-efficient system. An obvious reason for the move to 64-bit is the support of more than 4GB of physical memory, which is already achieved on Cortex-A15 and Cortex-A7.
Cortex-R
Cortex-R processors target high-performance real-time applications such as hard disk controllers, networking equipment media players, and other similar devices, Furthermore, it also great support for the automotive industry such as airbags, braking systems and engine management.
Cortex-R4: Cortex-R4 is well suited for automotive applications. It can be clocked up to 600 MHz, has an 8-stage pipeline with dual-issue, pre-fetch and a low latency interrupt system making it ideal for safety critical systems.
Cortex-R5: Cortex-R5 extends features offered by R4 and adding increased efficiency, reliability and enhance error management. The dual-core implementation makes it possible to build very powerful, flexible systems with real-time responses.
Cortex-R7: The Cortex-R7 significantly extends the performance. They feature an 11-stage pipeline and enable both out-of-order execution and high-level branch prediction. Tools can be implemented for lock-step, symmetric, and asymmetric multiprocessing. The generic interrupt controller is another significant feature that should be mentioned.
Cortex-M
Cortex-M designed specifically to target MCU market. The Cortex-M series is built on the ARMv7-M architecture (used for Cortex-M3 and Cortex-M4), and the smaller Cortex-M0+ is built on the ARMv6-M architecture. It is safe to say that the Cortex-M has become for the 32-bit world what the 8051 is for the 8-bit – an industry-standard core supplied by many vendors. The Cortex-M series can be implemented as a soft core in an FPGA, for example, but it is much more common to find them implemented as MCU with integrated memories, clocks and peripherals. Some are optimized for energy efficiency, some for high performance and some are tailored to a specific market segment such as smart metering
For applications that are particularly cost sensitive or are migrating from 8-bit to 32-bit, the smallest member of the Cortex-M series might be the best choice.
Cortex-M0: The Cortex-M0+ uses the Thumb-2 instruction set and has a 2-stage pipeline. Significant features are the bus for single-cycle GPIO and the micro trace buffer.
Cortex-M3&M4: The Cortex-M3 and Cortex-M4 are very similar cores. Each offers a 3-stage pipeline, multiple 32-bit busses, clock speeds up to 200 MHz and very efficient debug options. The significant difference is the Cortex-M4 core’s capability for DSP. The Cortex-M3 and Cortex-M4 share the same architecture and instruction set (Thumb-2). If your application requires floating point math, you will get this done considerably faster on a Cortex-M4 than you will on a Cortex-M3. That said, for an application that is not using the DSP or FPU capabilities of the Cortex-M4, you will see the same level of performance and power consumption on a Cortex-M3. In other words, if you need DSP functionality, go with a Cortex-M4. Otherwise, the Cortex-M3 will do the job.
Conclusion
Figure 2. Cortex overview
ARM processors offer a variety of capabilities for different purposes. With a little bit of thought and investigation, you will be able to find the right processor that suits your application needs. whether it’s for a high-end tablet or an ultra-low-cost wireless sensor node.
It is a challenge to make the right choice of Cortex core and turn the idea into reality. But a team of experienced professionals can take care of all the issues and implement concepts of any complexity.
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Our hardware team can produce prototypes in the shortest time according to your design ideas and needs. Our software team can help you customize all the functions of the cutting driver layer.
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