As we all know, ARM Holdings in the UK is a leader in the world of embedded microprocessors. ARM has always developed its microprocessor core architecture and licensed the intellectual property of these architectures to various chip manufacturers. The streamlined CPU architecture, efficient processing capabilities, and successful business model have brought ARM tremendous success, allowing it to quickly capture a majority of the 32-bit embedded microprocessor market share.

Currently, as the requirements for embedded systems are increasing, the overall performance of embedded microprocessors, which are at their core, is also facing increasingly severe tests. The processing capability of a high-end smartphone today can almost match that of a laptop from a few years ago. To meet market demands, ARM is also accelerating the development of their latest ARM architecture, with the Cortex series being such a product. So today, let’s take a closer look at the knowledge points of ARM Cortex series processors.

ARM Cortex Series Processors

After the classic ARM11 processor, ARM began to name its products with Cortex, dividing them into three categories: A, R, and M, aimed at serving various different markets.

     1. Cortex-A: For cutting-edge operating systems based on virtual memory and user applications

     2. Cortex-R: For real-time systems

     3. Cortex-M: Microcontrollers

ARM Cortex Series Processors – Cortex-A

The ARM Cortex-A series is a series of application processors for complex operating systems and user applications. Cortex-A series processors support ARM, Thumb, and Thumb-2 instruction sets.

The Cortex-A series processors from ARM are suitable for application areas that have high computational requirements, run rich operating systems, and provide interactive media and graphics experiences.

As shown in the figure, the green parts are all v7-A architectures, and the blue ones are v8-A architectures. Essentially, the green ones can support both 32 and 64 bits, except for A32, which only supports 32 bits. On the right side of each part, for example, the most efficient part at the top A15-A73 is the most efficient, followed by the part that focuses on overall efficiency, the middle part is relatively efficient, and the bottom bar is the best in terms of battery efficiency.

If we must rank them from high to low, they can be roughly sorted as follows: Cortex-A73 processor, Cortex-A72 processor, Cortex-A57 processor, Cortex-A53 processor, Cortex-A35 processor, Cortex-A32 processor, Cortex-A17 processor, Cortex-A15 processor, Cortex-A7 processor, Cortex-A9 processor, Cortex-A8 processor, Cortex-A5 processor.

ARM Cortex Series Processors – Cortex-M

The Cortex-M processor family focuses more on the low-performance end, but these processors are still quite powerful compared to many traditional processors used in microcontrollers. For example, the Cortex-M4 and Cortex-M7 processors are used in many high-performance microcontroller products, with maximum clock frequencies reaching 400MHz.

Of course, performance is not the only criterion for selecting a processor. In many applications, low power consumption and cost are critical selection criteria. Therefore, the Cortex-M processor family includes various products to meet different needs:

Unlike older classic ARM processors (such as ARM7TDMI, ARM9), Cortex-M processors have a very different architecture. For example:

— Only supports ARM Thumb instructions, extended to simultaneously support 16-bit and 32-bit instructions in the Thumb-2 version

— The built-in nested vector interrupt controller is responsible for interrupt handling, automatically handling interrupt priorities, interrupt masking, interrupt nesting, and system exception handling.

— Interrupt handling functions can be programmed using standard C language, and the nested interrupt handling mechanism avoids using software to determine which interrupt needs to be responded to. At the same time, the interrupt response speed is deterministic and low-latency.

— The vector table changes from jump instructions to the starting addresses of interrupt and system exception handling functions.

— The register set and certain programming modes have also changed.

These changes mean that many assembly codes written for classic ARM processors need to be modified, and older projects need to be changed and recompiled to migrate to Cortex-M products.

ARM Cortex Series Processors – Cortex-R

R4: The first embedded real-time processor based on the ARMv7-R architecture. It is dedicated to large capacity deep embedded SoC applications, such as hard disk drive controllers, wireless baseband processors, consumer product mobile MTK platforms, and electronic control units for automotive systems.

R5: Launched in 2010, based on the ARMv7-R architecture, expanding the functionality of the Cortex-R4 processor, supporting higher levels of system performance, improving efficiency and reliability, and enhancing error management in reliable real-time systems. These system-level features include low-latency peripheral ports (LLPP) and accelerator consistency ports (ACP), the former for fast peripheral read and write, and the latter for improving efficiency and achieving more reliable high-speed cache consistency with external data sources.

Based on 40 nm G process technology, the Cortex-R5 processor can operate at nearly 1 GHz, providing 1,500 Dhrystone MIPS performance. This processor offers a highly flexible and efficient dual-cycle local memory interface, allowing SoC designers to minimize system costs and power consumption.

R7: The Cortex-R7 processor is the highest performance processor in the Cortex-R series. It is the standard for high-performance real-time SoCs. The Cortex-R7 processor is designed for implementation based on advanced chip processes from 65 nm to 28 nm, with a design focus on improving energy efficiency, real-time responsiveness, advanced features, and simplifying system design. Based on 40 nm G process technology, the Cortex-R7 processor can operate at frequencies exceeding 1 GHz, providing 2700 Dhrystone MIPS performance. This processor offers a flexible local memory system that supports tightly coupled memory (TCM), local shared memory, and peripheral ports, allowing SoC designers to meet stringent real-time requirements within limited chip resources.

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