The British company ARM is a leader in the world of embedded microprocessors. ARM has always developed its own microprocessor core architectures and then licensed these architectural intellectual properties 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 large share of the 32-bit embedded microprocessor market.

Currently, with increasing demands on embedded systems, the comprehensive performance of embedded microprocessors, which are at their core, is also facing increasingly severe tests. The processing power 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, and the Cortex series is one such product. Today, let’s take a good look at the key points regarding ARM Cortex processors.

ARM Cortex Processor Series

ARM has renamed its products following the classic ARM11 to Cortex, dividing them into three categories: A, R, and M, aimed at serving various markets.

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

2. Cortex-R: Targeted at real-time systems.

3. Cortex-M: Microcontrollers.

ARM Cortex Processor Series—Cortex-A

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

ARM’s Cortex-A series processors are suitable for applications with high computational requirements, running rich operating systems, and providing interactive media and graphical experiences.

ARM Cortex Processor Series—Cortex-M

The Cortex-M processor family focuses more on the low-performance end, but these processors still outperform many traditional processors used in microcontrollers. For example, the Cortex-M4 and Cortex-M7 processors are applied 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 key selection criteria. Therefore, the Cortex-M processor family includes various products to meet different needs.

Unlike the older classic ARM processors (e.g., ARM7TDMI, ARM9), the Cortex-M processors have a very different architecture:

• Only supports ARM Thumb instructions, expanded to support both 16-bit and 32-bit instructions in the Thumb-2 version.

• Built-in nested vector interrupt control handles interrupt processing, automatically managing interrupt priority, interrupt masking, nested interrupts, and system exception handling.

• Interrupt handler functions can be programmed using standard C language, and the nested interrupt handling mechanism avoids using software to determine which interrupt needs to be processed. 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 old projects need to be updated and recompiled to migrate to Cortex-M products.

ARM Cortex Processor Series—Cortex-R

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

R5: Launched in 2010, based on the ARMv7-R architecture, it expands the functionality of the Cortex-R4 processor, supporting higher levels of system performance, increased efficiency and reliability, and enhanced error management in reliable real-time systems. These system-level features include high-priority low-latency peripheral ports (LLPP) and accelerator consistency ports (ACP), the former for fast peripheral read/write, and the latter for improved efficiency and 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 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 of performance. This processor supports tightly coupled memory (TCM), local shared memory, and flexible local memory systems for peripheral ports, allowing SoC designers to meet high standards for hard real-time requirements within limited chip resources.