This article introduces the naming of ARM series processors, with a focus on the Cortex-M series processors used in work.
Introduction
ARM has classic processors including ARM7, ARM9, and ARM11 families. After ARM11, products were renamed to Cortex and divided into A, R, and M categories, aiming to serve various markets. The Cortex series belongs to the ARMv7 architecture, which is the latest instruction set architecture of ARM as of 2010.
The ARMv7 architecture defines three clearly defined series: the “A” series targets cutting-edge virtual memory-based operating systems and user applications; the “R” series is aimed at real-time systems; and the “M” series is for microcontrollers.
Due to the different application fields, the technologies used in the Cortex processor series based on the v7 architecture are also different. Those based on v7A are called Cortex-A series, those based on v7R are called Cortex-R series, and those based on v7M are called Cortex-M series.
Series Introduction
1. Cortex-M Series:
Microcontroller Processors – Microcontroller processors are typically designed to be very small and have high energy efficiency. These processors usually have short pipelines and low maximum clock frequencies (although there are processors on the market that can run above 200MHz). Additionally, the new Cortex-M processor family is designed to be very easy to use. Therefore, ARM microcontroller processors are very successful and popular in the microcontroller and deep embedded system markets.
Provides low-cost optimization solutions for microcontroller-driven systems, applied to traditional microcontroller markets, smart sensors, automotive peripheral components, etc.
2. Cortex-A Series:
Application Processors – High-end processors aimed at mobile computing, smartphones, servers, and other markets. These processors operate at very high clock frequencies (over 1GHz) and support memory management units (MMUs) required by complete operating systems like Linux, Android, MS Windows, and mobile operating systems. If the planned product needs to run one of the above operating systems, you need to choose ARM application processors.
High-performance processors for open operating systems; applied to smartphones, digital TVs, smartbooks, and other high-end applications.
3. Cortex-R Series:
Real-time Processors – A high-performance processor series aimed at real-time applications, such as disk controllers, automotive transmission systems, and baseband control for wireless communications. Most real-time processors do not support MMUs, but typically have MPUs, caches, and other memory features designed for industrial applications. Real-time processors operate at relatively high clock frequencies (e.g., 200MHz to >1GHz) with very low response latencies. Although real-time processors cannot run full versions of Linux and Windows operating systems, they support a wide range of real-time operating systems (RTOS).
Aimed at real-time systems, meeting real-time control requirements; applied to automotive braking systems, power systems, etc.
Introduction to Cortex-M Processors
The Cortex-M series processors focus more on the low-performance end, but these processors are still quite powerful compared to many traditional processors used in microcontrollers. For example, 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 choosing 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:
Cortex-M4 Processor
It is an enhanced version of M3 with improved computing power, adding floating-point, DSP, and parallel computing to meet the needs of effective and easy-to-use control and signal processing functions in the mixed digital signal control market. The DSP performance of Cortex-M4 is better than that of 16-bit DSP chips, but not as good as that of 32-bit DSP chips. Its efficient signal processing capabilities, combined with the low power consumption, low cost, and ease of use of the Cortex-M processor series, aim to meet the flexible solutions of emerging categories aimed at motor control, automotive, power management, embedded audio, and industrial automation markets.
Cortex-M4 provides unparalleled capabilities to integrate 32-bit control with leading digital signal processing technologies to meet the high energy efficiency levels required by the market. The Cortex-M4 processor adopts an extended single-cycle multiply-accumulate (MAC) unit, optimized single-instruction multiple-data (SIMD) instructions, saturation arithmetic instructions, and an optional single-precision floating-point unit (FPU). These features are based on innovative technologies that characterize the ARMCortex-M series processors, including:
a) RISC processor core: high-performance 32-bit CPU with deterministic operations, low-latency 3-stage pipeline, reaching 1.25 DMIPS/MHz;
b) Thumb-2 instruction set: optimal mix of 16/32-bit instructions, code size 3 times smaller than 8-bit devices, no negative impact on performance. Provides optimal code density;
c) Low power modes: integrated sleep state support, multiple power domains, software control based on architecture;
d) Nested vectored interrupt controller (NVIC): low-latency, low-jitter interrupt response, no assembly programming required, interrupt service routines written in pure C language. Capable of excellent interrupt handling;
e) Tool and RTOS support: extensive third-party tool support, Cortex Microcontroller Software Interface Standard (CMSIS), maximizing software result reuse;
f) CoreSight debugging and tracing: JTAG or 2-pin serial wire debug (SWD) connection, supports multiprocessor, supports real-time tracing. In addition, this processor also provides an optional memory protection unit (MPU), offering low-cost debugging/tracing capabilities and integrated sleep states to increase flexibility. Embedded developers will be able to quickly design and launch impressive end products with the most features and the lowest power consumption and size.
The Cortex-M4 processor is designed to have various efficient signal processing capabilities suitable for the digital signal control market. The Cortex-M4 processor adopts extended single-cycle multiply-accumulate (MAC) instructions, optimized SIMD operations, saturation arithmetic instructions, and an optional single-precision floating-point unit (FPU). These features are based on innovative technologies that characterize the ARM Cortex-M series processors.
References
https://blog.csdn.net/erinblog/article/details/78156032
https://www.st.com/zh/microcontrollers-microprocessors/stm32f1-series.html
Source:Network