As we all know, ARM has renamed its products following the classic ARM11 processor to the Cortex name, dividing them into three categories: A, R, and M, aimed at serving various markets, which corresponds to the three letters of ARM’s English abbreviation. The Cortex series belongs to the ARMv7 architecture, which was the latest instruction set architecture of ARM until 2010. (The ARMv8 architecture was introduced at TechCon in 2011.) The ARMv7 architecture defines three clearly defined series: the “A” series for cutting-edge virtual memory-based operating systems and user applications; the “R” series for real-time systems; and the “M” series for microcontrollers. Now, we will introduce the “pork knuckle,” which is the Cortex-M family of processors under the Cortex series. Please listen carefully.
1. Development of the Cortex-M Family
After years of development, the Cortex-M family has evolved from the initial low-cost Cortex-M0 and the energy-efficient Cortex-M0+ processors to the currently flexible Cortex-M33 and the high-performance Cortex-M7 processors, resulting in seven different models of processors with varying performance parameters, as shown in the performance comparison below.
Of course, when evaluating a processor’s advantages and disadvantages, it is not just about performance; suitability is crucial. For example, high-performance processors often have high power consumption, which poses a heat dissipation problem, while low-power, high-efficiency processors may lack performance. Therefore, when selecting a processor, one must consider what functions the product leans towards, what applications it will be used in, etc. This way, a suitable processor can be selected based on actual needs.
The large number of processors in the Cortex-M family, with varying performance, meets the needs of different customers, allowing ATMEL to have over 40 ARM partners, including leading suppliers such as NXP Semiconductors, STMicroelectronics, Texas Instruments, and Toshiba. Using standard processors enables ARM partners to create devices with consistent architecture while allowing them to focus on creating excellent device implementations. This means that the core of everyone’s devices is the same, and using processors from the same company allows their devices to be well compatible, relieving suppliers from worrying about compatibility between devices and allowing them to focus on creating better products.
2. Why Choose Cortex-M
This section will briefly introduce the currently popular M0, M3, and M4, and discuss the reasons for choosing them.
1. Why Choose Cortex-M0
It is rightly said to be the smallest ARM processor with the lowest power consumption, as the Cortex-M0 processor consumes only 85 µW/MHz (0.085 milliwatts) within an area of less than 12K gates, unmatched by any other processor in the entire ARM series. The code density and energy efficiency advantages of M0 mean it is a naturally cost-effective upgrade for various applications in 8/16-bit devices while retaining tool and binary upward compatibility with the feature-rich Cortex-M3 processor.
Simplistically, M0 has only 56 instructions, making it easy to quickly master the entire Cortex-M0 instruction set (if needed); however, its C language-friendly architecture means this is not necessary. The available deterministic instructions and interrupt timing make calculating response times very easy.
M0’s optimized connectivity is designed to support low-power connections such as Bluetooth Low Energy (BLE), IEEE 802.15, and Z-wave, especially in such analog devices: these analog devices are increasing their digital capabilities to effectively preprocess and transmit data.
2. Why Choose Cortex-M3
As one of the few processors with high performance and low dynamic power consumption, the Cortex-M3 processor offers leading efficiency: 12.5 DMIPS/mW based on 90nm G technology. Combining integrated sleep modes with optional state retention functions, the Cortex-M3 processor ensures that there is no compromise for applications that require both low power consumption and excellent performance.
The full functionality allows the M3 processor to execute the Thumb®-2 instruction set for optimal performance and code size, including hardware division, single-cycle multiplication, and bit field operations. The Cortex-M3 NVIC is designed to be highly configurable, providing up to 240 system interrupts with individual priorities, dynamic priority resetting capabilities, and integrated system clocks.
3. Why Choose Cortex-M4
The ARMCortexM4 processor is the latest embedded processor developed specifically by ARM, enhancing the computing power based on the M3, adding floating-point, DSP, and parallel computing capabilities to meet the needs for effective and easy-to-use control and signal processing functions in the mixed digital signal control market. Its efficient signal processing capabilities combined with the low power consumption, low cost, and ease of use advantages of the Cortex-M processor series provide flexible solutions for emerging categories aimed at motor control, automotive, power management, embedded audio, and industrial automation markets.
In summary, as mentioned earlier, when selecting a processor, it is not just about the quality of the processor, but suitability is the most important!
Source: China Electric Network
