While the Cortex-M processor series may be positioned at the lower end of the performance spectrum, it still outshines many typical processors found in most microcontrollers (MCUs). For instance, the Cortex-M4 and Cortex-M7 processors, commonly used in high-performance MCUs, can operate at a maximum clock frequency of up to 400 MHz.
Of course, performance isn't the sole consideration when selecting a processor. In numerous applications, low power consumption and cost often rank as the top priorities for users. Hence, the Cortex-M processor family includes a variety of products to cater to diverse needs (refer to Table 1).
The distinction between Cortex-M and conventional ARM processors (such as ARM7TDMI and ARM9) lies in the significantly altered architecture. For example:
- It exclusively supports ARM Thumb instructions, which have been expanded in Thumb-2 to encompass both 16-bit and 32-bit instructions.
- For interrupt handling tasks, the Nested Vectored Interrupt Controller (NVIC) is embedded. The NVIC provides automatic priority scheduling, interrupt masking, nested configurations, and system exceptions.
- The interrupt handler (Handler) can be implemented as a regular C language function, featuring a vectorized interrupt processing mechanism. This eliminates the need for software to identify which interrupt requires servicing, ensuring decisive interrupted responses with minimal latency.
- Regarding the interrupt vector table, the branch instruction is redirected to the starting address of the interrupt and the system exception handler.
- Certain details related to the scratchpad block and programming modes have also been modified.
These changes imply that much of the combined-language code written for traditional ARM processors will need revision, and existing project files must be adjusted and recompiled when transitioning to Cortex-M.
An Overview of the Instruction Set
In most cases, software code is written in C or other high-level languages. Nonetheless, having a fundamental grasp of the instruction set supported by the Cortex-M processor can aid in determining which Cortex-M processor is best suited for a specific task. The Instruction Set Architecture (ISA) is a component of the processor architecture, and the Cortex-M processor can be categorized into several architectural types (refer to Table 2).
All Cortex-M processors support an instruction set known as Thumb. Following the introduction of Thumb-2 technology, the entire Thumb instruction set became quite extensive. However, different Cortex-M processors support subsets of instructions within the Thumb ISA, as illustrated in Figure 1.
The Cortex-M0/M0+/M1 processor is based on the ARMv6-M architecture and features a minimal instruction set comprising only 56 instructions, most of which are 16 bits, as depicted in Figure 1 for the smaller ellipse. Nevertheless, the scratchpad in the processor and the data being processed remain 32 bits. For most straightforward I/O control tasks and data processing, this compact instruction set suffices. Given its small size, only a limited number of logic gates are required to construct the processor. For example, the Cortex-M0 and Cortex-M0+ processors necessitate just 12,000 logic gates. However, some of these instructions cannot interact with higher-order registers (R8 to R12), and their capability to generate data dynamically is somewhat restricted. This reflects a trade-off between ultra-low-power processor design and performance.
The Cortex-M3 processor is based on the ARMv7-M architecture and supports a vast array of instruction sets, many of which are 32-bit instructions, enabling more efficient utilization of the higher-order registers. Additionally, it supports vector table branch instructions, conditional execution (via IT instructions), hardware division instructions, multiply-accumulate (MAC) operations, and variable bit-field operations.
The Cortex-M processors offer a range of capabilities tailored to various application requirements, making them versatile options for developers seeking optimized solutions across different domains.
3kw solar inverter,off grid solar inverter,soler inverter solar home system,hybrid solar system,off grid solar power system
Shenzhen Jiesai Electric Co.,Ltd , https://www.gootuenergy.com