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Author’s Note：Many readers have previously consulted me about the MPU and Cache usage related issues of the NXP S32K3xx series MCUs. The performance of a powerful dual-issue high-performance CPU core like the Cortex-M7 is often limited by the on-chip Embedded Flash (eFlash, with a working frequency ≤50MHz) when operating at high speeds (Core clock ≥150MHz), which cannot meet the CPU core’s instruction fetching requirements, leading to instruction pipeline “starvation“. To address this performance bottleneck during high-speed operation, the CPU core’s high-speed cache (Cache) was introduced. However, the introduction of Cache also brings about data consistency issues with multi-bus Masters (such as DMA and multi-core CPUs) and is closely related to the MPU configuration of the Cortex-M7 core (which supports up to 16 regions, with each region having up to 8 sub-regions, and various Cache strategies and data protection mechanisms suitable for different types of memory, such as Flash, SRAM, peripherals, etc.).
The use of the ARM Cortex-M7’s MPU and Cache presents a significant challenge for many developers transitioning from traditional 8-bit and 16-bit MCUs to 32-bit core MCUs in automotive electronic ECU application software and low-level software development — including related foundational knowledge concepts and configuration experience.
There are many blog articles and application notes from chip companies (such as AN0065) available online, but the content/knowledge points are either relatively scattered or lack clear and complete logical reasoning, which leads to more confusion for everyone. Recently, I happened to read an application note related to our YunTu, which is presented quite clearly and completely. I believe it is a valuable learning resource, and I would like to share it with everyone, hoping it will be helpful:
Tips：The source document of this application note can be downloaded from YunTu’s YCT tool:
For YCT downloads and obtaining documentation for YunTu automotive-grade MCU products, please refer to the following public account article (clicking the article title will directly jump to read):
《YunTu Automotive MCU Application Development and Technical Support (Development Environment Setup and Document Acquisition)》
May 10, 2024, in the Mountain City · Chongqing