Author: System on Chips

ARM Cortex-M CMSIS Framework and Its Role in Embedded Systems The ARM Cortex Microcontroller Software Interface Standard (CMSIS) is a vendor-independent hardware abstraction layer for microcontrollers based on ARM Cortex processors. CMSIS provides a standardized interface to processor features and peripherals, enabling consistent software development across different ARM-based devices. It includes core peripheral access, real-time…

Heterogeneous ARM Core Memory Sharing and Bus Architecture In modern embedded systems, heterogeneous ARM architectures are increasingly common, combining cores with different instruction sets, performance profiles, and even operating systems. A prime example is the integration of Cortex-A (application) and Cortex-M (microcontroller) cores on the same chip, such as the STM32MP1 series or NXP i.MX…

Persistent Data Storage Requirements in ARM Cortex-M4 The ARM Cortex-M4 microcontroller, based on the ARMv7-M architecture, is widely used in embedded systems for its balance of performance and power efficiency. One common requirement in such systems is the need to store persistent data, such as passwords, that must remain intact even after power cycles. This…

ARM Cortex-M7 High CPU Load Despite Higher Clock Speed The issue at hand revolves around a significant disparity in CPU load between two systems: one based on the ARM Cortex-M7 microcontroller (CYT4BFX) running at 160 MHz, and the other based on the ARM Cortex-M4 microcontroller (CYT2B9X) running at 80 MHz. Despite the Cortex-M7’s higher clock…

ARM Cortex-M4 Startup File Configuration and Application Integration The integration of the startup file (startup_stm32f4xx.s), application code (hello.c), and CMSIS files (system_stm32f4xx.c, stm32f4xx.h, and system_stm32f4xx.h) is a critical step in developing firmware for ARM Cortex-M4 microcontrollers. The startup file is responsible for initializing the microcontroller’s stack pointer, reset handler, and interrupt vector table. The application…

USB Connection Detection Challenges on Cortex-M7 OTG Peripheral Detecting a USB connection on a Cortex-M7 microcontroller, particularly when migrating from a K20 processor, involves understanding the differences in USB OTG (On-The-Go) peripheral implementations and register mappings. The K20 processor uses the LINESTATESTABLE field in the OTGSTAT register to reliably detect USB connections. However, the Cortex-M7,…

HSE, HSI, and PLL: Clock Sources and Multipliers in ARM Microcontrollers In ARM microcontrollers, the clock system is a critical component that determines the performance and power consumption of the device. The clock system typically consists of multiple clock sources and a Phase-Locked Loop (PLL) to generate the system clock. The High-Speed External (HSE) and…

ARM Cortex Pipeline Behavior with Nonpredicted Instructions Nonpredicted instructions in ARM architectures, such as ERET (Exception Return), have unique characteristics that can significantly impact pipeline performance. The ARM Technical Reference Manual (TRM) explicitly states that certain instructions are nonpredicted, meaning they do not follow the typical speculative execution path that most instructions do. This behavior…

Cortex-A55 AARCH32 State Configuration and Exception Handling at EL1 The ARM Cortex-A55 is a highly efficient mid-range processor core designed for a wide range of applications, from mobile devices to embedded systems. One of its key features is the ability to operate in both AARCH64 (64-bit) and AARCH32 (32-bit) execution states. However, transitioning the Cortex-A55…

ARM Cortex-M BusFault and MemManage Fault Instruction Skipping When developing firmware for ARM Cortex-M processors, encountering exceptions such as BusFault or MemManage Fault is not uncommon. These exceptions often arise due to invalid memory accesses, such as those caused by LDR (Load Register) or STR (Store Register) instructions attempting to access restricted or non-existent memory…