Author: System on Chips

ARM Cortex-M3 Reset Behavior and External Hardware Reset Requirements The ARM Cortex-M3 processor, as implemented in the STM32F107 microcontroller, does not natively support direct control of the nRST pin via software instructions. This limitation becomes particularly challenging when designing systems where the microcontroller must manage the reset behavior of external hardware circuits. In such scenarios,…

Understanding MPU Bufferable Attributes and Their Impact on Cortex-M4 Performance The ARM Cortex-M4 processor, widely used in embedded systems, provides a Memory Protection Unit (MPU) to enforce memory access rules and attributes. One of the key attributes configurable via the MPU is the "bufferable" attribute, which influences how write operations are handled by the processor’s…

ARM GICv4 and the Challenge of Hypervisor Interrupt Overhead in Virtualized Environments In modern ARM-based systems, virtualization has become a cornerstone for efficient resource utilization, enabling multiple guest operating systems (OS) to run concurrently on a single physical machine. However, one of the most significant performance bottlenecks in such environments is the handling of device…

Cortex-M4 Pipeline Behavior During Conditional Branches and NOP Insertion The Cortex-M4 processor, like many modern microprocessors, employs a pipeline architecture to enhance performance by allowing multiple instructions to be processed simultaneously. However, this pipeline can introduce complexities, especially when dealing with conditional branches and the insertion of NOP (No Operation) instructions. The observed behavior in…

ARM Cortex-M Memory Protection: MPU Limitations and TrustZone-M Advantages When securing firmware or application code in ARM Cortex-M systems, developers often rely on the Memory Protection Unit (MPU) to enforce memory access rules. The MPU divides memory into regions, each with configurable attributes such as read-only, write-only, or execute-never. While the MPU provides a basic…

ARMv7A User Mode Restrictions on CPSR.I Bit Modification The ARMv7A architecture, particularly when operating in User mode, imposes specific restrictions on the modification of the Current Program Status Register (CPSR) interrupt masks, specifically the I bit. The I bit in the CPSR controls the enabling and disabling of interrupts. When the I bit is set…

ARM Cortex-M4 Functional Unit Power Consumption Analysis The ARM Cortex-M4 processor, like many modern microcontrollers, is designed with power efficiency in mind. However, understanding the power consumption characteristics of its functional units—such as the Arithmetic Logic Unit (ALU), memory access units, and register banks—is critical for optimizing energy usage in embedded applications. Functional units are…

ARM Cortex-M23 Hard Faults During libc_init_array Execution in DS-5 Debugger When debugging an ARM Cortex-M23 application using the DS-5 Debugger, a hard fault occurs during the execution of the libc_init_array function. Specifically, the fault happens when the BLX R3 instruction is executed, and the value in the R3 register is 0xCFDFDFDF. This value points to…

ARMv7-M Program Counter Behavior During Instruction Execution The Program Counter (PC) in ARMv7-M architecture plays a critical role in determining the flow of instruction execution. Understanding its behavior is essential for debugging, especially when dealing with hard faults. The PC is not just a simple counter that increments after each instruction; its behavior can vary…

ARM Cortex-M3 Communication via WiFi and Bluetooth Modules The ARM Cortex-M3 microcontroller, such as the NXP LPC1768 or LPC1343, is a powerful and versatile processor widely used in embedded systems. One common requirement in such systems is enabling communication between two or more Cortex-M3 devices using wireless technologies like WiFi or Bluetooth. This post delves…