Author: System on Chips

ARM Cortex-A53 STP Instruction Memory Corruption on AHB Bus The ARM Cortex-A53 processor, a widely used 64-bit core in embedded systems, is known for its efficiency and performance. However, subtle issues can arise when executing certain instructions under specific conditions. One such issue involves the STP (Store Pair) instruction, which is designed to store two…

Incorrect Heap Address Assignment in Cortex-M4 Custom Startup Code The issue revolves around the incorrect initialization of the heap memory region in a custom C++ startup code for the ARM Cortex-M4 processor, specifically targeting the STM32F407VGT6 microcontroller. The heap is intended to be located in the Core Coupled Memory (CCM) region starting at address 0x10000000,…

Cortex-M0 Boot Behavior and Fixed Reset Vector at 0x0000_0000 The ARM Cortex-M0 processor, like other Cortex-M series processors, is designed to start execution from a fixed reset vector located at address 0x0000_0000. This behavior is hardwired into the processor’s design and cannot be changed through software configuration alone. Upon reset, the Cortex-M0 fetches the initial…

Stack Misalignment Leading to Hard Fault on Interrupt Return When working with the ARM Cortex-M4 processor, such as the one found in the STM32 F407 microcontroller, handling interrupts correctly is crucial for stable system operation. One common issue that arises during interrupt handling is improper stack alignment, which can lead to a hard fault when…

SVC Pendability and Exception Entry Behavior in ARM Cortex-M The SuperVisor Call (SVC) exception in ARM Cortex-M processors is a critical mechanism for implementing system calls and transitioning between privilege levels. However, its behavior during exception entry and handling can be nuanced, particularly when higher-priority interrupts preempt the SVC exception. The ARMv7-M architecture defines specific…

ARM Trusted Firmware Boot Process and Cortex-A57 Workarounds The issue revolves around the failure to boot ARM Trusted Firmware (ATF) on a QEMU virtual machine emulating a Cortex-A57 processor. The user is attempting to run bare-metal firmware at Exception Level 2 (EL2) using ATF to manage multi-core bootstrapping via the Power State Coordination Interface (PSCI)….

Cortex-M7 VFMA Instruction Pipeline Behavior and Performance Degradation The Cortex-M7’s VFMA (Vector Fused Multiply-Add) instruction is a powerful floating-point operation that combines multiplication and addition in a single cycle, theoretically improving performance for computationally intensive tasks such as polynomial evaluation. However, the observed behavior in the provided benchmarks reveals significant pipeline stalls and performance degradation…

SMC Call Misrouting to Sync Exception at NS.EL1 Instead of EL3 When working with ARM Cortex-A53 processors, particularly in systems requiring secure and non-secure world transitions, a common issue arises when Secure Monitor Calls (SMC) fail to trap to Exception Level 3 (EL3) as expected. Instead, the processor remains in Non-Secure EL1 and triggers a…

NVIC Set Enable and Clear Enable Register Behavior in Cortex-M4 The behavior of the Nested Vectored Interrupt Controller (NVIC) in ARM Cortex-M4 processors, particularly regarding the Set Enable (ISER) and Clear Enable (ICER) registers, can be a source of confusion for developers. When enabling an interrupt using the NVIC_ISER register, it is observed that the…

Cache and MMU Enable/Disable Sequence in Bootloader Initialization When developing a custom bootloader for an ARM Cortex-A9 processor, such as the one found in the NXP i.MX6 DualLite, managing the caches and Memory Management Unit (MMU) is critical to ensure proper system initialization. The bootloader must initialize a large block of memory (e.g., 50 MB)…