Author: System on Chips

Cortex-R8 AXI Unaligned Memory Access Behavior The Cortex-R8 processor, like many ARM cores, has specific requirements and behaviors when it comes to handling unaligned memory accesses. An unaligned memory access occurs when a data transfer operation targets an address that is not a multiple of the data size being accessed. For example, attempting to write…

ARM Cortex-M Interrupt Context Switching: Register State Changes When an interrupt occurs in an ARM-based processor, the architecture performs a series of automatic actions to save the current execution context and transition to the interrupt service routine (ISR). The Program Counter (PC/R15), Stack Pointer (SP/R13), and Link Register (LR/R14) are critical registers that undergo specific…

ARMv8 Page Size Determination Challenges in Non-Secure EL1 Stage 1 Determining the page size in ARMv8 architecture, particularly for Non-Secure EL1 Stage 1, is a critical task for system developers and kernel programmers. The ARMv8 architecture supports multiple page sizes, and the actual page size used can vary depending on the implementation and configuration of…

ARM Cortex-M4 LDRD Instruction and UNDEFINSTR Hard Fault Analysis The ARM Cortex-M4 is a widely used microcontroller core known for its efficiency and performance in embedded systems. However, certain edge cases can lead to unexpected behavior, such as the UNDEFINSTR (Undefined Instruction) hard fault. This issue is particularly perplexing when it involves the LDRD (Load…

Interrupt Detection Challenges in Preemptive Scheduling and UART Handling Interrupt detection and management are critical aspects of embedded systems, particularly when dealing with real-time operating systems (RTOS) and peripheral communication protocols like UART. The ARM Cortex-M series, including the Cortex-M0 and Cortex-M4, provides a robust framework for handling interrupts, but developers often face challenges in…

Understanding the Need for Secure Monitor Call (SMC) and Monitor Mode in ARM Cortex-A9 with TrustZone The ARM Cortex-A9 processor, particularly when equipped with TrustZone technology, introduces a robust security model that partitions the system into secure and non-secure states. This partitioning is crucial for isolating sensitive operations and data from non-secure applications. However, transitioning…

ARM Cortex-A53 FIQ Configuration Challenges at EL1 Configuring Fast Interrupt Requests (FIQs) at Exception Level 1 (EL1) on an ARM Cortex-A53 processor with a Generic Interrupt Controller version 2 (GICv2) presents a unique set of challenges, particularly when operating within the Linux kernel environment. The primary issue revolves around the lack of direct support for…

NSACR.TL Bit Flipping and Aperiodic Changes in Non-Secure State The Non-Secure Access Control Register (NSACR) in ARM Cortex-A9 processors with TrustZone technology is a critical register that governs access to certain features and functionalities in the non-secure state. One of the key bits in this register is the NSACR.TL bit (bit 17), which controls whether…

ARM Cortex-A9 MPCore MMU Configuration and System Hang During Initialization The ARM Cortex-A9 MPCore processor is a popular choice for embedded systems requiring multicore capabilities. However, configuring the Memory Management Unit (MMU) in a bare-metal environment, especially in a multicore setup, can be challenging. The primary issue discussed here revolves around the system hanging during…

STM32F103C8T6 USB Communication Failure and Debugging Access Problems The STM32F103C8T6, commonly referred to as the "Blue Pill" board, is a popular development platform for ARM Cortex-M3 microcontrollers. A recurring issue with this board involves USB communication failures and the inability to establish a debugging connection unless the Boot0 jumper is set to 3.3V. This problem…