Author: System on Chips

ARM Cortex-M4 PLD Instruction Behavior and Cache Preloading The ARM Cortex-M4 processor, a member of the ARMv7-M architecture family, is widely used in embedded systems for its balance of performance and power efficiency. One of the instructions that has raised questions among developers is the Preload Data (PLD) instruction. The PLD instruction is intended to…

ARM Cortex-R5 Exception Vector Table Configuration and TCM Memory Mapping The ARM Cortex-R5 processor, like many ARM cores, relies on an exception vector table to handle interrupts, exceptions, and other critical events. The vector table is a crucial part of the system’s operation, as it contains the addresses of the handlers for these events. The…

ARM Cortex-M0+ USART RX Character Loss and Interrupt Pending Anomalies The issue at hand involves the loss of UART RX characters on an STM32L071 microcontroller, which utilizes the ARM Cortex-M0+ core. The problem manifests when using the HAL_UART_ReceiveIT function to queue a single character buffer, which is then re-queued from the HAL_UART_RxCpltCallback function. The received…

ARMv8 Cortex-A53 Debug Data Transfer Register (DBGDTRTX_EL0) Access Challenges The Debug Data Transfer Register (DBGDTRTX_EL0) in ARMv8 architectures, particularly in the Cortex-A53 processor, is a critical component for debugging operations. It allows developers to transfer data between the processor and external debug tools. However, accessing this register can be fraught with challenges, especially when attempting…

Understanding NIC400 AHB-Lite Interface Roles: Manager vs. Subordinate The NIC400 interconnect fabric is a highly configurable and scalable network interconnect component designed by ARM for use in System-on-Chip (SoC) designs. It supports multiple AMBA protocols, including AHB-Lite, which is a simplified version of the Advanced High-performance Bus (AHB) protocol. AHB-Lite is widely used in embedded…

Cortex-A9 PL310 L2 Cache Clean-Invalidate Sequence and CPU Crash The Cortex-A9 PL310 L2 cache controller is a critical component for ensuring data coherency and performance in ARM-based systems. However, improper handling of cache maintenance operations, particularly clean-invalidate sequences, can lead to system instability or outright CPU crashes. This issue is particularly evident when performing cache…

ARM Cortex-A9 DDR RAM Access Issues During JTAG Debugging The core issue revolves around the inability to reliably access DDR RAM on the Cyclone V HPS (Hard Processor System) via JTAG using OpenOCD. The user successfully halts the Cortex-A9 processor and can read from certain memory locations (e.g., 0x00000000), but encounters errors when attempting to…

Cortex-A Exception Model and Context Switching Requirements The Cortex-A series processors, unlike their Cortex-M counterparts, employ a fundamentally different exception and interrupt handling model. Cortex-M processors utilize a simplified exception model tailored for real-time operating systems (RTOS) and embedded applications, where PendSV (Pendable Service Call) is a critical exception used for context switching. PendSV is…

Cortex-A78 NEON Instruction Pipeline Concurrency and Execution Timing The Cortex-A78 is a high-performance ARM processor core designed for advanced applications requiring significant computational power. One of its key features is the Advanced SIMD (NEON) engine, which accelerates vectorized operations. Understanding the timing and concurrency of NEON instructions is critical for optimizing performance, especially in scenarios…

ARM Cortex-M0+ Timer Interrupt Fluctuations Due to Tail Chaining and Priority Conflicts The issue at hand involves an ARM Cortex-M0+ microcontroller, specifically the NXP MKE04Z128VLH4, where two timer interrupts are configured with periods of 625 microseconds and 1 millisecond. The 625 microsecond timer interrupt exhibits fluctuations when observed via a GPIO toggle and a digital…