Architectures and Processors

ARM Cortex-M4 Register Corruption After WFI/Sleep Mode in FreeRTOS Issue Overview The core issue revolves around the corruption of the CPU register R7 after the Cortex-M4 processor exits sleep mode initiated by the WFI (Wait For Interrupt) instruction. This corruption manifests specifically during the first sleep cycle after system power-up, leading to an assertion failure…

ARM Cortex-A57 Hardware Prefetcher Behavior and Cache Benchmarking Challenges The ARM Cortex-A57 is a high-performance processor core designed for applications requiring significant computational power, such as mobile devices, networking equipment, and embedded systems. One of its key features is the inclusion of hardware prefetchers, which are designed to improve performance by predicting and preloading data…

Cortex-A53 Unaligned Access Faults with SCTLR.A = 0 in AArch32 Mode The Cortex-A53 processor, a widely used ARMv8-A core, is designed to handle both AArch64 and AArch32 execution states. In AArch32 mode, the processor supports unaligned memory accesses for certain instructions, such as LDR and STR, when the System Control Register (SCTLR) alignment check bit…

Cortex-M7 MPU Region Reprogramming Challenges During Runtime Updates The Cortex-M7 Memory Protection Unit (MPU) is a critical component for ensuring memory safety and access control in embedded systems. However, reprogramming MPU regions at runtime, especially when updating attributes and ranges dynamically, introduces significant challenges. The primary concern is ensuring that the MPU region updates do…

ARMv8 Memory Model Definitions: Reads-from-Memory and Local Read Successor The ARMv8 architecture defines two critical concepts in its memory model: Reads-from-Memory and Local Read Successor. These concepts are foundational to understanding how memory operations are ordered and observed in a multi-core or multi-threaded environment. The distinction between these two terms is subtle but significant, especially…

ARM Cortex-A53 L1 Data Cache ECC Testing and Bit Error Detection L1 Data Cache ECC Testing Methodology and Feasibility The ARM Cortex-A53 processor, commonly used in embedded systems and SoCs like the Xilinx Ultrascale+, incorporates Error Correction Code (ECC) mechanisms to detect and correct bit errors in the L1 Data Cache (L1D). Testing the L1D…

Cortex-A53 Deadlock Manifestation and DSB SY Command Correlation The Cortex-A53 processor, part of the ARMv8-A architecture, is widely used in embedded systems for its balance of performance and power efficiency. However, under certain conditions, the processor can enter a deadlock state, particularly when executing the Data Synchronization Barrier (DSB SY) instruction. This deadlock manifests as…

ARM Core PMU and DSU_PMU: Separate Hardware Components with Distinct Roles The ARM Core Performance Monitoring Unit (Core PMU) and the DynamIQ Shared Unit Performance Monitoring Unit (DSU_PMU) are two distinct hardware components designed to monitor different aspects of system performance. The Core PMU is integrated within each ARM Cortex core and is responsible for…

ARM Cortex-M7 and Cortex-M85 FP32 Multiply-Add Throughput Discrepancies The ARM Cortex-M7 and Cortex-M85 processors are both high-performance microcontrollers designed for embedded systems, but they exhibit significant differences in their floating-point (FP32) multiply-add throughput. The Cortex-M7, while capable, shows a throughput of approximately 5-6 clock cycles per fused multiply-add (FMA) operation when utilizing ARM libraries. This…

NEON Data Loading Strategies for Cortex-A35’s In-Order Execution The ARM Cortex-A35 is a power-efficient processor with in-order execution, which means instructions are executed in the order they are fetched, without dynamic reordering. This characteristic has significant implications for utilizing the NEON SIMD (Single Instruction, Multiple Data) engine efficiently. NEON is designed to accelerate multimedia and…