Architectures and Processors

Cacheable Memory Regions in ARM Cortex-M7 with MPU Disabled When the Memory Protection Unit (MPU) is disabled in an ARM Cortex-M7 processor, the memory attributes for different regions are determined by the default system address map. The Cortex-M7 core relies on this default address map to define the cacheability and memory attributes of various address…

ARM Cortex-M4 Cache Coherency Problems During DMA Transfers When working with ARM architectures, particularly in multi-core or multi-processing environments, understanding the relationship between shareability domains, cache maintenance, and memory barriers is critical. The ARM architecture provides mechanisms to ensure that memory operations are properly synchronized across different processing elements (PEs) within the same or different…

ARM Cortex-M7 Exception Handling and R7 Register Corruption During EXC_RETURN The ARM Cortex-M7 processor, known for its high performance and advanced features, is widely used in embedded systems. However, a critical issue has been observed where the R7 register is not preserved during exception return, specifically when executing the EXC_RETURN sequence. This issue manifests in…

Understanding SMMU and Huge Pages in ARM Architectures The System Memory Management Unit (SMMU) in ARM architectures plays a crucial role in managing memory access for devices that are not directly connected to the CPU. The SMMU translates virtual addresses to physical addresses, similar to how the CPU’s Memory Management Unit (MMU) operates. One of…

MemManageFault Triggered on Write to Read-Only Memory Region The MemManageFault is a critical exception in ARM Cortex-M4 processors that occurs when a memory access violation is detected. In this scenario, the fault is triggered by attempting to write to a read-only memory region configured via the Memory Protection Unit (MPU). When the fault occurs, the…

GPIO Access Issues on ARM Cortex-A55 in Secure EL3 State The core issue revolves around the inability to read or manipulate GPIO pins on the ARM Cortex-A55 core of the NXP i.MX93 processor while operating in the secure state at Exception Level 3 (EL3). The user is attempting to perform bare-metal development tasks, such as…

ARM Cortex-A Series PMU Events for Remote Memory Access and Snooping The ARM Cortex-A series processors, particularly those based on the ARMv8-A architecture, incorporate Performance Monitoring Units (PMUs) that provide detailed insights into system behavior, including memory access patterns and cache coherency operations. One critical aspect of performance analysis in multi-core and multi-cluster systems is…

ARM ACE5 DVM Operations: When to Use One-Part or Two-Part Messaging Distributed Virtual Memory (DVM) operations in ARM ACE5 are a critical aspect of managing memory coherence and virtual memory across multiple cores and devices in a system. The choice between one-part and two-part messaging in DVM operations is not arbitrary but is dictated by…

ARM CI-700 HN-F Invisible Cache Architecture and Context Switching Challenges The ARM CI-700 HN-F interconnect implements an invisible cache, a unique architectural feature that significantly impacts system performance and software behavior, particularly during context switches between cacheable and non-cacheable memory regions. Unlike traditional caches, the invisible cache operates beyond the point of coherency, meaning its…

ARM CPU with ASIC AES Encryption: Architectural Overview and Use Case The concept of integrating an ASIC-based AES encryption engine directly into the data bus of an ARM CPU is an intriguing architectural proposal. The primary goal is to create a system where all data flowing through the CPU’s data bus is transparently encrypted before…