Architectures and Processors

ARM Cortex-M4 Load/Store Instruction Cycle Variations in Pre/Post-Index Addressing Modes The ARM Cortex-M4 processor, a widely used microcontroller core, employs load and store instructions to move data between memory and registers. These instructions support various addressing modes, including pre-index and post-index addressing. Pre-index addressing calculates the memory address by adding an offset to the base…

Cortex-A7 Boot from SPI NOR: Understanding the Boot Process and XIP Limitations The Cortex-A7 processor, as part of the ARMv7-A architecture, is widely used in embedded systems due to its balance of performance and power efficiency. One common use case involves booting from external SPI NOR flash memory, which is a cost-effective and space-efficient solution…

Cortex-M4 and PSRAM Voltage Level Mismatch Challenges When interfacing an ARM Cortex-M4 microcontroller operating at 3.3V with a PSRAM (Pseudo Static Random Access Memory) device operating at 1.8V, voltage level compatibility becomes a critical concern. The Cortex-M4, a widely used 32-bit RISC processor, is often employed in embedded systems where memory interfacing is a common…

ARM Cortex-A53 Shareability Domains and Cache Coherency in Multi-Cluster Systems The ARM Cortex-A53 processor, a popular choice for embedded systems and mobile applications, is designed with a focus on power efficiency and performance. One of its key features is the support for multiple cache levels and shareability domains, which are critical for maintaining cache coherency…

ARM T32 IT Instruction: Purpose and Common Misunderstandings The ARM T32 (Thumb-2) instruction set includes the IT (If-Then) instruction, which is a powerful yet often misunderstood feature. The IT instruction is used to conditionally execute up to four subsequent instructions based on the state of the ARM condition flags. This capability is particularly useful in…

ARM Cortex-M4 Load/Store Instruction Offset Timing Anomalies The ARM Cortex-M4 processor, a widely used microcontroller core, exhibits a peculiar behavior when executing load and store instructions with specific offset values. This behavior manifests as unexpected variations in clock cycle consumption for offsets starting from 30 (decimal) and beyond. The anomaly is particularly noticeable when the…

ARM Cortex-M Boot and Remap Signal Functionality in System Design Kit The relationship between BOOT and REMAP signals in ARM Cortex-M System Design Kits (CMSDK) is a critical aspect of system initialization and memory mapping. These signals are often misunderstood due to their nuanced behavior and the lack of explicit documentation in some design kits….

LPC1768 USB Host Capability and FAT32 Limitations The LPC1768 microcontroller, based on the ARM Cortex-M3 core, is a popular choice for embedded systems due to its robust peripheral set, including USB host capabilities. However, interfacing the LPC1768 with a 1TB external USB hard disk presents several challenges, particularly when dealing with the FAT32 file system….

GICv2 Virtualization and SPI Interrupt Handling Across vCPUs In a hypervisor environment where the Generic Interrupt Controller version 2 (GICv2) is virtualized, handling Shared Peripheral Interrupts (SPIs) across virtual CPUs (vCPUs) can introduce complex scenarios. Specifically, when an SPI targets multiple physical CPUs (e.g., CPU0 and CPU1), and the hypervisor is responsible for managing the…

ARMv8 Exception Levels and TrustZone Integration in KVM Virtual Machines The ARMv8 architecture introduces a sophisticated security model through its TrustZone technology, which partitions the system into Secure and Non-Secure worlds. This partitioning is crucial for isolating sensitive operations, such as cryptographic functions, from the rest of the system. However, when virtualization is introduced via…