ARM VETX.32 Bitwise Rotate Performance Bottleneck on ARM7A The ARM VETX.32 instruction set includes specialized operations for vectorized bitwise manipulations, which are commonly used in embedded systems for tasks such as cryptography, signal processing, and data compression. One such operation is the in-place bitwise rotate, denoted as VETX.32 q1, q1, q1, #3, which rotates the…
Cortex-M0 Vector Table Fetch Behavior and VTOR Absence The ARM Cortex-M0 processor, unlike its more advanced siblings such as the Cortex-M3, M4, and M7, does not feature a Vector Table Offset Register (VTOR). This architectural decision has significant implications for how the processor handles interrupt vectors. On the Cortex-M0, the vector table is always fetched…
Secure SPI Peripheral Activation Limitations on STM32MP157-DK1 The STM32MP157-DK1 development board, featuring an ARM Cortex-A processor with TrustZone security, presents a unique challenge when attempting to configure SPI peripherals for secure-side operations. Specifically, the board restricts secure-side SPI usage to SPI 6, which is not externally accessible. This limitation raises questions about the feasibility of…
ARM Cortex-M33 Secure to Non-Secure State Transition Challenges The ARM Cortex-M33 processor, part of the ARMv8-M architecture, introduces a robust security model that partitions the system into Secure and Non-Secure states. This partitioning is crucial for applications requiring high levels of security, such as IoT devices, where sensitive data and critical operations must be isolated…
STM32F103 SCU Peripheral Missing in Keil MDK-ARM Environment The STM32F103 microcontroller, based on the ARM Cortex-M3 architecture, is a popular choice for embedded systems development due to its balance of performance, power efficiency, and peripheral integration. However, when starting with this microcontroller, especially for those transitioning from other ARM-based platforms, there can be confusion regarding…
ARM Cortex-M FPU Detection via Media and FP Feature Registers The ARM Cortex-M series of processors, widely used in embedded systems, often include a Floating-Point Unit (FPU) to accelerate floating-point arithmetic operations. However, not all Cortex-M processors implement an FPU, and even among those that do, the type of FPU (e.g., VFPv4, VFPv5-SP, VFPv5-DP) can…
ARM Cortex-M7 Cache Hit Rate Measurement Challenges The ARM Cortex-M7 processor is a high-performance embedded processor designed for real-time applications, featuring a Harvard architecture with separate instruction and data buses, and optional instruction and data caches. Unlike higher-end ARM processors such as the Cortex-R5, the Cortex-M7 does not include a Performance Monitoring Unit (PMU). The…
ARM Cortex-A53 EL3 to EL1 Transition Failure During ERET Execution The transition from Exception Level 3 (EL3) to Exception Level 1 (EL1) on the ARM Cortex-A53 processor is a critical operation that involves configuring several system registers and ensuring the correct state of the processor before executing the Exception Return (ERET) instruction. The provided code…
ARM Cortex-M4 Cache Coherency Problems During DMA Transfers The core issue revolves around the ARMv8 memory ordering model, specifically concerning the behavior of speculative stores in the context of lock acquisition code. The concern arises from the example code provided in the ARM Architecture Reference Manual (ARM DDI 0487D.a) section K11.3.1, which demonstrates how to…
ARM Cortex-R4F CPSR/SPSR J Bit: Purpose and Behavior The J bit in the Current Program Status Register (CPSR) and Saved Program Status Register (SPSR) of the ARM Cortex-R4F processor is a single-bit field that plays a specific role in the processor’s operation. The CPSR and SPSR are critical components of the ARM architecture, as they…