Architectures and Processors

ARMv8.1-A Access Flag Hardware Management Overview The ARMv8.1-A architecture introduces a feature known as hardware management of the Access flag, which is part of the memory management unit (MMU) functionality. The Access flag is a bit in the page table entries that indicates whether a particular page has been accessed. This flag is crucial for…

ARMv8 Stage 1 Translation and XN Bit Behavior in Hierarchical Descriptors The XN (Execute-Never) bit in ARMv8 architecture plays a critical role in memory protection by controlling whether a specific memory region can be used to fetch and execute instructions. In the context of ARMv8 Virtual Memory System Architecture (VMSA), the XN bit is present…

I2C Transaction Failure Between Raspberry Pi 3 Master and LPC1788 Slave The core issue revolves around the failure of I2C communication between a Raspberry Pi 3 acting as the I2C master and an LPC1788 microcontroller acting as the I2C slave. The Raspberry Pi 3 is unable to detect the LPC1788 slave device using the i2cdetect…

ARM Cortex-A9 Cache Coherency Challenges During Large DMA Transfers In ARM Cortex-A9-based systems, such as the CycloneV with dual Cortex-A9 cores, managing cache coherency during large Direct Memory Access (DMA) transfers can be particularly challenging. This is especially true when the Accelerator Coherency Port (ACP) is unavailable, forcing software to handle cache coherency manually. The…

ARM Cortex-M3 Heap Management and Runtime Environment Initialization The core issue revolves around the failure of the ARMCC V6.12 compiler to properly initialize the heap when using the C++ Standard Library’s std::queue on an STM32F103VB microcontroller. The program terminates in the _sys_exit() function, indicating a critical failure in the runtime environment. This failure is often…

EXC_RETURN Bit[4] and Floating Point Context Saving The ARM Cortex-M4 processor, particularly the M4F variant with a Floating Point Unit (FPU), handles the saving of the floating point context during exception handling through a combination of hardware mechanisms and configuration bits. The EXC_RETURN value, which is loaded into the Link Register (LR) upon exception entry,…

Keil MDK Device Pack Installation and NXP MKV46F256xxx15 Node Visibility The core issue revolves around the inability to locate the NXP MKV46F256xxx15 device node within the Keil Microcontroller Development Kit (MDK) environment. This problem typically manifests when users attempt to set up their development environment for NXP’s Kinetis KV4x series microcontrollers, specifically the MKV46F256xxx15 variant….

ARM Cortex-A9 MMU Translation Table Access and Interpretation The ARM Cortex-A9 processor, like many ARM cores, utilizes a Memory Management Unit (MMU) to handle virtual-to-physical address translation. The MMU relies on translation tables, which are hierarchical data structures stored in memory, to perform this translation. In Linux, the MMU translation tables are managed by the…

Cortex-A9 Boot Process and Secure World Initialization on NXP i.MX6 The Cortex-A9 processor, as part of the ARMv7-A architecture, supports TrustZone technology, which provides a secure environment for executing sensitive code. When the system boots, the processor starts in the secure state, specifically in the privileged Supervisor mode with the NS (Non-Secure) bit set to…

SPSR Initialization Issue with Unexpected RAZ Behavior The ARM Cortex-R4F processor, like many ARM cores, includes the Saved Program Status Register (SPSR), which is used to store the processor state when an exception is taken. The SPSR is a critical register for exception handling, as it allows the processor to restore the original state after…