Architectures and Processors

VTOR Bit Allocation and Vector Table Address Constraints in Cortex-M7 The Vector Table Offset Register (VTOR) in ARM Cortex-M7 processors plays a critical role in defining the starting address of the vector table, which contains the initial stack pointer value and the exception handlers’ addresses. The VTOR register allows the vector table to be relocated…

XDMAC CNDA Register Behavior During DMA Completion Interrupts The XDMAC (Extended Direct Memory Access Controller) is a peripheral commonly found in ARM Cortex-M7 microcontrollers, particularly those from Microchip (formerly Atmel). It is used to manage high-speed data transfers between memory and peripherals without CPU intervention. One of the critical registers in the XDMAC is the…

ARM Cortex-A7 8-Stage Pipeline Architecture and Neon Integration The ARM Cortex-A7 processor is a highly efficient, low-power processor core designed for embedded and mobile applications. It features an 8-stage pipeline that balances performance and power efficiency, making it suitable for a wide range of devices. The pipeline stages are designed to maximize instruction throughput while…

MPIDR_EL1 Register and Affinity Levels in ARM AArch64 The MPIDR_EL1 (Multiprocessor Affinity Register) is a critical system register in ARM AArch64 architecture that provides information about the topology of the processor cores. This register is essential for operating systems and firmware to identify the core and cluster on which they are executing. The MPIDR_EL1 register…

Cortex-A53 Write-Through Memory Downgraded to Non-Cacheable The Cortex-A53 processor, a widely used ARMv8-A core, simplifies its coherency logic by treating memory regions marked as Inner Write-Through (WT) or Outer Write-Through as non-cacheable. This behavior is a design choice to reduce the complexity of cache coherency management, particularly in systems with multiple cores or when dealing…

ARM Cortex-A9 PTM Trace Extraction Challenges in ETB Buffer The ARM Cortex-A9 processor, widely used in embedded systems, features Program Trace Macrocell (PTM) and Embedded Trace Buffer (ETB) for real-time instruction and data tracing. PTM generates compressed trace packets that are stored in the ETB, a circular buffer within the processor. However, extracting meaningful trace…

Cortex-A55 L1 Cache Behavior with Write-Through Memory and Non-Cached L2/L3 The Cortex-A55 processor, as part of the ARMv8 architecture, implements a sophisticated memory hierarchy that includes L1, L2, and L3 caches. However, the behavior of these caches can vary significantly depending on the memory type and cacheability attributes assigned to specific memory regions. One of…

HGRANT Signal Deassertion Timing in Non-Locked and Locked Transfers The HGRANT signal in the ARM Advanced High-performance Bus (AHB) protocol plays a critical role in bus arbitration, determining which master gains access to the bus at any given time. The behavior of HGRANT during both non-locked and locked transfers is governed by specific rules in…

VTOR Configuration Challenges in Cortex-M33 Dual Security States The ARM Cortex-M33 processor, part of the ARMv8-M architecture, introduces a dual-security state model, enabling both Secure and Non-Secure worlds to operate independently. One critical aspect of this architecture is the Vector Table Offset Register (VTOR), which defines the base address of the vector table used for…

ARM Cortex-M Interrupt Handler Misdirection in C++ Due to Name Mangling When working with ARM Cortex-M processors, particularly when implementing interrupt handlers in C++, a common issue arises where the interrupt service routine (ISR) is not correctly linked to the intended function. This misdirection often results in the processor executing a default handler or an…