Author: System on Chips

Cortex-A8 NEON Pipeline Stages and Multi-Cycle Instruction Behavior The Cortex-A8 NEON pipeline is a 10-stage pipeline designed to handle Single Instruction Multiple Data (SIMD) operations efficiently. The NEON engine is tightly integrated with the ARM core, allowing for parallel execution of scalar and vector instructions. The pipeline stages are divided into fetch, decode, issue, execute,…

GPT2 Timer Interrupt Not Triggering ISR Execution The core issue revolves around the failure of the ARM Cortex-A53 processor to execute the Interrupt Service Routine (ISR) for a GPT2 timer interrupt, despite the interrupt being correctly generated and pending in the Generic Interrupt Controller (GICv3). The timer interrupt is configured to trigger after 30 seconds,…

VTOR Register Configuration and Address Space Constraints in ARM Cortex-M3 The Vector Table Offset Register (VTOR) in the ARM Cortex-M3 processor is a critical component for managing the vector table’s location in memory. The vector table contains the initial stack pointer value and the addresses of exception and interrupt handlers. By default, the vector table…

GICT_ERRSTATUS.IERR and SYN_PPI_PWRDWN Errors During Redistributor Access The issue at hand involves the Generic Interrupt Controller (GIC) in a multi-cluster ARM-based system, specifically the GIC-600 implementation. The system comprises two clusters: Cluster 0 with 8 cores and Cluster 1 with 2 cores. When accessing the redistributor registers of Cluster 1, the GIC Translation (GICT) module…

PMU Event Counters Not Incrementing Despite Proper Configuration The Performance Monitoring Unit (PMU) in ARM Cortex-A72 processors is a powerful tool for profiling and analyzing system performance. However, a common issue arises when the event counters (PMXEVCNTR_EL0) remain at zero despite seemingly correct configuration and initialization. This problem is particularly perplexing because the cycle counter…

ARM Cortex-M Clock Stop Requirements During Signal Reconfiguration When working with ARM Cortex-M processors, particularly during low-power or system reconfiguration scenarios, it is often necessary to stop the CPU clock temporarily to modify certain critical signals such as reset, clamp, and EMA (External Memory Access) signals. This requirement arises from the underlying architecture and timing…

ARM Cortex-A76 Watchpoint Mechanism and Debug Exception Configuration The ARM Cortex-A76 processor provides a sophisticated debugging mechanism, including watchpoints, which allow developers to monitor specific memory addresses and trigger exceptions when certain access conditions are met. Watchpoints are configured using the Debug Watchpoint Value Register (DBGWVR) and Debug Watchpoint Control Register (DBGWCR). When a watchpoint…

ARM Cortex-M Stack Pointer Initialization Mechanism The ARM Cortex-M architecture employs a unique mechanism for initializing the Stack Pointer (SP) during the reset sequence. Unlike traditional processors where the stack pointer might be set explicitly by the first instruction in the reset handler, the Cortex-M series automatically loads the SP from the first entry of…

ARM Cortex-M33 WFI Behavior and UART4 Pending Interrupt Issue The STM32U599 microcontroller, based on the ARM Cortex-M33 core, is designed to provide low-power operation through the use of the WFI (Wait for Interrupt) instruction. The WFI instruction is a critical feature for power-sensitive applications, as it allows the CPU to enter a low-power state until…

ARM Chromebook Black Screen Due to nv-U-Boot SimpleFB and Kernel DTB Mismatch When upgrading the kernel and userland on an ARM-based Samsung Chromebook, a common issue arises where the screen turns black shortly after boot. This problem is often tied to the interaction between the nv-U-Boot firmware, specifically its SimpleFB implementation, and the kernel’s Device…