Architectures and Processors

AxUSER Signal Instability During VALID Assertion in AXI Transfers In the context of AMBA AXI (Advanced eXtensible Interface) protocol, the stability of control and data signals during the assertion of the VALID signal is a fundamental requirement for ensuring reliable data transfers between masters and slaves. The AxUSER signal, which carries user-defined information such as…

ARM Cortex-A72 Exception Handling During ICC_IAR1_EL1 Access at EL1 The ARM Cortex-A72 processor, part of the ARMv8-A architecture, provides a sophisticated interrupt handling mechanism through the Generic Interrupt Controller (GIC). One of the critical registers in this context is the ICC_IAR1_EL1 (Interrupt Controller Interrupt Acknowledge Register 1), which is used to acknowledge and retrieve the…

ECC Functionality in ARM Cortex-A53: Overview and Operational Context Error Correction Code (ECC) is a critical feature in modern processors, particularly in safety-critical and high-reliability systems. In the ARM Cortex-A53, ECC is implemented to detect and correct bit flips in memory, ensuring data integrity. The Cortex-A53, being a widely used core in embedded and mobile…

IWIC Clock Dependency During Sleep Mode with Q-Channel Clock Gating The ARM Cortex-M55 processor, like many modern microcontrollers, employs advanced power management techniques to minimize energy consumption during idle or low-activity periods. One such technique is clock gating, where the clock signal to specific modules or the entire processor is temporarily halted to save power….

ARM Cortex-A Series: TTBR Update and TLB Invalidation Synchronization When working with ARM architectures, particularly the Cortex-A series, one of the most critical operations is the modification of the Translation Table Base Register (TTBR) and the subsequent invalidation of the Translation Lookaside Buffer (TLB). The TLB is a cache that stores recent translations of virtual…

ARM Cortex-M85 Dhrystone Benchmark Performance Shortfall with GCC The ARM Cortex-M85 processor is a high-performance microcontroller core designed for embedded applications requiring robust computational capabilities. It is part of the Cortex-M series, which is widely used in real-time systems, IoT devices, and other embedded applications. One of the key metrics used to evaluate the performance…

ARM AArch64 Instruction Encodings: UNDEFINED vs. Unallocated Behavior The ARM AArch64 architecture defines specific behaviors for instruction encodings that are either UNDEFINED or unallocated. These terms are critical for understanding how the processor handles invalid or reserved instruction patterns, and they have significant implications for software compatibility and forward compatibility across different versions of the…

ARM Cortex-A72 GICv3 Interrupt Handling Issues During EL3 to EL1 Transition The ARM Cortex-A72 processor, when paired with the Generic Interrupt Controller (GIC) version 3, can exhibit complex interrupt handling issues during transitions between Exception Levels (ELs), particularly when moving from EL3 to EL1. These issues often manifest as interrupts not being correctly handled after…

Cortex-A9 Atomic Variable Deadlock in Multi-Core Bare-Metal Systems In multi-core ARM Cortex-A9 systems, particularly in bare-metal environments, implementing atomic operations across cores can lead to deadlocks or infinite loops if the memory management unit (MMU) configuration is not properly set up. This issue often manifests when using atomic variables in shared memory regions, where one…

Cortex-R52 GICv3 Interrupt Handling Sequence and Stack Overflow The Cortex-R52 processor, when paired with a GICv3 interrupt controller, can experience a critical issue during interrupt handling where the processor fails to restore the context after handling an interrupt. This issue manifests when interrupts are triggered frequently, and the IRQ is unmasked before writing to the…