Accessing PSTATE.nRW to Determine CPU Run State The Cortex-A57 processor, part of the ARMv8-A architecture, supports both AArch64 and AArch32 execution states. The execution state determines whether the processor is operating in 64-bit or 32-bit mode. The PSTATE.nRW bit is a critical register that indicates the current execution state of the CPU. When PSTATE.nRW is…
ARM Cortex-A9 to Cortex-A53 Program Execution Compatibility The transition from an ARM Cortex-A9 to an ARM Cortex-A53 processor involves several architectural considerations that can impact the execution of existing programs. The Cortex-A9, based on the ARMv7-A architecture, and the Cortex-A53, based on the ARMv8-A architecture, share some similarities but also have significant differences that must…
Cortex-M3 Frequency Limitations in 0.18 TSMC Process Nodes The Cortex-M3 processor, a widely used ARM core in embedded systems, is known for its balance of performance, power efficiency, and cost-effectiveness. However, determining its maximum operating frequency in a specific process node, such as TSMC’s 0.18µm technology, involves a complex interplay of factors. These factors include…
Cortex-R5 Divide-by-Zero Exception Handling Mechanism The Cortex-R5 processor, like many ARM cores, provides a mechanism to handle arithmetic exceptions such as divide-by-zero operations. This is controlled via the System Control Register (SCTLR), specifically the DZ (Divide-by-Zero) bit. When the DZ bit is set, the processor generates an Undefined Instruction exception upon encountering a divide-by-zero operation….
GIC-500 Stuck State After Cortex-A53 Software Reset The core issue revolves around the Generic Interrupt Controller (GIC-500) in the Armada 3720 SOC entering a stuck state after a software-initiated reset of the Cortex-A53 cores. The Cortex-M3 secure coprocessor is tasked with orchestrating the reset sequence, which includes resetting the Cortex-A53 cores, peripherals, and the GIC-500….
Understanding ADC Cycle Timing and Microcontroller Response When configuring an Analog-to-Digital Converter (ADC) on an ARM Cortex-M microcontroller, one of the most critical parameters to consider is the ADC cycle timing. The ADC cycle timing determines how long the ADC takes to complete a conversion, which directly impacts the performance and responsiveness of the microcontroller…
ARMv8-A Secure EL3 to Non-Secure EL2 Transition Exception Handling Issues Secure to Non-Secure State Transition and EL2 Entry Point Execution The core issue revolves around the transition from Secure EL3 to Non-Secure EL2 in the ARMv8-A architecture, where the system encounters an unexpected exception immediately after executing the first instruction at the EL2 entry point….
Understanding LDREX/STREX and the Challenge of Testing Failure Paths The ARM architecture provides a mechanism for atomic read-modify-write operations through the use of Load-Exclusive (LDREX) and Store-Exclusive (STREX) instructions. These instructions are fundamental for implementing synchronization primitives such as compare-and-swap (CAS), increment, decrement, and semaphore locks in multi-threaded or interrupt-driven environments. The LDREX instruction loads…
ARM Cortex-A53 PM_CCNTR Behavior During WFI and CPU Load Estimation The ARM Cortex-A53 processor, part of the ARMv8-A architecture, includes a Performance Monitoring Unit (PMU) that provides various counters to measure system performance. One such counter is the PM_CCNTR (Performance Monitor Cycle Counter), which increments at the frequency of the CPU clock. The PM_CCNTR can…
ARMv6-M MOV Instruction Limitations and High Register Access The ARMv6-M architecture, a subset of the ARMv6 architecture designed for microcontrollers, imposes certain limitations on instruction encoding and register usage to optimize for low-power and cost-sensitive applications. One such limitation is documented in the ARMv6-M Architecture Reference Manual, specifically in section "A6.7.40 MOV (register)" on page…