USART0 Communication Failure with Incorrect Baud Rate Configuration The ATSAM3X8E microcontroller, part of the SAM3X series from Microchip (formerly Atmel), is a powerful ARM Cortex-M3-based device widely used in embedded systems. One of its key peripherals is the Universal Synchronous Asynchronous Receiver Transmitter (USART), which facilitates serial communication. In this case, the user attempted to…
ARM Cortex-M UDIV Instruction Performance and Latency Issues The ARM Cortex-M series of processors, particularly those based on the ARMv7-M and ARMv8-M architectures, include support for hardware division through the UDIV (Unsigned DIVide) instruction. While this instruction simplifies division operations in software, it is often associated with performance bottlenecks, especially in real-time embedded systems where…
Understanding the EL3 Execution Requirement for Custom Applications on Cortex-A53 The requirement to run custom applications at Exception Level 3 (EL3) on a Cortex-A53 core, particularly on an i.MX8-based platform, presents a unique challenge. EL3 is traditionally reserved for firmware and security-critical code, such as the ARM Trusted Firmware (ATF) or BL31, which handles secure…
ARM Cortex-A53 and Cortex-A57 Instruction Execution Pipelines The ARM Cortex-A53 and Cortex-A57 processors, part of the Cortex-A5x family, exhibit distinct behaviors in terms of instruction execution due to differences in their microarchitectures. The Cortex-A53 is designed as an in-order processor, meaning it executes instructions in the exact sequence they are fetched from the instruction stream….
Cortex-A9 and Cortex-A53 Floating-Point Computing Capabilities The Cortex-A9 and Cortex-A53 are two widely used ARM processor cores, each with distinct architectural features that influence their floating-point computing capabilities. The Cortex-A9, part of the ARMv7-A architecture, is a dual-issue superscalar processor with an optional VFPv3 floating-point unit (FPU) and NEON media processing engine (MPE). The Cortex-A53,…
ARMv8 MMU Permission Faults During EL0 Access to EL1 Virtual Addresses In ARMv8 architectures, the Memory Management Unit (MMU) plays a critical role in enforcing memory access permissions and ensuring that user-space applications (EL0) cannot access kernel-space virtual addresses (EL1) without proper authorization. When an application running at EL0 attempts to access a virtual address…
ARM Cortex-A53 Misaligned Memory Access in Device Memory The core issue revolves around a Data Abort exception occurring during a memcpy operation on an ARM Cortex-A53 processor. The exception is triggered specifically during a store pair (STP) instruction, which attempts to write data to a memory region marked as Device memory. The ARM Cortex-A53, being…
ARMv8.7 FEAT_AFP and FPCR.NEP Bit Behavior in Floating-Point Operations The ARMv8.7 architecture introduces the FEAT_AFP (Additional Floating-Point) extension, which includes the FPCR.NEP (Non-standard Extended Precision) bit in the Floating-Point Control Register (FPCR). This bit, when enabled, modifies the behavior of certain floating-point operations, particularly those involving fused multiply-add (FMADD) instructions. The FPCR.NEP bit is located…
ARM Architecture Variability and Opcode Portability Across Cores The ARM architecture is a family of RISC-based processor designs that are widely used in embedded systems, mobile devices, and increasingly in server and desktop environments. One of the key characteristics of ARM processors is their scalability and adaptability, which allows them to be used in a…
ARM Cortex-M4F FPU Limitations and Double-Precision Floating-Point Overhead The ARM Cortex-M4F microcontroller, part of the Armv7E-M architecture, is equipped with a single-precision Floating-Point Unit (FPU) that natively supports 32-bit floating-point operations. This FPU is optimized for single-precision arithmetic, enabling efficient computation of 32-bit floating-point values. However, when double-precision (64-bit) floating-point operations are required, the Cortex-M4F…