Architectures and Processors

MEMATTR Signals in Cortex-M4: AHB-Lite Protocol Discrepancy The ARM Cortex-M4 processor utilizes the AMBA AHB-Lite 3 bus architecture, which is a simplified version of the Advanced High-performance Bus (AHB) protocol. AHB-Lite is designed to reduce complexity by removing features such as bus arbitration, burst support, and split transactions, making it suitable for single-master systems like…

APB5 Parity Bit Generation and Timing Constraints The Advanced Peripheral Bus (APB) is a part of the ARM Advanced Microcontroller Bus Architecture (AMBA) and is widely used in low-bandwidth, low-power peripheral interfaces. APB5, the latest version of the APB protocol, introduces several enhancements, including parity checking for error detection. Parity checking is a simple yet…

ARM SBSA Watchdog Timer Pretimeout Feature Overview The ARM Server Base System Architecture (SBSA) watchdog timer (WDT) is a critical component in ensuring system reliability by providing a mechanism to recover from system hangs or software failures. The SBSA watchdog timer operates in two modes: single-stage and double-stage. In single-stage mode, the watchdog timer triggers…

Understanding AXI4 Unaligned WRITE Transfers and WSTRB Signaling In the AXI4 protocol, unaligned WRITE transfers occur when the starting address (AWADDR) is not aligned to the data width specified by AWSIZE. For example, if AWSIZE is set to 2 (indicating a 32-bit transfer), the starting address should ideally be aligned to a 4-byte boundary (e.g.,…

ARM Cortex-M4 Memory Access Ordering: Architectural Guarantees vs. Implementation-Specific Behavior The ARM Cortex-M4 processor, like other ARM Cortex-M series processors, is designed with a focus on deterministic real-time performance and low-latency interrupt handling. A critical aspect of its design is memory access ordering, which governs how the processor handles reads and writes to memory. The…

ARM Cortex-A55 DSU Write Issuing Capability and Outstanding Transactions Analysis The ARM Cortex-A55 is a highly efficient mid-range CPU core designed for power-efficient performance in mobile and embedded applications. It is often paired with the DynamIQ Shared Unit (DSU) to manage shared resources among multiple cores in a cluster. One critical aspect of the Cortex-A55…

ARM Cortex-M7 PWM Signal Generation Capabilities and Constraints The ARM Cortex-M7 core, as found in the STM32F7xx and STM32H7xx microcontrollers, is a high-performance processor designed for real-time applications. One of its key features is the ability to generate Pulse Width Modulation (PWM) signals, which are essential for controlling motors, LEDs, and other devices that require…

ARM Cortex-A53 Double Precision Floating-Point Printout Anomaly The issue at hand involves the incorrect printout of a double-precision floating-point value on an ARM Cortex-A53 core. Specifically, when printing a negative double value using the %e format specifier, the Cortex-A53 incorrectly outputs the value as positive, whereas the same code running on an ARM Cortex-M4 core…

APB Slave Selection Mechanism and Address Decoding in Single-Master Systems In an Advanced Peripheral Bus (APB) system with a single master and multiple slaves, the master communicates with one slave at a time. The selection of the slave is determined by the PSEL (Peripheral Select) signal, which is generated based on address decoding. The PSEL…

ARM Cortex-A53 STUR Instruction and Synchronous Exception Overview The ARM Cortex-A53 processor, operating in AArch64 mode, is a widely used 64-bit ARM core known for its efficiency and performance in embedded systems. One of the instructions available in the A64 instruction set is the STUR (Store Register Unscaled) instruction, which is used to store a…