ARM Cortex-M4 Fixed-Point Arithmetic and Rounding Mechanism The provided assembly snippet demonstrates a common pattern used in ARM Cortex-M4 processors for handling fixed-point arithmetic, specifically focusing on rounding and overflow management. The snippet is as follows: add.w r1, r4, r5 add.w r1, r1, r1, lsr #0x1f asr r1, r1, #1 This sequence of instructions is…
CoreSight Trace Buffer (ETB) Continuation During CPU Exceptions In ARM-based embedded systems, CoreSight is a powerful debugging and trace technology that provides visibility into the execution of software on ARM processors. One of the key components of CoreSight is the Embedded Trace Buffer (ETB), which acts as a sink for trace data generated by the…
ARMv8.5-A Memory Tagging Exception Handling Failure in Use-After-Free Scenarios Memory Tagging Enabled but No Exception on Use-After-Free Access The core issue revolves around the ARMv8.5-A architecture’s memory tagging extension (MTE), which is designed to detect and prevent memory safety violations such as use-after-free errors. When MTE is enabled, each memory allocation is assigned a tag,…
AXI4 Slave Response Ordering Requirements and Protocol Violations The AXI4 protocol, as defined in the ARM AMBA specification, imposes strict requirements on the ordering of responses from slaves to ensure proper functionality and predictability in multi-master, multi-slave systems. The protocol mandates that responses for transactions with the same ID must be returned in the order…
AHB Protocol Timing and Signal Interaction During Burst Transfers The Advanced High-performance Bus (AHB) protocol is a critical component of ARM’s AMBA (Advanced Microcontroller Bus Architecture) family, widely used in SoC designs for high-performance data transfers. One of the key challenges in AHB-based systems is understanding the precise timing and interaction between the HREADY and…
ARM AXI Low-Power Interface for Peripheral Clock Management The ARM AXI (Advanced eXtensible Interface) protocol includes an optional low-power interface extension designed to manage clock gating for peripherals in a system-on-chip (SoC). This interface is particularly useful for optimizing power consumption in designs where certain peripherals may remain idle for extended periods. The low-power interface…
ARM AHB SINGLE Burst vs. INCR Burst of Length One The ARM Advanced High-performance Bus (AHB) protocol provides two mechanisms for performing single transfers: the SINGLE burst and the INCR (incremental) burst of length one. While both mechanisms achieve the same goal of transferring a single data unit, they serve different purposes in terms of…
Unaligned AXI Transfers: WSTRB vs. Start Address Adjustment In ARM-based SoC designs, handling unaligned memory transfers is a common challenge, especially when working with the AXI (Advanced eXtensible Interface) protocol. Two primary methods are often discussed for managing unaligned transfers: using the WSTRB (Write Strobe) signal and adjusting the start address of the transfer. Both…
ARM AXI Protocol Support for Unaligned Transfers The ARM AXI (Advanced eXtensible Interface) protocol is designed to support high-performance, high-frequency system-on-chip (SoC) designs. One of its key features is the ability to handle unaligned transfers, which are memory accesses that do not align with the natural boundaries of the data bus width. For example, a…
Core and Application Binary Separation in ARM-Based Embedded Systems In ARM-based embedded systems, particularly those utilizing Real-Time Operating Systems (RTOS), there is often a need to separate the core functionality from application-specific code. This separation allows for modular development, easier updates, and independent execution of multiple applications. The core functionality typically includes essential services such…