Architectures and Processors

JTAG State Persistence in Simulation Despite TMS Reset Attempts When working with the ARM Cortex-M0+ processor, a common issue arises during simulation where the JTAG state remains stuck in an undefined state (‘X’) despite attempts to reset it synchronously through the TMS pin while nTRST is tied high. This behavior contradicts the Cortex-M0+ integration guide,…

Understanding TTBR1_EL1 Alignment Requirements for 4KB Granule Translation Tables The alignment constraints for the Translation Table Base Register 1 (TTBR1_EL1) in ARMv8 architectures are a critical aspect of memory management, particularly when configuring translation tables for virtual memory. The alignment requirements are influenced by the translation granule size, the size of the virtual address space,…

ARM Cortex-A53 SMP Core Suspension in Secure OS Environments Cache Coherency and Secure State Challenges in Core Suspension Suspending an individual core in a Symmetric Multiprocessing (SMP) system, such as the ARM Cortex-A53 with four cores, while running a secure OS in the AA32 secure state, presents unique challenges. The primary concern revolves around maintaining…

Cortex-M7 Pipeline Architecture and Dual-Issue Execution The Cortex-M7 processor is a high-performance embedded processor designed for applications requiring high computational power and efficiency. One of its key features is the dual-issue superscalar pipeline, which allows the processor to issue two instructions per clock cycle under certain conditions. This architecture is significantly more complex than the…

ARM Cortex-M4 Byte Addressing and Instruction Size Confusion The ARM Cortex-M4 processor, like many modern microcontrollers, employs a byte-addressable memory system. This means that each byte in memory has a unique address, and the processor can access individual bytes, half-words (16 bits), or words (32 bits) from memory. This design choice is crucial for supporting…

ARM Cortex-M DesignStart Kit Hex File Compatibility Issues The ARM Cortex-M DesignStart Kit is a powerful platform for developing and testing firmware for ARM Cortex-M0 and Cortex-M3 processors. However, one common issue arises when attempting to use compiled hex files generated by the Keil MDK (Microcontroller Development Kit) on Windows with the DesignStart Kit, which…

ARM Cortex-M4 RAM Allocation and Data Corruption During USB Data Transfer When working with ARM Cortex-M4 microcontrollers, such as the NXP LPC4370, developers often encounter challenges related to memory allocation, especially when dealing with real-time data processing and high-speed peripherals like USB. In this case, the issue revolves around the use of the __DATA(RAM3) attribute…

ARMv8 ARM32 Jump Table Implementation for 256 Opcode Handlers When working with ARMv8 ARM32 assembly, one common requirement is to implement a jump table to handle multiple opcodes efficiently. This is particularly useful when emulating an 8-bit computer with 256 possible opcodes, where each opcode corresponds to a specific handler. The challenge lies in creating…

ARM Cortex-A15 LPAE Page Table Configuration and MAIR0.attr0 Interaction The ARM Cortex-A15 processor, part of the ARMv7-A architecture, supports the Large Physical Address Extension (LPAE), which allows for 40-bit physical addressing and introduces a more complex memory translation system. One of the key components of this system is the Memory Attribute Indirection Register (MAIR), which…

ARM Cortex-M4 Pipeline Behavior and Instruction Fetch Energy Impact The ARM Cortex-M4 processor, a widely used embedded microcontroller core, exhibits variations in current consumption based on the size and alignment of instructions being executed. This behavior is primarily influenced by the interaction between the processor’s pipeline, instruction fetch mechanism, and memory subsystem. The Cortex-M4 employs…