Author: System on Chips

AXI Slave Data Width Mismatch Between 128-bit AXI and 64-bit BRAM When designing a custom AXI slave IP to interface with a BRAM (Block RAM) that has a different data width than the AXI bus, careful consideration must be given to how data transfers are handled. In this case, the AXI bus is 128 bits…

Vector Table Remapping in ARM Cortex-M0/M0+: Functionality and Security Concerns Vector table remapping is a feature available in the ARM Cortex-M0+ processor, allowing the relocation of the vector table from its default address at 0x0 to a new address specified in the Vector Table Offset Register (VTOR). This feature is not present in the Cortex-M0,…

ARM Cortex-M Reset Function Address Mismatch: VMA vs. LMA The issue at hand revolves around the discrepancy between the Virtual Memory Address (VMA) and the Load Memory Address (LMA) of the Reset function in an ARM Cortex-M microcontroller. Specifically, the Reset function is placed in the .text section of the ROM, with an LMA of…

Debugger Memory Access via DCC and Cache Involvement When a debugger accesses memory using the Debug Communications Channel (DCC) on ARM Cortex processors, the memory access typically involves the cache subsystem. The DCC is a communication mechanism that allows the debugger to read from and write to memory while the processor is running or halted….

ARM Cortex-M3 Debug Halt Failure and DHCSR Register Behavior The ARM Cortex-M3 processor is widely used in embedded systems due to its balance of performance, power efficiency, and robust debugging capabilities. One of the key features of the Cortex-M3 is its Debug Halting Control and Status Register (DHCSR), which allows developers to halt the processor…

ARM Cortex-A9 Dual-Core AMP Mode Initialization Challenges The ARM Cortex-A9 dual-core processor is a popular choice for embedded systems requiring high performance and scalability. However, implementing Asymmetric Multiprocessing (AMP) mode on a baremetal system presents unique challenges, particularly when it comes to initializing the secondary core (CPU1) and ensuring proper synchronization between the two cores….

ARMv8 Memory Barriers and Shareability Domains: The Core Issue In ARMv8 architectures, memory barriers (DMB) are critical for enforcing memory ordering guarantees across different processing elements (PEs) and shareability domains. The primary issue under discussion revolves around the practical differences between DMB NSHLD (Non-shareable Load Barrier) and DMB ISHLD (Inner Shareable Load Barrier). Specifically, the…

ARM Cortex-M7 Flash Access Performance Variability Due to Address Alignment The ARM Cortex-M7 processor, known for its high performance and efficiency, can exhibit significant variability in execution time for certain operations, particularly when accessing data from flash memory. This variability is especially pronounced when performing looped load-byte (LDRB) operations from flash memory to core registers….

ARM Cortex-A55 TLB Coherency Issues During Context Switching with TTBR0 and TTBR1 In ARMv8-based systems, particularly those utilizing the Cortex-A55 processor, context switching between processes often involves managing Translation Lookaside Buffer (TLB) coherency when updating the Translation Table Base Registers (TTBR0 and TTBR1). The TLB is a critical component of the memory management unit (MMU)…

ARM Cortex-A53 NEON Intrinsics Misalignment and Cache Coherency Issues The issue described involves a "bus error" occurring when using the ARM NEON intrinsic vld2q_f32 on MediaTek MT676x series processors, specifically the MT6765 and MT6762. These processors are based on the ARM Cortex-A53 architecture, which implements the ARMv8-A instruction set. The vld2q_f32 intrinsic is designed to…