Author: System on Chips

ARM Cortex-M4 Hard Fault Handler Lockup Due to SVC Instruction Execution Issue Overview The core issue revolves around the execution of the Supervisor Call (SVC) instruction within the Hard Fault Handler on an ARM Cortex-M4 processor, specifically the STM32F407VG microcontroller. When the SVC instruction is executed inside the Hard Fault Handler, the system enters a…

AHB Bus Matrix Arbitration Delay in Uncontested Transactions The AHB (Advanced High-performance Bus) Bus Matrix is a critical component in ARM-based systems, facilitating communication between multiple masters and slaves within a System-on-Chip (SoC). A common issue observed in AHB Bus Matrix implementations is the presence of an initial arbitration delay, even in scenarios where there…

AHB Read-Ahead Behavior and PCIe BAR Configuration Challenges In systems where an AHB (Advanced High-performance Bus) is bridged to a PCIe (Peripheral Component Interconnect Express) interface, managing read-ahead behavior becomes critical, especially when dealing with prefetchable and non-prefetchable PCIe Base Address Registers (BARs). The core issue arises from the need to suppress read-ahead on the…

SMMUv2 Context Bank Interrupt Handling Challenges The ARM SMMUv2 (System Memory Management Unit version 2) specification mandates that each context bank must have its own dedicated interrupt signal. This requirement ensures that the software can precisely identify which context bank triggered an interrupt, enabling efficient handling of memory management events such as translation faults or…

Cortex-M7 PPB ROM Table Access Failures via Debug Port The Cortex-M7 processor, when interfaced with a debug probe such as ARM DS (Debugger and System Analyzer), relies on a hierarchical discovery process to identify and access debug components. This process involves reading ROM tables located in the Processor ROM, PPB (Private Peripheral Bus) ROM, and…

ARMv8-aarch64 Synchronous Bus Errors and Interrupts Collision in EL3 When working with ARMv8-aarch64 systems, particularly in secure environments like EL3, handling concurrent synchronous exceptions and interrupts can be challenging. The scenario described involves the TrustZone Controller (TZC-400) generating both a bus error (synchronous exception) and an interrupt when an illegal transaction occurs due to insufficient…

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,…

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…

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…

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….