Misaligned Byte Transfers on Word-Addressable APB Slaves The core issue revolves around the behavior of an AHB2APB bridge when handling narrow byte transfers, specifically when the AHB master initiates a single-byte read transaction targeting a word-addressable APB slave. The AHB master sends a starting address of 0x01 with HSIZE set to 0 (indicating a byte…
Exclusive Access Mechanisms in AXI3 and AXI4: A Comparative Analysis Exclusive access is a critical feature in ARM’s AXI (Advanced eXtensible Interface) protocol, designed to support atomic operations in multi-master systems. It allows a master to perform a read-modify-write sequence without interference from other masters, ensuring data integrity. In AXI3, exclusive access is defined as…
Understanding R5F Lockstep Mismatch Errors in Versal PLM The Versal VCK190 and VMK180 platforms utilize the ARM Cortex-R5F processor in lockstep configuration to enhance fault tolerance and reliability in safety-critical applications. Lockstep mode involves running two identical Cortex-R5F cores in parallel, with their outputs compared in real-time to detect discrepancies. When a mismatch occurs, it…
ARM Cortex Cache Indexing Mechanism and Physical Address Discrepancy In ARM architectures, particularly in ARMv8-A and ARMv9-A, the relationship between Physical Addresses (PA) and cache set numbers is a nuanced topic that often leads to confusion. The cache indexing mechanism is designed to optimize memory access patterns, reduce contention, and improve overall system performance. However,…
ARM Cortex-A9 MPCore CP15 Affinity Register Misread During Dual-Core Initialization The ARM Cortex-A9 MPCore processor is a widely used multicore architecture in embedded systems, known for its performance and flexibility. However, during the initialization of a dual-core system, a critical issue arises where the CP15 affinity register (MPIDR) is misread, causing both cores to incorrectly…
Understanding AXI-5 User Loopback Signaling in ARM Architectures The AXI-5 protocol, an evolution of the Advanced eXtensible Interface (AXI) specification, introduces several enhancements to improve performance, scalability, and flexibility in ARM-based systems. One of the notable additions is the User Loopback Signaling mechanism, which includes signals such as AWLOOP, BLOOP, ARLOOP, and RLOOP. These signals…
Cortex-A53 Debugger Disconnection During Hypervisor Boot at EL2 The core issue revolves around the loss of debugger control when booting a Cortex-A53 core on an S32G2 platform using a custom Type 1 Hypervisor. The hypervisor runs at Exception Level 2 (EL2) and is initialized by a Cortex-M7 core. While the system operates correctly when booted…
TCMRETRY Signal and ECC Error Detection in ARMv7 TCMs The TCMRETRY signal in ARMv7 processors is a critical component for handling Error Correction Code (ECC) errors in Tightly Coupled Memories (TCMs). TCMs are high-speed memory blocks closely integrated with the processor core, providing low-latency access for critical data and instructions. When ECC is implemented in…
ARM SVE Intrinsic Definitions Obfuscated by GCC Pragmas The ARM Scalable Vector Extension (SVE) is a powerful feature for high-performance computing, enabling vectorized operations on ARM architectures. Developers often rely on intrinsic functions provided in the arm_sve.h header file to leverage SVE capabilities. However, the implementation of arm_sve.h in GCC (specifically the aarch64-linux-gnu v14 compiler)…
ARM Cortex-A9 Cache Behavior During Secondary Core Initialization In ARM Cortex-A9 multi-core systems, cache initialization and management are critical for ensuring correct and efficient execution of code, especially in environments where each core runs its own instance of a Real-Time Operating System (RTOS). The Cortex-A9 processor features a unified L1 cache and an optional L2…