Architectures and Processors

APB State Machine and PREADY Signal Interaction The Advanced Peripheral Bus (APB) is part of the ARM AMBA (Advanced Microcontroller Bus Architecture) family and is widely used for low-bandwidth, low-power peripheral communications. The APB protocol is simple and efficient, making it ideal for connecting peripherals such as UARTs, timers, and GPIOs to a more complex…

AXI Protocol Burst Data Transfer and Write Response Timing The AXI (Advanced eXtensible Interface) protocol, part of the AMBA (Advanced Microcontroller Bus Architecture) family, is designed to support high-performance, high-frequency system designs. One of its key features is the ability to handle multiple outstanding transactions, which allows for increased system throughput and efficiency. However, this…

Understanding Unaligned Address Access in ARM AMBA Protocols Unaligned address access is a concept that arises in the context of memory transactions within ARM AMBA (Advanced Microcontroller Bus Architecture) protocols, particularly in AXI4 (Advanced eXtensible Interface 4) and APB4 (Advanced Peripheral Bus 4). The term "unaligned" refers to memory accesses where the starting address of…

PVBus Master ID Overwrite Requirement for GIC-400 Banked Registers In ARM-based SoC designs, the Generic Interrupt Controller (GIC-400) often requires banked registers to handle interrupts from multiple processors or clusters. Each processor or cluster typically has a unique master ID that is used to access its respective banked registers in the GIC-400. However, there are…

AxCACHE Attributes and Their Impact on Write Merging and Read Prefetching The AxCACHE signal in AMBA AXI protocols is a critical attribute that governs the behavior of transactions, particularly in terms of write merging and read prefetching. AxCACHE is a 4-bit signal associated with each transaction, and its bits control various aspects of memory access,…

ARM GICv3/v4 LPI State Machine: Missing "Active" State The ARM Generic Interrupt Controller (GIC) architecture, particularly in versions 3 and 4, introduces a unique type of interrupt known as Locality-specific Peripheral Interrupts (LPIs). Unlike Shared Peripheral Interrupts (SPIs), Software Generated Interrupts (SGIs), and Private Peripheral Interrupts (PPIs), LPIs do not have an "active" state in…

AHB to APB Burst Transfer Issue with Extra Read Request The CoreLink NIC-400 Interconnect is a highly configurable network interconnect designed to facilitate communication between multiple masters and slaves in an ARM-based SoC. In this scenario, an AHB-lite master is attempting to perform a burst transfer to an APB slave through the NIC-400 Interconnect. The…

Unaligned 32-bit Word Transfer on a 64-bit AXI Bus: A Detailed Breakdown In the context of ARM AMBA AXI (Advanced eXtensible Interface) protocols, understanding how unaligned transfers operate on a 64-bit bus is critical for both design and verification engineers. The scenario involves a 32-bit word transfer starting at an unaligned address (0x07) on a…

AXI Lock Signal Handling in Single-Port vs. Multi-Port Slaves The AXI protocol defines the AxLOCK signal as a mechanism for masters to request locked or exclusive access to a slave. In a typical single-port AXI slave implementation, the slave does not need to explicitly handle the AxLOCK signal. The slave simply processes the read or…

ARM Cortex-A53 Cache Debugging Mechanism Overview The ARM Cortex-A53 processor provides a sophisticated mechanism for debugging and inspecting its internal cache structures, including the Instruction Cache (I-Cache) and Data Cache (D-Cache). This mechanism is facilitated through a set of Implementation-Defined system registers, which allow direct access to the internal memory used by the cache and…