Architectures and Processors

AHB5 Multi-Slave Select Feature and Its Impact on Address Decoding The AHB5 protocol introduces a significant enhancement called "Multi-Slave Select," which fundamentally changes how address decoding and slave selection are handled in ARM-based SoC designs. Unlike AHB3, where a single HSEL (Hardware Select) signal is used to select a slave device, AHB5 allows a single…

APB3 Slave Responding Incorrectly During PSEL De-assertion The core issue revolves around the APB3 slave’s state transition behavior when the master de-asserts the PSEL signal. Specifically, the APB3 slave is responding incorrectly when PSEL is de-asserted, leading to an undefined state or an incorrect transition from the ACCESS state to the SETUP state instead of…

AXI3 Write Data Interleaving Mechanism and Misinterpretation of AWID-WID Relationship The Advanced eXtensible Interface (AXI) protocol, particularly AXI3, is designed to facilitate high-performance, high-frequency system designs by decoupling address/control and data phases. A critical feature of AXI3 is its support for write data interleaving, which allows a master to interleave write data bursts with different…

AHB RETRY Response Generation in Multi-Master Systems The AHB (Advanced High-performance Bus) protocol is a widely used on-chip communication standard for ARM-based SoCs. One of its key features is the ability to handle multiple masters sharing a single bus, which introduces complexities in bus arbitration and slave responses. The RETRY response is a critical mechanism…

ACE Protocol Snoop Request and Cache Eviction Collision In ARM-based SoC designs utilizing the ACE (AXI Coherency Extensions) protocol, a critical scenario arises when a cache eviction and a snoop request target the same address simultaneously. This situation creates a conflict between the cache’s eviction process and the interconnect’s snoop request, leading to potential coherency…

ARM AHB Protocol: BUSY Transfer Impact on Undefined-Length Bursts The ARM Advanced High-performance Bus (AHB) protocol is a widely used on-chip communication standard for high-performance system-on-chip (SoC) designs. One of the key features of AHB is its support for burst transfers, which allow efficient data movement between masters and slaves. Burst transfers can be of…

PSTRB Signal Functionality in APB4: Byte-Level Write Control The PSTRB signal in the APB4 protocol is a critical component for managing write operations at the byte level. It is a 4-bit signal that corresponds to the 32-bit write data bus (PWDATA) in a typical APB4 implementation. Each bit in the PSTRB signal controls the validity…

AXI Write INCR Burst with Unexpected AWVALID Assertions In the context of an AXI (Advanced eXtensible Interface) protocol-based system, a common scenario involves the use of INCR (incremental) bursts for write transactions. The AXI protocol allows for efficient data transfer through burst operations, where multiple data transfers occur in a sequence. However, during the execution…

AXI4 Protocol Specification and Outstanding Transaction Handling The AXI4 protocol, as defined by ARM, is designed to support high-performance data transfers between masters and slaves in a system-on-chip (SoC) environment. One of the key features of AXI4 is its ability to handle multiple outstanding transactions, which significantly improves data throughput and system efficiency. Outstanding transactions…

HWDATA Routing and Slave Selection in AMBA AHB Architecture The ARM AMBA AHB (Advanced High-performance Bus) protocol is a widely used on-chip communication standard for high-performance systems. One of the key aspects of AHB is its ability to handle multiple masters and slaves efficiently. The routing of data signals, particularly the HWDATA signal, is a…