1. Introduction to the Avalon® Interface Specifications 2. Avalon® Clock and Reset Interfaces 3. Avalon® Memory-Mapped Interfaces 4. Avalon® Interrupt Interfaces 5. Avalon® Streaming Interfaces 6. Avalon® Streaming Credit Interfaces 7. Avalon® Conduit Interfaces 8. Avalon® Tristate Conduit Interface A. Deprecated Signals B. Document Revision History for the Avalon® Interface Specifications
2.1. Avalon® Clock Sink Signal Roles 2.2. Clock Sink Properties 2.3. Associated Clock Interfaces 2.4. Avalon® Clock Source Signal Roles 2.5. Clock Source Properties 2.6. Reset Sink 2.7. Reset Sink Interface Properties 2.8. Associated Reset Interfaces 2.9. Reset Source 2.10. Reset Source Interface Properties
5.1. Terms and Concepts 5.2. Avalon® Streaming Interface Signal Roles 5.3. Signal Sequencing and Timing 5.4. Avalon® -ST Interface Properties 5.5. Typical Data Transfers 5.6. Signal Details 5.7. Data Layout 5.8. Data Transfer without Backpressure 5.9. Data Transfer with Backpressure 5.10. Packet Data Transfers 5.11. Signal Details 5.12. Protocol Details
5.1. Terms and Concepts
The Avalon® -ST interface protocol defines the following terms and concepts:
- Avalon® Streaming System—An Avalon® Streaming system contains one or more Avalon® -ST connections that transfer data from a source interface to a sink interface. The system shown above consists of Avalon® -ST interfaces to transfer data from the system input to output. Avalon® -MM control and status register interfaces provide for software control.
- Avalon® Streaming Components—A typical system using Avalon® -ST interfaces combines multiple functional modules, called components. The system designer configures the components and connects them together to implement a system.
- Source and Sink Interfaces and Connections—When two components connect, the data flows from the source interface to the sink interface. The Avalon® Interface Specifications calls the combination of a source interface connecting to a sink interface a connection.
- Backpressure—Backpressure allows a sink to signal a source to stop sending data. Support for backpressure is optional. The sink uses backpressure to stop the flow of data for the following reasons:
- When the sink FIFOs are full
- When there is congestion on its output interface
- Transfers and Ready Cycles—A transfer results in data and control propagation from a source interface to a sink interface. For data interfaces, a ready cycle is a cycle during which the sink can accept a transfer.
- Symbol—A symbol is the smallest unit of data. For most packet interfaces, a symbol is a byte. One or more symbols make up the single unit of data transferred in a cycle.
- Channel—A channel is a physical or logical path or link through which information passes between two ports.
- Beat—A beat is a single cycle transfer between a source and sink interface made up of one or more symbols.
- Packet—A packet is an aggregation of data and control signals that a source transmits simultaneously. A packet may contain a header to help routers and other network devices direct the packet to the correct destination. The application defines the packet format, not this specification. Avalon® -ST packets can be variable in length and can be interleaved across a connection. With an Avalon® -ST interfaces, the use of packets is optional.