Avalon® Interface Specifications

ID 683091
Date 9/26/2022
Document Table of Contents

5.6. Signal Details

The figure shows the signals that Avalon® -ST interfaces typically includes. A typical Avalon® -ST source interface drives the valid, data, error, and channel signals to the sink. The sink can apply backpressure with the ready signal.

Figure 21. Typical Avalon® -ST Interface Signals

More details about these signals:

  • ready—On interfaces supporting backpressure, the sink asserts ready to mark the cycles where transfers may take place. If ready is asserted on cycle <n>, cycle <n + readyLatency> is considered a ready cycle.
  • valid—The valid signal qualifies valid data on any cycle with data transferring from source to sink. On each valid cycle the sink samples the data signal and other source to sink signals.
  • data—The data signal carries the bulk of the information transferred from the source to the sink. The data signal consists of one or more symbols transferred on every clock cycle. The dataBitsPerSymbol parameter defines how the data signal is divided into symbols.
  • error—In the error signal, each bit corresponds to a possible error condition. A value of 0 on any cycle indicates error-free data on that cycle. This specification does not define the action that a component takes when an error is detected.
  • channel—The source drives the optional channel signal to indicate to which channel the data belongs. The meaning of channel for a given interface depends on the application. In some applications, channel indicates the interface number. In other applications, channel indicates the page number or timeslot. When the channel signal is used, all the data transferred in each active cycle belongs to the same channel. The source may change to a different channel on successive active cycles.

    Interfaces that use the channel signal must define the maxChannel parameter to indicate the maximum channel number. If the number of channels an interface supports changes dynamically, maxChannel indicates the maximum number the interface can support.