Vivado’s component.xml: IP-XACT dissection jots

This post was written by eli on July 13, 2016
Posted Under: FPGA,Vivado

These are a few jots I wrote down as I wrote some code that generates component.xml files automatically. The XML convention of this file IP-XACT format, a specification by the SPIRIT Consortium which can be downloaded free from IEEE. The “spirit:” prefixes all over the XML file indicates that the keywords are defined in the IP-XACT spec.

Block design files (*.bd), which is the only essential source Vivado needs for defining a block design, are also given by IP-XACT convention, however they serve a different purpose, and have a different format.

An IP-XACT file can be opened directly in Vivado (File -> Open IP-XACT File… or the ipx::open_ipxact_file Tcl command on earlier Vivados) and there are plenty of Tcl commands (try “help ipx::” at Tcl prompt, yes, with two colons).

Structure

Everything is under the <spirit:component> entry.

  • Vendor, library version etc
  • busInterfaces: Each businterface groups ports (to be listed later on) into interfaces such as AXI, AXI Streaming etc. These interfaces are one of those known to Vivado, and it seems like it’s not possible to add a custom interface in a sensible way.
  • model: views and ports, see below
  • fileSets: Each fileset lists the files that are relevant for one particular view. The pairing is done by matching the view’s fileSetRef attribute with the fileset’s name attribute.
  • description: This is some text that is displayed to the user. It can be long
  • parameters
  • vendorExtensions (Xilinx taxonomy, basic stuff, note the supportedFamilies entry)

The “model” entry has two subentries:

  • views: Different ways to consume the files of the IP: Synthesis in Verilog, synthesis in VHDL, synthesis in any language, files for describing GUI etc. It seems like Vivado is looking at the envIdentifier attribute in particular, and the fileSetRef for linking with a fileset.
    A view doesn’t have to contain all files required, but several views are used together for a given scenario. For example, when synthesizing in Verilog, the fileset linked to the view identified with “verilogSource:vivado.xilinx.com:synthesis” (typically named “xilinx_verilogsynthesis”) will probably contain the Verilog files. But if there’s also a fileset linked with a view identified with “:vivado.xilinx.com:synthesis” (typically named “xilinx_anylanguagesynthesis”), its files will be used as well as well. The latter fileset may contain netlists (ngc, edif), which the language-specific fileset may not.
  • ports. Enlists the top-level module’s ports. Input ports may have a defaultValue attribute, which defines the value in case nothing is connected to it. All ports appearing in the busInterfaces section must appear here, in which case Vivado includes them in a group. If a port doesn’t belong to any bus interface, it’s exposed as a wire on the block.

Notes

  • In the files listed in a fileset, each one is given a fileType attribute. This attribute has to be one listed in the IP-XACT standard section C.8.2 (e.g. verilogSource, vhdlSource, tclSource etc.). Other strings will be rejected by Vivado. For xci, ngc, edif etc, Vivado expects a userFileType attribute instead. One of fileType or userFileType must be present.
  • When instantiating the IP in a block design, Vivado expects the top-level module to have the name given in the modelName attribute in the relevant view. This is typically the name of one of the modules of the fileset.
  • The entries in vendorExtensions -> taxonomies is where the IP will appear in Vivado’s IP Catalog, when it’s listed by groups. The path is given as a directory path, with slashes (hence the leading slash, marking “root”). It’s fine to invent a name for a new root entry, in which case a new group is generated in the IP Catalog. Vivado accepts taxonomies it doesn’t know of.
  • Sub-core’s XCI files may go into a Verilog/VHDL Synthesis fileset, but the last file in the fileset must be in Verilog/VHDL.

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