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README.md

WB2AXIP: A Pipelind Wishbone B4 to AXI4 bridge

Built out of necessity, this core is designed to provide a conversion from a wishbone bus to an AXI bus. Primarily, the core is designed to connect a wishbone bus, either 32- or 128-bits wide, to a 128-bit wide AXI bus, which is the natural width of a DDR3 transaction (with 16-bit lanes). Hence, if the Memory Interface Generator DDR3 controller is running at a 4:1 clock rate, memory clocks to AXI system clocks, then it should be possible to accomplish one transaction clock at a sustained or pipelined rate. This bus translator is designed to be able to handle one transaction per clock (pipelined), although (due to Xilinx's MIG design) the delay may be up to 27 clocks. (Ouch!)

Since the initial build of the core, I've added the WB to AXI lite bridge. This is also a pipelined bridge, and like the original one it is also formally verified.

AXI to Wishbone conversion

Since the project began, a full-fledged AXI4 to Wishbone bridge has been added to the project. This converter handles synchronizing the write channels, turning AXI read/write requests into pipeline wishbone requests, maintaining the AXI ID fields, etc. It ignores the AXI xSIZE, xLOCK, xCACHE, xPROT, and xQOS fields. It supports xBURST types of FIXED (2'b00) and INCR (2'b01), but not WRAP (2'b10) or reserved (2'b11). It does not (yet) support bridging between busses of different widths, so both the AXI and the WB bus must have the same width.

AXI4 is a complicated protocol, however, especially when compared to WB.

Finally, whereas the bridge has been written, it has yet to be significantly tested or formally proven. If you are interested in helping to test it, please contact me at (zipcpu (at) gmail.com). Until that time, it must be said that the result is subject to change.

Formal Verification

This particular version of the tools includes an initial attempt at formally proving that the core(s) work.

Currently, the project contains formal specifications for Avalon, Wishbone, and AXI busses. Components with working proofs include the WB to AXI bridge as well as the WB arbiter needed for the AXI to WB. I also have a working proof for an Avalon to WB bridge that isn't posted here.

The AXI4 to Wishbone bridge remains a work in progress that isn't getting a lot of attention.

Commercial Applications

Should you find the GPLv3 license insufficient for your needs, other licenses can be purchased from Gisselquist Technology, LLc.

Thanks

I'd like to thank @wallento for his initial work on a Wishbone to AXI converter, and his encouragement to improve upon it. While this isn't a fork of his work, it takes its motivation from his work.