Protocol Bridges

Four protocol converters so subsystems on different buses interoperate: an AXI4-Lite fabric can reach APB or classic-Wishbone peripherals (axil_to_apb, axil_to_wb), and an APB or Wishbone requester can reach AXI4-Lite slaves (apb_to_axil, wb_to_axil). Each is a self-contained module — no submodules, no vendor cells, no registers.

The two AXI-fronted bridges carry an unusually strong claim: a SymbiYosys proof that their far-side protocol is legal for *any* requester and completer behaviour — every input free, zero assumptions. APB SETUP/ACCESS sequencing with stable control through a stalling completer, and Wishbone cycle-hold-until-termination, are proven rather than sampled. The testbench chains all four back-to-back so one master model exercises both directions of each protocol.