A FPGA on a SBus card...
Goal
The goal of this repository is to be able to interface a modern (2020 era) FPGA with a SBus host. SBus was widely used in SPARCstation and compatibles system in the first halt of the 90s. It was progressively displaced by PCI from the mid-90s onward.
So unless you're a retrocomputing enthusiast with such a machine, this is useless. To be honest, even if you are such an enthusiast, it's probably not that useful...
I'm a software guy and know next to nothing about hardware design, so this is very much a work-in-progress and is likely full of rookie mistakes.
The hardware
The board is a SBus-compliant (I hope...) board, designed to receive a ZTex USB-FPGA Module 2.13 as a dauguterboard. The ZTex module contains the actual FPGA (Artix-7), some RAM, programming hardware, etc. The SBus board contains level-shifters ICs to interface between the SBus signals and the FPGA, some Leds, a JTAG header, and a micro-sd card slot.
The gateware
The function embedded in the FPGA currently includes the PROM, lighting Led to display a 32-bits value, and a GHASH MAC (128 polynomial accumulator, used for the AES-GCM encryption scheme). The device is a fairly basic scale, but should be able to read from the PROM and read/write from the GCM space with any kind of SBus burst (1, 2, 4, 8 or 16 words).