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FPGA-Based Disk Controller for the Apple II (2017)
controller cards are weird, there are a crazy number of different types, and many are rare and expensive. Can an FPGA-based solution save the day for retro collectors? You bet! Nearly all the existing disk controllers connect the same 8-bit bus to the same 19-pin disk interface, so a universal clone is merely a question of replacing the vintage 80s guts of the card with a modern reprogrammable FPGA.
It’s a single IWM (the famous Integrated Wozniak Machine), combined with a small number of standard 7400-series logic chips, and a ROM to hold the boot code. Unlike some FPGAs, the MachXO2 family also has built-in flash memory to store the FPGA configuration, so it doesn’t need to be reloaded from an external source at power-up. I might add a microcontroller and an SD card socket for loading alternate firmware, but that would be a fairly ridiculous amount of extra baggage if it were used only for JTAG.
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