My Gpif (16 Bit and only SPI) and the Firmware running fine, as long I do not Using Bit 8 an higher.
If there is any Change on these Bits above, (Debugger is running), any thing from "USB RESET" or "UNKWON SETUP" Requests in various ways is happen.
Sometimes the FX3 make a full Reset (so I can Reload it in Control Center). I build 3 Boards, and all do the same, but in different manner.
Any Help ?
Have you tried the same in FX3 DVK?
When you say they're unused are you holding them high or low?
Is bit8 the only line causing the issue?