I needed a way to add classic I/O interfaces to my desktop PC, so I built a module that connects to usb, and has a classic bus interface on the other side. It uses a PSoC4 and its integrated digital blocks to generate the logic to drive the bus. The current version requires a two phase clock generator, so I used the MC6875.
http://hackaday.io/project/1937I'll later post the entire project.