Re: Q-bus or Unibus bus transactions in FPGA?

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> > Jon Elson spake the secret code > thusly: > > >Richard wrote: > >> > >>Has anyone implemented a Q-bus or Unibus bus interface logic in an > >>FPGA that is freely available or documented? [...] > >> > >Not on an FPGA (PDP-11 was before their time) but the bus protocol > >is quite simple. [...] > > Well, I didn't mean to imply that the FPGA was concurrent with the > PDP-11 :-), I was more hoping that another retro computing hobbyist > would have made something I could bootleg! > > I suppose I'll have to do my own bus handshake implementation from the > Q-bus docs (I think my processor or peripheral handbook that came with > the 11/03 has one in there somewhere). > > I wonder how hard it would be to get a PCB fabbed with the bus edge > connector?

There was a discussion of this on S.E.D. quite recently with one of it's denizens successfully getting a board with gold fingers fabricated at a very reasonable price.

X-Posted to s.e.d. for comments

Cheers

PeteS

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PeteS posted:

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Richard wrote:

I designed a Q-bus interface card about 16 years ago using a CPLD for decoding logic and another CPLD for board functions -- both written in ABEL. I used DEC's ChipKit for logic buffering to the bus itself. The physical dimensions of the board fingers came from one of DEC's manuals.

Alas, it was 16 years ago and 2 companies ago, so I don't have much to offer in the way of code. But, it has been done before, so it can be done again! As for the logic interface, there are so many logic families that modern FPGA's I/O can be programmed for, I'm sure something will match the characteristics of the Q-bus (Unibus), then you don't need the ChipKit.

Cheers Tom